Articles in This Issue
Abstract
Plastic concrete is widely used in hydraulic cut-off walls of earth and rockfill dams because of its low permeability, high deformability, and good workability. The addition of bentonite clay is also among the primary factors that can influence its performance as it greatly decreases the hydraulic conductivity. Mechanical performance and crack resistance are enhanced by the fiber reinforcement of polypropylene (PP) and steel fibers. This paper investigated the interaction of calcium bentonite dosage, fiber type and content, cement content, and water-to-binder ratio (W/(C +B)) on the flowability, compressive strength, and permeability of 29 plastic concrete mixtures to be used in cut-off wall construction. The experimental tests were performed in accordance with ASTM D6103 on flowability, ASTM C39 on compressive strength and BS EN 12390-8:2019 on permeability. The findings revealed that the best mixtures had a flowability of over 14 cm, compressive strength of 1.23 to 25.78 MPa and permeability coefficients of 10⁻⁹ to 10⁻⁷ cm/s. Adding more bentonite was a very effective way of decreasing permeability, but frequently had adverse effects on compressive strength and workability. Polypropylene fibers showed a more favorable contribution to crack resistance and workability compared to steel fiber. The findings indicate that close fine-tuning of the water to binder ratio (W/(C+B)) as well as dosages of superplasticizer is essential in attaining balanced performance. The study presents a guideline to enhance durable, non-pervious, plastic concrete that can be used in hydraulic works and prepares the groundwork in future investigations of long-term durability and chemical integrity.
Abstract
This study investigates the thermal properties of Limestone Calcined Clay Cement (LC3) concrete that includes steel fibres under elevated temperatures of 100°C, 200°C, 400°C, and 600°C. LC3 serves as an eco-friendly substitute for conventional cement, providing lower carbon emissions and enhanced durability. In this research, concrete specimens incorporating LC3 and steel fibres (The volume of taken as 0.5%, 1%, 1.5% and 2% of cement) were subjected to a range of elevated temperatures. The parameters such as residual compressive strength, mass loss, surface changes and flexural were analyzed. The Scanning Electron Microscopy (SEM) images of Ordinary Portland cement (OPC) and LC3 normal concrete at 100oC and 600oC were studied. Results indicated that steel fibre reinforcement significantly improved the residual strength and structural integrity of LC3 concrete at high temperatures. The LC3 retained 10–15% higher strength than OPC at 600°C. These findings suggest that steel fibre-reinforced LC3 concrete can be a feasible option for structural applications where thermal resistance is critical, contributing both to sustainability and fire safety in construction.
Abstract
Municipal solid waste management in Syria remains primitive in many cases, both in terms of waste collection and disposal methods, particularly in areas that have experienced severe population density due to the war. Waste recycling processes are neglected, and waste is often disposed of in specific plots of land, often far from residential areas. This research aims to identify criteria related to decision-making for selecting the optimal site for a landfill, in line with the local context and Syrian conditions. This was achieved by reviewing several previous studies and interviewing local experts interested in this type of research. (21) criteria were identified and divided into (6) main groups: (environmental criteria, site-related criteria, external and weather conditions, economic and social criteria, and criteria related to sustainable transportation). The relative importance of these criteria was then calculated using the Fuzzy Hierarchy Process (FAHP). After obtaining the weights, these criteria were used to evaluate the current site of the Safita landfill using the Fuzzy Inference System (FIS). The evaluation results were very weak due to decision makers' neglect of many factors and conditions that must be met at the selected site. A set of recommendations and proposals were identified for consideration when selecting the optimal site for a landfill, consistent with the local context of the study area (Syria), and for improving existing sites.
Abstract
Deep excavations in urban areas require reliable retaining systems to ensure stability and prevent damaging adjacent infrastructure. Contiguous pile walls (CPWs) are widely used in space-constrained projects, although their behavior in silty soils under staged excavation conditions is less well explored. This study experimentally investigates the lateral displacement behavior of CPWs using a physical model, focusing on four governing parameters: pile spacing, surcharge load, soil unit weight, and moisture content. A rigid model chamber was constructed with instrumented CPWs, where dial gauges measured the lateral displacement during sequential excavation. Results show that surcharge load and moisture content are the most adverse parameters: lateral displacement increased by up to 200% under a 50 kPa surcharge and by more than 50% with higher moisture content. In contrast, increased soil unit weight had a substantial effect on decreasing lateral displacement by more than 50%. Pile spacing regulated the efficiency of soil arching with the closer spacing mobilizing stronger load transfer and limiting deflection and wider spacing weakening the arching and increasing movement. These findings offer practical recommendations for the design and monitoring of excavation support systems in urban settings, where displacement control is critical for maintaining the stability of the walls and preventing damage to adjacent infrastructure.
Abstract
This study investigates the effect of partially replacing conventional mineral limestone dust (LD) filler with nano-calcium carbonate (NCC) and nano-silica (NS) on the moisture damage resistance and mechanical strength of hot mix asphalt (HMA). Asphalt mastic samples were prepared using a 40/50 penetration grade asphalt binder, with NCC and NS incorporated at 0%, 5%, 10%, 15%, and 20% by weight of total filler. A constant filler-to-binder ratio of 0.72 was maintained across all mixtures. Performance was evaluated through indirect tensile strength (ITS), tensile strength ratio (TSR), compressive strength, and index of retained strength (IRS) tests. Results indicated resistance to moisture damage can be significantly enhanced by partially substituting NCC and NS for the LD filler. The optimum ITS was observed at 10% nano-filler content, showing a 33.0% increase for NCC and a 33.2% increase for NS mixtures compared to the control mixture. At same replacement level, TSR reached 91% for NCC and 92% for NS mixtures. Compressive strength improved by 4.27% and 5.95% for NCC and NS mixtures, respectively, at 20% replacement, while IRS improved to 95% for NCC and 94% for NS mixtures at the same level of replacement. According to Field Emission Scanning Electron Microscopy (FESEM), using NS and NCC nano-fillers, significantly enhances particle dispersion and reduced air voids compared to mixtures without nano fillers. Overall, mixtures with nano filler improved matrix density and filler–binder cohesion, also achieved the most compact structure, leading to better durability and moisture resistance.
Abstract
The accumulation of large amounts of construction and demolition waste in Iraq, especially after the 2014 conflicts, has created a serious environmental problem. To achieve sustainable goals, recycling these materials in the construction sector supports the principles of the circular economy and reduces the demand for natural aggregates, as recycling represents one aspect of crisis recovery. This study investigates the mechanical performance and bond strength of Self-Compacting Concrete (SCC) containing demolition brick aggregate (DBA) and discarded brick aggregate (CBA) at 100% replacement ratios for fine and coarse aggregates, with and without 10% crumb rubber (CR) as a volumetric replacement for fine aggregate. Ten SCC mixes were designed and experimentally evaluated after 28 days. The results showed that adding 10% rubber to the reference mix resulted in a 13.5% decrease in compressive strength and a 16.8% decrease in bond strength. Complete replacement of natural aggregate with recycled brick aggregate resulted in significant decreases in compressive and bond strengths of up to 60% and 50%, respectively. Furthermore, incorporating crushed rubber into the recycled brick aggregate further decreased the compressive and bond strengths. The predominant failure patterns observed in the bond strength test were splitting and sliding failure. The combination of these two types of waste aggregate could promote the use of sustainable SCC in practical applications