Scholarly article on topic 'Concrete using agro-waste as fine aggregate for sustainable built environment – A review'

Concrete using agro-waste as fine aggregate for sustainable built environment – A review Academic research paper on "Civil engineering"

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Abstract of research paper on Civil engineering, author of scientific article — Jnyanendra Kumar Prusty, Sanjaya Kumar Patro, S.S. Basarkar

Abstract High demand of natural resources due to rapid urbanization and the disposal problem of agricultural wastes in developed countries have created opportunities for use of agro-waste in the construction industry. Many agricultural waste materials are already used in concrete as replacement alternatives for cement, fine aggregate, coarse aggregate and reinforcing materials. This paper reviews some of the agro-waste materials, which are used as a partial replacement of fine aggregate in concrete. Different properties of fresh and hardened concrete, their durability and thermal conductivity when admixed with agro-wastes are reviewed. Agro-waste used in self-compacting concrete and mortar are also reviewed and their properties are compared. It has been seen that the agro-waste concrete containing groundnut shell, oyster shell, cork, rice husk ash and tobacco waste showed better workability than their counterparts did. Agro-waste concrete containing bagasse ash, sawdust ash and oyster shell achieved their required strength by 20% of replacement as fine aggregate, which were maximum among all agro-waste type concrete. Close relations were predicted among compressive strength, flexural strength, tensile strength, ultrasonic pulse velocity and elastic modulus of agro-waste concrete. Addition of bagasse ash as fine aggregate in mortar increased the resistance of chloride penetration whereas inclusion of cork in mortar showed better thermal resistance and improved cyclic performance. After the review, it is of considerable finding that more research is deserved on all fine aggregates replacing agro-waste materials, which can give more certainty on their utilization in concrete.

Academic research paper on topic "Concrete using agro-waste as fine aggregate for sustainable built environment – A review"

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Gulf Organisation for Research and Development International Journal of Sustainable Built Environment

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Review Article

Concrete using agro-waste as fine aggregate for sustainable

built environment - A review

Jnyanendra Kumar Prusty a'*, Sanjaya Kumar Patrob, S.S. Basarkarc

a School of Civil Engineering, KIIT University, Bhubaneswar, Odisha, India Department of Civil Engineering, VSS University of Technology, Burla, Odisha, India c ITD Cementation India Ltd., Mumbai, India

Received 15 April 2015; accepted 12 June 2016

Abstract

High demand of natural resources due to rapid urbanization and the disposal problem of agricultural wastes in developed countries have created opportunities for use of agro-waste in the construction industry. Many agricultural waste materials are already used in concrete as replacement alternatives for cement, fine aggregate, coarse aggregate and reinforcing materials. This paper reviews some of the agro-waste materials, which are used as a partial replacement of fine aggregate in concrete. Different properties of fresh and hardened concrete, their durability and thermal conductivity when admixed with agro-wastes are reviewed. Agro-waste used in self-compacting concrete and mortar are also reviewed and their properties are compared. It has been seen that the agro-waste concrete containing groundnut shell, oyster shell, cork, rice husk ash and tobacco waste showed better workability than their counterparts did. Agro-waste concrete containing bagasse ash, sawdust ash and oyster shell achieved their required strength by 20% of replacement as fine aggregate, which were maximum among all agro-waste type concrete. Close relations were predicted among compressive strength, flexural strength, tensile strength, ultrasonic pulse velocity and elastic modulus of agro-waste concrete. Addition of bagasse ash as fine aggregate in mortar increased the resistance of chloride penetration whereas inclusion of cork in mortar showed better thermal resistance and improved cyclic performance. After the review, it is of considerable finding that more research is deserved on all fine aggregates replacing agro-waste materials, which can give more certainty on their utilization in concrete. © 2016 Published by Elsevier B.V. on behalf of The Gulf Organisation for Research and Development.

Keywords: Agro-waste concrete; Agricultural waste; Fine aggregate; Sustainable concrete

Contents

1. Introduction..............................................................................................................................................................00

1.1. Agricultural wastes used as a fine aggregate replacement in concrete......................................................................00

1.1.1. Sugarcane bagasse ash (SCBA)........................................................00

* Corresponding author.

E-mail addresses: jkumar.prusty@gmail.com (J.K. Prusty), litusanjay@yahoo.com (S.K. Patro), sunil.basarkar@itdcem.co.in (S.S. Basarkar). Peer review under responsibility of The Gulf Organisation for Research and Development.

http://dx.doi.org/10.1016/j.ijsbe.2016.06.003

2212-6090/© 2016 Published by Elsevier B.V. on behalf of The Gulf Organisation for Research and Development.

1.1.2. Groundnut shell...................................................................00

1.1.3. Oyster shell......................................................................00

1.1.4. Sawdust.........................................................................00

1.1.5. Wild giant reed....................................................................00

1.1.6. Rice husk........................................................................00

1.1.7. Cork...........................................................................00

1.1.8. Tobacco waste....................................................................00

2. Physical and chemical properties of agricultural wastes..................................................................................................00

3. Mix proportion of agro-waste based concrete................................................................................................................00

4. Fresh properties of concrete........................................................................................................................................00

4.1. Slump test........................................................................................................................................................00

4.2. Compaction factor test ......................................................................................................................................00

4.3. Air content........................................................................................................................................................00

4.4. Flow table test ..................................................................................................................................................00

4.5. Penetration and ball-drop ..................................................................................................................................00

4.6. Water requirement and unit weight......................................................................................................................00

4.7. Slump flow diameter and T50cm slump flow ..........................................................................................................00

4.8. V-funneltest......................................................................................................................................................00

4.9. J-Ring test........................................................................................................................................................00

5. Hardened properties of concrete..................................................................................................................................00

5.1. Compressive strength..........................................................................................................................................00

5.1.1. Bagasse ash......................................................................00

5.1.2. Groundnut shell...................................................................00

5.1.3. Oyster shell ............................................................................................................................................00

5.1.4. Sawdust ash......................................................................00

5.1.5. Wild giant reed........................................................................................................................................00

5.1.6. Rice husk ash..........................................................................................................................................00

5.1.7. Cork...........................................................................00

5.1.8. Tobacco waste....................................................................00

5.2. Tensile strength..................................................................................................................................................00

5.3. Flexural strength................................................................................................................................................00

5.4. Elastic modulus (E-value)..................................................................................................................................00

5.5. Ultrasonic pulse velocity (UPV)..........................................................................................................................00

5.6. Shrinkage and creep ..........................................................................................................................................00

6. Durability..................................................................................................................................................................00

6.1. Freezing and thawing........................................................................................................................................00

6.2. Chemical attack ................................................................................................................................................00

6.3. Carbonation ......................................................................................................................................................00

6.4. Permeability ......................................................................................................................................................00

6.5. Water absorption test ........................................................................................................................................00

7. Thermal conductivity ..................................................................................................................................................00

8. Cyclic behaviour ........................................................................................................................................................00

9. Future recommendation ..............................................................................................................................................00

10. Conclusion ..............................................................................................................................................................00

References ................................................................................................................................................................00

1. Introduction

Concrete is a mixture of cement, fine aggregate and coarse aggregate, which is mainly derived from natural resources. Increasing population, expanding urbanization, climbing way of life due to technological innovations has demanded a huge amount of natural resources in the construction industry, which has resulted in scarcity of resources. This scarcity motivates the researchers to use, solid wastes generated by industrial, mining, domestic and agricultural activities. It is observed that in India more than 600 MT wastes have been generated from agricultural

waste, which is seriously leading to a disposal problem. Reuse of such wastes as sustainable construction materials take care of the issue of contamination, as well as the issue of area filling and the expense of building materials (Madurwar et al., 2013). The Major quantity of solid wastes generated in India is reported in Fig. 1. Shafigh et al. (2014) expressed that research on the utilization of agricultural waste, as an aggregate substitution is generally new and more research is needed for long-term durability properties of concrete. They also studied the relationship between the concrete made using this type of materials; environmentally friendly concrete and green building rating systems.

