ملخص البحث :

Ultra-high-performance concrete (UHPC) is a form of cementitious composite that has been the most innovative product in concrete technology over the last three decades. Ultra-highperformance concrete has been broadly employed for the design of numerous forms of construction owing to its excellent mechanical characteristics and durability, and studies on its behavior have grown fast in the last decades. While the utilization of ultra-high-performance concrete in bridge engineering (BE) is limited owing to its high costs, little is recognized about the utilization of UHPC in various BE elements. As a result of these issues, a comprehensive review of the current UHPC development trends should be conducted to determine its present state and perspective. This study presents a review of the state-of-the-art UHPC applications in BE. This review also discusses the current status, limitations, challenges, and areas for the further investigation of UHPC in BE. The aim of this research to help various construction stakeholders understand the distinctive characteristics, benefits, and barriers to the broad utilization of ultra-high-performance concrete applications. The understanding of UHPC will aid in increasing its entire market share in both the national and worldwide building sectors.

ملخص البحث :

Challenges posed by industrial solid waste, particularly Electrical Cable Waste (ECW), have been increasingly recognized due to their environmental implications and substantial decomposition timelines. ECW, a byproduct of aggressive demolition and reconstruction in Iraq, has seen limited investigation regarding its potential use as an aggregate substitute and fiber additive in concrete applications. This study endeavors to repurpose ECW as a partial replacement for natural sand and as fiber reinforcement, with a focus on both short-term and long-term performance. A fixed ratio of natural sand was substituted with ECW (10%), and waste fibers were integrated at varying concentrations (0.5%, 1%, 1.5%, 2%, 2.5%, and 3%). For comparative purposes, a control mix devoid of ECW and fibers was also examined. Evaluations were conducted on the flow rate, along with compressive strength, flexural strength, and density at intervals of 7, 28, and 360 days. Results indicate that despite a reduction in flowability and a decrease in hardened density to under 2000 kg/m3, inclusion of ECW can yield a sustainable lightweight mortar without significant compromise on strength. This study thus underscores the potential of waste repurposing as a viable solution for waste management and environmental enhancement. Additionally, this approach can help mitigate natural resource depletion, such as that of natural sand, fostering a move towards sustainable construction practices.

ملخص البحث :

The difficulty of decomposing solid waste over time has made it a significant global problem because of its environmental impact and the need for large areas for disposal. Among these residues is the waste of the rendering mortar that is produced (falls to the ground) while applied to wall surfaces. The quantity of these materials may reach 200 to 500 g/m2. As a result of local urban development (in Iraq), thousands of tons of these wastes are produced annually. On the other hand, the emission of greenhouse gases in the cement industry has had a great environmental impact. One of the solutions to this problem is to reduce the cement content in the mix by replacing it with less emissive materials. Residues from other industries are considered a relatively ideal option due to their disposal on the one hand and the reduction of harmful emissions of the cement industry on the other hand. Therefore, this research aims to reuse rendering mortar waste powder (RMWP) as a possible alternative to cement in mortar. RMWP replaced the cement in proportions (0, 10, 15, 20, 25, and 30% by weight). The flow rate, flexural and compressive strengths, ultrasonic pulse velocity, bulk density, dynamic modulus of elasticity, electrical resistivity, and water absorption tests of the produced mortar were executed. Microstructural analysis of the produced mortar was also investigated. Results indicated that, for sustainable development, an eco-friendly mortar can be made by replacing cement with RMWP at a rate of 15%, resulting in a 17% decrease in compressive strength while maintaining or improving durability properties. Moreover, the microstructure became denser and more homogeneous in the presence of RMWP.

ملخص البحث :

Sustainability and reducing environmental damage caused by CO2 emissions have become issues of interest to researchers in the construction sector around the world. Reducing the cement content in concrete by partially substituting it with by-products or waste falls within this field as the cement industry is responsible for 7% of global CO2 emissions. On the other hand, self-compacting concrete (SCC) is one of the special types of concrete that contains a large amount of powder (most of which is cement) to ensure its flow under the influence of its weight without separating its components. Therefore, to produce eco-friendly SCC, many researchers have replaced part of the cement with clay brick waste powder (CBWP) since brick units are among the most widely used building materials after concrete. Accordingly, this study aims to review previous research that included using CBWP in SCC. The effect of these wastes on the fresh, mechanical, durability and microstructural properties of cement was reviewed. Additionally, a comparison between the environmental impacts of SCCs with different CBWP contents has been conducted using the life cycle assessment (LCA) approach. It was found that the highest value of CBWP that can be used without negatively affecting the different properties of concrete is 10% by weight of cement. Moreover, regarding environmental impact, using CBWP as a substitute for cement reduces environmental damage, and the lowest environmental impact that can be achieved per strength unit (MPa) is 37.5%.

ملخص البحث :

Carbon dioxide emissions are one of the problems that arouses the interest of scientists because of their harmful effects on the environment and climate. The construction sector, particularly the cement industry, is a significant source of CO2. On the other hand, solid waste constitutes a major problem facing governments due to the difficulty of decomposing it and the fact that it requires large areas for landfill. Among these wastes are LCD waste glass (WG) and used rope waste. Therefore, reusing these wastes, for example, in concrete technology, is a promising solution to reduce their environmental impact. Limited studies have dealt with the simultaneous utilization of glass waste as a substitute for cement and rope waste (nylon) fiber (WRF). Therefore, this study aimed to partially replace cement with WG with the addition of rope waste as fibers. Thirteen mixtures were poured: a reference mixture (without replacement or addition) and three other groups containing WG and WRF in proportions of 5, 15 and 25% by cement weight and 0.25, 0.5 and 0.75% by mortar weight, respectively. Flow rate, compression strength, flexural strength, dry density, water absorption, dynamic modulus of elasticity, ultrasonic pulse velocity and electrical resistivity were tested. The results indicate that the best ratio for replacing cement with WG without fibers was 5% of the weight of cement. However, using WRF increased the amount of glass replacement to 25%, with an improvement in strength and durability characteristics.