Evaluating the use of recycled aggregates in concrete to achieve sustainability in the construction sector

Abstract

There is a growing global trend towards achieving sustainability in construction by finding practical solutions for recycling construction and demolition waste. This transforms the waste from an environmental problem into a valuable resource, providing an effective way of securing sustainable building materials.

Research in this field has increased significantly.

This study aims to evaluate the feasibility of using recycled aggregate in structural elements. A stress-strain diagram was developed for concrete made with recycled aggregate at replacement rates of 50%, 75% and 100%. The study then involved an experimental programme involving reinforced concrete columns measuring 20 x 20 x 100 cm with longitudinal reinforcement of 4T12 mm and 11 transverse bracing bars, each with a diameter of 8 cm, reinforced at the top and bottom. These columns were constructed using concrete with 50%, 75% and 100% recycled aggregate. A plasticiser was added to improve workability. Experiments were conducted at two values of bidirectional eccentricity: E1 (180 x 100 mm) and E2 (230 x 100 mm). Finally, a programme was developed in Visual Basic for Applications (VBA) – Excel to analyse the cross-section of a rectangular column subjected to bidirectional eccentricity, and to compare the experimental results with those obtained from recycled aggregate.

The results revealed a high degree of similarity in the stress-strain diagrams for natural and recycled aggregates, with a lower peak and increased deformation in the downward branch. Concrete strength decreased by 7.5%, 15% and 18.8% when recycled aggregate was used at 50%, 75% and 100% respectively.

The research concluded that recycled aggregate can be used in specific proportions, provided that good particle grading is achieved and a suitable plasticiser is added. The failure mechanism was similar in columns subjected to eccentric compression and constructed with natural aggregate compared to those constructed with recycled aggregate. The experimental and analytical results

were similar.