The current Green Building Rating (GBR) systems evaluate the sustainability of buildings according to various categories of which the construction material is one such category in most of the systems. Issues like emission of carbon dioxide, use of energy, water, aggregates, fillers and demolition waste in concrete look less compatible with environmental requirement of a modern sustainable construction industry. At the same time, concrete made using agricultural wastes has shown better thermal property in research which can result in sustainability points in the energy and atmosphere category of the LEED rating system (Shafigh et al., 2014).

as coarse aggregate in coastal regions. Sawdust is generated from mechanical processing of raw wood from saw mill industry. These are dried by leaving in sun and sieved properly before using in concrete (Oyedepo et al., 2014). Cork and tobacco wastes are collected and processed from cork oak trees and cigarette making industries which were used as fine aggregate replacement in concrete. The shape, size and availability of mentioned agro-wastes are discussed below. The purpose of this review is to study the properties such as workability, mechanical properties, durability, thermal conductivity of agricultural wastes used as a partial replacement of fine aggregate in concrete.

1.1. Agricultural wastes used as a fine aggregate replacement in concrete

The Agricultural wastes used as fine aggregate in concrete are sugarcane bagasse ash, groundnut shell, oyster shell, sawdust, giant reed ash, rice husk ash, cork and tobacco waste. The major differences of these agro-wastes are the place from where they collected and the processes to convert into a fine aggregate. It can be observed that sugarcane, giant reed, and rice husk are produced worldwide and they have a similar type of processing, those are burnt to convert into sugarcane bagasse ash, giant reed ash and rice husk ash. These are used as partial replacement of fine aggregate which provide additional pozzolanic property in concrete. Groundnut shells are crushed in mill to convert into fine aggregate prior to use in concrete. Oyster shells are the sea shells generally available in coastal areas. These are used as partial replacement of fine as well

1.1.1. Sugarcane bagasse ash (SCBA)

The fibrous residue (about 40-45%) of sugarcane after crushing and extraction of its juice is known as "bagasse" (Loh et al., 2013). The bagasses are reused as fuel for heat generation which leaves behind 8-10% of ash, known as sugarcane bagasse ash (SCBA) Modani and Vyawahare, 2013. Sugarcane bagasse consists of approximately 50% of cellulose, 25% of hemicellulose and 25% of lignin (Modani and Vyawahare, 2013). Rukzon and Chindaprasirt (2012) reviewed that a lot of sugarcane bagasse from the sugar factory is accessible in Thailand. Sugarcane bagasse is partly utilized as fuel in sugar plant but the rest is treated as waste and unutilized. As production of sugar cane is more than 1500 million tons in the world and in India, about 10 million tons ofsugarcane bagasse ash are treated as a waste material, it can therefore be advantageous to use it as a fine aggregate replacement in concrete to mitigate the disposal problem as well as to minimize the use of natural aggregates (Modani

3% 3% 4%

1% ■ Coal Combustion Residues

■ Bagasse

■ Coal Mine

■ Municipal Waste

■ Rice Husk

■ Lime Stone

■ Jute Fibre

■ Construction

■ Rice Wheat Straw

■ Blast Furnace

■ Groundnut Shell

■ Iron Tailing

■ Marble Dust

■ Waste Gypsum

■ Red Mud

■ Hazardous Waste

■ Copper Tailing

■ Lime Sludge

■ Zinc Tailing

Fig. 1. Status of solid waste generated in India (Madurwar et al., 2013).

and Vyawahare, 2013). Fig. 2 shows the raw sugarcane bagasse and the sugarcane bagasse ash which is used as fine aggregate replacement in concrete. Sales and Lima (2010) analysed the SCBA samples to determine the crystallinity by X-ray diffractometry, leachability and particle morphology by scanning electron microscopy (SEM). The X-ray diffractometry test result revealed the absence of an amorphous halo in the diffractograms (Sales and Lima, 2010). Quartz appeared as the principal element of SCBA. The SEM analysis revealed that the SCBA samples were composed of grains with varied shapes and sizes up to 150 im. Authors (Sales and Lima, 2010) suggested that these findings reinforce the hypothesis of using SCBA as a substitute for fine aggregate which has binding properties.

1.1.2. Groundnut shell

Groundnut shell can be found in large quantities as agricultural farm waste in Nigeria, producing up to 2.699 million metric tons per year (Sada et al., 2013). Groundnut shell was first planted in South Africa mainly Brazil and later spread to other part of America, Asia, and northwestern Argentina (Tata et al., 2015). The outer part of groundnut is called groundnut shell. Over a period of years, it is treated as a solid waste. Utilization of groundnut shell in the construction industry is expected to solve the pollution problem and increase the economic base of farmers, which encourage them to increase the production (Sada et al., 2013). Groundnut shell is already used for developing roof

sheet materials (Akindapo et al., 2015), sandcrete blocks (Mahmoud et al., 2012), as cement replacement (Olutoge et al., 2013; Buari et al., 2013; Kanagalakshmi et al., 2015) and as fine aggregate replacement (Sada et al., 2013; Tata et al., 2015) in concrete. Fig. 3 shows the groundnut and its crushed shell which can be used as fine aggregate in concrete.

1.1.3. Oyster shell

Aquaculture is one of the key businesses in island nations. The southwestern seaside territory of Taiwan primarily develops oysters. As per the information of fishery commercial enterprises, the oyster shell yield was 300,000 tons over the last five years, which would initiate environmental pollution concerns (Kuo et al., 2013). Yang et al. (2010, 2005) stated the same problem created by oyster shell in South Korea, can be solved by their utilization in the construction industry. One of the most popular uses of oyster shell in construction industry throughout history has been in its burnt form as lime known as quicklime. Recently researchers (Kuo et al., 2013; Yang et al., 2010, 2005) studied the properties of oyster shell based concrete using oyster shell as fine aggregate, which are discussed briefly in following sections. Fig. 4 shows the shape of the oyster shell used in concrete. Oyster shell grows over the years and it is found in several sizes. The shells are spiral in structure and having rough surface

Fig. 4. Oyster shell.

texture. It should be crushed properly as per the code requirement prior to use in concrete.

1.1.4. Sawdust

Sawdust is the main component of particleboard. It has a variety of other practical uses including serving as mulch, an alternative to clay cat litter, or as a fuel. It can present as a hazardous material in manufacturing industry, in terms of its flammability (Ganiron, 2014). The use of sawdust for making lightweight concrete has received some attention over the past years (Udoeyo and Dashibil, 2002). Mageswari and Vidivelli (2009) reported, that as a substitution material for natural sand, sawdust ash might be the right choice as fine aggregate in concrete. It can considerably reduce the dumping problem and simultaneously helps

the preservation of natural fine aggregate. Fig. 5 shows the shape of the sawdust which is treated as a waste material. Many researchers tested the behaviour of sawdust ash in concrete and reported that sawdust possessed unique characteristics, which make it competitive among other construction materials (Mageswari and Vidivelli, 2009).

1.1.5. Wild giant reed

Giant reed is an aggressive wild agricultural species which can be found all over the world. It has hollow, rigid, woody stalks which are nearly one inch in diameter and can grow over 13 feet in height as shown in Fig. 6. Continuous reduction of natural resources and at the same time the environmental hazards posed by the disposal of several waste materials create an opportunity to use this waste

material in concrete (Ismail and Jaeel, 2014). Research work on the utilization of giant reed fibres and giant reed ash is reviewed in this paper.

1.1.6. Rice husk

Rice husk is one of the fundamental agrarian wastes obtained from the external covering of rice grains amid the processing procedure. Fig. 7 shows the shape of the rice husk and its ash. The rice husk has no useful application and is treated as a waste material that creates the pollution problem (Givi et al., 2010). Because of low nutrition property of rice husk, it is unsuitable and does not have edibility yet in a few nations, it has been utilized generally as fuel for rice plants and electric power plants as a compelling technique to reduce the volume of rice husk waste (Madandoust et al., 2011). Many researchers in the past had used rice husk ash as a cement replacement material in concrete (Givi et al., 2010; Madandoust et al., 2011; Zaid and Ganiyat, 2009). After colossal researches Iam and Makul (2013) tested the properties of self-compacting concrete using rice husk and limestone as a fine aggregate replacement. It was reported that use of rice husk ash in self-compacting concrete reduced the unit weight, flowability, porosity, water absorption, compressive strength, ultrasonic pulse velocity and the cost. Shafigh et al. (2014) reported the use of rice husk as cement replacing material, fire making, litter material, marking the concrete, board production, as silicon carbide whiskers to

reinforce ceramic cutting tools and aggregate replacement in concrete in low-cost housing.

