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The concern about the environment has motivated several studies on the use of pozzolanic materials as a partial replacement for cement in concrete and mortar. However, there are few data about such a use in concrete designed for the production of precast elements, which is usually called dry or no-slump concrete, due to the low humidity required in the process of molding and pressing. This paper reports a preliminary study on the use of metakaolin in no-slump concrete, analyzing five concrete mixtures with five levels of substitution, in five curing times, aiming to determine the most appropriate percentages of replacement, i.e., those that promote increase in compressive strength and reduction in water absorption by immersion. Due to the large number of variables involved, the statistical experimental design named Central Composite Rotational Design (CCRD) was used, and the results were analyzed using the Response Surface Methodology (RSM). The response surface analysis showed that for all concrete mixtures, the best results within the parameters established can be found with the use of metakaolin in percentages of 10% at 20% of replacement in the cement mass at 49 days of curing.

Uso de metacaulim em concreto seco: uma abordagem por superfície de resposta