The mechanical properties and resistance against the coupled deterioration of sulfate attack and freeze-thaw cycles of tailing recycled aggregate concrete

The objective of this study is to prepare recycled aggregate concrete (RAC) using iron ore tailings (LOTs) and test their properties. Three different types of concrete were prepared in this study: natural aggregate concrete (NAC), RAC, and tailing recycled aggregate concrete (TRAC). During testing, a digital image correlation (DIC) system was used to evaluate the transverse strain and axial strain of the concrete samples. The cubic compressive strength and uniaxial compressive stress-strain relationship were analysed, and the three-dimensional pore distribution was investigated based on computed tomography (CT) images. Moreover, the resistance of the three different concrete types to freeze-thaw (F-T) cycles in water and 5% Na2SO4 solution was investigated. Through rapid F-T cycle experiments, the surface damage, weight loss rate, residual compressive strength, and relative dynamic elastic modulus (RDEM) were analysed. The test results revealed that the incorporation of LOTs markedly enhanced the mechanical properties and improved the pore structure of RAC. Furthermore, there was an insubstantial variability of the failure modes between TRAC and control group (NAC and RAC). However, increasing the LOT content resulted in a steeper descending branch of the stress-strain curves, indicating an increase in the brittleness of the concrete. The F-T degradation degree of the concrete in the 5% Na2SO4 environment was greater than that in water. The LOT content should not exceed 20% in consideration of the coupled action of F-T cycles and sulfate attack. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

This study aimed to prepare recycled aggregate concrete using iron ore tailings and test their properties. The incorporation of LOTs significantly enhanced the mechanical properties and improved the pore structure of the concrete. Additionally, the F-T degradation degree of the concrete in the 5% Na2SO4 environment was greater than that in water, and the LOT content should not exceed 20% in consideration of the coupled action of F-T cycles and sulfate attack.