Deflection control for reinforced recycled aggregate concrete beams: Experimental database and extension of the fib Model Code 2010 model

Recycled aggregate concrete (RAC) has emerged as a viable solution for solving some of the environmental problems of concrete production. However, design guidelines for deflection control of reinforced RAC members have not yet been proposed. This study presents a comprehensive analysis of the applicability of the fib Model Code 2010 (MC2010) deflection control model to reinforced RAC beams. Three databases of long-term studies on natural aggregate concrete (NAC) and RAC beams were compiled and meta-analyses of deflection predictions by MC2010 were performed. First, the MC2010 deflection control model was tested against a large database of long-term tests on NAC beams. Second, a database of RAC and companion NAC beams was compiled and initial and long-term deflections were calculated using the MC2010 model. It was shown that deflections of RAC beams are significantly underestimated relative to NAC beams. Previously proposed modifications for MC2010 equations for shrinkage strain and creep coefficient were used, and new modifications for the modulus of elasticity and empirical coefficient β were proposed. The improved MC2010 deflection control model on RAC beams was shown to have equal performance to that on companion NAC beams. The proposals presented in this paper can help engineers to more reliably perform deflection control of reinforced RAC members.This is the peer-reviewed version of the article: N. Tošić, S. Marinković, and J. de Brito, ‘Deflection control for reinforced recycled aggregate concrete beams: Experimental database and extension of the fib Model Code 2010 model’, Structural Concrete, vol. 20, no. 6, pp. 2015–2029, 2019 [https://doi.org/10.1002/suco.201900035

Shear strength of reinforced recycled concrete beams without stirrups

A new method of mixture proportioning is used for investigating the shear performance of reinforced concrete (RC) beams made with coarse recycled concrete aggregate (RCA). In this method, RCA is treated as a two-phase material comprising mortar and natural aggregate therefore to proportion the concrete mixture with RCA, the relative amount and properties of each phase are considered separately. Using the new mix proportioning method, several beams were designed and tested to study the effect of a number of parameters including the shear span-to-depth ratio and beam size on the serviceability and strength of RCA concrete beams without shear reinforcement. For each beam its load–deflection curve, shear deformations, diagonal cracking load, crack pattern, ultimate shear strength and failure mode were determined. The results showed that the shear performance of RC beams made with RCA can be comparable, or even superior, to that of beams made entirely with natural aggregates at both serviceability and ultimate limit states, provided the proposed mixture proportioning method is used. Furthermore, the simplified methods of ACI and CSA standards as well as Eurocode 2 were found applicable to all reinforced RCA-concrete beams. </jats:p

Shear strength of reinforced recycled concrete beams with stirrups

An experimental study is conducted to investigate the shear behaviour and strength of concrete beams made with coarse recycled concrete aggregate. The distinguishing feature of the beams is the manner in which their concrete mixture is proportioned. A new method of concrete mixture proportioning is used wherein recycled concrete aggregate is treated as a two-phase material comprising residual mortar and natural aggregate, and the relative amount and properties of each phase are considered. Using this method, several beams are made of recycled concrete aggregate-concrete and tested to study their serviceability and shear strength. For each beam its load–deflection curve, shear deformations, diagonal cracking load, crack pattern, ultimate shear strength, and failure mode are determined. The results show that the shear performance of reinforced recycled concrete aggregate-concrete beams is comparable, or even superior, to that of beams made entirely with natural aggregates at both the serviceability and ultimate limit states, and the current Canadian Standards Association, American Concrete Institute and Eurocode provisions for shear design can be used without any modification to design recycled concrete aggregate-concrete beams, provided the aforementioned mixture proportioning method is used. </jats:p