Properties of high-workability concrete with recycled concrete aggregate

Abstract

This study presents the effects of recycled concrete aggregate (RCA) on the key fresh and hardened properties of concrete. RCA was used to produce high-workability concrete substituting 0-100% natural coarse aggregate (NCA) by weight. The slump and slump flow of fresh concretes were determined to ensure high workability. In addition, the compressive, flexural and splitting tensile strengths, modulus of elasticity, and permeable voids of hardened concretes were determined. The test results revealed that RCA significantly decreased the workability of concrete. RCA also affected the compressive strength, modulus of elasticity, and permeable voids of concrete. At the age of 28 days, the concrete with 100% RCA provided 12.2% lower compressive strength and 17.7% lesser modulus of elasticity than the control concrete. Also, 100% RCA increased the permeable voids of 28-day old concrete by 8.2%. However, no significant negative impact of RCA was observed on the flexural and splitting tensile strengths of concrete.

Evaluation of Industrial By-Products as Sustainable Pozzolanic Materials in Recycled Aggregate Concrete

“…This could be attributed to the surface roughness and greater angularity of RA because of the adhered old mortar on its surface, which decreases the workability of concrete and makes it more difficult to finish properly. The trend of decreasing the slump of RAC observed in this study also confirmed the reported findings in previous research by Safiuddin et al (2011) [45], which was due to the porous adhered cement paste on the RA, and thus, increased the overall water absorption and decreased its workability. The slump values of concrete containing RHA decreased compared to the control RAC as the replacement ratio was increased.…”

Use of Recycled Concrete Aggregate in Concrete: A Review

“…In their study, the NCA concrete gained strength gradually and had a higher flexural strength than RCA concrete at later age. Safiuddin et al (2011a) reported that RCA did not produce any significant negative impact on the flexural strength of concrete. Nevertheless, RCA concrete with adequate flexural strength can be produced for different applications, sometimes even with 100% replacement of NCA (Yrjanson 1989; ACI 555R-01 2001).…”

“…The magnitude of the effects varies with the nature and quantity of reclaimed cement paste/mortar that is present in RCA (ACPA 2009). The basic physical properties of RCA summarized from the available literature (Hansen 1992;ECCO 1999;González-Fonteboa, Martínez-Abella 2008;Anderson et al 2009;Safiuddin et al 2011a) are shown in Table 1 and discussed hereafter.…”

“…This is due to the porous nature of adhered cement paste/mortar originated from old concrete (González-Fonteboa, Martínez-Abella 2008;Safiuddin et al 2011a). The higher pore volume of RCA makes it weak and less dense, as compared to NCA.…”

“…In addition, the higher pore volume of RCA can affect the porosity, strength, and transport properties (water absorption, permeability, etc.) of concrete (Safiuddin et al 2011a). …”