Constr. Mater., Volume 4, Issue 3 (September 2024) – 9 articles

Concrete is one of the most commonly used materials in civil engineering construction, and it continues to have increased production. This puts pressure on the consumption of its constituent materials, including Portland cement and aggregates. There are environmental consequences related to the increased emission of CO₂ that are associated with the production process of Portland cement. This has led to the development and use of alternative cementitious materials, mainly in the form of condensed silica fume, pulverised fuel ash, and ground granulated blast furnace slag. All of these are by-products of the silicon, electrical power generation, and iron production industries, respectively. In recent years, attention has turned to the possible use of sustainable bio-waste materials that might contribute to the replacement of Portland cement in concrete. This research investigates the effects of using rice husk ash as cement replacement material on the 1 to 28-day concrete properties, including the compressive strength, workability, and durability of concrete. The findings indicate that including rice husk ash in concrete can improve its strength at 3–28 days for percentage replacements of 5% to 20% (ranging from 2.4% to 18.7% increase) and improvements from 1 day for 20% replacement (with 11.1% increase). Any percentage replacement with rice husk ash also reduced the air permeability by 21.4% and therefore improved the durability, while there was a small reduction in the workability with increased replacement. Full article

This paper examines the properties of sewage sludge ashes (SSAs) from the incineration of sewage sludge with added limestone for toxic gas treatment. It also evaluates the potential valorization of SSA in cement composites as supplementary cementitious materials (SCMs). The work involves a thorough characterization of four SSAs, including physical, chemical, and mineralogical properties. It also includes assessing the behavior of SSA in water solution through electrical conductivity measurements. The reactivity of ashes was evaluated using the R³ method and mechanical properties. The results revealed that all SSAs present comparable mineralogical and chemical properties, with varying proportions. Major elements such as Ca, Si, Fe, P, and S are predominant in the ashes, with traces of heavy metals. In an aqueous solution, a gradual formation of ettringite was detected only for two SSA. The heavy metal leachability was negligible, confirming that SSA is a non-hazardous waste. Finally, the reactivity and strength activity index assessments revealed a low and slow reactivity of SSA compared to metakaolin or slag. The SSA that favored ettringite formation in aqueous solution presented the lowest compressive strength at 28 days after incorporation in mortar. Despite originating from different incineration sites, these ashes fall under the same category of SCM reactivity. Full article

The rapid increase in plastic usage today poses a significant threat to our environment and the planet. It contributes to global warming and negatively impacts biodiversity. Most plastic ends up in landfills, where it can take up to 1000 years to decompose. Shockingly, only 9% of the plastic produced annually is recycled, while an astounding 2 million plastic bags are used every minute worldwide. This paper highlights the primary goal of plastic recycling, with a particular focus on using plastic to manufacture roof tiles. The motivation behind this approach is that everyone deserves a decent roof over their heads. To achieve this, a well-balanced mixture of waste polypropylene (PP), quartz sand, and fly ash minerals was utilized in producing plastic roof tiles. The research employed a hot press process to prepare samples of all composite materials, and no cracks or fractures were observed on the surface of these samples. The results of this innovative process exceed the standards set for most building materials in terms of both mechanical and thermal properties, demonstrating a compressive strength of 99.8 MPa, a flexural strength of 35.6 MPa, and an impact energy absorption of 7.93 KJ/m². Importantly, all samples exhibited zero percent water absorption, making these roof tiles ideal for insulation purposes. Additionally, the resulting roof tiles are lightweight and cost-effective compared to conventional options. Full article

Solid waste management is a major environmental challenge, especially in developing countries, with increasing amounts of waste glass (WG) and waste plastic (WP) not being recycled. In Ethiopia, managing WG and WP requires innovative recycling techniques. This study examines concrete properties with WG and WP as partial replacements for fine aggregate. Tests were conducted on cement setting time, workability, compressive strength, splitting tensile strength, and flexural strength. Concrete of grade C-25, with a target compressive strength of 25 MPa, was prepared by partially replacing fine aggregate with WP and WG. The mechanical properties were evaluated after 7 and 28 days of curing. At a 20% replacement level, workability decreased at water–cement ratios of 0.5 and 0.6 but remained stable at 0.4, leading to the selection of the 0.4 ratio for further testing. A 10% replacement of fine aggregate, using a ratio of 3% WP and 7% WG, was found to be optimal, resulting in an increase in compressive strength by 12.55% and 6.44% at 7 and 28 days, respectively. In contrast, a 20% replacement led to a decrease in compressive strength by 14.35% and 0.73% at 7 and 28 days, respectively. On the 28th day, the splitting tensile strength at the optimal replacement level was 4.3 MPa, reflecting an 8.5% reduction compared to the control mix. However, flexural strength improved significantly by 19.7%, from 12.46 MPa to 15.52 MPa. Overall, the incorporation of WG and WP in concrete enhances flexural strength but slightly reduces splitting tensile strength. Full article