1.1.7. Cork

Cork is a renewable resource. It is a natural lightweight cellular material separated from the bark of Cork Oak trees. Fig. 8 shows the processing of cork and its particle size. The world's cork creation is evaluated at 340,000 tons per year from approximately 22,000 km2 of cork forests and it is assessed that yearly, 68,000-85,000 tons of cork remains an under-utilized waste (Panesar and Shindman, 2012). Variety of analysts utilized cork as a part of construction industry mainly in cement mortar because of its unique composition and cell structure, which gives low density, low thermal conductivity, good sound absorption and water resistance (Panesar and Shindman, 2012). Novoa et al. (2004) considered the low density and low stiffness of cork and introduced it in a mortar formulation to diminish the material weight and brittleness respectively. Cork also exhibited low strength and extensive compressive strain, prompting more energy absorbing material (Novoa et al., 2004).

1.1.8. Tobacco waste

Large quantities of tobacco waste are produced annually by processing and cigarette making (Shafigh et al., 2014). Fig. 9 shows the shape of tobacco waste used in concrete. Ozturk and Bayrakl (2005) carried out a study to

Fig. 8. Cork processing and its particle size.

Fig. 9. Tobacco waste.

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••• äK— Upper limit (ASTM C33)

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Analysis of sand (Sada et al., 2013), groundnut Shell (GNS) Sada et al., 2013, waste oyster shell (WOS) Kuo et al., 2013 and cork (Bras

determine the possible use of tobacco waste in concrete. They tested different properties with varying percentage replacement of tobacco waste and pumice. Based on density, lightweight concretes are divided into three groups. Low density and low compressive strength which is used in isolation, middle density and middle compressive strength concretes used for briquette producing and the carrier lightweight concretes are used in constructing foundations and supporting parts (Short et al., 1978; Bhatty and Reid, 1989). Ozturk and Bayrakl (2005) found the low density and compressive strength of tobacco waste which can be used as an isolation material in concrete. All the material properties of tobacco waste are discussed in the following sections.

2. Physical and chemical properties of agricultural wastes

The particle size distribution of sand and different agro-waste used in concrete and mortar is illustrated in Fig. 10. It can be seen that sand and groundnut shell follow the limits of particle size as per ASTM C33 standard (American Society for Testing and Materials, 1978). Similarly, waste oyster shell followed the limits of BS 882 (British Standard Institute, 1992). It can be observed that the overall passing percentage of cork (Bras et al., 2014) was similar as that of sand and other materials.

The physical properties of sand, crushed granite and different agricultural waste which are used in agro-waste concrete are presented in Table 1. It can be observed that properties such as specific gravity and fineness modulus of agro-wastes were nearly similar or less than the range of natural sand presented in that same table. Sales and Lima (2010) reported that specific gravity (2.45), bulk density (2040 kg/m3) and water absorption (0.88%) of SCBA met the requisites of Brazilian standards NM 52 (2004), NM 45 (2004) and NM 30 (2001) respectively. According to Shafana and Venkatasubramani (2014)'s report, specific gravity and fineness modulus of SCBA satisfied the guidelines of IS 2386 part-3 (Indian Standard, 1963) and part-1 (Indian Standard, 1963b) respectively. Bulk density of GNS (254.55 kg/m3), SDA (1250 kg/m3) and WGR (535 kg/m3) is very much smaller than the range of sand (1428-1744) which indicates that the agro-waste contains more voids in comparison to the conventional fine aggregate and it can adversely affect the workability, strength and durability of the agro-based concrete or mortar. Water absorption of GNS (1.61%) falls within the range of natural river sand (0.74-2.9%) however, water absorption of OS ranging 2.9-7.66% which is higher than the range of natural aggregates as well as the other agro-wastes. Cork shows 0.1% of water absorption that indicates good water resistance property.

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Table 1

Physical properties of sand, granite and agricultural waste used as replacement of fine aggregate.

Properties Sand Crushed Granite SCBA1 GNS2 OS3 SDA5 WGR6 RHA4 Cork

Modani and Vyawahare Modani and Vyawahare Modani and Sada Kuo et al. Mageswari Ismail Iam and Panesar and

(2013), Rukzon and (2013), Rukzon and Vyawahare (2013), et al. (2013), and Vidivelli and Makul Shindman (2012),

Chindaprasirt (2012), Sada Chindaprasirt (2012), Shafana and (2013) Yang (2009) Jaeel (2013) Novoa et al. (2004),

et al. (2013), Kuo et al. Sada et al. (2013), Kuo Venkatasubramani et al. (2014) Bras et al. (2014),

(2013), Yang et al. (2010), et al. (2013), Yang et al. (2014), Shah et al. (2010), (2013), Moreira et al.

(2005), Mageswari and (2010), (2005), Mageswari (2014) (2005) (2014), Carvalhoet al.

Vidivelli (2009), Ismail and and Vidivelli (2009), Iam (2013)

Jaeel (2014), Iam and and Makul (2013),

Makul (2013), Novoa et al. Shafana and

(2004), Bras et al. (2014), Venkatasubramani (2014),

(2013), Shafana and Shah et al. (2014)

Venkatasubramani (2014),

Shah et al. (2014)

Specific gravity 2.38-2.64 2.6-2.83 1.25-2.54 - 2.1-2.48 2.5 - 2.03 -

Fineness Modulus 2.21-3.44 5.96-7.52 1.42-2.12 - 2-2.8 1.78 - - -

Bulk Density (kg/m3) 1428-1744 1365-1744 837-2040 254.55 - 1250 535 - 112.4

Water Absorption (%) 0.74-2.9 0.57-1.8 0.88 1.61 2.9-7.66 - - - 0.1

Moisture Content (%) 0.94-0.97 0.81 - - - - - - -

Silt Content (%) 5.7-13 - - - - - - - -

Flakiness index (%) - 1 - - - - - - -

Elongation index (%) - 9.61 - - - - - - -

1 SCBA-Sugarcane Bagasse Ash.

2 GNS-Groundnut Shell.

3 OS-Oyster Shell.

4 RHA-Rice Husk Ash.

5 SDA-Saw Dust.

6 WRG-Wild Giant Reed.

Table 2

Chemical properties of agro-waste.

Chemical Sugarcane Bagasse ash Oyster Shell Saw Dust Rice Husk Tobacco Waste

Compounds Modani and Vyawahare (2013), Shafana and Kuo et al. (2013), Mageswari and Ash Ozturk and

(%) Venkatasubramani (2014), Shah et al. (2014) Yang et al. (2005) Vidivelli (2009) Iam and Makul (2013) Bayrakl (2005)

SiO2 62.43-90 2-13.28 65.3 89.87 -

AI2O3 2.85-4.28 0.5 4 0.14 -

Fe2O3 4.76-6.98 0.2 2.23 0.94 -

CaO 1-11.8 51.06-77.81 9.6 0.49 -

MgO 0.07-3.61 0.51 5.8 - -

SO3 1.48 0.06-1.09 - - -

K2O 3.19-3.53 0.06-0.51 0.11 2.16 -

P2O5 0.23-2 - 0.43 - -

Fe 2-4 - - - 0.46

N 0.2-0.3 - - - -

Na2O - 0.58 0.07 0.25 -

TiO2 0.02 - - - -

Mn2O3 0.02 - - - -

P2O5 0.18 - - - -

SrO 0.09 - - - -

K2+Na2 5-10 - - - -

Cl - 2.92 - - -

MnO - - 0.01 - -

SO2 - - 0.45 - -

Zn - - - - 0.0098

Mn - - - - 0.026

Cu - - - - 0.0021

Ca - - - - 5.72

Mg - - - - 0.8

K - - - - 1.03

Na - - - - 0.09

P - - - - 0.2

Organic matter - - - - 66.21

LOI 1.86-4.73 44.16 - 4.81 -

The chemical properties of agricultural wastes are presented in Table 2. It can be observed that the chemical composition of SCBA, RHA and SD is dominated by silicon dioxide (SiO2). The sum of SiO2, Al2O3 and Fe2O3 of SCBA, RHA and SD is higher than 70%, the required chemical composition of natural pozzolana as per ASTM C618 (American Society for Testing and Materials, 2005). Thus, the utilization of these mentioned agro-wastes as fine aggregate replacement could help in the hydration process of the agro-based concrete or mortar. Oyster shell (OS) differs from the other agro-wastes by its CaO content (51.06— 77.81%) and LOI (44.16%). The ASTM C618 standard (American Society for Testing and Materials, 2005) and Brazilian standard (NBR 12653) Brazilian Standard, 1992 limits the LOI content of 6%. It can be observed that SCBA and RHA satisfy the limitation of mentioned standards, however oyster shell does not. Tobacco waste contains the highest percentage of organic matter (66.21).

