Effect of quartz powder and mineral admixtures on the properties of high-performance concrete

Introduction. This study focuses on the use of silica fume partially replacing cement with 0, 5, 7.5, 10, 12.5 and 30 % constant replacement of fly ash by weight of cement in concrete. Concrete is probably the most extensively used construction material in the world. But the conventional concrete is losing its uses with time and high-performance concrete (HPC) is taking that place. HPC has superior mechanical properties and durability to normal strength concrete. Because of, the microstructure of HPC is more homogeneous than that of normal concrete (NC) due to the physical and chemical contribution of the mineral admixtures as well as it is less porous due to reduced w/c ratio with the addition of a superplasticizer. The inclusion of additives helped in improving the properties of concrete mixes due to the additional reduction in porosity of cement paste and improving the particle packing in the interfacial transition zone (between cement paste and the aggregates).In this experimental investigation the behavior of HPC with silica fume and fly ash with and without quartz powder were studied. The water-binder ratio was kept 0.3 and 20 % quartz flour as partial replacement of fine aggregate for all cases. Materials and methods. Used materials in Vietnam, as follow, Sulfate-resisting Portland cement - PCSR40 (type V) of company Luks Cement (Vietnam) Limited was used in the work. Crushed granite of fraction 9.5…20 mm - as coarse aggregate, Natural sand from Huong river of 0.15…2.5 mm fraction with the fineness modulus of about 3.0 and quartz powder with an average particle size of 5…10 μm were used as fillers; Sika® Viscocrete®-151 is a superplasticizer based on a blend of 3rd generation PCE polymers was used as a plasticizing admixture. The flg ash from Pha Lai thermal power plant and Sika silica Sikacrete® PP1 (particle size < 0.1 μm) was used as a mineral active admixture. The study of strength and technological properties of high-performance concrete was performed by using standard methods. Results. Established by icate that, the workability and strength increase at a certain level and after that, they decline with further increase in the replacement level of silica fume is 12.5 %, on the basis of 30 % FA replacement, the incorporation of 10 % SF showed equivalent or higher mechanical properties and durability compared to the reference samples. Conclusions. HPC consists of mineral admixtures such as silica fume and fly ash use combine quartz powder and superplasticizer helped in improving the strength and durability of concrete mixes due to the additional reduction in porosity of cement paste and an improved interface between it and the aggregate. With 30 % fly ash is optimum dosage used to replacement of cement, incorporation 10 % SF (by weight) and combine of partial replacement of fine aggregate by 20 % quartz powder. On the other hand, a few mathematical equations can be used to derive the durability properties of concrete based on its compressive strength.