Al-Qadisiyah Journal for Engineering Sciences

Abstract Interlayer bonding strength is a critical factor influencing the durability and performance of asphalt pavement systems. This study investigates the combined effects of tack coat type, application rate, and substrate surface texture on the interfacial shear strength (ISS) between asphalt layers. Four surface conditions, new wear, binder, aged-worn, and milled, were simulated to represent varying field scenarios. The interface morphology was quantitatively analysed using both the sand patch method and 3D laser scanning. Seven tack coat formulations were evaluated, including a conventional tack coat, hard-grade cutback, and a novel hybrid material modified with Styrene-Butadiene-Styrene (SBS) and polylactic acid (PLA) labels MS4-70 and MSP5-70, respectively. The Tack coats were applied at three residual rates (0.1, 0.23, and 0.35 L/m² ). Direct shear testing was conducted to assess ISS under various conditions. The results reveal that surface roughness and tack coat type significantly impact bonding performance. Milled surfaces showed the highest texture and yielded superior shear performance due to enhanced mechanical interlock and bonding area. Conversely, the wear surface, characterised by a dense gradation and smooth profile, exhibited the lowest ISS values. The hybrid MSP5-70 tack coat represents a new generation of modified bonding that consistently produces the highest ISS values compared to conventional tack coats (CRS-1, CSS-1h, and RC70). These findings underscore the importance of tailored tack coat formulations and texture-specific application strategies for enhancing pavement structural integrity.

Abstract Enhancing and retrofitting existing structural components is a critical process that aims to restore or improve the performance, safety, and durability of constructions. Foundations in particular can be susceptible to damage, failures, or differential settlements for a number of different reasons, including improper design parameters, lack of soil investigations, additional weights produced by story extensions, lateral loads resulting from seismic events, or changes to the structure’s purposes post-construction. Thus, the need for effective and economic strengthening methods is essential. Available techniques used to increase the structural and geotechnical foundation capacity are discussed in detail in this review paper. The geotechnical underpinning techniques involve soil improvements by piling, micro-piling, grouting, helical piers, and geosynthetic reinforcements, as well as structural enhancement approaches including concrete jacketing and footing enlargement. In terms of geotechnical improvement, micropiles were found to be the most effective in enhancing and stabilizing the foundation, and helical piers were the fastest and easiest to install in the soil. On the other hand, enlarging the footing offered better load distribution and enhancement to the shear capacity.

Abstract This study aims to experimentally investigate the two-way shear performance of high-strength concrete flat slabs containing integrated ducts. A total of eight slab specimens containing ducts were manufactured, along with one solid slab functioning as the reference. The experimental program focused on two primary parameters: the horizontal distance of the duct opening from the column face (evaluated at 0, 50, and 100 mm for 50 × 50 mm and 50 × 150 mm openings) and the effect of duct width (evaluated at 50 and 150 mm). The performance of slab specimens was adversely affected by increases in duct width and nearness to the column face. As the duct width expanded from 50 mm to 150 mm, an apparent reduction in load capacity occurred, peaking at 43.9% at the column face. Similarly, closer placement of the duct led to a steeper reduction. Serviceability decreased considerably, with specimens having wider ducts at 0 mm or 50 mm often failing to reach the service load. In contrast, those at 100 mm experienced excessive deflection, up to 94% higher than the control, indicating a severe loss of stiffness. Toughness consistently declined, with a maximum reduction of 51.9% at the column face. It was observed that all slab specimens, even the solid control specimen, exhibited the same failure mode, known as punching failure.

Abstract Pervious concrete is an environmentally friendly paving concrete that has attracted significant attention due to its environmental advantages, particularly in mitigating the influences of urban heat and improving stormwater runoff. This study aims to investigate the influence of three types of lightweight coarse aggregates on the physical properties of pervious concrete mixtures. These types are pumice and two types of lightweight expanded clay aggregates (LECA): low density (LD) and high density (HD). Previous concrete mixtures were modified by styrene butadiene rubber (SBR) at 5% by cement mass and prepared. The physical properties of this type of concrete, including porosity, permeability, and hardened density, were investigated. The results indicated that replacing the normal coarse aggregate with a volumetric ratio of 10% lightweight coarse aggregates resulted in a significant increase in permeability and porosity while at the same time reducing density. The highest value of permeability was achieved by the mix containing 10% of LD without SBR, with an increment of 35.9%, compared to the control mix. The porosity was increased by 28.6% in the mix containing 10% of PA without SBR, compared to the control mix. On the other hand. Regardless of the type of lightweight coarse aggregate used, the addition of SBR to the lightweight aggregate mixtures significantly decreases the porosity and permeability while increasing density. Based on the findings of this study, it can be concluded that the type of aggregate chosen has a significant effect on the physical properties of pervious concrete.

