Abstract
The present study was conducted to experimentally verify if the coefficient of thermal expansion (COTE) of recycled aggregate concrete is proportional to the volume of the original virgin aggregate in the total recycled aggregate concrete mix. Three types of recycled concrete aggregate (RCA) were crushed from: railroad concrete sleepers; precast (PC) culverts; commercial recycling plant. RCA concretes were mixed using two concrete mixing methods: conventional mix method and equivalent mortar volume (EMV) method. And by varying the replacement ratio, three test series were made. Test results showed that at the same RCA replacement ratio of 68%, the COTE of RCA concrete prepared by the EMV mix design was over 6–7% lower than that of RCA concrete made with the conventional mix method. It was also similar to or 1–2% lower than that of the natural coarse aggregate concrete. This may be because the conventional mix method does not take into account the residual mortar content attached to RCA. This results in a decrease in the volumetric ratio of the original virgin aggregate and a relative increase in the volumetric ratio of the mortar (or cement paste).
Highlights
Smith [36,37] reported that the coefficients of thermal expansion (COTE) decreased by up to 40% as recycled concrete aggregate (RCA) replacement ratio increased by 50%, and explained that the cause of the decrease was the use of high-quality RCA
In Equation (1), WRCA denotes the weight of RCA dried in a dryer after the first sampling; WOVA is the weight of the original virgin aggregate (OVA) obtained by drying the sample in a dryer after removing the residual mortar (RM)
At the same RCA replacement ratio of 68%, the COTE of RCA concrete prepared by equivalent mortar volume (EMV) mix design was over 6–7%
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Our previous study showed that the COTE of concrete with 100% RCA replacement ratio increased by 5–9% in comparison with that of reference concrete containing natural aggregates [25]. Khayat and Sadati [34] reported that RCA concrete of which replacement ratio was within 15–40% did not show a significant difference in the COTE compared to the conventional concrete. Smith [36,37] reported that the COTE decreased by up to 40% as RCA replacement ratio increased by 50%, and explained that the cause of the decrease was the use of high-quality RCA (with limestone as the original virgin aggregate). One of the main purposes of the present study was to examine the difference of the COTE between the two mixes
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