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International Journal of Scientific and Engineering Research
ISSN Online 2229-5518
ISSN Print: 2229-5518 3    
Website: http://www.ijser.org
scirp IJSER >> Volume 3,Issue 3,March 2012
Investigation on Fly Ash as A Partial Cement Replacement in Concrete
Full Text(PDF, )  PP.I02-114  
Faseyemi V.A
Concrete, Fly Ash, specific Gravity, Compressive Strength, Density and RCPT
The use of high volume fly ash (HVFA) concrete fits in very well with sustainable development. High performance concrete is being widely used all over the world. High volume fly ash concrete mixtures contain lower quantities of cement and higher volume of fly ash (up to 60%). The use of fly ash in concrete at proportions ranging from 35 to 60% of total cementitious binder has been studied extensively over the last twenty years and the properties of blended concrete are well documented. The replacement of fly ash as a cementitious component in concrete depends upon the design strength, water demand and relative cost of ash compared to cement. This study investigated the strength properties of fly ash concrete. The specific gravity and chemical properties of fly ash, cement, coarse and fine aggregate were determined. The density of coarse aggregate was 2.8, fine aggregate was 2.6, water absorption of coarse aggregate 0.6%, water absorption of fine aggregate was 2%, fineness modulus of fine aggregate was 2.90 and fineness modulus of coarse aggregate was 6.90. Ordinary Portland cement was replaced with fly ash from 30 to 60% in steps of 30%, 40%, 50% and 60% by weight, mix proportioning was based on 1:2:4 mix ratio. Cubes (150 x 150 x150mm) were produced, cylinder (150 x 300mm) were used for determination of rapid chloride determination. All the cubes and the cylinder cubes were cured for 7 and 28 days respectively. The cubes and cylinder cubes were subjected to compressive strength tests after density determination at 7 and 28 days respectively. The specific gravity of fly ash was 2.20. The main constituents of fly ash as shown are silicon (as SiO2), aluminium (as Al2O3) and iron oxide (as Fe2O3). The total amount of SiO2, Al2O3, Fe2O3 was 80.38% for fly ash. These values are more than the minimum requirement (50% minimum) specified by ASTM C618 for type C ash. Calcium oxide (CaO) content was 3.50% fly ash. The chemical properties of fly ash are in compliance with the standard and due to high overall content, it was used as cement replacement. This study has shown that increase in the level of fly ash from 15% to 60% lead to an increase in the compressive strength of hardened concrete, while intake of fly ash up to 75% lead to reduction in the compressive strength of hardened concrete and it was observed that 75% replacement of fly ash did not meet up with the require compressive strength at 28 days. This study also shown that the ion chloride penetration satisfied the required standard of ASTM C1202 - 97.
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