Effect of fly ash to water-cement ratio on the characterization of the concrete strength

Abstract

Fly ash (FA) is burning coal product which is used as supplementary cementitious materials (SCM) as the conjunction with cement. The use of FA is considered by its pozzolanic properties i.e. SiO2, Al2O3 and CaO to hardened concrete. The potential of FA as SCM has been well-known over the globe but that significant utilization has to be studied based on its compound's characteristics and pozzolanic activity. For this case, the amount of FA is added 30% by mass of total cementitious material, concrete with fly ash (NFA) and another blended without FA as normal concrete (NC) made of ordinary Portland cement. This amount is indicated as dosage in moderate to high volume of FA classification. This replacement pairs with water to cement ratio (W/C) with the value of 0.47 and 0.30 e.g., NC1, NC2 and NFA1, NFA2, respectively. These W/C uses considering effect FA on water demand of concrete proportioned for equal slump. The results showed that NC2 and NFA2 in the age of 28-day inform higher compressive strength, 30% and 28%, respectively. Another indication from the comparison of NC2 and NFA2 were also in good agreement that the use of FA decrease the compressive strength around 3% to 6%.