3. Mix proportion of agro-waste based concrete

Selected mix proportions of agro-waste based concrete are presented in Table 3. Researchers have attempted different target strengths ranging from 20 MPa to 51.6 MPa using different cement types, agro-waste types, replacement levels

of fine aggregate and water-cement ratio. Different codes such as IS 10262: 2009 (Indian Standard, 2009), ACI 211.1 (American Concrete Institute, 1991), KCI (Korea Concrete Institute, 1999), AIK (Korea Concrete Institute and Architectural Institute of Korea, 1999), and CSA A23.3-09 (Canadian Standards Association, 2009) have been followed by different researchers (Modani and Vyawahare, 2013; Sales and Lima, 2010; Yang et al., 2010; Panesar and Shindman, 2012; Shafana and Venkatasubramani, 2014; Shah et al., 2014) for mix proportioning the agro-waste concrete. Researchers (Modani and Vyawahare, 2013; Shafana and Venkatasubramani, 2014; Shah et al., 2014) targeted different strengths of M20, M25 and M30 by replacing SCBA of maximum 50% of fine aggregate in concrete. Sales and Lima (Sales and Lima, 2010) have used three different types of cement, sulphate resisting Portland cement, blast furnace slag cement and slag modified Portland cement to achieve three different target strengths. They have designed the concrete with SCBA based on the ABCP (Brazilian Portland cement association) method which was adopted from ACI method (American Concrete Institute, 1991). Yang et al. (2010) reported that substitution ratio of oyster shell was determined considering chloride ion amounts contained in OS to satisfy the requirement of the Korea Concrete Institute (KCI) Korea Concrete Institute,

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1999 and Architectural Institute of Korea (AIK) Korea Concrete Institute and Architectural Institute of Korea, 1999 codes. Panesar and Shindman (2012) followed the Canadian standard (CSA 23.2-09 Canadian Standards Association, 2009) for proportioning cork based concrete. They replaced the cork from 0 to 20% of fine aggregate with a w/c ratio of 0.4. They have used superplasticizer of 0.82% to maintain the workability of cork based concrete. The corresponding fresh and hardened properties are discussed in following sections.

4. Fresh properties of concrete

4.1. Slump test

Slump test, is a very common test to assess the workability of any kind of concrete. Table 4 represents the slump value of different agro-waste based concretes in different replacement levels. It can be observed that in the case of bagasse ash (Modani and Vyawahare, 2013), groundnut shell (Sada et al., 2013), oyster shell (Kuo et al., 2013) and giant reed (Ismail and Jaeel, 2014) based concrete, the slump value was maximum at 0% replacement and then it decreased in further increasing the amount of agro-waste. This type of behaviour in slump value was due to the high water absorption of agro-wastes which declined the flow ability of the mix at same w/c ratio. However, it can be observed that the slump value of tobacco waste based concrete was increased as the substitution of tobacco waste increased (Ozturk and Bayrakl, 2005).

Modani and Vyawahare (2013) reported that the slump value of sugarcane bagasse ash concrete decreased, when the substitution of bagasse ash increased and it became unworkable when the replacement was 40%. Sada et al. (2013)'s experiment showed that the slump value of groundnut shell concrete was less, compared to all other agro-waste based concretes. Authors (Sada et al., 2013) suggested that, these low workable concrete could be used in road construction and light weight concretes. Kuo et al. (2013) reported that waste oyster shell, as a sand replacement showed the slump value in the range between 215 and 265 mm which is highest among all agro-waste based normal concrete. In contradictory, Yang et al. (2005) reported that the slump value of oyster shell based concrete was near about 90 mm at 0% replacement and became unworkable at 20% replacement level. Thus, they suggested to add selected admixture while targeting better slump value. Ismail and Jaeel (2014) found the decreasing slump value, using giant reed fibres and giant reed ashes as fine aggregate replacement in concrete. They reasoned that the reduction of slump value was due to the angularity of particles and the water absorption of ash.

4.2. Compaction factor test

Table 5 shows the compacting factor values of bagasse ash and groundnut shell for different replacement percent-

Table 4

Slump value of agro-waste concrete in different percentage of replacement.

Percentage of Bagasse ash Groundnut Oyster shell Giant reed ash Giant reed fibre Tobacco waste

replacement Modani and Vyawahare shell Yang et al. Ismail and Jaeel Ismail and Jaeel Ozturk and Bayrakl

(2013) Sada et al. (2013) (2010) (2014) (2014) (2005)

0 110 52 265 58 65 -

2.5 - - - 55 61 -

5 - 38 250 54 59 -

7.5 - - - 52 56 -

10 78 - 250 49 55 -

12.5 - - - 48 54 -

15 - 20 250 - - -

20 65 - 215 - - 110

25 - 15 - - - -

30 32 - - - - 140

40 7 - - - - -

50 - 5 - - - 150

75 - 5 - - - -

All slump values are in mm.

Table 5

Compacting factor values of agro-waste concrete.

Percentage of Bagasse ash Groundnut

replacement Modani and Vyawahare shell

(2013) Sada et al.

(2013)

0 0.92 0.88

5 0.84 0.89

10 0.81 -

15 0.75 0.88

20 0.64 -

25 - 0.82

50 - 0.78

75 - 0.75

ages. It can be observed that this parameter decreases when the percentage of replacement increases. These values are reduced from 0.92 to 0.64, which conveys, good workability property to the very low workability of agro-waste concrete. Sada et al. (2013) reported that the use of groundnut shell reduced the concrete's workability due to high absorption of water.

4.3. Air content

Yang et al. (2005) analysed the effect of the substitution ratio of oyster shell in concrete using the pressure method. They measured constant values of air contents, when the air entrained; water-reducing admixtures were not used. However, when they used water-reducing admixture, the air content significantly increased. It is to be noted that this factor depends on the degree of increment with substitution ratio and type of oyster shell.

4.4. Flow table test

Workability of fresh mortar was determined using a flow table test. The measurement was done as per

provisions of American Society for Testing Materials (1999) and Bras et al. (2014). Bras et al. (2014) fixed a target value of 175 ± 10 mm in terms of water and high range water reducer (HRWR) quantity for each mortar. Based on this target value, adjustments were adopted in selected mortar compositions in terms of water-binder ratio and high range water reducer (HRWR) percentage. It was observed that the workability decreased in the case of increasing the cork dosage, which is due to the reduction of binder paste (Bras et al., 2014). For cork dosage less than 20%, all mortars exhibited good workability even after 30 min of the mix preparatory.

4.5. Penetration and ball-drop

Kuo et al. (2013) conducted the penetration and balldrop test under various replacements of oyster shell in concrete. They observed that the penetration became 2.74 MPa at 210-260 min, when the replacement increased from 0% to 5%, which conforming the required 3-5 h for early strength controlled low strength materials. It has been observed that the addition of waste oyster shell affected the time of penetration (Kuo et al., 2013).

The ball-drop test value is the preliminary index of the bearing capacity of the material. Kuo et al. (2013) carried out the ball-drop test with diameter of indentation as 4.9 cm, at 5% replacement of waste oyster shell, and this value was increased gradually as the replacement ratio increased. The indentation diameter was 4.9-5.9 cm that is less than 7.6 cm, indicating that the mix ratio had the sufficient bearing ratio for the construction (Kuo et al., 2013). The test results are represented in Fig. 11.

