Over the years, the cost and environmental issues with the utilization of conventional building materials such as cement and river sand for housing projects kept increasing with the increase in the human population. This has led researchers to explore alternative building materials that are affordable and sustainable. This study is aimed at developing a sustainable composite using quarry dust (QD) and rice husk ash (RHA). Different percentages of QD and RHA (5%, 10%, 15%, 20% and 25% wt/wt) were used for the partial replacement of river sand and cement respectively to produce non-conventional composite samples and conventional composite samples were produced using cement and river sand. The produced composites were moulded into block samples and cured at different curing ages (7, 14, 21, 28 and 56 days). Compressive strength results of the block samples were obtained using a Universal testing machine. The compressive strength of the samples increased with an increase in the curing age. The bulk density of non-conventional composite samples was found to be lower than that of conventional composite samples. The failure pattern of the conventional composite samples showed several localized shear surfaces/multiple cracks while that of non-conventional composite samples indicated delamination of outer surfaces. The study indicates that QD and RHA could be used for partial replacement of river sand and cement respectively in developing sustainable building materials.

It is essential to give easier preparation and maintenance methods for geopolymers to facilitate practical application of metakaolin-fly ash based geopolymers (MK-FA geopolymers) in the engineering field. In this article, 16 sets of samples were prepared by orthogonal experiments design (OED) to quantify the order of contribution of three hypothetical influence factors in the growth of compressive strength. Test results revealed that the promotion of the calcium phase was significant. The calcium phase and fly ash acted synergistically during the early stage of strength development, with the former accelerating the hydration process of the precursor materials and the latter providing additional silicon and aluminum phases, which facilitated the formation of the polymeric skeleton and the densification of the matrix. In the later stages of the experiment, the promotion of gel particle formation by calcium effectively mitigated the disadvantage of reduced average reactivity due to the incomplete hydration of fly ash. Moreover, the highest compressive strength was obtained for the MK-FA geopolymer prepared according to the theoretical optimum ratio derived from the orthogonal analysis, which demonstrated the correctness and feasibility of the OED.

Three combinations of single fibers and nine combinations of hybrid fibers were tested to analyze the mechanical properties and crack propagation behavior of ultra-high-performance concrete (UHPC) by digital image correlation. It was found that in comparison to single fibers, the long fibers had a more pronounced effect than short fibers. The hybrid combination of medium length fiber (Vf = 0.5%) and long fiber (Vf = 1.5%) generated a better flexural behavior in terms of post-crack strength, deflection, toughness, than the other hybridization series. A digital image correlation (DIC) technique was applied to record the evolution of surface deformation. The hybrid use of longer fiber replaced the shorter fiber, long fiber replaced medium length fiber and short fiber, medium length fiber replaced short at lower replacement ratios (0.5% and 1.0%), the crack shapes were presented linear variation and showed an abrupt change and did not have a constant increment at higher replacement ratios (1.5% and 2.0%).

Highlights • The LCA of bamboo/sugar cane fibers’ geopolymers composites were studied. • The sugar cane bagasse treated with low liquid ammonia shows the lowest impact. • Bamboo and sugar cane fibers are responsible for 2–4% more carbon dioxide emissions. • Natural fibers have less environmental impact compared to PP, PE, and PVA fibers. Global warming and greenhouse gas emissions are significant concerns of the modern world. The cement industry causes 5–7% of CO2 gas emissions. Despite this critical environmental burden, cement is needed to develop future societies. Geopolymers are an alternative that has significantly fewer emissions than Ordinary Portland Cement. A geopolymer that considers the inclusion of natural fibers (bamboo and sugar cane bagasse) was developed. Two pre-treatments were considered for the fibers to remove lignin and starch. A life cycle assessment was performed on this geopolymer composite to evaluate its performance and compare the environmental impact of other options. The low liquid ammonia treated sugar cane bagasse fiber geopolymer had a better environmental performance with 857.9 kg CO2 eq per 1 m3 of pure binder (no aggregates). The other fiber alternatives had 2–4% more CO2 emissions. The geopolymer had excellent impact scores compared to different options and current OPC. The sensitivity analysis showed a concise and complete system that varies slightly when variables could provide uncertainty. Graphical Download : Download high-res image (148KB) Download : Download full-size image

Highlights • The analysis shows how increasing the number of wet/dry cycles accelerates the corrosion and the corresponding deterioration in steel strength, ductility, and hardness over a relatively short period of time. • Increasing the number of wet/dry cycles resulted in increased depth of corrosion damage, while the rate of corrosion gradually decreased. The corrosion that developed involved mixed corrosion modes, including deep pitting that led to cavities. • A mathematical model, utilizing the measurement of four physicochemical parameters at the interface between the soil and the mild steel surface, was used to provide an approximate prediction of the depth of corrosion damage in buried steel structures with time. In-service monitoring of the increasing network of buried corrugated metal pipes and culverts is essential to ensure continued operability via proactive assessments of potential failure and damage. A worst-case scenario for such structures is sudden failure resulting from deterioration due to prolonged corrosion effects. This paper proposes an accelerated laboratory corrosion test utilizing repeated wet/dry cycles to simulate the effects of chloride deposits on corrugated mild steel structures buried in cohesionless soil. The test was initiated by applying a 3.5% NaCl electrolyte solution to cohesionless soil above buried corrugated steel coupons, which were then subjected to repeated wet/dry cycles. To investigate the deterioration of mild carbon steel buried in a corrosive environment, the present work examines changes in the structural geometry and mechanical properties. The analysis shows how increasing the number of wet/dry cycles accelerates the corrosion and corresponding deterioration in steel strength, ductility, and hardness over a relatively short period of time. This paper also presents a mathematical model to provide an approximate prediction of corrosion damage for buried mild steel in soils, based on measurements of four physicochemical indicators at the interface between the steel surface and the surrounding soil. This could help to determine triggers for the maintenance or replacement of corroded buried mild steel structures, in the event of degradation in performance and workability.

