Scholarly article on topic 'Properties of Normal Concrete, Self-compacting Concrete and Glass Fibre-reinforced Self-compacting Concrete: An Experimental Study'

Properties of Normal Concrete, Self-compacting Concrete and Glass Fibre-reinforced Self-compacting Concrete: An Experimental Study Academic research paper on "Economics and business"

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Abstract of research paper on Economics and business, author of scientific article — Subhan Ahmad, Arshad Umar, Amjad Masood

Abstract Hardened properties of normal concrete (NC) and self-compacting concrete (SCC) are compared. Also, the influence of glass fibres on fresh and hardened properties of SCC is investigated. Three concrete mixtures; normal concrete (NC), SCC and SCC with glass fibres were prepared with a water-cement ratio of 0.35. It was found that addition of glass fibres slightly reduced the workability properties of SCC. Compressive strength and splitting tensile strength of SCC were found to be slightly higher than NC. However, modulus of rupture and modulus of elasticity of SCC was found to be lower than NC. Addition of glass fibres in SCC had limited effect on compressive strength and modulus of elasticity but increased modulus of rupture and splitting tensile strength significantly.

Academic research paper on topic "Properties of Normal Concrete, Self-compacting Concrete and Glass Fibre-reinforced Self-compacting Concrete: An Experimental Study"

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Procedía Engineering 173 (2017) 807-813

Procedía Engineering

www.elsevier.com/locate/procedia

11 th International Symposium on Plasticity and Impact Mechanics, Implast 2016

Properties ofNormal Concrete, Self-Compacting Concrete and Glass Fibre-reinforced Self-Compacting Concrete: An Experimental Study

Subhan Ahmada*, Arshad Umarb, Amjad Masoodb

a Department ofCivilEngineering, Indian Institute ofTechnology, Roorkee, 247667, India bDepartment of CivilEngineering, Aligarh Muslim University, Aligarh, 202002, India

Abstract

Hardened properties of normal concrete (NC) and self-compacting concrete (SCC) are compared. Also, the influence of glass fibres on fresh and hardened properties of SCC is investigated. Three concrete mixtures; normal concrete (NC), SCC and SCC with glass fibres were prepared with a water-cement ratio of 0.35. It was found that addition of glass fibres slightly reduced the workability properties of SCC. Compressive strength and splitting tensile strength of SCC were found to be slightly higher than NC. However, modulus of rupture and modulus of elasticity of SCC was found to be lower than NC. Addition of glass fibres in SCC had limited effect on compressive strength and modulus of elasticity but increased modulus of rupture and splitting tensile strength significantly.

© 2017 The Authors.PublishedbyElsevierLtd. Thisis an open access article under the CC BY-NC-ND license (http://creativecommons.Org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the organizing committee of Implast 2016

Keywords: Self-compacting concrete; Fly ash; Glass fibre; Mechanical properties

1. Introduction

Self-compacting concrete, also referred to as self-consolidating concrete, is the concrete that is able to flow under its own weight and completely fill the formwork, while maintaining homogeneity even in the presence of congested reinforcement, and then consolidating without the need of vibration [1]. Self-compacting concrete was developed in Japan in 1980's [2].

* Corresponding author. Tel.: +91-8477921220 E-mail address: subhn.dce2015@iitr.ac.in

1877-7058 © 2017 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY-NC-ND license

(http://creativecommons.org/licenses/by-nc-nd/4.0/).

Peer-review under responsibility of the organizing committee of Implast 2016

doi:10.1016/j.proeng.2016.12.106

Self-compacting concrete contains a large amount of powder (particles < 0.125 mm) which is required to maintain adequate yield value and viscosity of the fresh mix, therefore reducing bleeding, segregation and settlement. Since, the use of a large amount of cement increases cost and results in greater temperature rise, the use of fly ash could increase the slump of the concrete mix without increasing its cost. Earlier studies have revealed that the use of fly ash can increase the slump of SCC mix without increasing its cost, though reducing the dosage of superplasticizer required to obtain similar slump flow compared to concrete made with Portland cement only [3]. Use of fly ash also improves the rheological properties of SCC and reduces the heat of hydration of the cement resulting in reduced cracking potential [4].

Low tensile and flexural strengths of concrete can be improved by introducing fibres. In this study Cem-FIL Alkali resistant (AR) glass fibres are used for this purpose since ordinary glass fibre cannot be used in Portland cement concretes because of chemical attack by the alkaline cement paste [5]. The main objectives of present study are

i. To compare the hardened properties (compressive strength, splitting tensile strength, modulus of rupture and modulus of elasticity) of SCC with NC.

ii. To investigate the influence of glass fibres on fresh and hardened properties of SCC.

