Time-Dependent Shrinkage Model for Recycled Fine Aggregate Thermal Insulation Concrete

Abstract

In this study, the shrinkage performance of recycled aggregate thermal insulation concrete (RATIC) with added glazed hollow beads (GHB) was investigated and a time-dependent shrinkage model was proposed. Two types of recycled fine aggregate (RFA) were used to replace natural fine aggregate in RATIC: RFA from waste concrete (RFA1) and waste clay brick (RFA2). Besides, the mechanical properties and thermal insulation performance of RATIC were also studied. Results showed that the pozzolanic reaction caused by RFA2 effectively improved the mechanical properties of RATIC; 75% was the optimal replacement ratio of RATIC prepared by RFA2. Added RFA decreased the thermal conductivity of thermal insulation concrete (TIC). The total shrinkage strain of RATIC increased with the increase of the replacement ratio of RFA. The 150d total shrinkage of RATIC prepared by RFA1 was 1.46 times that of TIC and the 150d total shrinkage of RATIC prepared by RFA2 was 1.23 times. The addition of GHBs led to the increase of early total shrinkage strain of concrete. Under the combined action of the higher elastic modulus of RFA2 and the pozzolanic components contained in RFA2, the total shrinkage strain of RATIC prepared by RFA2 with the same replacement ratio was smaller than that of RATIC prepared by RFA1. For example, the final total shrinkage strain of RATIC prepared by RFA2 at 100% replacement ratio was about 18.6% less than that of RATIC prepared by RFA1. A time-dependent shrinkage model considering the influence of the elastic modulus of RFA and the addition of GHB on the total shrinkage of RATIC was proposed and validated by the experimental results.

Influence of the Mix Proportion and Aggregate Features on the Performance of Eco-Efficient Fine Recycled Concrete Aggregate Mixtures

“…Likewise, fine recycled concrete aggregates (FRCA) comprise the original virgin aggregate (OVA) and residual cement paste (RCP). The properties of RCA concrete made of CRCA have been extensively investigated [3,[10][11][12][13][14][15][16][17]; therefore, numerous documents such as ACI-555R [18], BS EN 1744-6:2006and BS EN 933-11:2009 along with RILEM technical reports, such as [19,20], provide guidelines and criteria on how to deal with and use CRCA for proportioning RCA concrete. Yet, although RCA's use in concrete has grown over the past years, concerns related to its mechanical properties, durability and long-term behaviour prevent its widespread use for structural purposes [6,9,14,21,22], especially due to the lack of efficient quality control and proportioning procedures.…”

“…Yet, although RCA's use in concrete has grown over the past years, concerns related to its mechanical properties, durability and long-term behaviour prevent its widespread use for structural purposes [6,9,14,21,22], especially due to the lack of efficient quality control and proportioning procedures. On the other hand, FRCA is considered a very low-quality material due to its high amount of RCP adhered to the fine particles [15,21]; thus, much less has been developed and accomplished with the use of FRCA. The amount of RCP varies depending upon the type and quality of the OVA (i.e., lithotype, texture, shape, etc.…”

“…15, 1355 is the only mixture where the viscosity did not change as a function of the to (i.e., viscosity approximately constant and equal to 8 N•m/rad/s). The highe the lower the viscosity for all the other mixtures.…”