Journal of Engineering Research and Studies E-ISSN

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1 Research Article STUDY EFFECT OF POLYESTER FIBRES ON ENGINEERING PROPERTIES OF HIGH VOLUME FLY ASH CONCRETE Indrajit Patel, C D Modhera Address for Correspondence Applied Mechanics Department, B & B Institute of Technology, Vallabh Vidya Nagar, Gujarat, Professor, Department of Applied Mechanics, SVNIT, Surat, Gujarat, , inpatel34@gmail.com cdm@svnit.ac.in ABSTRACT Aim to improve engineering and durability properties of conventional High Volume Fly Ash (HVFA) concrete experimental work has been carried out as part of PhD study. Though HVFA concrete has development history of more than four decades the use has not been significant and notable due to many reason including slower early strength development, resistance to bending, impact and abrasion for its application on wide base. The replacement of Portland cement in context of Indian Standard is of order 35% by mass of cementing material. Even the blended cement contains 25% of fly ash. This will not address the issue of green concrete and sustainability of concrete technology. Inclusion of 50% or more fly ash reflects to application of HVFA for low to high strength and high performance concrete with or without adding micro sized material like silica fume or micro quartz. The experimental work as part of Ph.D. work includes mix design for M25,30,35 and M40 grade HVFA concrete with different percentage of class F fly ash 50,55 and 60%.To improve the engineering properties viz. compressive, flexural, impact strength and abrasion resistance 12mm triangular shaped polyester fibre is use at rate of 0.25% by the mass of cementitious material. The test results for compressive strength at 3,7,28 and 56 days for plain HVFA concrete for all grades with and without meets codal requirement. The use of polyester fibres has increased the compressive strength to order of 12 to 15 %. Flexural strength using center point loading also meets the required parameters and fibre reinforced HVFA shows 16 to 23% increase compared to plain HVFA concrete at 28 and 56 days. There is notable increase in ductility of HVFA concrete which is the need of days for deign & construction of earthquake resistant structures. KEY WORDS: Fly Ash, Polyester fibre, Compressive Strength, Flexural Strength. INTRODUCTION and fibre reinforced HVFA concrete is Scope of the present work as a part of Ph.D. research work includes preparing trial and final design mix for HVFA replacing cement by 50,55,60% flyash for M25,M30,M35 and M40 grade of concrete. For improving the mechanical and durability properties of HVFA concrete 12 mm triangular shaped polyester fibre were added in proportion of 0.25 of cementing material by mass. Literature review has also been made for use of polyester fibre in normal concrete in terms of improvement in compressive and flexural strength, impact and abrasion resistance and resistance to alkaline condition. The paper includes final mix composition, test results of compressive and flexural strength measure at different age. Comparative studies of workability through slump measurement, compressive & flexural strength of all designated samples with plain presented in the article. All the ingredients were procured from local sources, tested as per relevant standard and confirmed the same meeting required standards. MATERIALS 53 grade Ordinary Portland cement conforming to BIS was used. Class F fly ash from Wanakbori Thermal Power station, Gujarat conforming to BIS was used in the present study. Scanning Electron Microscopic view for fly ash is shown fig. [1] Admixtures: High range water reducing admixtures for fibre reinforced HVFA samples Poly carboxylate based super plasticizer was used. Aggregates: Crushed stones of 20mm down and 10mm down were used as coarse aggregate. Local

2 river sand was used as fine aggregate in the concrete mixtures. Figure: 1 SEM view of fly ash Fiber: 12mm size triangular-trilobal shaped polyester fibre confirming to type III fibres under ASTM C: 1116 were used as a supplementary reinforcing material to enhance the mechanical properties of hardened concrete. The microscopic view of the same is figure [2] EXPERIMENTAL SET UP Final design mix was prepared for all the designated mix as shown table [1]. Latter in second stage with the same proportion 0.25% of polyester fibre was added. Figure 2. SEM view of polyster fibre For each batching of the sample and design mix the slump values were measured after 60 min retention period using standard slump cone and results were confirmed as per BIS: For compression strength standard 150mm cube were casted to measure strength at 3, 7, 28 and 56 days. Sample were casted and tested as per BIS 516 Comparative study was made for strength development for different dose of flyash as well as with inclusion of 12mm triangular shaped polyester fibre content i.e Flexural strength was measured at the age of 14,28 and 56 days for all samples using central point load over span of 400mm, for specimen size 100x100x500mm. Test procedure was carried out as per BIS-516

