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The main characteristic of ready mix mortar is to remain workable for up to 72hours after mixing. This greater duration of workability is obtained by use of hydration stabilizing admixtures and air-entrained admixtures. Thus, the behavior of this mortar depends on the compatibility between Portland cement and these two admixtures. Within this context, the objective of this article is to evaluate the influence of Portland cement type and water content on the properties of ready mix mortars in fresh state. Three types of Portland cement and four water/dry material ratios were evaluated. The produced mortars were analyzed with respect to their properties in fresh state: consistency index, specific gravity, air entrained content and rheological behavior by squeeze-flow. The properties were determined for three storage durations (0, 24 and 48 hours). The results show that both types of cement (mainly, the rheological behavior) and water content (mainly, the air entrained content, consistency and rheological behavior) influenced the ready mix mortar properties. Therefore, these two parameters must be evaluated for mortar dosages in order to obtain the required properties in fresh state.

Resumo O desenvolvimento de novas tecnologias e o incentivo ao reaproveitamento de resíduos vêm crescendo em função da redução dos prazos nas construções e da preocupação com o meio ambiente. O objetivo deste trabalho foi avaliar a influência da adição de resíduo de polimento de porcelanato (RPP) proveniente de dois lotes de uma empresa em argamassas autoadensáveis. Foram mantidos constantes a relação água/cimento e os teores de aditivos para cada porcentagem de adição de RPP. Observou-se que a granulometria e a área superficial específica afetaram a fluidez e as propriedades mecânicas. A adição do RPP0 (menor área superficial específica e partículas mais grossas) resultou em menor teor de ar incorporado e o aumento de resistência a partir de 10% de adição. Já, o RPP1 (área superficial específica maior e partículas mais finas) diminuiu a fluidez das argamassas mantendo alto o teor de ar incorporado, resultando em ganhos menores de resistência à compressão. Os resultados demonstraram que a influência do teor ar incorporado prevaleceu sobre a possível melhora no empacotamento das partículas e o efeito de nucleação. No entanto, independente do teor e tipo de RPP utilizado, os resultados viabilizaram o uso desses finos em argamassas autoadensáveis.

Quarries have invested in equipment to increase production and improve the quality of their products, such as vertical shaft impact crushers (VSI). This type of crusher works with autogenous comminution of the material to improve the shape of the coarse aggregates. However, there are few studies about the influence of crushers in the shape of fine aggregate grains. In this context, gneiss and granite fine crushed aggregates, produced in cone crushers and VSI were studied. Parameters such as coefficient of volumetric shape, aspect ratio, and circularity were used to compare these aggregates with the river sand. The results showed that there is a difference between the shape of the sand river and the fine crushed aggregates. Among the crushed aggregates, those from the VSI showed improvements in grain shape, compared to aggregates from cone crushers. However, this improvement decreases with the reduction of grain size. Mortars produced with the studied aggregates were also evaluated. It was verified their influence on the consistency, the air content and compressive strength at 28 days. For the study in the mortar, the crushed aggregates were separated in fractions by sieving and composed to obtain the same granulometric distribution for all the aggregates. The mortars made with the crushing aggregates from the VSI showed higher fluidity, lower air content and higher compressive strength when compared to the crushed aggregates produced in the cone crusher.