Scholarly article on topic 'Use of Unprocessed Rice Husk Ash and Pulverized Fuel Ash in the Production of Self-compacting Concrete'

Use of Unprocessed Rice Husk Ash and Pulverized Fuel Ash in the Production of Self-compacting Concrete Academic research paper on "Materials engineering"

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Abstract of research paper on Materials engineering, author of scientific article — Gritsada Sua-iam, Natt Makul

Abstract We investigated the properties of self-compacting concrete (SCC) mixtures comprising ternary combinations of Type 1 Portland cement (OPC), untreated rice husk ash (RHA), and pulverized fuel ash (FA). The SCC mixtures were produced with a controlled slump flow in the range between 67.5 to 72.5cm diameter with a constant total powder materials content of 550kg/m3. RHA and/or FA were used to replace in powder materials with 20 or 40 wt%. The fresh and hardened properties including water requirement, workability, density, compressive strength development and ultrasonic pulse velocity were determined. Self-compacting concrete mixtures formulated using ternary blends exhibited significant improvements in physical properties compared to SCC mixtures containing only RHA or FA.

Academic research paper on topic "Use of Unprocessed Rice Husk Ash and Pulverized Fuel Ash in the Production of Self-compacting Concrete"

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I I k I Procedia 5 (2013) 298 - 303 -

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2013 International Conference on Agricultural and Natural Resources Engineering

Use of Unprocessed Rice Husk Ash and Pulverized Fuel Ash in the Production of Self-Compacting Concrete

Gritsada Sua-iam, Natt Makul*

Department of Building Technology, Faculty of Industrial Technology, Phranakhon Rajabhat University, Bangkok 10220, Thailand

Abstract

We investigated the properties of self-compacting concrete (SCC) mixtures comprising ternary combinations of Type 1 Portland cement (OPC), untreated rice husk ash (RHA), and pulverized fuel ash (FA). The SCC mixtures were produced with a controlled slump flow in the range between 67.5 to 72.5 cm diameter with a constant total powder materials content of 550 kg/m3. RHA and/or FA were used to replace in powder materials with 20 or 40 wt%. The fresh and hardened properties including water requirement, workability, density, compressive strength development and ultrasonic pulse velocity were determined. Self-compacting concrete mixtures formulated using ternary blends exhibited significant improvements in physical properties compared to SCC mixtures containing only RHA or FA.

© 2013 TheAuthors.Publishedby ElsevierB.V.

Selectionand peerreviewunder responsibility ofInformation EngineeringResearch Institute

Keywords: Self-compacting concrete; Rice husk ash; Pulverized fuel ash; Workability, Mechanical properties

1. Introduction

Self-compacting concrete (SCC) is a type of high fluidity and strength concrete developed in Japan in 1988 to increase productivity and durability in concrete construction. SCC mixtures contain superplasticizer admixtures, limited amounts of aggregate, and low water-powder ratios [1]. The characteristics in the fresh state of SCC include high penetrating ability filling ability, and resistance to segregation. Higher cement content and lower coarse aggregate content are required to avoid segregation. Mixtures containing only

* Corresponding author. Tel., Fax.: +662-522-6637 E-mail address: shinomomo7@hotmail.com

2212-6678 © 2013 The Authors. Published by Elsevier B.V.

Selection and peer review under responsibility of Information Engineering Research Institute doi: 10.1016/j.ieri.2013.11.107

Portland cement are costly and are susceptible to aggressive substances (ions and molecules), thermal cracking, and high autogenous shrinkage [2]. The cost of SCC may be reduced by replacing a portion of the cement with pozzolanic materials derived from industrial by-products. Previous research has also demonstrated that mineral admixtures such as pulverized fuel ash (FA) or rice husk ash (RHA) improve the workability and mechanical properties of SCC mixtures [3-5]. Nearly 32 million tons of RHA were produced in Thailand in 2011 [6]. The pozzolanic activity of RHA is dependent on the particle size and surface area. These properties may be tailored using grinding processes, although at considerable cost. Unground RHA may also be used as a cement replacement material by improving the grinding process to increase the ash particle size [7] or mixing with a filler material [8]. For instance, blends of RHA and FA exhibit improved strength and corrosion resistance [9]. Both of these by-product materials are locally available in Thailand, and their use can decrease the cost of SCC and assist in reducing secondary environmental problems related to waste disposal.