2. Experimental program

2.1 Materials used

Ordinary Portland cement confirming to IS: 8112-1989 [6] was used in the study. The cement was uniform in colour i.e. grey with a light greenish shade and was free from any hard lumps. Physical properties and chemical composition of OPC-43 used are given in Table 1 and 2, respectively. Class F fly ash used in the study was obtained from Qasimpur thermal power station. Sand confirming to Indian Standard Specification IS: 383-1970 [7] was locally obtained. Maximum size of coarse aggregate used was 12.5mm with water absorption 1.14% and specific gravity 2.7. Tap water was used in all the mixes, and the temperature of water was normally about 25°C. A polycarboxylic ether based super-plasticizer complying with ASTM C 494 [8] type F with density 1.10 and pH approximately 5.0 was used in the study. A viscosity modifying admixture meeting ASTM C 494 [8] type S, specific performance admixtures requirements was also used in the study. Alkali resistant glass fibres (Cem-FIL AR) were used in the experimental work having specific gravity and tensile strength as 2.68 and 1500 MPa, respectively. Length of the fibres used in the study was 12 mm.

Table 1 Physical properties of cement

Test Values obtained Requirement of IS: 8112-1989

Normal consistency (%) 28 _

Initial setting time (min) 55 30 (minimum)

Final setting time (min) 175 600 (maximum)

Compressive strength (MPa)

3 days 24.1 23

7 days 33.9 33

28 days 44.8 43

Soundness (mm) 2.5 10 (maximum)

Specific gravity 3.15 -

Subhan Ahmad et al. / Procedía Engineering 173 (2017) 807 - 813 Table 2 Chemical composition of OPC 43 used

Chemical composition Value obtained (%)

Silicon dioxide (Si02) 19.50

Aluminum oxide (A1203) 9.57

Ferric oxide (Fe203) 3.36

Calcium oxide (CaO) 60.00

Magnesium oxide (MgO) 1.63

Sulphur trioxide (SO3) 2.53

Sodium oxide (Na20) 0.82

Potassium oxide (K20) 1.21

Loss on ignition 1.23

2.2 Mixproportions

Three concrete mixtures; normal concrete (NC), self-compacting concrete (SCC) and SCC with glass fibres (SCC-G) were prepared by adjusting water-binder ratio and super-plasticizer dosage. Fine and coarse aggregate content were fixed to 725 kg / m3 and 775 kg / m3 respectively. Desired flowability was achieved at a water-binder ratio of 0.35 and superplasticizer dosage of 0.8%. Further, 0.3% of viscosity modifying admixture (VMA) was also added to reduce bleeding and segregation. Mix proportions decided after several trial mixes are presented in Table 3. Mixing was done in a free-fall type mixer. Casting, curing and storage of concrete were as per Indian Standards except there was no compaction during casting of SCC.

Table 3 Mix proportions

Material Mix

NC SCC SCC-G

Cement (kg/m3) 600 530 530

Fly ash (kg/m3) 0 70 70

Fine aggregate 725 725 725

Coarse aggregate (kg/m3) 775 775 775

Water (kg/m3) 210 210 210

Super-plasticizer (%) 0 0.8 0.8

VMA (%) 0 0.3 0.3

Glass fibres (kg/m3) 0 0 0.6

2.3 Test Methodsfor Evaluating the Fresh Properties of SCC

Slump Flow Test (EN 12350: Part 8-2010) [9]

The slump-flow and T500 time is a test to assess the flowability and the flow rate of self-compacting concrete in the absence of obstructions. The result is an indication of the filling ability of self-compacting concrete. The T500 time is also a measure of the speed of flow and hence the viscosity of the self-compacting concrete. The fresh concrete is poured into a cone as used in slump test. When the cone is withdrawn upwards the time from commencing upward movement of the cone to when the concrete has flowed to a diameter of 500 mm is measured; this is the T500 time. The largest diameter of the flow spread of the concrete and the diameter of the spread at right angles to it are then measured and the mean is the slump-flow.

V-funnel Test (EN 12350: Part 9-2010) [10]

The V-funnel test is used to assess the viscosity and filling ability of self-compacting concrete. A V shaped funnel (Fig.l) is filled with fresh concrete and the time taken for the concrete to flow out of the funnel is measured and recorded as the V-funnel flow time.

Fig.l. V-funnel (Adapted from [14].) Fi§-2- L"box assembly (Adapted from [14].)