4.6. Water requirement and unit weight

Iam and Makul (2013) reported that the water requirement increased with increasing rice husk ash content, which

•S 300

jâ, о

.1 200 H

H Reached penetration pressure 2.74 MPa of the time Ball drop

0 5 10 15

WOS content (%)

Fig. 11. Effect of waste oyster shell content on penetration and ball-drop test (Kuo et al., 2013).

is due to increasing surface area, and high-unburned carbon content of rice husk ash. However, the use of rice husk ash combined with limestone reduced the water requirement. The unit weight of self-compacting concrete decreased with increasing percentage of rice husk ash.

Unit weight of tobacco waste concrete varied between 0.50 and 0.56 kg/m3, indicating that the concrete samples were in the heat isolation lightweight concrete categories (Sahin et al., 2000).

4.7. Slump flow diameter and T50cm slump flow

Iam and Makul (2013) used rice husk ash as fine aggregate replacement in self-compacting concrete (SCC) and reported that the slump flow diameter ranged between 690 and 700 mm up to 80% of the replacement level. They also combined the rice husk ash and limestone by different percentages as a fine aggregate replacement in SCC and observed the slump flow diameters were between 600 mm and 710 mm, which comes within the workability requirement range of 650-800 mm as per American Society for Testing Materials (2014) and EFNARC (2002).

The time required for the self-compacting concrete to reach the slump flow of 50 cm diameter were within 37 s, the range considered acceptable in EFNARC (2002) guidelines (Iam and Makul, 2013). Iam and Makul (2013) observed that the slump flow time of SCC increased with increasing rice husk ash as well as limestone. The increased slump flow time varies from 6 to 15 s and 6-16 s for SCC mixtures containing RHA and RHA with limestone respectively. Authors (Iam and Makul, 2013) predicted that the slump flow time increased due to the increased surface area of rice husk ash, which increased the viscosity of paste. This increased viscosity reduces the risk of segregation at the time of placement of concrete.

4.8. V-funnel test

V-funnel test was taken to measure the required time for concrete mixtures to flow through a funnel and provide an evaluation of viscosity and segregation resistance of

concrete mixtures (Iam and Makul, 2013). Flow times were acceptable up to 20% replacement of rice husk ash, which are within the acceptable limit provided by EFNARC (2002) guideline, that is, between 8 s and 12 s.

4.9. J-Ring test

Iam and Makul (2013) adopted the J-ring test to check the passing ability of concrete under its own weight to completely fill all voids and to obtain the blocking assessment. According to American Society for Testing Materials (2014), 0-25 mm defines no visible blocking, 25-50 mm defines minimal to noticeable blocking and greater than 50 mm defines noticeable to extreme blocking. Authors (Iam and Makul, 2013) reported that up to 40% replacement of rice husk ash indicated small degree of blocking, while more than 60% of replacement indicated extreme blocking behaviour and a combination of rice husk ash and limestone indicated a good passing ability and good resistance to segregation around congested reinforced areas.

5. Hardened properties of concrete

5.1. Compressive strength

5.1.1. Bagasse ash

Researchers (Modani and Vyawahare, 2013; Shafana and Venkatasubramani, 2014; Shah et al., 2014) have conducted the compressive strength of bagasse ash concrete as

35 30 25 -20 15 -10 5 0

7 Days

□ M20 [5] HM25 [48] HM30 [38]

Percentage replacement

45 40 35 30 25 20 15 10

28 Days

□ M20 [5] BM25 [48]

□ M30 [38]

10 15 20 25 30 Percentage replacement

Fig. 12. Compressive strength of bagasse ash concrete at (a) 7 days and (b) 28 days of curing.

per IS 516: 1959 (Indian Standard, 1959). Concrete using sugarcane bagasse ash as fine aggregate shows an increasing compressive strength at 10% replacement than the control concrete, but further increase of bagasse ash decreased the strength as reported by Modani and Vyawahare (2013). Shafana and Venkatasubramani (2014) reported the same result with sugarcane bagasse ash concrete in which com-pressive strength improved by increasing the curing period.

Fig. 12(a) and (b) represents the compressive strength of bagasse ash concrete in different mix proportions and curing periods. In case of M25 (Shah et al., 2014) and M30 (Shafana and Venkatasubramani, 2014) grade of concrete, it can be observed that concrete achieved its minimum compressive strength at 20% replacement of bagasse ash. Almeida et al. (2015) reported that the use of sugarcane bagasse ash as fine aggregate did not affect the compressive strength of mortar.

5.1.2. Groundnut shell

Sada et al. (2013) performed an experiment using groundnut shells as a fine aggregate replacement having a mix ratio of 1:2:3, in which they observed that the compres-sive strength increased at 5% replacement than the control concrete. However, it decreased by further increment of replacement, which behaved like a lightweight concrete. They also reported that groundnut shell concrete could not be used in important structural members, which are exposed to water, since moisture affects the weight and strength (Sada et al., 2013).

5.1.3. Oyster shell

Yang et al. (2010) tested the compressive strength of oyster shell concrete over a long period of 1 year based on American Society for Testing and Materials (1979). They reported that oyster shell substitution as a fine aggregate showed a drastic increase of compressive strength from 7 days to 28 days curing period and after 28 days, effect was apparent. The compressive strength variance was not proportional to the substitution ratio, which is clear from Fig. 13. Yang et al. (2005) tested the compres-

35 30 25 20 15 10 5 0

mo% □ 10% □ 20%

7days 28days

MIX 1:1.85:2.62 [16]

7 days 28days

MIX 1:6.4:2 [15]

Fig. 13. Compressive strength of oyster shell concrete.

sive strength using oyster shell as fine aggregate with and without admixture. They reported the compressive strength of concrete increased at oyster shell substitution of 5%, but the substitution ratio can be increased up to 10% using admixture in the concrete mix. Kuo et al. Kuo et al. (2013) also examined the same result regarding the oyster shell concrete and the compressive strength decreased due to the porous structure and the absorption rate of oyster shell sand.

From Fig. 13 it can be observed that in the mix 1:1.85:2.62 (Yang et al., 2010) the strength increased marginally at 20% replacement of oyster shell than the control concrete, but in the case of controlled low strength concrete (mix 1:6.4:2 Kuo et al., 2013) the strength decreased at all replacement levels than the control concrete.

5.1.4. Sawdust ash

Mageswari and Vidivelli (2009) have cast the concrete using sawdust ash as fine aggregate in both cube and cylinder. They followed the procedure of compressive strength test as per IS 516: 1959 (Indian Standard, 1959). It has been seen that the strength of concrete containing 5%, 10% and 15% mix ratio of sawdust ash was higher than that of control concrete. However, concrete containing 20%-30% of sawdust ash displayed a reduction in compressive strength than that of plain concrete.

5.1.5. Wild giant reed

Ismail and Jaeel (2014) added giant reed ash and giant reed fibre in concrete as fine aggregate to check the com-pressive strength of concrete. Casting, compaction and curing were accomplished according to BS 1881 (British Standard Institute, 1983). They reported that in earlier stages of the replacement, compressive strength increased and at higher percentages, it decreased in comparison to the strength of control concrete. However, for all cases the compressive strength was higher than the minimum requirement. Fig. 14 represents comparison of the strength of giant reed ash and giant reed fibres, which confirms that at 7.5% of replacement, giant reed ash concrete provides optimal strength. The cause of such behaviour of giant reed ash concrete is due to the content of silica; giant reed ash may have pozzolanic activity. However, silica with an alumina content of their structure may form additional calcium silicate hydrate (C-S-H) by reacting with calcium hydroxide occurring because of cement hydration, which increases the strength of concrete (Ismail and Jaeel, 2014).

