Abstract
Recycled aggregate concrete (RAC), i.e., concrete produced with recycled concrete aggregate (RCA) has been heavily investigated recently, and the structural design of RAC is entering into design codes. Nonetheless, the service load deflection behavior of RAC remains a challenge due to its larger shrinkage and creep, and lower modulus of elasticity. A novel solution to this challenge is the use of layered concrete, i.e., casting of horizontal layers of different concretes. To investigate the potential benefits and limits of layered concrete, this study contains a numerical parametric assessment of the time-dependent sustained service load deflections and environmental impacts of homogeneous and layered NAC and RAC one-way slabs. Four types of reinforced concrete slabs were considered: homogeneous slabs with 0%, 50% and 100% of coarse RCA (NAC, RAC50 and RAC100, respectively) and layered L-RAC100 slabs with the bottom and top halves consisting of RAC100 and NAC, respectively. In the deflection study, different statical systems, concrete strength classes and relative humidity conditions were investigated. The results showed that the layered L-RAC100 slabs performed as well as, or even better than, the NAC slabs due to the differential shrinkage between the layers. In terms of environmental performance, evaluated using a “cradle-to-gate” Life Cycle Assessment approach, the L-RAC100 slabs also performed as well as, or slightly better than, the NAC slabs. Therefore, layered NAC and RAC slabs can be a potentially advantageous solution from both structural and environmental perspectives.
Highlights
The use of recycled concrete aggregate (RCA) in the production of recycled aggregate concrete (RAC) is a promising way of addressing the sustainability challenges of concrete construction
The results presented in this study are based only on numerical analyses and assumptions adopted in the Life Cycle Assessment (LCA) model, they provide a strong impetus for further experimental research on layered natural aggregate concrete (NAC) and Recycled aggregate concrete (RAC) slabs as a structurally and environmentally advantageous solution
This paper presented the results of a numerical structural deflection and environmental assessment of layered and homogeneous NAC and RAC one-way slabs
Summary
The use of recycled concrete aggregate (RCA) in the production of recycled aggregate concrete (RAC) is a promising way of addressing the sustainability challenges of concrete construction. FGMs can be defined as materials whose composition, structure or properties change over any direction [13] Within this topic, Xiao [14] used RAC and NAC to produce functionally graded concrete (FGC) and conducted ultimate load testing of one-way slabs produced with layers of RAC (with 50% and 100% of coarse RCA) and NAC, distributed in three horizontal layers. In order to fill this knowledge gap, this paper describes a comprehensive numerical study on the time-dependent service load deflection and environmental assessment of FGCs incorporating RAC For this purpose, a parametric study is conducted on one-way reinforced concrete slabs, designed according to ultimate limit states (ULS) and serviceability (i.e., deflection) limit states (SLS), and compared in terms of time-dependent sustained service load deflection behavior and environmental impact using LCA. The results are complemented with LCA to holistically present the optimal configuration of concrete for one-way slabs
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