2. Experimental details

2.1. Materials

A Type 1 Portland cement (OPC) complying with ASTM standards [10] was used in all of the mixtures. The pulverized fuel ash and rice husk ash were obtained from a thermal power plant. The physical properties and chemical composition of powder materials are showed in Table 1. A polycarboxylic ether (PCE)-based superplasticizer in accordance with ASTM standard type F [11] was used as a lubricant component in the SCC mixtures. Silica sand with a nominal maximum size of 4.75 mm and crushed calcium-based limestone rock with a nominal maximum size of 16.0 mm were also used as aggregates.

Table 1. Chemical composition and physical properties of powder materials.

Type 1 Portland Cement Pulverized fuel ash Rice husk ash

Chemical composition (% by mass)

Silicon dioxide (SiO2) 17.21 40.51 93.44

Aluminum oxide (Al2O3) 3.81 21.52 0.21

Iron (III) oxide (Fe2Os) 3.60 13.41 0.18

Magnesium oxide (MgO) 1.17 2.10 0.43

Calcium oxide (CaO) 67.55 13.99 0.76

Sodium oxide (Na2O) 0.20 1.44 0.05

Potassium oxide (K2O) 0.29 2.20 1.98

Sodium oxide (SO3) 3.25 4.00 0.16

Loss on Ignition (% by mass) 2.44 0.49 1.27

Physical properties

Mean particle size (^m) 24.28 43.86 39.34

Specific gravity 3.15 2.58 2.24

Specific surface area (cm2/g) 632 1487 370

2.2. Mix proportions

The SCC proportions were designed to produce a controlled slump flow in the range between 67.5 to 72.5 cm diameter. The OPC in the mixtures was replaced with 0, 20, or 40 wt% of RHA and/or FA according to the composition chart in Table 2. The mixtures were identified using the notation RHAyFAz, in which y and z are the replacement percentage of RHA and FA %wt of total powder materials. The polycarboxylate-based superplasticizer (HRWR) dosage was fixed at a 2.0 wt% of total powder materials.

Table 2. Mix proportion of SCC mixes.

Materials (kg/m3)

Cementitious

Aggregate

Total powder Cement Rice husk ash Pulverized fuel ash Fine Coarse

Control 550 550 0 0 813 708 2.0

RHA20 550 440 110 0 813 708 2.0

RHA40 550 330 220 0 813 708 2.0

FA20 550 440 0 110 813 708 2.0

FA40 550 330 0 220 813 708 2.0

RHA10FA10 550 440 55 55 813 708 2.0

RHA20FA20 550 330 110 110 813 708 2.0

2.3 Testing procedures

The properties of the SCC mixtures in the fresh state were tested, including density, flow-type slump or slump flow, slump flowing time required to reach 50 cm, and J-ring flow. The test procedures and evaluations were executed in accordance with the relevant ASTM standards [11]. The V-funnel flow time was determined by recording the time in seconds required for the mixture to flow through the funnel after opening the bottom plate in accordance with EFNARC standards [12]. The compressive strength development and pulse velocity (UPV) tests were performed on hardened concrete specimens. The compressive strength development were tested at the ages of 3, 7, 28, and 91 days after pouring in accordance with ASTM standards [11].

3. Results and Discussion

3.1. Properties of fresh SCC

In order to maintain the controlled slump flow in the range between 67.5 to 72.5 cm diameter, SCC mixtures mixed with RHA required greater amounts of water requirement than those mixed with FA. The increase in water requirement is because of the porous structure, larger particle size, and high specific surface area of rice husk ash [2-5, 8-9]. The filling and lubricating effect of water is insufficient to offset the increased water demand resulting from the increased surface area of RHA. As shown in Table 3, the slump flow of the control SCC and mixtures containing FA were within the limits generally prescribed in concrete specifications [11-12]. The slump flow values were primarily dependent on the replacement level of RHA, and increased amounts of RHA resulted in increased both slump flow and flowing times tested by V-funnel. In contrast, increasing amounts of RHA absorbed much more water and produced a readily-crumbled SCC. This was confirmed in the V-funnel flow time results in which the 40% RHA mixture was extremely stiff, inducing

blocking behaviour [8]. Combination of FA with RHA can decrease the required water-powder material ratio and improved the workability due to the spherical shape and fine particle size, which enhanced the packing density and reduced the flow resistance [2-4]. Increasing amounts of FA and RHA resulted in a reduction in SCC mixture density, due to these materials are lower specific gravity than OPC particles [4, 8].

Table 3. Properties of SCC mixtures in the fresh state.