Abstract Construction and demolition waste is recognized as a major waste stream made by humans around the world. The use of crushed old concrete in a type of recycled aggregate concrete (RAC) has been a promising technique to promote construction sustainability. However, the mechanical behaviors and the durability of RAC are inferior to those of concrete incorporating natural aggregate. Therefore, the creation of effective methods to lessen these harmful consequences is crucial. It stands to reason that the dilatation of concrete can be restricted by placing it in a confinement state. Due to the confinement provided by the steel casing, a steel tube filled with concrete can be considered suitable for improving the working mechanism of the RAC. In this paper, a series of comparison tests were conducted to investigate the behavior of square double skin steel tubes filled with self-compacting concrete (SCFDST) columns under different loading conditions. Ten specimens consisting of five normal SCFDST and five recycled aggregate self-compacting concrete filled double skin steel tube (RSCFDST) columns were tested under (axial, uniaxial, and biaxial) compression loads. Loading eccentricity and full replacement of coarse aggregate were adopted as the main parameters in the experiments. Overall, the failure mode, ultimate capacities, and general deformational behavior have been presented in this paper. According to the results, comparable structural behavior and failure shapes were observed between the RSCFDST columns and their normal SCFDST counterparts with an acceptable reduction in ultimate bearing capacity. The ultimate bearing capacity of both RSCFDST and conventional SCFDST are significantly harmed by eccentricity, while the ductility of the columns was improved by the RAC replacement. The failure mode of normal SCFDST and RSCFDST columns was overall buckling under a uniaxial and biaxial compression load, whereas compression failure was the failure mode of the axially loaded columns. As expected, due to the confinement effect of the steel tubes, the strength of the sandwich concrete was enhanced, and all tested columns exhibited ductile failure.

Abstract An innovative experimental approach was developed to enhance NaCl removal using porous broad-crested weirs with different alumina-limestone configurations in an open-channel flow under controlled hydraulic conditions. Eight experimental cases were systematically evaluated, examining pure limestone, pure alumina, and mixed arrangements (Al-Ls-Al, Ls-Al-Ls) under two flow rates over 240 minutes. Results demonstrate that pure alumina achieved superior performance with 5.88\% average removal efficiency, significantly outperforming pure limestone (2.01-4.27\%) and mixed configurations (4.41-5.01\%). Limestone exhibited significant hydraulic dependency, with removal efficiency increasing by 112\% when flow rate increased from through flow to through flow limit conditions, while alumina demonstrated consistent performance across both flow regimes. All configurations showed initial rapid removal followed by a gradual approach toward equilibrium efficiency, with the most significant removal occurring within the first 10 minutes. Mixed material configurations (Al-Ls-Al and Ls-Al-Ls) achieved removal efficiencies that fell between those of pure materials, indicating no enhancement beyond the individual material properties. The study reveals that while alumina provides optimal NaCl removal, limestone under enhanced flow rates offers economically viable alternatives, achieving 71\% of alumina's performance. Porous broad-crested weirs represent promising technology for sustainable water treatment applications.

Abstract This paper examines the characteristics of soft clayey soils prevalent in the central and southern regions of Iraq. The study focuses on assessing the impact of electro-osmosis (E.O.) on both the shear strength of these soils and the efficiency of pile driving, including the installation of experimental piles. The investigation employs laboratory equipment and locally sourced Baghdad soft clay soil to conduct a comprehensive test program. This program encompasses conventional soil tests and utilizes two specialized soil boxes designed for E.O. to collect essential parameters for pile prototype installation. The primary objective is to explore how E.O. affects the pile driving process. The shear strength was evaluated through four vane shear tests, with vertical E.O. voltage applied at varying depths. The findings indicate that the shear strength in anode regions exceeds control results by up to 100%, with a decrease in strength observed as testing moves towards the cathode. Another significant finding is the Percentage Reduction in Blows, which typically ranges from 65% to 90%. These outcomes were derived from four tests conducted at a soil water content of 25%.

Abstract For jointed precast concrete pavements, this study suggests a novel demountable dowel bar system made of glass fiber reinforced polymer (GFRP). The conventional steel dowel systems have limited reuse, corrosion, and concentrated stress. On the other hand, the suggested solution features a stainless steel sleeve that accommodates the GFRP bar, providing both removability and durability. Under monotonic loading circumstances, four slab specimens measuring 300 mm, 400 mm, and 800 mm in width were put to the test. The findings demonstrated that, in contrast to specimens with traditional steel dowels, those with GFRP dowels had distinct failure processes. The suggested system's potential application in modular pavement systems was indicated by its encouraging load-bearing capability and flexibility.