Optimal Allowable Residual Mortar Content in Recycled Aggregates Crushed from Parent Concrete Implementing Different Waste Materials

摘要

The reuse of certain industrial and construction waste materials as a substitute to certain conventional materials in concrete mixtures will diminish the environmental problems that may be generated by diverting these materials to the landfill in addition to the conservation of raw materials. However, using concrete having waste materials (parent concrete) to produce recycled aggregates and to substitute partially natural aggregates, will adversely affects the quality of the new concrete. The type of waste material in the parent concrete and the adhered mortar attached to the natural aggregate particles are main factors affecting the obtained concrete quality. Therefore, this study has focused on detecting the acceptable amount of adhered mortar on the recycled aggregates without significantly affecting concrete properties. The ultrasonic pulse velocity has been implemented as an indication of concrete quality. The results showed that the type and the amount of the old residual mortar content (RMC) have significant effect on the behaviour of ultrasonic pulses in concrete, and hence on its strength. The results indicate that 10% RMC will have accepted reduction in concrete strength.