Effects of contaminants on the properties of concrete paving blocks prepared with recycled concrete aggregates

The use of recycled aggregates for preparing concrete products has been successfully implemented and gaining wider acceptance. However, the allowable level of contaminating materials (e.g., crushed clay bricks, crushed ceramic tiles, waste glass cullet, wood chips, etc.) in the recycled concrete aggregate, in the some of the current specifications, is low (<1%) due to stringent quality control standards that are usually taken from specifications for raw granular virgin materials. This paper presents a recent study on the properties of concrete paving blocks prepared with recycled concrete aggregates that are contaminated by materials (tiles, clay bricks, glass, wood) commonly found in the construction and demolition waste. The density, compressive strength, tensile splitting strength, water absorption value, abrasion resistance, skid resistance and some durability parameters were measured for laboratory prepared samples. The results show that it is feasible to allow a higher level of contamination in the recycled concrete aggregates for making the concrete products. Recommendations are made on how the specifications could be revised to facilitate a wider application of recycled aggregates that is contaminated by foreign materials.