Removal of cement mortar remains from recycled aggregate using pre-soaking approaches

Abstract

With a rising tide of adoption of recycled aggregate (RA) for construction, investigation on ways to improve the quality of RA has been overwhelming. The adoption of RA brings benefits including savings in the limited landfill spaces and the use of natural resources. However, the poorer quality of RA often limits its utilization to low grade applications such as sub-grade activities, filling materials and low grade concrete. The major reason that affects the quality of RA is the large amount of cement mortar remains on the surface of the aggregate, resulting in higher porosity, water absorption rates and thus a weaker interfacial zone between new cement mortar and aggregates, which weakens the strength and mechanical performance of concrete made from RA. This paper attempts to study three pre-soaking treatment approaches; namely ReMortar HCl , ReMortar H2SO4 and ReMortar H3PO4 in reducing the mortar attached to RA. The results show that the behaviour of RA has improved with reduction in water absorption, without simultaneous exceeding the limits of chloride and sulphate compositions after the treatment. This work has also compared the compressive strength, flexural strength and modulus of elasticity of concrete made from the approaches, which shows marked improvements in quality when compared with those using traditional approaches.

Feasibility of Using Nanoparticles of SiO2 to Improve the Performance of Recycled Aggregate Concrete

“…For these reasons, most codes of practice allow the natural aggregate in concrete to be only partially (20-30%) replaced by RA, especially in structural applications [6]. Many researchers have attributed this performance of RAC to the heterogeneous nature of the RA caused by the attached mortar exist on its surface [7,8].…”

“…Several studies focused on developing approaches to enhance the properties of the RA particles, whereas many other studies tried to improve the RAC properties through focusing on the technology of concrete production [1,10], for example, separating the mortar that is attached to the natural aggregate from its surface using different approaches [7,8,10]. Despite the fact that the properties of the RA particles were improved using these approaches, they resulted in several drawbacks such as energy consumption, compromising durability aspects, and high cost [1,8].…”

Water Absorption Study Recycled Aggregates for Use Pavement Material

“…As seen in ing to the stone particles in the RCA creates a relat ively weak, porous and cracked layer [13] thereby resulting in a decreased density of the RCA relative to NA. It is likely that the porous layer described above, in addition to residual unhydrated cement, lead to an increase in the water absorption rate of RCA [1].…”

Study of recycled concrete aggregate quality and its relationship with recycled concrete compressive strength using database analysis

“…There are different treatment options, with some authors proposing one or a combination of mechanical grinding processes (also increasing the number of crushing processes (171)), others using thermal treatments (microwave or conventional heating) (7) and, finally, others using chemical treatments (pre-soaking or cycle soaking the recycled aggregates in different acidic solvents, namely hydrochloric acid, sulphuric acid, and phosphoric acid) (172). In this regard, an investigation has been carried out that deals with the influence of different polymer treatments on recycled aggregates that has been already used in the protection of structures (grout, render, etc.)…”