Mechanical Properties of High-Strength Self-Compacting Concrete.

In this research work, the mechanical properties of high-strength self-compacting concrete (HSSCC) were studied. Three mixes were selected, having compressive strengths of more than 70, 80, and 90 MPa, respectively. For these three mixes, the stress-strain characteristics were studied by casting cylinders. It was observed during the testing that the binder content and water-to-binder ratio influence the strength of HSSCC, and slow changes in stress-strain curves were seen as the strength increased. The use of HSSCC results in reduced bond cracking, leading to a more linear and steeper stress-strain curve in the ascending branches as the strength of the concrete increases. Elastic properties such as modulus of elasticity and Poisson's ratio of HSSCC were calculated using experimental data. In HSSCC, since the aggregate content is lower and the size of the aggregates is smaller, it will have a lower modulus of elasticity compared to normal vibrating concrete (NVC). Thus, an equation is proposed from the experimental results for predicting the modulus of elasticity of HSSCC. The results suggest that the proposed equation for predicting the elastic modulus of HSSCC for strengths ranging from 70 to 90 MPa is valid. It was also observed that the Poisson's ratio values for all three mixes of HSSCC were found to be lower than the typical value for NVC, indicating a higher degree of stiffness.

Investigating the Flexural Behavior of a Two-Span High-Performance Concrete Beam Using Experimentally Derived Stress Block Parameters.

High-performance concrete (HPC) is increasingly used in construction due to its superior strength and durability. However, current stress block parameters used for designing normal-strength concrete cannot be safely applied to HPC. To address this issue, new stress block parameters have been proposed through experimental works, which are used for designing HPC members. In this study, the behavior of HPC was investigated using these stress block parameters. Two-span beams made of HPC were tested under five-point bending, and an idealized stress block curve was derived from the experimental stress-strain curve for grades 60, 80, and 100 MPa. Based on the stress block curve, equations for the ultimate moment of resistance, depth of the neutral axis, limiting moment of resistance, and maximum depth of the neutral axis were proposed. An idealized load-deformation curve was also developed, which identified four significant events: first cracking, yielding of reinforced steel, crushing of concrete with spalling of cover, and ultimate failure. The predicted values were found to be in good agreement with the experimental values, and the average location of the first crack was identified to be 0.270 L, measured from the central support on either side of the span. These findings provide important insights for the design of HPC structures, contributing to the development of more resilient and durable infrastructure.

Al2014-Alumina Aerospace Composites: Particle Size Impacts on Microstructure, Mechanical, Fractography, and Wear Characteristics.

An Al2014-alumina (Al2O3) composite's characteristics are significantly influenced by the reinforcement particle size variation. Therefore, this study examines the microstructure, mechanical, fractography, and wear performance of an Al2014-Al2O3p composite made using a unique two-stage stir casting method and various alumina weight fractions (9, 12, and 15 wt %). Three categories of alumina particle size are used, i.e., fine particle size (FPS, 8 µm), intermediate particle size (IPS, 53 µm), and coarse particle size (CPS, 88 µm). The shapes of the composites were characterized using scanning electron microscopy. According to scanning electron microscopic analyses of the microstructure, the FPS dispersion was more uniform than IPS and CPS, whereas CPS causes agglomeration. Additionally, the studies show that the FPS composite outperformed CPS and IPS composites in terms of mechanical characteristics and wear performance. The fractography study shows conical and equiaxed dimple failure in the Al2014 matrix and the circular cavities.

Development of Eco-Friendly Concrete Mix Using Recycled Aggregates: Structural Performance and Pore Feature Study Using Image Analysis.

The shortage of natural aggregates has compelled the developers to devote their efforts to finding alternative aggregates. On the other hand, demolition waste from old constructions creates huge land acquisition problems and environmental pollution. Both these problems can be solved by recycling waste materials. The current study aims to use recycled brick aggregates (RBA) to develop eco-friendly pervious concrete (PC) and investigate the new concrete's structural performance and pore structure distributions. Through laboratory testing and image processing techniques, the effects of replacement ratio (0%, 20%, 40%, 60%, 80%, and 100%) and particle size (4.75 mm, 9.5 mm, and 12.5 mm) on both structural performance and pore feature were analyzed. The obtained results showed that the smallest aggregate size (size = 4.75 mm) provides the best strength compared to the large sizes. The image analysis method has shown the average pore sizes of PC mixes made with smaller aggregates (size = 4.75 mm) as 1.8-2 mm, whereas the mixes prepared with an aggregate size of 9.5 mm and 12.5 mm can provide pore sizes of 2.9-3.1 mm and 3.7-4.2 mm, respectively. In summary, the results confirmed that 40-60% of the natural aggregates could be replaced with RBA without influencing both strength and pore features.

Current solid waste management strategies and energy recovery in developing countries - State of art review.

Solid waste generation has rapidly increased due to the worldwide population, urbanization, and industrialization. Solid waste management (SWM) is a significant challenge for a society that arises local issues with global consequences. Thus, solid waste management strategies to recycle waste products are promising practices that positively impact sustainable goals. Several developed countries possess excellent solid waste management strategies to recycle waste products. Developing countries face many challenges, such as municipal solid waste (MSW) sorting and handling due to high population density and economic instability. This mismanagement could further expedite harmful environmental and socioeconomic concerns. This review discusses the current solid waste management and energy recovery production in developing countries; with statistics, this review provides a comprehensive revision on energy recovery technologies such as the thermochemical and biochemical conversion of waste with economic considerations. Furthermore, the paper discusses the challenges of SWM in developing countries, including several immediate actions and future policy recommendations for improving the current status of SWM via harnessing technology. This review has the potential of helping municipalities, government authorities, researchers, and stakeholders working on MSW management to make effective decisions for improved SWM for achieving sustainable development.