No abstract

This paper aims at evaluating the pozzolanic properties of ornamental stone processing waste after heat treatment at 1200 °C (HTOSPW) and analyzing the influence on the mechanical strength of concrete produced with HTOSPW addition at the contents of 5% and 10% by mass of Portland cement. The HTOSPW shows promising results regarding the pozzolanic activity, revealing chemical and physical characteristics typical of pozzolanic materials in addition to being approved in the pozzolanicity tests performed. As for the concretes produced with HTOSPW addition, a significant increase in mechanical strength was observed, especially for concretes with a 10% addition.

The incorporation of waste glass as a partial replacement for cement in concrete can provide an alternative destination for the waste, reduce the consumption of cement (minimizing CO2 emissions and consumption of natural resources), and improve the concrete performance. Thus, this research evaluated the performance of concrete incorporating waste glass sludge (GS), resulting from the process of stoning and polishing of soda-lime flat glass, as a supplementary cementing material. Mechanical strength and durability properties were assessed through compressive strength, alkali-silica reactivity, electrical resistivity and chloride permeability, diffusivity and migration tests. Mixtures containing metakaolin (ME) were also evaluated. The results indicated that the use of the waste ground to an adequate size can replace up to 20% of cement. At this content, it caused a reduction of chloride penetration of over 80%, reduced ASR and conserved compressive strength. The combination of waste with metakaolin replacing 20% of cement also improved all the concrete properties, increasing the compressive strength up to 12% at 28 days.

Releva-se, a necessidade da execução de concretos homogêneos a fim de garantir a qualidade das estruturas de concreto armado. O mencionado fato torna-se ainda mais relevante, pois as premissas de cálculos de projeto consideram os elementos estruturais contemplando características similares em qualquer seção transversal. Neste contexto, tem-se diretriz expressa na norma de amostragem de concreto fresco, NBR NM 33 (ABNT, 1998), que preconiza a retirada de amostras após a descarga de pelo menos 15% do volume total da betonada e antes da descarga de 85%, para que se possa atestar o grau de homogeneização do concreto. Em contrapartida ao que recomenda a norma, sabe-se que na maioria das obras recolhem-se as amostras de concreto antes do início da concretagem. Este trabalho tem por objetivo verificar o grau de homogeneidade do concreto dosado em central e fornecido por meio de caminhão betoneira. Para efeito, foram realizadas análises em 4 obras distintas, verificando-se o índice de consistência e as propriedades mecânicas dos concretos em duas etapas: coleta no início da concretagem e no intervalo de descarga preconizado pela norma. Pôde-se constatar que não há diferença significativa entre o concreto recolhido no início da concretagem e o concreto recolhido no intervalo recomendado pela norma.