Abstract:
This study investigates the impact of widely used mineral fillers in selfcompacting concrete compositions applied in vibration-free reinforced concrete production
technology, as a means of enhancing rheological characteristics and cost-effectiveness.
Three distinct types of mineral fillers, including the well-studied fillers microsilica and
metakaolin, as well as the lesser-explored filler Kazakhstani natural opal-chalcedony opoka,
are examined in this research. In addition to the evaluation of conventional rheological and
performance properties of concretes containing these fillers, the internal processes within
the cement–filler matrix are analyzed. This includes X-ray phase analysis and microstructural examination of cement hydration products in combination with a superplasticizer
and each of the three minerals. The findings confirm the potential for optimizing the
rheological parameters of the concrete mixture by substituting up to 15% of the cement
with mineral fillers, achieving optimal viscosity and workability. It is established that
compositions with the addition of microsilica and metakaolin have a more homogeneous
structure, mainly represented by low-basicity calcium hydrosilicates of the CSH(B) type,
along with an increase in compressive strength of up to 10%. The addition of these mineral
fillers to C30/35 strength class self-compacting concrete resulted in improved frost resistance up to F300, a reduction in volumetric water absorption by up to 30%, and a decrease
in shrinkage deformations by 32%. The developed SCC compositions have successfully
passed production testing and are recommended for implementation in the operational
processes of reinforced concrete product manufacturing plants.