L-box Test (EN 12350: Part 10-2010) [11]

The L-box test setup shown in Fig.2 is used to assess the passing ability of self-compacting concrete to flow through tight openings including spaces between reinforcing bars and other obstructions without segregation or blocking. There are two variations; the two bar test and the three bar test. The three bar test simulates more congested reinforcement. A measured volume of fresh concrete is allowed to flow horizontally through the gaps between vertical, smooth reinforcing bars and the height of the concrete beyond the reinforcement is measured.

2.4 Tests on Hardened SCC

The hardened concrete was tested for compressive strength, modulus of rupture and modulus of elasticity as per IS: 516-1959 [12] and for splitting tensile strength according to IS: 5816-1999 [13].

3. Results and discussion

3.1 Fresh Properties ofSCC

Results of fresh properties ofthe SCC mixtures are presented in Table 4. Fresh properties ofboth the mixes are in good agreement with the guidelines prescribed by EFNARC, 2005 [14].

Table 4 Fresh properties of SCC mixes

Slump flow T500 L-box V-funnel time

Mix (mm) (s) ratio (s)

SCC 720 3.0 0.91 7.5

SCC-G 710 3.5 0.90 8

Acceptance criteria (EFNARC, 2005) 600-800 2-5 0.8-1.0 6-12

Slump flow and T500 time for SCC was found to be 720 mm and 3 s, respectively. Addition of glass fibres in SCC reduced the slump flow by 10 mm and increased the T500 time by 0.5 s. L-box ratio for SCC and SCC-G was found to be 0.91 and 0.9, respectively. V-funnel time of SCC (7.5 s) was increased by 0.5 s after the addition of glass fibres.

3.2 Hardened Properties ofSCC

Results of compressive strength, splitting tensile strength, modulus of rupture and modulus of elasticity are given in Table 5.

Table 5 Mechanical properties of hardened concretes

Mix Compressive strength Splitting tensile Modulus of rupture Modulus of Elasticity (MPa)

(MPa) strength (MPa) (MPa)

7 day 28 day Value Relationship

NC 32.85 43.42 4.00 4.67 25500 4327<fc

see 33.66 44.44 4.30 4.60 25050 4196^/T

SCC-G 35.64 46.88 4.75 4.90 25750 4205^'

Compressive Strength

Compressive strength of SCC was found to be increased by 2.5% and 2.35% after 7 and 28 days, respectively. The increase of compressive strength of SCC may be attributed to the improved interface between the aggregate and hardened paste due to the absence of vibration. Adding glass fibres in SCC increased its 7 and 28 days compressive strength by 6% and 5.5%, respectively. Other researchers [15, 16] also reported the increase in compressive strength after the addition of fibres. 7 and 28 days compressive strengths of hardened concretes are shown in Fig.3.

Splitting Tensile Strength

Splitting tensile strength of SCC was found to be 7.5% higher than NC. Increase in splitting tensile strength may also be attributed to better homogeneity coming from vibration free production. Addition of glass fibres increased splitting tensile strength of SCC by 13.1%. Increase in splitting tensile strength was also reported by other researchers [16, 17]. Splitting tensile strength of hardened concretes are shown in Fig.4.

_ 50 j

20 ■ H H "7days

I II H ■ days

NC SCC SCC-G Concrete type

Fig.3. Compressive strength of hardened concretes

Fig.4. Splitting tensile strength of hardened concretes

Modulus ofRupture

Fig.5. shows the modulus of ruptures of hardened concretes. Modulus of rupture of SCC and NC was 4.6 MPa and 4.67 MPa, respectively. Addition of glass fibres increased the modulus of rupture of SCC by 6.5%. Increase in modulus of rupture of SCC-G may be due to the restraining of cracks by fibres. Other researchers also found that modulus of rupture of SCC increases after the addition of fibres [15, 18].

Modulus ofelasticity (MOE)

Modulus of elasticity of SCC was found to be slightly lower than that of NC. This may be due to the fact that SCC has higher amount of cement paste and MOE of cement paste is smaller than that of coarse aggregate. Dehn et al. [19], Dinakar et al. [20] and Jacobs and Hunkeler [21] also found that for a given strength, MOE of SCC is lower than that of CC. Addition of glass fibres slightly increased the MOE of SCC. Relationships between MOE and cylindrical compressive strength (/c) of SCC and SCC-G are in good agreement with the results of Dinakar et al. [20] and Persson [22]. Moduli of elasticity of different mixes are shown in Fig.6.

_ 30000 n

| 25000 ♦ $ ♦

£ 20000 u

S 15000 0)

o 10000 in

■§ 5000 -a o

NC SCC SCC-G

Concrete type

Fig.6. Modulus of elasticity of hardened concretes

3. Conclusions

Following conclusions can be drawn from the results of experimental program described in this study.

