Propriedades residuais de compósitos cimentícios de alto desempenho com pó de vidro submetidos a altas temperaturas

Abstract

High performance cementitious composites are a technological trend in Brazil and in the world due to their better rheological, mechanical, durability properties, and rational use of raw materials in relation to conventional cementitious composites. The use of supplementary materials, especially pozzolanic, allows obtaining composites with improved properties. Glass, which contains large amounts of amorphous silica in its composition, requiring relatively simple processing processes to obtain its powder, has potential for use as a pozzolanic material. Construction elements are subject to performance situations, including high temperatures. The high performance cementitious composite, which has inherent characteristics of high strength, tend to show greater fragility at high temperatures. This work seeks to investigate the mineralogical, microstructural, physical and mechanical properties of high performance cementitious composites with glass powder in partial replacement of cement, when subjected to high temperatures. To evaluate their properties, cementitious composites were made and characterized without and with the incorporation of glass powder in partial volumetric substitution to cement in the proportions of 10, 20 and 50%. The samples without and with glass powder were subjected to temperatures of 200ºC, 400ºC, 600ºC and 800ºC and their residual properties after cooling were evaluated. Samples heated to 800ºC were rehydrated by immersion in water for 56 days and characterized. The results of the rheological, physical and mechanical characterizations show that the incorporation of 10, 20 and 50% of glass powder results in composites with properties of workability, resistance and water absorption similar to the reference mixture, that is, without glass powder. , demonstrating the viability of glass powder as a pozzolanic material. At high temperatures, the physical and mechanical properties of the reference cementitious composite and with glass powder show similar results up to 400ºC. At temperatures of 600ºC and 800ºC, the differences are evident, with the glass powder mixture presenting a lower performance in compressive strength and higher in rigidity and porosity. Upon rehydration, the reference mixture recovered approximately 98% of its compressive strength and 75% of its stiffness, while the glass powder trace recovered approximately 32% in both properties due to the presence of non-rehydratable or low strength products such as wollastonite, melilite and aluminosilicate.