Yuanzhen Liu

Mechanical properties of thermal insulation concrete with recycled coarse aggregates after elevated temperature exposure

Abstract Thermal insulation concrete with recycled coarse aggregate (RATIC) provides an excellent alternative to energy saving and the reuse of waste concrete in buildings. In this paper, experiments were conducted to investigate the mechanical properties of the RATIC material after exposure to elevated temperatures, including failure feature and residual strengths. The effects of temperatures and the replacement percentage of recycled coarse aggregate (RCA) on the compressive and tensile strengths of the RATIC were first assessed experimentally. Then, the formulas for both compressive and tensile strengths were developed as a function of temperatures using the regression analysis. The test results show that the RATIC is prone to explosive spalling due to the compact structure of cement paste and low thermal conductivity. The compressive strength of the RATIC increases slightly under the temperature of 400 °C and then decreases significantly with an increasing exposed temperature. In contrast, the splitting tensile strength of the RATIC decreases significantly after the material was exposed to a high temperature of 200 to 800 °C. With the increasing RCA percentage, the RATIC experiences more strength deterioration in tension than compression, while little difference was observed regarding thermal exposure and failure modes of the RATIC.

Microbial network of the carbonate precipitation process induced by microbial consortia and the potential application to crack healing in concrete

Current studies have employed various pure-cultures for improving concrete durability based on microbially induced carbonate precipitation (MICP). However, there have been very few reports concerned with microbial consortia, which could perform more complex tasks and be more robust in their resistance to environmental fluctuations. In this study, we constructed three microbial consortia that are capable of MICP under aerobic (AE), anaerobic (AN) and facultative anaerobic (FA) conditions. The results showed that AE consortia showed more positive effects on inorganic carbon conversion than AN and FA consortia. Pyrosequencing analysis showed that clear distinctions appeared in the community structure between different microbial consortia systems. Further investigation on microbial community networks revealed that the species in the three microbial consortia built thorough energetic and metabolic interaction networks regarding MICP, nitrate-reduction, bacterial endospores and fermentation communities. Crack-healing experiments showed that the selected cracks of the three consortia-based concrete specimens were almost completely healed in 28 days, which was consistent with the studies using pure cultures. Although the economic advantage might not be clear yet, this study highlights the potential implementation of microbial consortia on crack healing in concrete.

Publisher Correction: Microbial network of the carbonate precipitation process induced by microbial consortia and the potential application to crack healing in concrete

A correction to this article has been published and is linked from the HTML version of this paper. The error has been fixed in the paper.

Comparison of seismic performance between thermal insulation concrete and normal concrete shear walls

Abstract Thermal insulation concrete (TIC) with glazed hollow beads (GHBs) is a new type of building materials meeting the needs of energy-saving building. The TIC is advantageous in applications due to its excellent bearing capacity and thermal insulation properties. This paper discusses the seismic performance of the shear wall with TIC. Based on the seismic tests of two specimens under low frequency cyclic horizontal loads with constant vertical actions, the hysteretic behavior, energy dissipation capacity, stiffness degradation and failure pattern of the shear wall were investigated. A finite element model was developed and nonlinear analyses were made to simulate the quasi-static test of the shear wall using ABAQUS software. Both modal and time-history analyses of a test building with TIC were also performed using SAP2000 software. The test results show that, compared with the normal concrete shear wall (SW), the shear wall with TIC (specimens named GSW) has better energy dissipation capacity and ductility, while the failure pattern is similar.

Calculation on effective thermal conductivity of recycled aggregate thermal insulation concrete with added glazed hollow beads

Abstract In this paper, available structural models and equations for predicting the effective thermal conductivity (ke) of recycled aggregate thermal insulation concrete, including series, parallel, Maxwell-Eucken, eEffective medium theory, and Gongs model are discussed and extended to three phases by considering the effect of glazed hollow beads (GHBs). The solid porosity of GHBs is estimated and used in the equations. A unified model for calculating ke values is proposed, where the fractal dimension of GHBs is considered. A simple expression characterizing the fractal dimension of GHBs is derived. Nine batch specimens with different concrete mixtures are tested to determine the ke values which are compared with the predicted values. The predicted values from Unified-2 model are found to be in good agreement with the experimental results.