A Study on the Mechanical Properties of Recycled Aggregate Concrete based on Bonded Mortar Content

Abstract

Sustainable development is gaining recognition around the globe these days. Governments are under pressure, on many fronts, to drive in sustainable development in policies, practice, and operations to secure the planet’s future. Adding to this, increased populations, and the need for more infrastructures, have unfortunately led to the unacceptable depletion of raw materials, increasing amounts of construction waste and increased deterioration of the natural environment in many places worldwide. Demolition of existing concrete structures produces a massive quantity of Recycled Aggregate (RA). RA mainly composed of two materials of different nature: natural aggregate and bondedmortar. Presently, due to lack of confidence on the quality and properties of RA, it is being used in low-quality concrete, subgrade applications and as filling material. Literature shows that Bonded Mortar Content (BMC) is responsible for higher water absorption and porosity of RA. Consequently, it is necessary to determine the BMC for reuse in making Recycled Aggregate Concrete (RAC). This objective of the study is to determine the BMC accurately and to relate to the RAC properties such compressive strengths. This aspect can be useful for recycling plants, as they will be able to adjust the production processes to improve aggregate quality for example by means of several crushing processes. This thesis attempts to study three pre-soaking treatment approaches: 1:3 HCl, 1:6 HCl and 35% Na2SO4 in reducing the mortar attached to RA. The results show that the behavior of RA has improved with reduction in water absorption. This work has also compared the compressive strength of concrete made from the approaches, which shows marked improvements in quality when compared with those using traditional approaches.