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Highlights: - Salt-scaling resistance in the presence of recycled concrete aggregates, - A strong bond between RCAs and new mortar was obtained after a freeze-thaw test, - Pulse velocity after exposure to freezing-thawing cycles negligibly decreased, - The scaling rate increased with the increase in the water–cement ratio, - The electrical resistivity of concrete after exposure to cycles has been investigated. Concrete wastes such as recycled concrete aggregates (RCA) make up a significant part of construction and demolition waste (C&DW) which can be used to minimize usage of natural aggregates and reduce carbon footprint. This paper studies the salt-scaling resistance of recycled aggregate concrete produced with pretreated RCAs. The test method for evaluating salt-scaling resistance in concrete according to DIN EN 1340 : 2003 was performed. Four series of concrete mixes using natural aggregates, RCAs, manually pretreated RCA, and modified RCA in a desiccator were subjected to the different tests in terms of bulk electrical resistance in two directions (X and Y) before and after freeze-thaw cycles, ultrasonic pulse velocity, and weight loss of the surface layer of concrete specimens. Moreover, Scanning Electron Microscopy (SEM) of mixes was conducted and the microstructure of mixes considering the interface transition zone was studied. Results show that after exposure to cycles of freezing and thawing, the quality of concrete regarding ultrasonic pulse velocity did not change. The electrical resistance of specimens decreased significantly in X-direction and slightly in Y-direction after applying freeze-thaw cycles in all mixes. Nevertheless, surface modification of RCAs can increase electrical resistance and improve durability of concrete. SEM images show that the interface transition zone before and after freeze-thaw cycles remained unchanged which means strong bond between aggregate, new mortar, and old mortar. An estimation of the total charge passed indicated th

Today, the use of recycled aggregates as a substitute for a part of the natural aggregates in concrete production is increasing. This approach is essential because the resources for natural aggregates are decreasing in the world. In the present study, the effects of recycled concrete aggregates as a partial replacement for fine (by 50%) and coarse aggregates (by 100%) were examined in the self-compacting concrete mixtures which contain air-entraining agents and silica fumes. Two series of self-compacting concrete mixes have been prepared. In the first series, fine and coarse recycled mixtures respectively with 50% and 100% replacement with air entraining agent were used. In the second series, fine recycled (with 50% replacement) and coarse recycled (with 100% replacement) were used with silica fume. The rheological properties of the self-compacting concrete (SCC) were determined using slump-flow and J-ring tests. The tests of compressive strength, tensile strength, and compressive stress-strain behavior were performed on both series. The results indicated that air-entraining agent and silica fume have an important role in stabilization of fresh properties of the mixtures. The results of tests indicated a decrease in compressive strength, modulus of elasticity, and energy absorption of concrete mixtures containing air entrained agent. Also, the results showed that complete replacement (100%) with coarse recycled material had no significant effect on mechanical strength, while replacement with 50% fine recycled material has reduced compressive strength, tensile strength, and energy absorption.

Sasanipour, H., & Aslani, F. (2020). Durability properties evaluation of self-compacting concrete prepared with waste fine and coarse recycled concrete aggregates. Construction and Building Materials, 236, Article 117540. https://doi.org/10.1016/j.conbuildmat.2019.117540

Sasanipour, H., Aslani, F., & Taherinezhad, J. (2021). Chloride ion permeability improvement of recycled aggregate concrete using pretreated recycled aggregates by silica fume slurry. Construction and Building Materials, 270, article 121498. https://doi.org/10.1016/j.conbuildmat.2020.121498

Sasanipour, H., & Aslani, F. (2020). Durability assessment of concrete containing surface pretreated coarse recycled concrete aggregates. Construction and Building Materials, 264, article 120203. https://doi.org/10.1016/j.conbuildmat.2020.120203

Sasanipour, H., & Aslani, F. (2019). Effect of specimen shape, silica fume, and curing age on durability properties of self-compacting concrete incorporating coarse recycled concrete aggregates. Construction and Building Materials, 228. Available here.

Nili, M., Sasanipour, H., & Aslani, F. (2019). The effect of fine and coarse recycled aggregates on fresh and mechanical properties of self-compacting concrete. Materials, 12(7), Article 1120. Available here