Abstract
Abstract Cement is considered the basic component with the highest environmental impact in construction, in terms of CO2 emissions. As for the aggregates, the process of comminution of rocks, in addition to artificial sand, generates stone powder that ends up being stored outdoors, generating environmental damages. Thus, the replacement of cement by stone powder appears as an attractive alternative towards the sustainable concretes. In this context, the objective of this paper is to determine the maximum packing density in Portland cement, silica fume and stone dust pastes, to determine the optimal cement substitution content for the stone powder. In addition, it is intended to verify the influence of excess water on the consistency of the mixtures produced. The substitution was done in contents equal to 0%, 7%, 14% and 21% by volume and, for each content, the packing density was determined analytically by CPM model and combinations were reproduced experimentally. Excess water was checked by the mini Kantro cone test. The results showed that the higher cement substitution content of the stone powder obtained the higher packing density, experimental and analytical, and the higher workability, allowing economic and environmental advantages. Analyzing each material, the stone powder resulted in the highest packing density and silica fume is the lowest one. Therefore, finer particles resulted in lower packaging densities, due to the greater specific surface area, which demands more water. The agglomeration resulted in more empty gaps between the grains. In addition, mixtures flowability increased with the increase of the stone powder content. As the excess water is responsible for mixture lubrication, a higher packing density for a given volume of water improves the flowability.
Highlights
Sand natural extraction is responsible for vegetal cover removal, water courses degradation and environmental damage, which makes it difficult to obtain environmental licenses for new deposits [1; 2; 3; 4]
For silica fume it is not plausible to perform this test, since it would demand SP content much higher than the other materials and that recommended by the manufacturer. n The stone powder presented the highest value of packing density, when the materials were analyzed separately, due to a wider particle size distribution. n According to results obtained by applying CPM [16] and experimental method [14], paste composition with 68% Portland cement, 21% stone powder and 11% silica fume by volume was which had the highest particle packing density
This corresponds to values of 74% Portland cement, 18% stone powder and 8% silica fume, by mass. n Due to the high fineness of silica fume particles, the packing density of this material was much lower than cement and stone powder
Summary
Sand natural extraction is responsible for vegetal cover removal, water courses degradation and environmental damage, which makes it difficult to obtain environmental licenses for new deposits [1; 2; 3; 4]. Conciling the need to reduce cement consumption in concrete with the use of crushing waste, such as stone powder, is an eco friendly alternative. It should be noted, that the stone powder is an inert material with a grain size greater than cement [4; 8], which makes it difficult to use this residue in obtaining higher resistances. The cement paste can be considered as a fluid that acts as a binder between aggregates grains This reduction in paste consumption contributes to lower shrinkage and creep and, a more resistant, durable and eco friendly concrete [13; 14]. It is intended to verify the influence of excess water on the consistency of the pastes produced
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