Study of compressive strength of sand-lime bricks produced with coal tailings using mixture design

In this paper, the compressive strength of sand-lime bricks produced by replacing natural sand with coal mining tailings was studied and optimized using a response surface model obtained by mixture design of experiment techniques. Bricks with natural sand, coal tailings and hydrated lime were produced according to the proportions defined by the mixture design. The compressive strength of the bricks produced (4.99 MPa at 16.27 MPa) were used to obtain a cubic model (Scheffe ' polynomial) that relates the compressive strength as a function of the proportions of the raw material. The validated model was used to analyze the influence of variables and obtain which proportions of raw materials maximize this property. The results show that hydrated lime is the variable with the greatest impact on the compressive strength of bricks and the replacement of sand by tailings can affect compressive strength. As a result of the research, the mixing proportions that maximize the compressive strength were: without tailings (90% sand and 10% hydrated lime) with 21.96 MPa and with tailings (90% tailings and 10% hydrated lime) with 15.79 MPa.