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Purpose The durability of concrete containing recycled aggregates, sourced from concrete specimens that have been tested in laboratory testing facilities, remains understudied. This paper aims to present the results of experiments investigating the effect of incorporating such type of concrete waste on the strength and durability-related properties of concrete. Design/methodology/approach A total of 77 concrete cylinders sized Ø100 × 200 mm with varying amount of recycled concrete aggregate (RCA) (0%–100% by volume, at 25% increments) and maximum aggregate size (12.5, 19.0 and 25.0 mm) were fabricated and tested for slump, compressive strength, sorptivity and electrical resistivity. Disk-shaped specimens, 50-mm thick, were cut from the original cylinders for sorptivity and resistivity tests. Analysis of variance and post hoc test were conducted to detect statistical variability among the data. Findings Compared to regular concrete, a reduction of slump (by 18.6%), strength (15.1%), secondary sorptivity (31.5%) and resistivity (17.0%) were observed from concrete containing 100% RCA. Statistical analyses indicate that these differences are significant. In general, an aggregate size of 19 mm was found to produce the optimum value of slump, compressive strength and sorptivity in regular and RCA-added concrete. Originality/value The results of this study suggest that comparable properties of normal concrete were still achieved by replacing 25% of coarse aggregate volume with 19-mm RCA, which was processed from laboratory-tested concrete samples. Therefore, such material can be considered as a potential and sustainable alternative to crushed gravel for use in light or nonstructural concrete construction.

This study investigated the effect of sea water on the corrosion behavior of reinforcing steel in concrete. A 3% sodium chloride solution was used to simulate sea water. The solution was used as mixing water as well as immersion media. Combinations of mixing and immersion media considered in this study were normal-normal water (NN), normal-sea water (NS), seawater-normal water (SN), and seawater-seawater (SS). Corrosion measurement used were Impressed Voltage Test (IVT) and gravimetric method. Results showed that corrosion current curves, gravimetric mass loss, the average and maximum current passed are severe in SS but negligible in NN. The difference between NS and SN, however, is not well defined but was shown to differ in terms of corrosion current behavior before and after cracking. Incorporating chloride in the mix, regardless of its environment, was found to cause rapid crack development in concrete. Statistical analysis suggested that the presence of chloride had no influence on the outcome of percent mass loss with respect to the control sample except in SS combination.

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Weathering steel (WS) is known to develop higher corrosion resistance than ordinary steel under atmospheric condition due to the formation of a protective, dense rust layer. This aspect, however, has not been studied so far in cement-based materials, which are characterized by high alkalinity and limited oxygen. To address the need for durable RC structure in extreme environments, it is necessary to study the behavior of WS in concrete. Here, a basic investigation was conducted to compare the short-term behavior of a newly developed WS with 1% Ni (NT) to conventional WS with 1% Cr (CT) and carbon steel (PC). One set of steel bars was exposed to solutions with varying air and pH to simulate concrete condition under chloride-containing environment. Another set was embedded in mortar under wet-dry cycle. Corrosion degree based on mass loss, coupled with half-cell potential, and corroded area was obtained. Results indicate that alkalinity or low oxygen appreciably reduces the corrosion rate of steels regardless of composition. These conditions make the corrosion behavior of NT comparable with other conventional steels. It is recommended to explore using longer time and wider cracks in future studies to achieve clearer difference between the steels.