Investigation of mechanical and durability properties of lightweight concrete with waste rubber aggregate

This thesis investigates the effects of substituting fine raw perlite aggregate with different ratios of fine waste rubber aggregate (FWRA) on lightweight concrete produced using raw perlite aggregate. In the study, a total of seven different lightweight concrete series were prepared, including a reference mix without FWRA, as well as those produced by substituting 5%, 10%, 20%, 30%, 40%, and 50% FWRA for fine raw perlite aggregate. The prepared concrete samples were subjected to compressive strength, splitting tensile strength, ultrasonic pulse velocity, electrical resistivity, water absorption, capillarity, and freeze-thaw tests after 28 days of curing. Some of these tests were also performed after 90 days of curing to investigate the effect of curing time. The findings show that increasing the FWRA substitution ratio leads to a decrease in density, mechanical properties, and ultrasonic pulse velocity of the lightweight concrete, while capillarity coefficients and water absorption percentages increase. Electrical resistivity decreased with FWRA substitution up to 30%; however, higher substitution ratios resulted in increased electrical resistivity, with the highest value observed in concrete containing 50% FWRA. Data from freeze-thaw tests revealed that FWRA-containing concrete exhibited better freeze-thaw resistance. SEM images were consistent with data from tests. Overall, a 5% FWRA substitution appears to be the most suitable option for lightweight concrete production, while substitution levels above 10% lead to a noticeable deterioration in concrete properties.