Mix Design and Properties of Recycled Aggregate Concretes: Applicability of Eurocode 2

Abstract

This work is devoted to the study of fresh and hardened properties of concrete containing recycled gravel. Four formulations were studied, the concrete of reference and three concretes containing recycled gravel with 30, 65 and 100 % replacement ratios. All materials were formulated on the basis of S4 class of flowability and a target C35 class of compressive strength according to the standard EN 206-1. The paper first presents the mix design method which was based on the optimization of cementitious paste and granular skeleton, then discusses experimental results. The results show that the elastic modulus and the tensile strength decrease while the peak strain in compression increases. Correlation with the water porosity is also established. The validity of analytical expressions proposed by Eurocode 2 is also discussed. The obtained results, together with results from the literature, show that these relationships do not predict adequately the mechanical properties as well as the stress-strain curve of tested materials. New expressions were established to predict the elastic modulus and the peak strain from the compressive strength of natural concrete. It was found that the proposed relationship E-f c is applicable for any type of concrete while the effect of substitution has to be introduced into the stress-strain (e c1 -f c ) relationship for recycled aggregate concrete. For the full stress-strain curve, the model of Carreira and Chu seems more adequate.

On Probability Distribution of Chloride Diffusion Coefficient for Recycled Aggregate Concrete

“…Compared with natural coarse aggregates (NCA), recycled coarse aggregates (RCA) have substantial characteristics in terms of uncertainties that arise from their complex composition (Wardeh et al 2015). It is well-known that the properties of recycled aggregate concrete (RAC) are different from those of natural aggregate concrete (NAC) (Yehia et al 2015;Wardeh et al 2015).…”

“…Compared with natural coarse aggregates (NCA), recycled coarse aggregates (RCA) have substantial characteristics in terms of uncertainties that arise from their complex composition (Wardeh et al 2015). It is well-known that the properties of recycled aggregate concrete (RAC) are different from those of natural aggregate concrete (NAC) (Yehia et al 2015;Wardeh et al 2015). Previous theoretical analyses carried out in the framework of structural reliability theory and lab experiments have shown that: (1) higher scatter of the compressive strength of RAC affects the margins of structural safety (Breccolotti and Materazzi 2010); (2) the compressive strength of RAC varies with the RCA replacement percentage and it follows a normal probability distribution (Li et al 2006); and (3) the durability of RAC can be strongly affected by the porosity and the high water absorption of the RCA (Debieb et al 2010;Kou and Poon 2006).…”

Freeze–Thaw Resistance and Drying Shrinkage of Recycled Aggregate Concrete Proportioned by the Modified Equivalent Mortar Volume Method

“…It was pointed out in 17 studies (Fathifazl 2008) that the elastic modulus of RCA concrete decreased by 0-45%, compared to that of the companion natural aggregate concrete. Other researchers also confirmed that RCA concretes had lower elastic modulus than normal aggregate one (Tavakoli and Soroushian 1996;Eguchi et al 2007;Padmini et al 2009;Limbachiya et al 2012;McNeil and Kang 2013;Wardeh et al 2015). This means that the elastic modulus of RCA concrete is a function of that of the mortar and also has a proportional relationship with the volume of the mortar (Fathifazl 2008).…”

Physical and mechanical characteristics of recycled aggregate obtained from construction and demolition waste.

“…Se pudo observar que la densidad de los agregados reciclados es menor en relación con los naturales; esta leve disminución se debe también a aquella fracción de mortero que queda adherido y cuya porosidad es mayor a la piedra natural lo cual genera que la densidad se vea levemente afectada (Safiuddin, 2011, McNail, K y Kang, 2013Wardeh et al, 2014).…”