5.1.6. Rice husk ash

Iam and Makul (2013) have cast the self-compacting concrete samples using rice husk ash (RHA), limestone (LS) and a mixture of RHA and LS in cylinder of 150 mm diameter and 300 mm length. Samples were tested after aging for 1, 7, 28 and 91 days in accordance with American Society for Testing and Materials (1979). Compressive strength value was very low at 100% replacement of rice husk ash and it was maximum at 10% replacement of only

45 40 35

-a 30 -

25 20 15

E3 7days 0 7days Ql4days Sl4days CD28days Sl28days

Percentage of replacement

Fig. 14. Compressive strength of Giant Reed Ash (GRA) and Giant Reed Fibres (GRF) based concrete at mix 1: 1.78: 2.23 (Ismail and Jaeel, 2014).

limestone. The compressive strength value decreased, when the replacement level increased. They attributed lower compressive strength due to greater porosity as indicated by the higher water requirement of rice husk ash and limestone. However, they found that rice husk ash was able to fill the micro-voids in improved way within the cement particles (Iam and Makul, 2013).

5.1.7. Cork

Bras et al. Bras et al. (2013) tested the compressive strength of mortar containing cork as fine aggregate and indicated that addition of cork generated a mortar having lower compressive strength. These values may be expected due to higher water binder ratio than the control mortar and an increase of cork as sand replacement. They also explained that when cork replacement is higher than 50%, there was no major difference in compressive strength of mortar that is just 20% of the compressive strength of control mortar (Bras et al., 2013).

Compressive strength of lightweight polymer mortar containing waste cork was higher than that of normal mortar as reported by Novoa et al. (2004). Moreira et al. (2014) tested the compressive strength of lightweight screed containing expanded cork according to NP EN 12390-3:2011 (Portuguese Standards, 2011) at the age of 7, 28, 56, and 84 days. They reported that the compressive strength increased, with increase of cement content and it reduced with increase of percentage cork granulates.

5.1.8. Tobacco waste

The 28 day cube compressive strength of tobacco waste lightweight concrete sample was within 0.2-0.6 N/mm2 which varied on the mix ratio. It has been observed that minor amount of organic matter, which is tobacco waste, resulted in a high compressive strength of concrete. The compressive strength of tobacco waste was under 1 N/ mm2 due to which, this lightweight concrete can be suggested to be used as an insulating material for coating and separation material into construction (Ozturk and Bayrakl, 2005).

From the above compressive strength analysis, it can be observed that, in case of agro-waste concrete containing bagasse ash, saw dust ash and oyster shell, minimum strength of concrete is achieved by a maximum 20% replacement, but with further increase of replacement, strength decreased. However, the maximum compressive strength of concrete containing groundnut shell and giant reed (both GRA and GRF) was achieved at 5% and 7.5% respectively. Cork and rice husk ash also showed good strength in mortar and self-compacting concrete as fine aggregate replacement.

5.2. Tensile strength

Researchers (Modani and Vyawahare, 2013; Mageswari and Vidivelli, 2009; Shafana and Venkatasubramani, 2014) have conducted the tensile strength of agro-waste based concrete in accordance with IS 5816: 1999 (Indian Standard, 1999). Modani and Vyawahare (2013) reported that the tensile strength of concrete decreased by addition of sugarcane bagasse ash whereas in case of other agro-waste materials, tensile strength was initially increased and then decreased as increasing the percentage of replacement. Shafana and Venkatasubramani (2014) also observed that bagasse ash increased the tensile strength with optimum strength gain achieved at 10% replacement value. Fig. 15 represents the relation between compressive strength and tensile strength of M20 and M30 grade of concrete with the substitution of bagasse ash. Relation in M20 grade of concrete shows that, tensile strength of bagasse ash concrete can be predicted very closely like conventional concrete in the following form:

ft = 0.7/0f R2 = 0.784 (1)

where f t and fck are tensile and compressive strength of concrete in MPa. However, in case of M30 grade of bagasse ash concrete the regression coefficient, R2 is more appropriate than the M20 grade of concrete.

ft = 0.644/k521 R2 = 0.985 (2)

Compressive strength (MPa)

Compressive strength (MPa)

Fig. 15. Correlation between compressive strength and tensile strength of bagasse ash concrete (a) M20 grade (Modani and Vyawahare, 2013) and (b) M30 grade (Shafana and Venkatasubramani, 2014).

where f t and f ck are tensile and compressive strength of concrete in MPa.

Yang et al. (2005) observed the development of tensile strength using oyster shell in high strength concrete. The 28 day tensile strength was higher at a smaller replacement percentage, than the control concrete, but it reduced as increasing the substitution ratio of oyster shell (Yang et al., 2005). They also performed a regression analysis to compare the relation between compressive strength and tensile strength with the substitution of oyster shell, giving the following relationship.

ft = 0.18 xfC)3/4 (3)

where fc and ft are the compressive and tensile strength of concrete.

At 5%, 10% and 15% replacement of sawdust ash as fine aggregate in concrete there was increasing of tensile strength and above the 20%, replacement displayed a reduction in strength (Mageswari and Vidivelli, 2009).

5.3. Flexural strength

Bagasse ash concrete was cast in beam specimen size 100 mm x 100 mm x 500 mm and cured in water for 28 days. After 28 days, beams were tested as per IS 516: 1959 (Indian Standard, 1959). The results indicated that the flexural strength increased by 10% replacement and it reduced with further increase of percentage (Shafana and Venkatasubramani, 2014). Fig. 16 shows the flexural strength variation of bagasse ash concrete at different substitution ratios and curing period.

0 10 15 20 25 30

Percentage replacement

Fig. 16. Flexural strength of sugarcane bagasse ash concrete (Shafana and Venkatasubramani, 2014).

Ismail and Jaeel (2014) conducted the flexural strength test of giant reed based concrete in accordance with American Society for Testing and Materials (2015). They explained that the replacement of giant reed ash (GRA) and giant reed fibres (GRF) in concrete showed an increasing strength up to 7.5% and the strength decreased by 10% and 12.5% even below the strength of control concrete as shown in Fig. 17. The increase in compressive and tensile strength can be attributed to presence of organic bindings in giant reed fibres in acidic or alkali environment, which decomposed into monosaccharide-hexose and pentose. This monosaccharide dissolved in water easily and resulted in the formation of hydrophilic adsorption layers upon cement grains (Ismail and Jaeel, 2014). Novoa et al. (2004) and Bras et al. (2013) conducted the flexural strength test as per RILEM CPT PCM-8 (1995) standard test method and EN-1015-11 (1999) standard. They reported the same result, regarding the flexural strength of mortar that it reduces with increase in the percentage of cork.

Fig. 18 shows the regression analysis of GRA and GRF concrete. From the figure, it is observed that GRA concrete gives more predictable relation than the GRF concrete in a particular mix ratio. Flexural strength of GRA concrete can be predicted from the compressive strength from the following;

fr = 0.68f0f R2 = 0.93 (4)

Eq. (5) also gives the relation to predict flexural strength from its compressive strength with a regression coefficient R2 = 0.75.

fr = 0.88ff (5)

where fr and fck are flexural strength and compressive strength of concrete in MPa.

5.4. Elastic modulus (E-value)

Yang et al. (2010) tested the elastic modulus of concrete with the substitution of oyster shell over a period of 1 year as per ASTM C469 (American Society for Testing and Materials, 2014). The elastic modulus test results are pre-

tg n 4

□ 7 Days D7 Days D14 Days D14 Days D28 Days D28 Days

2.5 5 7.5 10

Percentage of replacement

Fig. 17. Comparison of flexural strength between Giant Reed Ash (GRA) and Giant Reed Fibre (GRF) (Ismail and Jaeel, 2014).

a P 5.5 -

gt 4.5

ret 4 -

« r 3.5

GRA ■ GRF

fr = 0.68 (fck)056

R2 = 0.93

fr = 0.8 8 (fck)047

R2 = 0.75

15 20 25 30 35

Compressive strength (MPa)

Fig. 18. Correlation between flexural strength and compressive strength of GRA and GRF concrete at mix 1:1.78:2.23 (Ismail and Jaeel, 2014).

SR-10%

SR-20%

14 days 28 days 6 months

Curing period

1 year

Fig. 19. Elastic modulus of oyster shell concrete (Yang et al., 2010).