3 Table: 1 HVFA DESIGN MIX M25 SAM- PLE C FA C+FA W SP W/C+ FA SA ND <20MM <10M SLUM P MM DENSITY KG/M3 A A A M30 SAMPLE C FA C+FA W SP W/C+FA SAND <20MM <10M SLUMP MM DENSITY KG/M3 B B B M35 SAMPLE C FA C+FA W SP W/C+FA SAND <20MM <10M SLUMP MM DENSITY KG/M3 KG.M3 C C C M40 SAMPLE C FA C+FA W SP W/C+FA SAND <20MM <10M SLUMP MM DENSITY KG/M3 D D D A: M25, B=M30,C=M35,D=M40 1= 50 2=55 3=60 % flyash 0= no fibre 1=0.25 % fibre RESULTS AND DISCUSSION The batching for all the designed mix and inclusion of varied flyash as well as polyester fibres have made as per the standard procedure. Slump for all the batches were measured after 60 min. retention period and comparative study for different mix meets desired value ranging from 85 mm to 115 mm as desired for RMC standards. W/C ratio is of order 0.25% to 0.40% with in limits specified under guide lines of HVFA and BIS. Compressive strength measurement for all the mix with 0.0 and 0.25% fibre dose was measured 3, 7, 28, 56 days as shown in table [2]. Comparison of compressive strength according to variation in fibre content 0.0 and 0.25% at end of 28 days and 56 days for all mix is shown graphically in figure [3]& [4]. 28 days & 56 days flexural strength comparative study is shown study in fig.[5] & [6]

4 Table 2: Compressive Strength N/MM2 Mix Days/ 50% flyash 55% flyash 60%flyash Fiber Figure days compressive strength

5 Figure 4: 56 days compressive strength Table 3: Flexural Strength N/MM2 Mix Days/ 50% flyash 55% flyash 60%flyash Fiber

6 Figure 5: 28 days flexural strength Figure 6: 56 days flexural strength

7 15 DEFLECTION AT 28 DAYS IN MM M25 M30 M35 M40 0.0% Fiber DEFLECTION AT 56 DAYS IN MM M25 M30 M35 M40 0.0% Fiber Fig 7 Deflection Comparison CONCLUSION The compressive strength gaining is comparatively slower at 3 and 7 days for all mix particularly for high 60% of flyash and higher mix M35 and M40. Targeted values at 7 days for plain HVFA concrete is of the 72% to 78% which is as better as normal concrete without flyash. Beyond 7 days the increase in strength is of order 65 to 76% and all mix shows satisfactory values at age of 28 days. Inclusion of fibre at the rate of 0.25% by mass of the cementitious material does not have much effect on the w/c ratio and 60 min. slump values as well. For higher proportion of cementing material in higher concrete grade the dosage of plasticizer was increased to 1.00% to achieve desired slump and workability. Increase in compressive strength at 7 days age for all mix with fibre varies between 7.00 to 9.50% Increase in 28 days compressive strength as compared to plain HVFA concrete is of the order 9.75 to 15 % All sample shows required flexural strength at 14, 28 and 56 days age. Increase in strength between 14 to 28 days is of order 22 to 30% and 28 to 56 days is 7.50 to 13.5%. 55% cement replacement shows optimum gain of compressive and flexural strength for all grade of plain and fibre reinforced HVFA concrete. With considerable reduction in cost of cementing material and including marginal proportion of polyester fibre strong and durable eco friendly concrete can be produced and applied in the construction sectors like pavement, foundations, mass concrete and gravity structures.

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