This paper investigates the basic influential trends of varying compositions and properties of High Calcium Fly Ash(HCFA) waste on rheological properties of Self-Compacting Concrete (SCC). HCFA was implemented as either a replacement component within a cement mixture (HCFA 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 HCFA (C-class) on the effectiveness of admixtures. The research reveals the negative effects of raw calcium fly ash (without grinding) upon its workability, as it is added to a concrete mix. With the activation of HCFA (by grinding), its properties improve and, as a result, yields a positive effect of the additive to concrete mixes. Undeniably, in many cases, the problem is the loss of workability. However, this does not concern cement composites. The current findings are not sufficient in effectively controlling for SCC mixtures with HCFA. The potential of the application of HCFA as a partial replacement for cement in concrete and other cement components has been examined. The subject of this article is an analysis of the effects of HCFA content on the properties of selected cements and concretes. The paper presents test results for the self-compacting concrete SCC as it is modified by HCFA and SCC mixes with cement modified by HCFA. The results include an investigation of samples as they belong to classes of slump flow SF, classes of viscosity T-500, rheological properties: yield value g and plastic viscosity h and the compressive strength tests: f(cm),(7d) and f(cm),(28d). The concrete mix was tested with a varying amount of HCFA (10-20-30%), as equivalent to cement. The studies have confirmed the feasibility of using HCFA in cements and new generation concretes while maintaining the implicit technological parameters, especially workability, for concrete mixtures. Further research is required and the impact of the variability of the physical and chemical properties of HCFA and cement type must be taken into consideration.
