REPLACEMENT OF CEMENT BY FILLER TO REDUCE C02 AND NANO-SLLICA TO ENSURE HIGH-PERFORMANCE COMPOSITES

High-performance cementitious composites (HPC) represent a class of materials known for higher mechanical strength compared to traditional ones. Incorporating nanomaterials like metakaolin (MK) and microsilica (MS) can lead to greater improvements in mechanical properties. However, these materials, and mainly cement, entail environmental impact as they require high-temperature transformation processes. So, even high-strength concretes must address environmental concerns, necessitating innovative approaches. The replacement of cement with inert fillers has emerged as a strategy for reducing cement content and environmental impact, since their production involves grinding rather than high-temperature processes, resulting in lower CO2 emissions. However, their inert nature limits reactivity, compromising the performance. This study seeks to evaluate the feasibility of producing HPC by partially replacing cement with quartz fillers (QF). This substitution was accompanied by the addition of small quantities ofnano-silica to evaluate if losses in rheology and strength, caused by increased filler content, could be compensated. It was developed 5 mixtures: MO (reference); and Ml to M4, with cement replacement by contents of 4 to 16% ofNS and QF. It was measured rheological and mechanical performance. Results show that nano-silica's high surface area enhances hydration reactions, contributing to the mechanical performance, andean increase the packing of particles due to its very fine particle size distribution, contributing to rheological performance. Nevertheless, these benefits are restricted to a maximum content: after the limitwhere voids between coarser particles are fully filled by NS, it does not contribute to packing anymore, but the surface area continues to grow directly proportional to NS increase, with negative impacts on final rheological performance.