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Sewage sludge ash (SSA), obtained by the incineration of sewage sludge, which is a byproduct of water treatment, could be used as a cement replacement material (CSR) to promote sustainability. SSA characteristics differ due to its different sources, compositions, and incineration methods. On the other hand, extensive investigations have highlighted the CSRs' ability to control alkali–silica reaction (ASR) as a destructive phenomenon, threatening durability. Hence, this study was conducted in order to study the ability of SSA with two finenesses, three replacement levels, and also its ternaries with trass or pumice, as natural pozzolans, to control ASR. The utilized SSA did not meet the requirements of a pozzolan at either finenesses. The results revealed that despite the fact that SSA generally reduced ASR expansion significantly, it only managed to control ASR at 50% replacement level. This was true for both finenesses. Furthermore, ternaries improved resistance against ASR expansion significantly, providing the ability to control ASR at lower replacement levels of SSA. The Si/Ca ratio was the key reason of SSA's ability to control ASR as it contained 1.5 and 2.5 times more SiO2 and Al2O3 than Portland cement respectively, and about one third of its CaO. Scanning electron microscopey (SEM), energy dispersive spectroscopy (EDS), and mapping confirmed that the relative amounts of Si, Al, and Ca in the SSA was crucial. [ABSTRACT FROM AUTHOR]

In the past few decades, recycling crushed concrete pieces and producing recycled concrete aggregate (RCA) has emerged as an effective way for controlling and managing construction and demolition wastes. Among all construction applications of RCA, its consumption in road facilities has increased significantly over the last few years. In this paper, the feasibility of utilising RCAs as an unconfined aggregate in road structure courses was evaluated. For this purpose, six types of natural aggregates (NAs) and three types of RCAs were selected. Then, various physical, mechanical, and durability tests including water absorption, specific weight, proctor test, impact test, crushing test, Los Angles abrasion test, California bearing ratio (CBR) test, sulfate soundness test and different frost soundness tests such as CSA A23.2-24A and AASHTO T103 were conducted on the specimens. The results indicated that all RCAs were acceptable for general applications in road construction. Although the sulfate soundness test suggested that RCAs were durable, they failed in both frost soundness tests. CSA frost soundness tests had the best correlation with the physical and mechanical properties of the aggregates compared to the other durability tests. Also, the AASHTO test method with its defined time-temperature cycles was not satisfactorily applicable to RCAs. [ABSTRACT FROM AUTHOR]

Because of the advances in material science, new materials are launched to market that make it possible to produce concretes with more desirable properties for technical applications. These new concretes that cannot be made using the common materials and mixing ratios are called high-performance concretes. High-performance concretes are usually made with a low water-to-cement (w/c) ratio and high cement contents. High-performance concrete and its properties have gained the attention of engineers in recent years. One of the major shortcomings of cement-based materials such as concrete is their shrinkage. In this study, the effect of shrinkage-reducing admixture (SRA) on the shrinkage and durability of concrete is investigated. To examine SRA effects on shrinkage, free and constrained shrinkage tests are carried out while taking into account the impact of changing w/c ratio and cement content. Moreover, to study the durability of high-performance concrete, tests are carried out on durability parameters, including electrical resistance, depth of water penetration under pressure, and the percentage of water absorbed by the concrete. The results show that the use of shrinkage-reducing material decreases free shrinkage of concrete. When applying a lower w/c ratio and higher contents of cementitious materials, the use of this substance has a greater impact. Constrained shrinkage test results also indicate that the use of SRA additive causes a significant increase in the time of shrinkage crack formation during the test. The results of the durability tests indicate significantly improved durability properties of concrete aged 28 days. [ABSTRACT FROM AUTHOR]

In this research, different aggregates used in pervious concrete, namely zeolite, perlite, and pumice were compared in terms of their ability to remove nitrate from water. Also, several other properties of aggregates were evaluated. Regarding water absorption, pumice and perlite aggregates had the lowest (about 10%) and the highest (40%) absorption, respectively. The results showed no reactivity of aggregates in terms of alkali-silica reaction. Permeability tests indicated that the maximum (1.64 cm/s) and the minimum (1.4 cm/s) permeability corresponded to pumice and perlite aggregates, respectively. The required time for reaching equilibrium concentration in the nitrate removal test was 30 min when perlite and pumice were used, while it was 60 min for zeolite. Moreover, when HCl and H2SO4 were applied as an activating agent, this time did not decrease significantly for all aggregates. For all three raw aggregates, nitrate absorption process followed Langmuir isotherm and the absorption capacity was about 70 mmol/g. Overall, pumice was selected as the best raw aggregate among other aggregates tested in this study due to its lower water absorption, having no alkali-silica reactivity, highest permeability, and highest nitrate removal ability based on the presence of metal ions. [ABSTRACT FROM AUTHOR]