Mechanical properties of high-volume fly ash roller compacted concrete designed by maximum density method

In order to study the effect of high volume fly ash on mechanical properties of roller compacted concrete, in addition to control mixture containing no fly ash, in two different series of mixtures cement or aggregate was partially replaced with fly ash. The maximum aggregate size was 25 mm in all of the mixtures which were designed using maximum density method. The cement content of the control mixture was 250 kg/m(3). In one series of the mixtures 20, 40 and 60 wt% of cement was replaced with fly ash. In another series, a part of aggregate (equal to 20, 40 and 60 wt% of cement) was replaced with fly ash. Totally 28 mixtures having four different water/binder ratios (0.30, 0.35, 0.4 and 0.45) were prepared. Among these, seven mixtures containing optimum water content were selected for further research. It was observed that in the mixtures where cement was substituted with fly ash, increasing the fly ash content caused reduction in compressive, splitting tensile and flexural strength values at all of the ages up to even 180 days. On the other hand, when aggregate was replaced with fly ash, increasing the fly ash content increased the strength values of the mixture at all ages compared to these of the control specimen. (C) 2012 Elsevier Ltd. All rights reserved.