Effect of zeolite and microsilica on the strength of SCC concrete containing PP fibers

Abstract Recent advances in concrete technology have resulted in the development of self-compacting concrete (SCC), a highly flowable concrete capable of consolidating under its own weight without the need for external vibration. Pozzolanic materials containing reactive silica (SiO₂) possess limited intrinsic cementitious properties; however, when incorporated as finely divided particles into cementitious systems, they react with calcium hydroxide (CH) generated during cement hydration, producing additional cementitious compounds that enhance the microstructure and overall performance of concrete. The present study investigates the combined influence of natural zeolite, microsilica, and polypropylene (PP) fibers on both the fresh and hardened properties of SCC. Concrete mixtures were proportioned according to established mix design procedures and prepared under controlled laboratory conditions. Natural zeolite was used as a partial cement replacement at levels ranging from 0 to 20% by weight of cement, while PP fibers were incorporated at volumetric contents between 0 and 0.2%; microsilica was maintained at 6.25% of the total binder content in all mixtures. Fresh concrete performance was assessed through slump flow, T₅₀₀, V-funnel, and L-box tests to evaluate flowability, viscosity, and passing ability. The hardened properties were examined using compressive strength, splitting tensile strength, flexural strength, and water absorption tests. The experimental results demonstrated that mixtures without PP fibers consistently exhibited the lowest compressive strength at all curing ages. The highest compressive strength was obtained with a PP fiber dosage of 0.1% by volume, resulting in an average improvement of approximately 11% compared with fiber-free mixtures. In addition, replacing 10% of cement with natural zeolite provided the optimum performance, increasing compressive strength by nearly 13% relative to the control mixture.