Recycled aggregate from C&D waste & its use in concrete – A breakthrough towards sustainability in construction sector: A review

Properties and composition of recycled aggregates from construction and demolition waste suitable for concrete production

Construction and Demolition (C&D) waste constitutes a major portion of total solid waste production in the world, and most of it is used in land fills. Research by concrete engineers has clearly suggested the possibility of appropriately treating and reusing such waste as aggregate in new concrete, especially in lower level applications. This paper discusses different aspects of the problem beginning with a brief review of the international scenario in terms of C&D waste generated, recycled aggregates (RA) produced from C&D waste and their utilization in concrete and governmental initiatives towards recycling of C&D waste. Along with a brief overview of the engineering properties of recycled aggregates, the paper also gives a summary of the effect of use of recycled aggregate on the properties of fresh and hardened concrete. The paper concludes by identifying some of the major barriers in more widespread use of RA in recycled aggregate concrete (RAC), including lack of awareness, lack of government support, non-existence of specifications/codes for reusing these aggregates in new concrete.

Use of aggregates from recycled construction and demolition waste in concrete

Influence of moisture states of natural and recycled aggregates on the slump and compressive strength of concrete

Performance enhancement of recycled concrete aggregate – A review

Compressive strength, chloride diffusivity and pore structure of high performance metakaolin and silica fume concrete

Enhancing the durability properties of concrete prepared with coarse recycled aggregate

In this study, the fresh and hardened properties of self-compacting concrete (SCC) using recycled concrete aggregate as both coarse and fine aggregates were evaluated. Three series of SCC mixtures were prepared with 100% coarse recycled aggregates, and different levels of fine recycled aggregates were used to replace river sand. The cement content was kept constant for all concrete mixtures. The SCC mixtures were prepared with 0, 25, 50, 75 and 100% fine recycled aggregates, the corresponding water-to-binder ratios (W/B) were 0.53 and 0.44 for the SCC mixtures in Series I and II, respectively. The SCC mixtures in Series III were prepared with 100% recycled concrete aggregates (both coarse and fine) but three different W/B ratios of 0.44, 0.40 and 0.35 were used. Different tests covering fresh, hardened and durability properties of these SCC mixtures were executed. The results indicate that the properties of the SCCs made from river sand and crushed fine recycled aggregates showed only slight differences. The feasibility of utilizing fine and coarse recycled aggregates with rejected fly ash and Class F fly ash for self-compacting concrete has been demonstrated.

Properties of self-compacting concrete prepared with coarse and fine recycled concrete aggregates

Two types of nano-TiO2 particles were blended into cement pastes and mortars. Their effects on the hydration and properties of the hydrated cement pastes were investigated. The addition of nano-TiO2 powders significantly accelerated the hydration rate and promoted the hydration degree of the cementitious materials at early ages. It was demonstrated that TiO2 was inert and stable during the cement hydration process. The total porosity of the cement pastes decreased and the pore size distribution were also altered. The acceleration of hydration rate and the change of microstructure also affected the physical and mechanical properties of the cement-based materials. The initial and final setting time was shortened and more water was required to maintain a standard consistence due to the addition of the nano-TiO2. The compressive strength of the mortar was enhanced, practically at early ages. It is concluded that the nano-TiO2 acted as a catalyst in the cement hydration reactions.

Shi-Cong Kou

Papers

Compressive strength, chloride diffusivity and pore structure of high performance metakaolin and silica fume concrete

Enhancing the durability properties of concrete prepared with coarse recycled aggregate

Properties of self-compacting concrete prepared with coarse and fine recycled concrete aggregates

Hydration and properties of nano-TiO2 blended cement composites

Use of recycled aggregates in molded concrete bricks and blocks