Thermal characterization of soil-cement bricks using mining tailings

Abstract

Soil-cement bricks are earth construction materials that have been gaining prominence due to their environmental advantages. The Brazilian Technical Standard NBR 8491 establishes physical and mechanical procedures to characterize these bricks. However, the thermal characterization is an important assessment, since it is related to the building’s thermal performance. The objective of this study is to thermally characterize a panel of soil-cement bricks produced with mining tailings. For such, its absorptance (α) was evaluated using the ALTA II spectrometer, and its thermal transmittance (U) and thermal resistance (R_T) through the hot box method (ISO 9869). The results enabled the calculation of the thermal capacity (C_T), thermal lag (φ) and solar factor (F_SO) of the panel, which were compared to the Brazilian Technical Standards NBR 15575-4 and NBR 15220 for Bioclimatic Zone 8. As a result, the soil-cement body panel showed values of α = 0.71, U = 2.47 Wm^-2K^-1, C_T = 273.4 kJm^-2K^-1, φ = 6.02 h and F_SO = 6.81%, meeting the requirements established in the first standard, but failing to attend the second. To comply with the Brazilians specifications, it is suggested to paint bricks with lighter colors focusing on decreasing its absorptance value. Thus, soil-cement bricks may be an environmental alternative to dispose of the waste generated during the mining process, contributing to sustainability.

Keywords:
compressed earth blocks; ecological bricks; hot box method; sustainable mining; tailings characterization