Influence of porosity on thermal conductivity, mechanical strength and permeability coefficient of pervious concrete

Abstract

Aiming at the development of technologies for adaptation and mitigation of the effects of temperature increase in the civil construction sector, in order to promote better thermal-mechanical performance, this study aimed to evaluate the influence of porosity on the thermal conductivity of pervious concrete, evaluating its mechanical resistance and permeability coefficient. Pervious concrete was dosed by the method of Nguyen et al. (2014) with void rates of 15, 20, 25 and 30%. The permeability coefficient, the compressive strength and the flexural tensile strength were determined by Brazilian technical standards and their specific mass, total porosity and thermal conductivity by international standards. The statistical analysis of the results showed that only the tensile strength in flexion does not present a significant difference with the variation in porosity. The total porosity of the pervious concrete was 23.1, 28.9, 33.3 and 34.0%, respectively to the void indices used as an input parameter in the dosing method of 15, 20, 25 and 30%, whose specific masses ranged, respectively, from 2153 to 1857 kg.m^-3. The two lower porosity strokes reached compressive strength above 20 MPa, and the tensile strength in flexion of the four strokes was above 4.0 MPa. The average permeability coefficient of pervious concretes assumed values ​​between 8.2 and 21.8 ms^-1. The thermal conductivity and total porosity have an inversely linear relationship with excellent adjustment and their average values ​​decreased from 0.55 to 0.44 Wm^-1.K^-1 as the total porosity increased from 23.1 to 34.0%. In view of the above, it is considered that pervious concrete can be applied in civil construction as an alternative material for the purpose of improving thermal comfort, given its thermal conductivity, permeability coefficient and good mechanical performance, referring to the best performance feature, with voids index of 20% and total porosity of 23.1%.