Slump flow J-ring test V-funnel Density (%Control)

Mix Diameter T50cm Diameter blocking Time w/b

(cm) (s) (cm) (s)

Control 70 4 68 No 7 0.26 100

RHA20 70 6 68 No 14 0.42 93

RHA40 68 7 64 Minimal 24 0.57 87

FA20 70 4 70 No 8 0.28 97

FA40 72 5 68 No 10 0.30 94

RHA10FA10 70 5 70 No 12 0.36 95

RHA20FA20 70 6 69 No 20 0.49 94

3.2. Properties of hardened SCC

As shown in Fig. 1 the RHA/FA SCC mixtures were lower compressive strengths than that of the SCC mixture containing OPC (control), and increased with decreasing w/b ratio at all ages. Increasing RHA and FA content resulted in lower compressive strength. SCC mixtures prepared using FA developed higher compressive strength than mixtures prepared using RHA. The increased strength was due to filling and dispersing effects as well as the availability of an increased number of nucleation and precipitation sites [2, 9]. Incorporation of RHA decreased the compressive strength due to greater porosity, leading to a higher water requirement [7-8] and increased void content [5]. Incorporation of FA and RHA blends improved the compressive strength development as the smaller particles of FA filled voids within the mixture, decreasing porosity and water demand.

90 i —*— Control —■— RHA20

80 - —□— RHA40 —FA20

—O—FA40 —A—RHA10FA10

70 - —A— RHA20FA20

60 50 40 30 20 10 0

14 21 28 35 42 49 56 63 70 77 84 91

Test age (days)

Fig. 1. The compressive strength development of SCC mixture with/without FA/RHA.

The average penetration velocities of ultrasonic pulse of the SCC mixtures are showed in Fig. 2. The velocity was dependent on the density of the internal structure of the concrete. The velocities were higher in mixtures containing FA because the fine particles filled large voids and reduced the porosity [9]. RHA mixtures had a greater number of capillary pores, and the width of C-S-H gel/pore interfacial transition zone and air-voids have attenuated the pulse propagation, dropping the velocity through the SCC specimen [5]. In general, the UPV decreased with increasing FA and RHA content [4, 8].

4. Conclusions

The experimental results from the investigation of the properties of self-compacting concrete (SCC) mixtures containing OPC, untreated RHA, and FA allowed concluding remarks that:

1. Mixtures containing a combination of FA and RHA exhibited decreased water requirements and improved workability.

2. In suitable proportions, SCC mixtures containing RHA and FA can develop adequate early-age compressive strength.

RHA20FA20

RHA10FA10

£ FA40

CD O Ö

8 FA20

<4-1 O D

g RHA40

Control

Fig. 2. Ultrasonic pulse velocity of SCC mixtures.

References

[1] Okamura H, M. Ouchi M. Self-compacting concrete. J Adv Concr Technol 2003;1(1):5-15.

[2] Liu M. Self-compacting concrete with different levels of pulverized fuel ash. Constr Build Mater 2010;24(7):1245-52.

[3] Wang A, Zhang C, Sun W. Fly ash effects: I. The morphological effect of fly ash. Cem Concr Res 2003;33(12):2023-29.

[4] Khatib JM. Performance of self-compacting concrete containing fly ash. Constr Build Mater 2008; 22(9):1963-71.

[5] Safiuddin Wd, West JS, Soudki KA. Hardened properties of self-consolidating high performance concrete including rice husk ash, Cem Concr Compos 2010;32(9):708-17.

□ 91 □ 28 □ 7 ■ 3

-1-1-1-1-1-1-1-

.0 1.5 2.0 2.5 3.0 3.5 4.0 4.5 5.

Ultrasonic pulse velocity (km/s)

[6] Food and Agriculture Organization of the United Nations. Crop Prospects and Food Situation. FAO Corporate Document Repository. Rome; 2012.

[7] Zerbino R, Giaccio G, Isaia GC. Concrete incorporating rice-husk ash without processing. Constr build Mater 2011;25(1):371-8.

[8] Sua-iam G, Makul N. Utilization of limestone powder to improve the properties of self-compacting concrete incorporating high volumes of untreated rice husk ash as fine aggregate. Constr Build Mater 2013;38:455-64.

[9] Chindaprasirt P, Rukzon S. Strength, porosity and corrosion resistance of ternary blend Portland cement, rice husk ash and fly ash mortar, Constr Build Mater 2008;22(8):1601-6.

[10] American Society for Testing and Material. Annual Book of ASTM Standard Vol. 4.01. Philadelphia; 2011.

[11] American Society for Testing and Material, Annual Book of ASTM Standard Vol. 4.02. Philadelphia; 2009.

[12] EFNARC. Specification and guidelines for self-compacting concrete, Surrey; 2002.