Fig. 20. Relation between compressive strength and ultrasonic pulse velocity in oyster shell concrete (Kuo et al., 2013).

that value obtained from the code (Yang et al., 2005). The elastic modulus of cork modified polymer mortar was less than that of conventional mortar, due to viscoelas-ticity properties of polymers, which are reported by Novoa et al. (2004). They Novoa et al. (2004) also included the predicted elastic modulus based on Kelvin-Voigt model for the rule of mixture,

- E V + E V

- ^c' c \ ^m' m

where E refers to elastic modulus and V refers to volume fraction. The indices comp, c and m are relative to final composite, cork and matrix.

sented in Fig. 19. They observed that at 20% replacement the elastic modulus value decreased approximately 1015% compared to other replacement level. They reasoned, it might be more due to the lower elastic modulus of oyster shell than the natural fine aggregate. Yang et al. (2005) measured elastic modulus at 28 days to evaluate the effect of substitution of oyster shell on the elastic modulus of concrete. They reported that the elastic modulus depended on the type of oyster shell, substitution ratio and use of admixture. Elastic modulus decreased approximately 10% by increasing the substitution ratio of 20% of oyster shell. They also compared the experimental value with the value obtained from the relation proposed by ACI code (American Concrete Institute, 1997) and CEB-FIP model equation (CEB-FIP, 1993) and the resulting experimental value was higher even without using the admixture than

5.5. Ultrasonic pulse velocity (UPV)

Ultrasonic pulse velocity (UPV) is a form of nondestructive testing in which ultrasonic pulsing are used to test the quality of concrete and detect the depths and widths of crack so as to determine the density variation of the concrete (Kuo et al., 2013). Kuo et al. (2013) tested the ultrasonic pulse velocity of concrete with the substitution of oyster shell as per ASTM C597 (American Society for Testing and Materials, 2009). They reported that at 5% replacement, UPV value was higher than the control concrete and in all other level of replacement, it was lower than the control concrete. It can be expected that the lower UPV value may be due to the weakness of C-S-H gel. The relation between compressive strength and ultrasonic pulse velocity of oyster shell concrete is presented in Fig. 20.

From the regression analysis, it can be observed that the compressive strength of oyster shell concrete can be predicted using following relationship from its UPV value with a regression coefficient of R2 = 0.87.

fck = 0.06(UPV)493 (7)

Iam and Makul (2013) measured the UPV value of self-compacting concrete after aging for 1, 7, 28 and 91 days in accordance with ASTM C597 (American Society for Testing and Materials, 2009) and reported its variation was from 0.7 km/s to 4.4 km/s. Highest UPV value was achieved in control concrete and lowest value was at 100% replacement of rice husk ash. They also noticed that the UPV value increased by an addition of rice husk ash, which was likely due to micro filling and pozzolanic effect on property of concrete pore structures. They found good relation between compressive strength and ultrasonic pulse velocity of self-compacting concrete with rice husk ash mixture having R2 = 0.9403 which is shown in Fig. 21.

5.6. Shrinkage and creep

Yang et al. (2010) conducted a series of tests to evaluate the behaviour of drying shrinkage of concrete using oyster shell as fine aggregate. Experimental values were compared with the value obtained from several codes (ACI American Concrete Institute, 1997; CEB-FIP, 1993), and BP model equations (Bazant and Wittmann, 1982) and showed a good agreement between these two values. The increase in drying shrinkage based on regression analysis was 7% and 28% in the substitution ratio of 10% and 20%, respectively, compared with the control concrete. They analysed that the shrinkage increased due to the lower rigidity of oyster shell and effect of size of fine powder (Yang et al., 2010). Kuo et al. (2013) reported that the shrinkage of specimen increased if the natural aggregate of higher Young's modulus was replaced by waste oyster shell as fine aggregate having a lower Young's modulus, which meant that larger replacement percentage resulted in greater shrinkage.

Fig. 21. Relation between compressive strength and ultrasonic pulse velocity of self-compacting concrete made with replacement of RHA (Iam and Makul, 2013).

Yang et al. (2010) conducted a series creep test to know the effect of creep on oyster shell concrete and reported that at 0% replacement, the creep was larger than that at 10% replacement even at an early age.

6. Durability

Durability is the important characteristics of hardened concrete to check when it contains any replacement materials of cement or aggregate. Many researchers conducted the durability test such as freezing and thawing, carbona-tion, chemical attack, permeability and water absorption, etc. of concrete having agricultural waste as a fine aggregate replacement.

6.1. Freezing and thawing

Yang et al. (2010) studied the freezing and thawing test of oyster shell-mortar. Freezing and thawing tests were performed according to ASTM C666 (American Society for Testing and Materials, 2015). According to their study, the variance rates of the dynamic modulus of elasticity and weight of the concrete substituted by oyster shell showed smaller and more satisfactory values respectively than those of control concrete. They reported that oyster shell shows improved performance of freezing and thawing resistance of concrete, which is because the fine grain of oyster shell fills the entrapped air voids scattered in concrete specimen (Yang et al., 2010).

6.2. Chemical attack

Yang et al. (2010) did the chemical attack experiment on concrete with the substitution of oyster shell by depositing the concrete specimens in sulphuric acid and hydrochloric acid. After a certain age, they tested the specimen and reported that the attack of concrete increases gradually with age. The attack of sulphuric acid was continued as age increased. They also found that there is no effect of the substitution ratio of oyster shell on weight loss of concrete specimen (Yang et al., 2010). Kuo et al. (2013) observed the same result of sulphate attack on oyster shell concrete. Weight loss of concrete specimen increased from 1.17% to 4.822%, according to the increasing of age period. There is some effect of the substitution ratio of oyster shell.

Ismail and Jaeel (2014) observed the effect of alkali on concrete containing giant reed ash and giant reed fibres. They observed that modified concrete with giant reed fibres could be affected by alkali faster than the control concrete since they affected the lignin complex molecules causing fibre fracture.

Almeida et al. (2015) applied colorimetric treatment to the mortar specimens for analysis of chloride penetrations. Fig. 22 shows the average chloride penetration values in millimetres obtained at different immersion times in a 3.5% NaCl solution. The M30 (30% substitution of bagasse ash) and M50 (50% substitution of bagasse ash) samples

30 60 90

Imersion period (days)

Fig. 22. Average chloride penetration values at different ages for the mortar samples (Almeida et al., 2015).

showed significantly different chloride penetration values in the first month of conditioning but showed same magnitude at later stage. The RM (Referenced Mortar) specimen showed less resistance to chloride penetrations because it showed the highest average chloride penetration values at all of the studied ages. Thus, the addition of bagasse ash increased the chloride penetration resistance of mortar.

6.3. Carbonation

Yang et al. (2010) conducted carbonation test to evaluate the effect of substitution ratio of oyster shell on carbon-ation characteristics of concrete. These tests were performed in a chamber under the temperature of 30 ± 3 °C, relative humidity of 60 ± 5%, and 10% carbon dioxide. After splitting, a 1% of phenolphthalein alcohol liquid was sprayed on the fractured specimen surface and the thickness of the discoloured portion was measured. As a result, it has been observed that the carbonation depth increased with increasing carbonation age. Almeida et al. (2015) measured the carbonation depth of sugarcane bagasse ash mortar (at 0%, 30%, and 50% substitution ratio) using colorimetric treatment. They reported that, initially the carbonation depth magnitude was similar for

each replacement level. However, at 365 days carbonation period, carbonation depth was significantly increased for mortar containing 50% replacement of bagasse ash than the controlled mortar and mortar containing 30% of bagasse ash. Fig. 23 shows the colorimetric treatment of mortar for carbonation depth analysis.

Almeida et al. (2015) also mentioned that the carbona-tion depth could be decreased by reducing the water cement ratio and by the packing effect of cementitious matrix provided by bagasse ash fineness. The reduction of water cement ratio and incorporation of finer materials lead to a denser and stronger mortar matrix.

