International Concrete Abstracts Portal

There has been a trend toward replacing the production of Type I/II and II/V cements with Type IL cement or portland limestone cement (PLC). PLC exhibits greater variability from source to source which can lead to challenges such as altered initial setting characteristics, variations in compressive strength gain rates, and changes in bleed rates. This necessitates adjustments to mixture designs, placing and finishing techniques, and polishing methods.

Corrosion of steel reinforcement is one of the primary contributing factors to bridge deck deterioration. Based on the extent of corrosion, different corrosion mitigation strategies can be used to extend the service life of a bridge deck. Bridge deck overlays are efficient tools in reducing active corrosion. While there are multiple overlay solutions that are commonly deployed, including concrete-based and polymer-based systems, ultra-high performance concrete (UHPC) overlays have gained interest from bridge owners in recent years. Another corrosion mitigation strategy is the application of corrosion-inhibiting chemicals and sealers to a concrete surface to reduce the ingress of deleterious ions. The purpose of this paper is to compare different corrosion mitigation strategies and study the effects of such techniques on the bond between the UHPC overlay and the substrate concrete. UHPC overlays were found to be effective in reducing corrosion rates by more than 50 percent. Sealers and corrosion inhibitors applied to the concrete substrate in combination with placing a UHPC overlay reduced the corrosion rates even further. However, sealers and corrosion inhibitors appeared to negatively affect bond strength, potentially increasing the likelihood of overlay delamination.

There is a growing concern regarding the accumulation of marine waste and the negative environmental impacts of cement-based materials. To address these issues, this study explores new possibilities for upcycling marine dredged sediments (MDS) from the Magdalen Islands in Quebec as an alternative to sand, which can be challenging to procure for islands. The characterization of these MDS showed their inert quartz nature. However, by employing packing density optimization methods, it was found that MDS can be effectively used as a partial replacement for sand. The study demonstrates that a 20% volumetric replacement of sand with MDS yields a maximum theoretical packing density of 0.796 and an experimental density of 0.747. The physical and mechanical properties of five mortar mixtures with varying volumetric ratios of MDS to sand from 0 to 50% were evaluated. The findings indicate that increasing the MDS dosage results in a slight reduction of slump flow. However, replacing 20% of the sand with MDS provides the maximum packing density and results in a 12% enhancement in 28-day compressive strength (with a slight increase in bulk electrical resistivity). These results highlight the importance of the development of closely packed granular skeletons in cementitious systems for the development of environmentally friendly alternatives to conventional cement-based materials.

The shortage of high-quality fine aggregate as an essential component of concrete has become an emerging worldwide concern for the construction industry. Concrete typically comprises up to 30% fine aggregate, which largely influences the strength and durability of the final product. Therefore, finding suitable substitutes for natural fine aggregate has become an important aspect of current concrete research.

In this study, we investigated the suitability of using remediated thermal-treated soil and tar-containing asphalt as secondary raw materials in a self-compacting concrete (SCC) mixture. The remediated materials were used as both (1) fine aggregate replacement to replace all the river sand and (2) partial filler/supplementary cementitious material (SCM) replacement. The modified Andreasen and Andersen (A&A) particle packing model was used to determine the optimal replacement level. Based on the optimal mixture design, the impact of the replacement on the fresh and mechanical properties of SCC was evaluated. Additionally, the pozzolanic reactivity of the fine fraction (<125 μm) within the secondary sand was assessed and compared to that of limestone powder. Our findings confirm that using remediated thermal-treated soil and tar-containing asphalt can produce a more circular, sustainable SCC by replacing high-quality natural sand and limestone filler and reducing the environmental impact of conventional SCC. This study contributes to finding viable alternatives to natural fine aggregate and promotes the use of recycled materials in construction.

This study focuses on the feasibility of replacing fly ash with limestone and calcined clay in strain-hardening cementitious composites (SHCC). Three types of composites were considered: a reference one containing fly ash and the other containing two distinct calcined clays (moderate and high metakaolin content) as supplementary cementitious materials (SCM). Mixtures utilized portland cement (PC) with clinker factors of 0.4 and 0.3, reinforced with 2 vol.% high-density polyethylene (HDPE) fibers. At first, the R³ bound water test was carried out to explicitly assess the reactivity of fly ash and the two calcined clays. Subsequently, the compressive and direct tensile behavior of the SHCCs after 28 days of curing age was evaluated. The results revealed that the SHCCs incorporating calcined clays outperformed their counterpart in terms of compressive strength, tensile strength, and ultimate strain, owing to their high pozzolanic activities, and physical properties, particularly their distinct morphologies. Crack analysis conducted through digital image correlation (DIC) highlighted that the SHCCs with calcined clays established a stronger fiber/matrix interface. In conclusion, this research provides valuable insights into the design of ductile SHCC with novel limestone calcined clay cement (LC³), for enhanced sustainability and cost-effectiveness.