Abstract
Recycled aggregates were widely used in the concrete industry as a replacement of natural aggregates in the last two decades. In this study, the resistance of concrete mixtures having various levels of recycled aggregate as a replacement of natural coarse aggregate to the attack of magnesium and sodium sulfates was investigated. Five mixtures made with 0%, 25%, 50%, 75%, and 100% recycled aggregate were partially immersed in magnesium and sodium sulfate solutions having concentrations of 2.5%, 4.5%, and 6.5% and subjected to drying-wetting cycles for a total of 10 weeks. Mass losses of concrete specimens owing to the attack of sulfate solutions and the effect of drying-wetting cycles were recorded weekly. Results show that the incorporation of recycled aggregate decreased the compressive strength of concrete at ages of 7 and 28 days. The decline in the compressive strength was more significant when the replacement percentage exceeds 50%. Mass losses of concrete specimens were found to be increased as the level of recycled aggregate increased. Mass losses of concrete specimens having 100% recycled aggregate were approximately as twice as those of concrete specimens having 0% recycled aggregate owing to 10 weeks of partial immersion in magnesium sulfate solutions of concentrations of 2.5%, 4.5%, and 6.5%. The attack of sodium sulfates was less aggressive than that of the magnesium sulfates. Results also show that the reduction in the compressive strength is directly proportional to the mass loss following a linear equation of R-squared value of 0.937.
Highlights
After 2003 and because of the unstable security situation in Iraq, hundreds and thousands of concrete walls were manufactured and used to protect the government and private buildings
The research on the durability of recycled concrete under the joint action of dryingwetting and sulfate attack is scarce and is almost limited to evaluating mass loss of recycled aggregate concrete (RAC) specimens exposed to 50 g/l sodium sulfate solution under drying-wetting cycles [26]
As a step forward, this paper investigates reduction in compressive strength of RAC mixtures with different replacement rates of recycled coarse aggregates under magnesium and sulfate attack
Summary
After 2003 and because of the unstable security situation in Iraq, hundreds and thousands of concrete walls were manufactured and used to protect the government and private buildings. E effect of using RA, as a partial or complete replacement of coarse aggregate, on different properties of concrete was extensively investigated by many research studies. Ere are some research studies about the effect of sulfate attack or drying-wetting on recycled aggregate concrete in the accessible literature. The research on the durability of recycled concrete under the joint action of dryingwetting and sulfate attack is scarce and is almost limited to evaluating mass loss of RAC specimens exposed to 50 g/l sodium sulfate solution under drying-wetting cycles [26]. As a step forward, this paper investigates reduction in compressive strength of RAC mixtures with different replacement rates of recycled coarse aggregates under magnesium and sulfate attack. A relationship between mass loss and reduction in compressive strength of specimens partially immersed in various concentrations of sulfate solutions is stipulated
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