Evaluation of compressive strength, porosity and interstitial transition zone in mortars with recycled fine aggregates

The use of recycled aggregates in substitution to natural materials is increasing in civil construction, aiming to solve problems from the construction industry regarding supply of natural raw materials and cost of providing adequate desti-nation for waste materials. While the use of coarse aggregate is already relatively accepted, the viable application of re-cycled fine aggregate still demands more research. The present work had the objective of evaluating a recycled fine ag-gregate originated from construction and demolition waste available at Distrito Federal. Therefore, two mortars were produced, one reference (ARN) using all fractions of Brazilian standard sand, and one using recycled aggregate (AR1). Those mortars were subjected to compressive strength tests and mercury intrusion porosimetry at 3, 7, and 28 days of curing, and to scanning electron microscopy, only at 28 days. It was observed that the use of recycled aggregates in-creased the total porosity of the mortars, decreased the pore structure refinement and increased the width of microcracks located in the transition zone. As a consequence, mechanical performance was 15% inferior to the reference mortar at all ages.