Condutividade térmica de concretos com nanosílica

Abstract

Nowadays, in Brazil, most buildings are dependent on high electricity consumption, a consequence of often disregarding strategies for thermal performance and energy efficiency of the built environment. In this context, several researches are being carried out to study the feasibility of incorporating additives and additions to concrete, targeting materials with lower thermal conductivities that achieve a better thermal performance. One of these additions is nanosilica, which has already been studied in relation to durability and compressive strength of concrete, but little is being explored regarding its thermal conductivity. In this direction, the addition of nanosilica provides a filler and pozzolanic effect in the cement matrix, which results in a greater refinement of the pores, however, in adequate levels and dosages, this partial substitution of cement by nanosilica is believed to cause an inverse effect, leading to the creation of small voids in the cement paste, reducing the density of concrete and significantly suppressing heat transfer. Thus, in this work, the effect of adding nanosilica to the thermal conductivity of concrete was studied from the development of concrete with the addition of 0%, 5% and 10% of colloidal nanosilica in mass substitution to cement. The specific mass, water absorption, void index, compressive strength and thermal conductivity of the developed concrete were evaluated, the results of which were analyzed by the Analysis of Variance (ANOVA) and later submitted to the Tukey test. In general, the results indicate that the addition of colloidal nanosilica causes a significant increase in the specific mass of the concrete, as well as in the compressive strength values for the traces with the addition of 10% of colloidal nanosilica in mass substitution to cement at the ages of 48 hours and 7 days. Regarding the thermal conductivity of the concrete studied, no significant variations were observed in their values, according to the Analysis of Variance, comparing the traces with and without the addition of colloidal nanosilica to the reference trace.