Asphalt mix air void content is a dominant parameter for asphalt mix design. The air void content of the mix affects the mechanical property of stiffness, while both characterize compacted asphalt mix materials. On the other hand, asphalt mix as a composite material can be characterized by its dielectric value. Considering the above, the aim of the present paper is to develop a simple methodology for the characterization of asphalt mix materials using their dielectric properties through an investigation of the interaction of dielectrics and air voids, as well as air voids and stiffness. For this purpose, an experimental laboratory study was conducted, which involved the compaction of asphalt mixes with different aggregate types and air void content. Upon this, the specimens were tested for their air void content, the dielectric constant, and the stiffness modulus. The analysis of the results showed strong correlations between the three characteristics. These findings were further verified with a new set of specimens and laboratory measurements. The final goal is to use the developed methodology for the estimation of asphalt mix stiffness considering that the effect of air content on the resulting stiffness cause indirect relationships between stiffness and dielectrics. Full article

This study investigates the prediction of the thermal conductivity of lightweight earth and raw earth blocks incorporating plant aggregates. Given the high variability of raw materials, it is not currently possible to predict the thermal performance of this type of material before sample production. This is a major obstacle to using these eco-materials, although their use is widely encouraged to improve building performance under evolving regulatory frameworks such as The French RE2020 standard. The incorporation of plant aggregates into earth-based materials offers improved insulation properties without compromising their mechanical integrity, positioning them as promising sustainable alternatives. Mean-field homogenization techniques, including the Mori-Tanaka as well as double inclusion models, are used to develop predictive tools for thermal behavior, using rigorously selected experimental data. The selected methods are particularly relevant. The Mori-Tanaka model appears to be better suited when the proportion of aggregates is limited, whereas the double inclusion scheme proves its worth when a higher proportion of aggregates is incorporated. This study emphasizes the influence of aggregate types and processing methods on thermal conductivity, highlighting the need for precise formulation and processing techniques to optimize performance. This paper demonstrates the relevance of the applied homogenization techniques applied. It enables the real morphology of the materials studied, such as aggregate shape and intrinsic cracking, to be taken into account. It contributes to the advancement of eco-material modeling toward predictive digital twins, with the goal of simulating and optimizing complex material behavior under various environmental conditions. Full article

This study’s aim is to fully characterize ferronickel slag from New Caledonia, considered a multiphase mineral containing amorphous material. The methodology consisted of combining chemical, mineral, and morphological characterization techniques, such as ICP-AES, TGA, Q-XRD, microscopy, spectroscopy, etc. The ferronickel slag consisted of 44 wt. % forsterite, with the inclusion of iron as a substitution for magnesium (Mg_1.8Fe_0.2SiO₄), 1.7 wt. % chromite and 54 wt. % amorphous phase containing iron, magnesium, aluminum, and silica (Mg/Si = 0.4; Fe/Si = 0.2; Al/Si = 0.1). This material was slightly reactive in a cementitious medium, thus limiting its use as an SCM in the construction sector. The ferronickel slag was then subjected to an attrition-leaching carbonation process at 180 °C and a partial pressure of CO₂ of 20 bar. The obtained product, carbonated at 80% of its capacity, was also characterized. It was composed of carbonates (37% of magnesite and 4% of siderite), remaining forsterite (7 wt. %), chromite (1 wt. %), and 50% of an amorphous phase, mainly composed of silica and aluminum. The complete characterization of those products helped in understanding the chemistry of the carbonation process and finding valorization paths for the carbonated products in the construction sector. The carbonated product may be used either as an SCM in blended cement or as a precursor of magnesium–silicate binders. Full article

The simple for dead load and continuous for live load (SDCL) steel bridge system offers an accelerated construction solution for steel bridges. The available details for the SDCL steel bridge system consist of a cast-in-place normal strength concrete (NSC) diaphragm. This paper presents a study on developing a continuity detail SDCL system in seismic areas using ultra-high-performance concrete (UHPC) as the diaphragm to simplify construction, improve durability, and increase tolerances. This paper is part of a large study on the non-seismic and seismic application of the SDCL steel bridge system using the UHPC diaphragm. The numerical investigation and validated modeling techniques developed in the study were used in this paper to focus on the detail required for the seismic areas. A series of numerical models were developed and subjected to types of loadings that would occur in the bridge under earthquake excitations. Based on the analysis results, a set of design recommendations was developed. The UHPC connection includes simple girder-end detail, the straight development of deck reinforcement in the diaphragm, and partial use of UHPC in the diaphragm. The developed detail can improve the on-site construction time, durability, and constructability of SDCL steel bridge systems. Full article

Microbial corrosion of waterproof coatings causes structural damage to buildings and renovation materials and severely threatens human health. In practical applications, coatings with different base materials show different durabilities to external environmental influences. There is little literature on the antimicrobial durability performance of waterproof coatings. Therefore, this paper selected four standard waterproofing coatings, including polyurethane coatings, cement-based coatings, asphalt-modified polymer coatings, and polymer emulsion coatings, as the main body of this study. Their antimicrobial abilities against Gram-negative Escherichia coli, Gram-positive Staphylococcus aureus, Candida albicans, and mold were tested after experiencing three kinds of harsh environments: Ultraviolet ray (UV), water immersion, and low temperature. The results show that the extreme climates significantly reduced the ability of the four coatings to resist mold, and the highest growth rate of bacteria was 54.64%. Under UV conditions, the polymer emulsion coatings were significantly more resistant to Candida albicans, and the optical density of the bacterial liquid showed a negative growth trend. The microstructural integrity of the polymer emulsion coatings was found to be damaged by Scanning Electron Microscope (SEM) observation. This work improves the durability application research on these coatings and provides a valuable reference for developing new environmentally friendly, antibacterial, and anticorrosive waterproof coatings. Full article