Engineering and Technology Journal

Interest in using recycled concrete aggregate (RCA) as a partial or full replacement for natural coarse aggregate (NCA) in concrete production has increased significantly in recent years. This shift contributes to reducing landfill usage and conserving natural resources. This study presents an experimental investigation into the behavior of sixteen rectangular beams cast with varying RCA ratios to examine the effects on ultimate load capacity and concrete strain. The beams, each measuring 1600 mm in length, 170 mm in width, and 260 mm in height, were reinforced with two longitudinal 12 mm steel bars, and 8 mm stirrups spaced at 75 mm intervals. The beams were categorized into four groups, with each group consisting of four beams containing RCA at replacement levels of 0%, 25%, 50%, and 75%, respectively. Group one beams were cast without rebar splice lengths, while the remaining three groups incorporated splice lengths of 10, 20, and 30 times the bar diameter (db), respectively. The experimental results indicate that RCA has a marginal impact on the ultimate load capacity. Specifically, for beams with a splice length of 10 db, RCA replacement at 25%, 50%, and 75% led to ultimate load reductions of 3.19%, 6.53%, and 11.7%, respectively. For beams with a 20 db splice length, the reductions were slightly lower at 2.78%, 5.05%, and 9.99%, respectively. In contrast, for beams with a 30 db splice length, the reductions were almost identical to those observed in beams without any splice length, measuring at approximately 1.59%, 2.82%, and 6.64%, respectively

Sustainable construction procedures use recyclable material; thus, the construction process and design choices are focused on planet health. SCC is a new generation of concrete that offers the achievement of high durability and flexibility in Rubberized Self-Compacting Concrete (RSCC) by employing recycled tire rubber and Self-Compacting Concrete (SCC). This review investigates the mechanical and cracking characteristics of rubberized self-compacting concrete and rubber content effects. Formwork requirement is brought down by the concrete’s ability to compact itself, thereby increasing user satisfaction. Energy is effectively absorbed, the flexibility of concrete is increased, and tire disposal is made simpler with rubber granules. Rubber penetration lowers the concrete's stiffness and leads to a change in its strength failure behavior. This review evaluates the fundamentally new mechanical and fracture mechanics characteristics of RSCC, including crack growth, fracture energies, and rendered resistance to crack initiation. Afterward, the bond between rubber and cement decreases, the strength reduces, and the samples fail. Although having lower compressive strength, rubber particles improve the overall toughness to yield and help to resist cracks and defects. This research also indicated that RSCC can assist a large number of hybrid-design systems, and various load combinations were evaluated. More work remains to be done to enhance the RSCC. Therefore, it is necessary to continue the research to define materials that have the needed characteristics for modern constructions so for their economic and ecological efficiency. Second, more research has to be done concerning the production of rubber particles and RSCC

Deep excavation projects in areas with high groundwater levels, such as industrial zones with large, heavy structures, present significant challenges. Secant piling techniques offer an effective solution for these conditions. These retaining walls are constructed by overlapping reinforced concrete and plain concrete piles to form a continuous barrier against soil and water ingress. This research investigates the effectiveness of secant pile walls as a deep excavation support system, focusing on the impact of various parameters on ground movement, analyzed using the DeepEX program. The case study centers on the Al Dawoodi/Al Mansur District in Baghdad, Iraq. Key factors examined include excavation depth, water level fluctuations, pile diameter, wall stiffness, soil properties, and the bonding between piles. The results revealed that lowering the groundwater level decreases the total lateral earth pressure while enhancing lateral resistance. For a constant excavation depth of 12.85 m, the total active stress at a depth of 9 m decreases as the water table level drops. When the water table is at -1.8 m, the total active stress is 92.952 kN/m²; at -3.5 m, it decreases to 87.837 kN/m²; and at -5.5 m, it further reduces to 82.016 kN/m². Additionally, deeper excavations result in greater horizontal displacement at the top of the wall. Increasing the pile diameter from 0.6 m to 1.2 m reduces lateral displacement from 0.503 m to 0.467 m but increases the bending moments from 832.56 kN.m/m to 1430.22 kN.m/m within the secant pile wall. Furthermore, the interlock ratio between the piles significantly influences wall performance. As this ratio increases, the bending moment also rises, with moment resistance increasing from 1134.72 kN.m/m to 1209.94 kN.m/m when

The use of recycled concrete aggregate (RCA) in structural applications has considerably increased in order to minimize the environmental effects of concrete buildings. Bond is a crucial characteristic of reinforced concrete that relates to the adhesion between the reinforcing steel and the surrounding concrete. This systematic review presents a comprehensive examination of the bond characteristics of steel bars and recycled coarse aggregate concrete RAC In addition, several components influencing both the load-slip curve and the failure mechanisms of RAC specimens were presented and discussed. Furthermore, prediction equations for bond strength and models of the bond-slip relationship between RAC and steel bars were summarized to enhance understanding of their applicability. The systematic review concentrated on scientific research articles to collect high-quality data, which can offer more in-depth insight into the bond behavior. The results show that several aspects influence the bond behavior of RAC specimens. These elements include the substitution rate of RCA, the steel bars' kind and size, the compressive strength, the length of embedment, and the performance of the aggregate. Both corrosion of steel rebars and cycles of freeze-thaw have an impact on the bonding performance between recycled aggregate concrete RAC and steel bars. The bonding performance between RAC and steel bars deteriorates as corrosion of steel rebars and damages from freeze-thaw approaches a particular threshold. Finally, the bonding strength of RAC exhibits an initial rise followed by a subsequent reduction with an increase in the rate of replacement of RCA

