The effect of high-calcium fly ash on selected properties of self-compacting concrete

This paper investigates the basic influential trends of varying compositions and properties of high calcium fly ash (HCFA) on selected properties of self-compacting concrete (SCC) and high-performance SCC (HPSCC). HCFA was implemented as either a replacement component within a cement mixture (2 types of fly ashes, also activated by grinding) or as an additive to cement (also in combination with other additives as F-class ash and ground granulated blast furnace). A discussion of the results encompasses the influence of high-calcium fly ashes (C-class) on the effectiveness of admixtures. The research reveals the negative effects of raw calcium fly ash (without grinding) upon its rheological properties and workability, as it is added to a concrete mix. With the activation of fly ash (by grinding), its properties improve and, as a result, yields a positive effect of the additive to concrete mixes. The paper presents test results for the SCC as it is modified by HCFA, SCC mixes with cement modified by HCFA and HPSCC modified by HCFA. The results include an investigation of samples as they belong to classes of slump flow, classes of viscosity and the compressive strength tests. The concrete mix was tested with a varying amount of HCFA (10-20-30%).