Highlights • The first model for multi-objective alum sludge-to-supplementary cementitious material supply chain design. • Objectives maximizing social benefit by quantifying job opportunities, greenhouse gas emission savings, and economic return. • Pareto-optimal solutions show trade-offs among multiple objectives. • A real case study in Australia is investigated to test the applicability and viability of the supply chain network design. Most alum sludge is disposed of in landfill sites in Australia, resulting in significant environmental pollution and management cost. Effective management of sludge in a more sustainable manner remains a critical social, environmental, and economic concern. To simultaneously solve the dilemma of sludge management, economic expenditure of disposal, greenhouse gas emissions, and social impacts, this study proposed a multi-objective model for supply chain design of alum sludge-derived supplementary cementitious material as a viable solution. This study identified and quantified the potential social benefit by considering different impacts of new working opportunities based on their type and location, optimized the greenhouse gas emission saving for the potential supply chain, and assessed the economic benefit of the optimal untapped supplementary cementitious material value chain. The viability and applicability of the model are demonstrated through a case study in Australia, where potential utilization paths for available alum sludge are valued. A set of Pareto-optimal solutions was generated using the ɛ-constraint method, and three compromise Pareto-optimal solutions showed a clear trade-off among three objectives. The result analysis of each single-objective optimization indicates that the maximum working opportunity brought by the proposed supply chain was over 3.6 million working hours. Besides, up to 5.5 billion tonnes of greenhouse gas emissions saving was reported when maximizing the environmental objective, and the maximum economic benefit in the form of net present value was over 200 million Australian dollars in simulated 20 years. The Pareto-optimal solutions report a trade-off among three objectives, and two compromised solutions are proposed based on the level of objective values.

This study investigated the effect of nutrient types on the hydration of cementitious materials incorporated with co-cultured bacteria. The medium consisted of co-cultured bacteria (Sporosarcina pasteurii and Bacillus thuringiensis), urea, nutrient, and calcium lactate. Different nutrient types were added in the form of a bacterial culture solution or medium solution in the mixing process of cementitious specimens. Thirteen different types of specimens were fabricated with various media, dry-cured for 56 days, and subsequently, isothermal calorimeter analysis, X-ray diffraction analysis, and thermogravimetry analysis were performed to investigate the hydration kinetics and hydrates of the specimens. Finally, compressive strength of the specimens was measured. When bacteria, calcium lactate, and each nutrient were incorporated, as a comparison of compressive strength with the control specimens on the 28thday, 8% compressive strength was increased when TSB was incorporated, but NB and YE were incorporated, the compressive strength decreased by 21% and 22%. The results showed that the incorporation of nutrients and co-cultured bacteria suppressed the hydration of the specimens, whereas the reduction in compressive strength caused by delayed hydration was significantly compensated by CaCO3 amount which was increased by 3.3 times owing to the bio-mineralization of the co-cultured bacteria with TSB.

Highlights • Alkali-activated slag (AAS) was mixed with Ni- and Cr-wastewater. • AAS with or without Ni- and Cr-wastewater were immersed in sulfur oxidizing fungi. • Sulfur oxidizing fungi yields sulfuric acid, which acts as a corrosive material. • The production rate of biogenic sulfuric acid depends mainly on fungal biomass. • Heavy metals wastewater enhanced the resistivity of AAS to biogenic sulfuric acid. The role of Ni and Cr wastewater on the mitigation of the deterioration rate of alkali-activated slag (AAS), caused by biogenic sulfuric acid produced by a sulfur oxidizing fungus (SOF: Aspergillums Niger), is evaluated. The cationic leaching rate, the fungal biomass and the pH of a medium are the compositional parameters which determine the ability of a prepared AAS to resist SOF. After the first 30 days of immersion the fungal strain demonstrated low reactivity, resulting in low Ca, Na, Ni and Cr leaching rates. Increasing the curing time to 180 days caused an enhancement in fungal growth and biogenic sulfuric acid production rates, which were associated with an increase in cationic leachability and AAS corrodibility (through the calcification of calcium silicate hydrate and the formation of gypsum). Nevertheless, the sample containing Ni and Cr wastewater showed the lowest leachability, gypsum content and compressive strength regression, indicating the high efficiency of these heavy metals in mitigating the harmful effects of biogenic sulfuric acid, via the retardation of fungal growth and reactivity. Regardless of variations in heavy metals’ leachability over time, all SOF-media recorded Ni and Cr concentrations lower than the permissible limit in typical leaching procedures, as well as a soluble threshold limit concentration.