CONCRETO PERMEÁVEL COM AGREGADO RECICLADO: OTIMIZAÇÃO DE TRAÇO COM ANÁLISE MULTIPARAMÉTRICA

Abstract

A proper pervious concrete grade is fundamentally based on its permeability and its mechanical strength, despite these features being on opposite ends of the spectrum. In Pervious Concrete with Recycled Concrete Aggregate (RCA), balancing these two characteristics, is even a greater challenge due to its properties such as unit mass and specific mass being lower and water absorption higher in RCA than in Regular Concrete. Therefore, most studies have shown that there is a decrease in mechanical strength when using RCA. Despite being similar to pervious concrete with natural aggregate (NA), making pervious concrete with recycled concrete aggregate (RCA) cannot be carried out only by replacing one type of aggregate for another equivalent. This paper aimed to analyze and define pervious concrete mix ratio with recycled aggregate focusing on optimizing mechanical strength and permeability. Through preliminary tests and literature review, two variables had been defined [water/cement (w/c) and cement: aggregate] in three mix proportion levels (maximum, central, and minimum), in a total of nine mix ratios, which were tested for mechanical strength and hydraulic properties. Permeability had not been a limiting factor because all batches had always been above the minimum standard (10-3 m.s-1) to be considered a pervious concrete according to Brazilian regulations. All mix ratios had reached an average of at least a bending tensile strength of 1.0 MPa, making it possible to be used as pervious concrete cast on site for Pedestrian Walkways. Some mix ratios had reached averages greater than 2.0 MPa, which can be used in lightly trafficked pavements according to ABNT/NBR (Brazilian Norms acronym) 16416. A greater volume of cement paste had resulted in a greater mechanical strength, regardless of its w/c content. The use of RCA aggregate had been the main limiting factor to reach higher mechanical strengths. Through statistical analysis, strong positive correlations between the amount of cement paste and mechanical strength, and strong negative correlations between permeability and void content had been found.