Influence of Parent Concrete Properties on Compressive Strength and Chloride Diffusion Coefficient of Concrete with Strengthened Recycled Aggregates

Abstract

Parent concrete coming from a wide range of sources can result in considerable differences in the properties of recycled coarse aggregate (RCA). In this study, the RCAs were obtained by crushing the parent concrete with water-to-cement ratios (W/Cparent) of 0.4, 0.5 and 0.6, respectively, and were strengthened by carbonation and nano-silica slurry wrapping methods. It was found that when W/Cparen was 0.3, 0.4 and 0.5, respectively, compared with the mortar in the untreated RCA, the capillary porosity of the mortar in the carbonated RCA decreased by 19%, 16% and 30%, respectively; the compressive strength of concrete containing the carbonated RCA increased by 13%, 11% and 13%, respectively; the chloride diffusion coefficient of RAC (DRAC) containing the nano-SiO2 slurry-treated RCA decreased by 17%, 16% and 11%; and that of RAC containing the carbonated RCA decreased by 21%, 25% and 26%, respectively. Regardless of being strengthened or not, both DRAC and porosity of old mortar in RCAs increased with increasing W/Cparent. For different types of RCAs, DRAC increased obviously with increasing water absorption of RCA. Finally, a theoretical model of DRAC considering the water absorption of RCA was established and verified by experiments, which can be used to predict the DRAC under the influence of different factors, especially the water absorption of RCA.

A Comparative Study of the Properties of Recycled Concrete Prepared with Nano-SiO2 and CO2 Cured Recycled Coarse Aggregates Subjected to Aggressive Ions Environment

“…The above results suggest that both the curing methods can significantly decrease the crushing index of RCA, and it shows slight improvement in the water absorption, apparent density and void fraction. This is because CO 2 and nano-SiO 2 reacted with CH in the mortar attached to the surface of the aggregate to generate CaCO 3 and C–S–H, respectively, thus filling the excessive pores in the mortar attached to the surface of aggregate and improving the quality of RCA [ 24 , 25 ].…”

¿Por qué el efecto del árido de hormigón reciclado en la resistencia a compresión del hormigón autocompactante no es homogéneo? Una revisión bibliográfica

“…Dado que la zona más débil de las ZIT son los puntos de contacto entre el mortero adherido y la matriz cementicia, es la zona donde se suelen producir los problemas de adhesión entre ambos materiales/fases (39). Un mortero adherido de mayor resistencia, posible gracias al uso de un hormigón de partida de mayor resistencia, hace que esta zona sea menos sensible a la aplicación de una fuerza y que el fallo no se produzca tan fácilmente (40). • En segundo lugar, en los casos en los que el AHR se rompe en vez de experimentar fenómenos de despegue, es evidente que la situación más beneficiosa es la presencia de un mortero adherido que tenga la mayor resistencia posible (41).…”

Unlocking the role of pores in chloride permeability of recycled concrete: A multiscale and a statistical investigation

“…Certain properties of the pores including size, tortuosity, and total porosity are highly correlated with chloride penetration. Although there have been some attempts to propose relationships between the pore structure and chloride diffusivity within concrete, the outcomes varied among several research groups [18][19][20][21][22] . For example, Zhang et al [23] demonstrated that there was a close correlation between DCland pore structure parameters including the total specific pore volume and the most probable pore diameter, as measured by MIP.…”