• Compressive and splitting tensile strengths of SCC were found to be slightly higher than the corresponding properties of NC.

• Modulus of rupture and modulus of elasticity of SCC were found to be slightly smaller than the corresponding properties ofNC.

• Addition of 0.6 kg/m3 of glass fibres slightly reduced the fresh properties of SCC.

• Addition of glass fibres increased compressive strength and modulus of elasticity slightly but increased splitting tensile strength and modulus of rupture by considerable amount.

Fig.5. Modulus of rupture of hardened concretes

References

[1] Concrete Society. Self-compacting Concrete, A Review, The concrete Society and BRE,2005,Technical Report 62, 2005

[2] Ozawa K, Maekawa K, Kunishima M, Okamura H. Performance of concrete based on the durability design of concrete structures. In: Proc of the second east Asia-Pacific conference on structural engineering and construction; 1989

[3] Yahia A, TanimuraM, Shimabukuro A, Shimoyama Y. Effect ofrheological parameters on selfcompactiblity of concrete containing various mineral admixtures. In: Proc of the first RILEM international symposium on self-compacting concrete. Stockholm; 1999. p. 523-35

[4] Kurita M, Nomura T. Highly-flowable steel fiber-reinforced concrete containing fly ash. In: Malhotra VM, editor. Am Concr Inst SP 178, June 1998. p. 159-75

[5] Mehta, P. K. and Monteiro, P.J.M. Concrete Microstructure, Properties and Materials. Third edition, 2006, Tata McGraw-Hill Publishing Co Ltd, New Delhi, 2006, pp 478

[6] IS: 8112-1989. Specifications for 43-Grade Portland cement. New Delhi, India: Bureau of Indian Standards

[7] IS: 383-1970. Specifications for coarse and fine aggregates from natural sources for concrete. New Delhi, India: Bureau oflndian standards

[8] Admixture, Water-Reducing. "ASTM C 494/C 494M." Type B 3

[9] BS EN 12350-8:2010. Testing fresh self-compacting concrete. Slump flow test

[10] BS EN 12350-9:2010. Testing fresh self-compacting concrete. V-funnel test

[11] BS EN 12350-10: 2010. Testing fresh self-compacting concrete. L-box test

[12] IS: 516-1959. Indian standard code ofpractice- Methods of test for strength ofconcrete. New Delhi, India: Bureau oflndian Standards

[13] IS 5816: 1999. Indian Standard code ofpractice-Method oftest for splitting tensile strength ofconcrete. New Delhi, India: Bureau of Indian Standards

[14] EFNARC. 2005, Specification and guidelines for self-compacting concrete

[ 15] Umar, A. and Al-Tamimi, A.2011,"A critical study of the effect of viscosity modifying admixture and glass fibres on the properties ofself-compacting concrete (SCC)", Journal ofStructural Engineering, Vol. 38, No. 2, June - July 2011 pp. 153-162.

[16] Aslani, Farhad, and Shami Nejadi. 2013, "Self-compacting concrete incorporating steel and polypropylene fibers: Compressive and tensile strengths, moduli ofelasticity and rupture, compressive stress-strain curve, and energy dissipated under compression." Composites Part B: Engineering 53: pp.121-133.

[17] Mazaheripour, H., et al. 2011, "The effect ofpolypropylene fibres on the properties offresh and hardened lightweight self-compacting concrete." Construction andBuildingMaterials 25.1: pp.351-358.

[18] Umar, A. Masood, A., Ahmad, S (2016). "A comparative study ofthe performance ofself-compacting concrete using glass and polyvinyl alcohol fibres". International Conference on Hybrid And Composite Materials, Chemical Processing (HCMCP)-2016. St. Peter's Engineering College, Hyderabad, Telangana, India, 25th-27th October, pp. 27-33.

[19] Dehn F, Holschemacher K, WeiXe D. 2000, "Self-compacting concrete time development ofthe material properties and the bond behaviour" The Leipzig annual civil engineering report., Germany LACER No. 5, ISSN 1432-6590. p.l 15-24.

[20] Dinakar P, Babu KG, Santhanam M. 2008, "Mechanical properties ofhigh-volume fly ash self-compacting concrete mixtures". Struct Concr;9(2):pp.l09-16.

[21] Jacobs, Frank, and Fritz Hunkeler. 1999, "Design ofself-compacting concrete for durable concrete structures." In First international RILEM symposium on self-compacting concrete. Rilem Publications SARL, pp. 397-410.

[22] Persson, Bertil. 2001, "A comparison between mechanical properties ofself-compacting concrete and the corresponding properties of normal concrete." Cement and concrete Research 31.2: pp.193-198