Use of recycled concrete aggregates from precast block for the production of new building blocks: An industrial scale study

Abstract

Large amounts of construction and demolition (C&D) waste are generated annually and will increase in the future. Until now, only a small fraction of concrete by-products is re-used as recycled concrete aggregates (RCA) for the manufacture of concrete. In this paper, the feasibility of using RCA obtained from old precast concrete block was investigated for the industrial scale production of new blocks. Concrete building blocks with different substitution rates (0%, 30% and 100%) of natural aggregates (NA) by the same volume fraction of RCA were manufactured in a factory and the mechanical properties and durability of concrete blocks were monitored. The results show that incorporating RCA slightly decreases the compressive strength and impairs the durability of concrete blocks. However, the compressive strength of concrete blocks made with 100% RCA could reach 11.1 MPa after 28 days, which 2 is within the requirement in Belgian codes for this type of block. The concrete blocks produced with 30% and 100% of RCA reached the strength, capillary water absorption, drying shrinkage and freeze-thaw resistance requirements for concrete blocks specified by Belgian codes. A cradle-to-gate life cycle assessment (LCA) was performed on both "classical" blocks with only NA and with substitution of NA by RCA. When considering the additional use of RCA from a nearby C&D waste recycling centre, the substitution of 30% or 100% of NA by RCA led to a reduction in the land use category, in addition to supporting the implementation of the circular economy.

Use of Recycled Fine Aggregates from C&DW for Unbound Road Sub-Base

“…RCA are composed of a mix of natural aggregates and adherent hardened cement paste [ 29 , 30 , 31 , 32 ]. The latter is usually much more porous than natural aggregates [ 33 , 34 ] and leads to a large water demand which makes RCA less easy to recycle into concrete [ 1 , 35 , 36 , 37 ]. Properties of RCA such as water absorption and porosity can deeply influence the fresh properties of concrete as well as mechanical properties and durability of concrete made with RCA [ 16 , 38 , 39 , 40 , 41 ].…”

Modelling thermal and humidity transfers within green roof systems: effect of rubber crumbs and volcanic gravel

“…These issues can be somewhere solved by the substitution of natural aggregates with recycled materials and porous aggregates such as rubber crumbs, volcanic porous gravel, and the crushed brick, reducing the consumption of natural materials and providing a suitable thermal behaviour in the extensive green roof, as already confirmed by other researchers (Coma et al 2016;Berardi et al 2014;Jafari and Toufigh 2017;. In addition, the recycled and porous materials have greater porosity and more water retention capacity than the natural aggregate Zhao et al 2020;Courard et al 2020), providing a suitable condition to irrigate the vegetation of green roofs, particularly during the warm periods. In this regard, to save the raw materials, the recycled crushed brick was proposed by Ngan (2004) to be utilized for the drainage layer and growing media.…”

Alternative hydraulic binder development based on brick fines: Influence of particle size and substitution rate

“…In view of all the results obtained (comparison between performances and energetic cost), the B2 fines would present the best compromise in accordance with the results. Of course, other parameters should be taken into account (transport, resources,...) for an accurate evaluation of environmental impact and life cycle analysis [40,41].…”