6.4. Permeability

Yang et al. (2010) determined the permeability ratio of mortar in accordance with ASTM C109 (American Society for Testing and Materials, 2016) and compared with the substitution ratio of oyster shell. The permeability ratio of mortar having 10% and 20% of oyster shell was approximately 80% less than that of standard mortar. They also explained that the improvement of permeability was due to the effect of small particle size, more flakiness and elongation of oyster shell (Yang et al., 2010). Panesar and Shindman (2012) tested the rapid chloride permeability test on cement-cork mortar by an increasing percentage of cork, taking different size of the cork, cork gradation and weathered cork. The procedure employed was ASTM C1202 (American Society for Testing and Materials, 2012). They observed that cork content had more effect on the permeability of mortar than the size and weathered cork (Panesar and Shindman, 2012). The water vapour permeability test of cement-cork mortar and lime-cork mortar was performed according to European norm EN1015-19 (1988), EN 1015-19 (1999) and Bras et al. (2014). It has been observed that there was no effect of cork on changes of permeability. Cement based mortars were less permeable to water vapour than lime based mortar (Bras et al., 2014). But according to Moreira et al. (2014), addition of expanded cork granulates in the mix induced greater water vapour permeability.

6.5. Water absorption test

Water absorption and porosity are important indicators of durability of hardened concrete and reduction of these values can greatly affect the long-term performance and serviceability of concrete (Ismail and Jaeel, 2014). The water absorption test was carried out to determine the sorptivity coefficient of a concrete specimen. It is observed that this coefficient increases with increase in percentage of sugarcane bagasse ash and decreases with an increase in compressive strength (Modani and Vyawahare, 2013). Ismail and Jaeel (2014) used 100 mm cubes for water absorption test and tested in accordance to BS 1881-122 (British Standard Institute, 1983). They explained that concrete

Fig. 23. Mortar specimen after colorimetric treatment at 365 days of carbonation period containing 50% replacement bagasse ash (Almeida et al., 2015).

containing giant reed fibres attained higher percentage of water absorption as compared to giant reed ash concrete and control concrete. It is also observed that water absorption percentage increased as increasing the percentage of replacement of giant reed ash in concrete mixes. Kuo et al. Kuo et al. (2013) reported that the absorption rate of replacing waste oyster shell sand is increased by 1.1-1.6% than the control concrete since waste oyster shell sand has a higher porosity and absorption rate.

7. Thermal conductivity

Panesar and Shindman (2012) tested the thermal resistance and thermal conductivity of concrete containing cork and expanded polystyrene (EPS) based on the procedure described in American Society for Testing and Materials (2010). They reported that the mixture containing 10% and 20% of cork reduced the thermal conductivity by approximately 16% and 30% respectively. They also explained a relation that thermal conductivity increased as the density increased. Thermal conductivity not only controlled by the density, but also influenced by the size, gradation and percentage of replacement of cork (Panesar and Shindman, 2012). Bras et al. (2014) observed that, for mortars with a high substitution ratio of cork granulates lead to a linear decrease of thermal conductivity as well as density. In another study, Bras et al. (2013) reported the same result that mortar containing cork granulates shows linear decreasing thermal conductivity and

that the decrease was higher than the mortar containing expanded polystyrene (EPS). Moreira et al. (2014) added different substitution ratio of expanded cork granulates with cement mortar. They noticed the declining thermal conductivity coefficient like other researchers and reported that thermal conductivity decreased due to lower cement content in mortar mixes. The thermal conductivity of producing tobacco waste materials was in the range of 0.1940.220, which indicated that it could be used as a coating and dividing materials in concrete (Ozturk and Bayrakl, 2005).

8. Cyclic behaviour

Carvalho et al. (2013) tested the cyclic behaviour of a composite material made from a mortar incorporated with granulated cork. Specimens with 0%, 15% and 30% of cork addition, in volume mix, were prepared and tested. Cyclic uniaxial and diagonal compression tests were carried out to characterize the cyclic behaviour of the composite materials. It has been observed that, for whole set of mortar study, there is a tendency for improvement of performance when the cork granulates are added, either uniaxial or diagonal compression test. Fig. 24 shows the cyclic test of mortar incorporated with granulated cork.

They also concluded the improvement behaviour of energy dissipation capacity and conformed that inclusion of cork granulates in controlled volume fractions in construction mortar was beneficial for the seismic protection of building (Carvalho et al., 2013).

9. Future recommendation

Based on the review done on concrete made with agricultural waste as partial replacement of fine aggregate, the following future studies can be recommended.

1. Limited research work has been reported on utilization of agro-waste as fine aggregate in concrete/mortar. Thus a complete study of engineering properties on every agro-waste based concrete could be conducted and compared with the conventional concrete.

2. Compressive strength is the only hardened property which conducted on every mentioned agro-waste based concrete. However, other mechanical properties such as tensile and flexural strength, elastic modulus, UPV could be studied on all agro-waste based concrete and relate with conventional concrete.

3. Durability is an important property to observe before establishing any kind of concrete for practical application. There are limited durability studies reported on agro-waste based concrete. Therefore a brief study on durability properties of every type of agro-waste concrete can be done.

4. It has been seen that only rice husk ash was used as fine aggregate in self-compacting concrete. Thus other agro-wastes could be used as partial replacement of fine aggregate in self-compacting concrete and observed their effect on properties of SCC.

5. Further research work is required regarding these agro-wastes as a fine aggregate replacement in concrete to confirm the strength variation and thermal property.

10. Conclusion

Literature and experimental studies on fine aggregate replacement by agro-waste in concrete, self-compacting concrete and mortar have been reviewed. Following important conclusions have been drawn from these studies:

1. Different workability tests of agro-waste based concrete and mortar are reviewed. It has been concluded that slump value of agro-waste concrete containing bagasse ash, groundnut shell, oyster shell, giant reed ash, giant reed fibres and rice husk ash decreased as the percentage of replacement increased. However, in case of tobacco waste concrete, slump value increased as the replacement increased. Compacting factor, penetration, and ball drop increased up to 5% replacement of groundnut shell and oyster shell respectively. In case of flowability and V-funnel test, cork and rice husk managed improved workability up to 20% of replacement.

2. It has been observed that, in case of agro-waste concrete containing bagasse ash, sawdust ash and oyster shell, minimum strength of concrete was achieved by addition of optimal 20% of replacement but with fur-

ther increase, strength was decreased. However, the maximum compressive strength of concrete containing groundnut shell and giant reed (both GRA and GRF) was achieved at 5% and 7.5% respectively. Cork and rice husk ash also showed good strength in mortar and self-compacting concrete as fine aggregate replacement.

3. It has been observed that concrete containing sawdust ash gave maximum tensile strength up to 15% of replacement in comparison to bagasse ash and oyster shell. The regression analysis of bagasse ash concrete gives a close prediction of tensile strength from its compressive strength. Giant reed ash concrete shows its maximum flexural strength at 7.5% replacement. GRA concrete gives more predictable flexural strength than the GRF concrete and bagasse ash concrete.

4. Elastic modulus of agro-waste based concrete depends on types of material used, substitution ratio and use of admixture. The experimental elastic modulus of oyster shell concrete was higher than that of the value obtained from ACI code. The elastic modulus of cork modified polymer mortar was less than that of conventional mortar, due to viscoelasticity properties of polymers.

5. Strong co-relation between compressive strength and ultrasonic pulse velocity of oyster shell based concrete has been observed. Rice husk ash based self-compacting concrete showed better relation than oyster shell based concrete which was expected due to micro filling and pozzolanic effect on property of concrete pore structures.

6. Groundnut shell as a fine aggregate replacement cannot be used in water sensitive structures and waterlogged areas since the moisture affects the weight and strength.

7. A complete review was done on durability properties of agro-waste concrete and agro-waste mortars. It has been observed that chemical attack on agro-waste concrete increased with age. Addition of bagasse ash as fine aggregate in mortar increased the resistance of chloride penetration. Carbonation depth was increased by increasing the substitution of agro-waste in concrete and mortar, but it can be decreased by reducing the water cement ratio.

8. The percentage of cork used as a sand replacement has a significant effect on mechanical strength, microstructure and thermal resistance of cork cement composites. It has been observed that, the size of the cork plays an important role in strength achievement. Lower size of the cork gives more strength to concrete.

9. All properties of tobacco waste concrete satisfied the property of heat insulation materials, which can be recommended for use as a coating and separation materials in construction.

10. The cyclic behaviour of cork-based mortar was observed. It has been seen that for the whole mortar study, there is an improvement of performances of specimen due to the inclusion of cork, which is beneficial for seismic protection of building.

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