Pre-treatment of Recycled Concrete Aggregates with Sulphuric Acid and Water: Effect on Strength and Water Absorption

Abstract

The use of recycled aggregates obtained from construction and

demolition waste can generally result in the conservation of natural

aggregates and a decrease in the need for landfills. However, one

major issue surrounding the use of recycled aggregates is the

cement paste that is attached to the surface of the aggregates, which

will need to be removed. In this paper, two methods were adopted

for the removal of the adhered cement paste on the surface of the

recycled aggregates – one involving the use of water and the other

involving the use of dilute sulphuric acid. Five concrete mixes were

prepared – four using the treated recycled concrete aggregates and

a control mix prepared with natural aggregates. Compressive

strength and water absorption tests were conducted on the

hardened concrete samples. The results obtained showed that

concretes made from recycled concrete aggregates have inferior

strength and water absorption properties to those made from

natural aggregates. Comparing the two methods of treatment, it

was observed that higher strengths were obtained for the concrete

samples containing water treated recycled aggregates, while lower

water absorption values were obtained for the concrete samples

containing acid treated recycled aggregates. Based on the findings

of the study, it was seen that there is potential in the use of recycled

concrete aggregates in the production of concrete for structural

applications