The growing negative effects of nonbiodegradable trash, including waste tires, underscore the necessity for sustainable alternatives in construction materials. This study examines the feasibility of manufacturing foamed concrete tiles reinforced with fibers, utilizing a superplasticizer (SP) with suitable quantities of waste tire rubber (WTR) from nonbiodegradable tires to reduce environmental pollution. Initially, standard concrete tiles with a density of 2400 kg/m³ and dimensions of 500 × 500 × 50 mm3 (Class A, IQS 1107) were manufactured for comparison. Subsequently, four types of foamed concrete tiles with a density of 1100 kg/m³ were produced: conventional foamed concrete tiles, foamed concrete tiles enhanced with SP, fiber-reinforced foamed concrete tiles utilizing polypropylene (PP), and fiber-reinforced rubberized foamed concrete tiles containing SP, PP, and WTR. To assess the effect of density, fiber-reinforced rubberized foamed concrete tiles were produced with densities of 800 and 1400 kg/m³. In examined foamed concrete tile preparations, a fraction of sand (≤ 2.36 mm) was substituted with WTR at optimal proportions of 50% for coarse WTR (4.75–10 mm) and 34% for fine WTR (≤ 2.36 mm). The comparison of foamed concrete tiles, with and without PP and WTR, against ordinary concrete tiles revealed a reduction in the rupture force while achieving a weight reduction of more than half. The failure modes transformed from brittle to ductile upon adding these wastes. Additionally, when the density of the rubberized samples increased to 1400 kg/m³, water absorption decreased by 3.9 and 9.43 after 0.5 and 24 hours, respectively, which aligns with IQS requirements

This study explores the potential of renewable energy in Owerri Municipal, Nigeria, using Geographic Information Systems (GIS) to identify optimal locations for renewable energy projects. The objective is to contribute to sustainable energy development by assessing the spatial distribution of renewable energy resources, evaluating environmental and socio-economic factors, and generating suitability maps for various renewable energy technologies. This was achieved by integrating GIS-based analysis with comprehensive data on solar radiation and Land Use Land Cover (LULC) types. Classifying LULC was a critical step in remote sensing, offering insights into various land cover classes' spatial distribution and dynamics. An aspect model was employed to determine slope orientation with maximum solar exposure. Proximity to road networks and grid stations in Owerri Municipal was also analyzed to identify the most accessible and motorable locations. Land surface temperature (LST), a measure of the earth's surface temperature, was also examined using data from the thermal Band-10 of the Landsat 8 OLI satellite. Combining these datasets and applying the weighted overlay tool, this research identified locations with the highest potential for renewable energy generation while minimizing negative environmental and socio-economic impacts. The results aim to assist policymakers, investors, and project developers in making informed decisions regarding renewable energy projects in Owerri Municipal and serve as a valuable reference for similar initiatives in other regions.

Identifying vulnerable agricultural lands at risk of meteorological drought is challenging for researchers. Its complexity lies in the fact that agricultural lands are irrigated by two sources: rain and rivers. In this research, we have developed a geostatistical model to separate river-dependent lands unaffected by meteorological drought waves and land vulnerable to the risk of meteorological drought. The inputs of this geostatistical model are the vegetation index and the humidity index extracted from Landsat 8, the rainfall from CHIRPS, and the LULC from ESA. The correlation between the Normalized Difference Vegetation Index (NDVI), the Normalized Difference Moisture Index (NDMI), and the rainfall was tested using the Pearson Correlation Coefficient (PCC) for more than five million pixels representing agricultural lands in Dhi-Qar Iraq. The Getis-Ord Gi* statistical index was used to cluster each pixel according to PCC value. This model achieved accurate results as it was validated using ground truth and the BEAST (Bayesian Estimator of Abrupt Change, Seasonality, and Trend) model, and the results of this model were promising. It was concluded that 42% of the lands in the study area are vulnerable to the risk of meteorological drought, rivers permanently irrigate 37%, and 21% are cultivated in the winter season only.

The contamination of vital life supplies by industrial waste, especially dairy effluent, is a growing global concern. This study investigates the impact of advanced oxidation processes (AOP) on treating dairy wastewater utilizing UV/H2O2 AOP. Utilized ultraviolet lamps in conjunction with hydrogen peroxide oxidant reagent (0.6, 1.2, 1.8, and 2.4 ml/L) in batch experiments under varying parameters to optimize the treatment of dairy wastewater before and following its introduction to the advanced oxidation process (AOP) system, by measuring Biological Oxygen Demand (BOD) and Chemical Oxygen Demand (COD). The impacts of varying circulation durations in a photocatalytic system (60-360 minutes), flow rates (200, 400, and 600 ml/min), pH levels (10, 7.5, and 5), H2O2 concentrations (0.6, 1.2, 1.8, and 2.4 ml/L), and UV light intensities (1 lamp, 2 lamps). Enhanced COD and BOD removal efficiencies can be achieved by employing an advanced oxidation process (AOP) under optimal conditions, which include four reactors connected in series, each equipped with two lamps, a flow rate of 200 ml/min, a pH of 5, a hydrogen peroxide concentration of 1.2 ml/L, and a circulation duration of 360 minutes. Under these conditions, the COD removal was around 86.40%, while the BOD reached 86.23%. The COD and BOD removal efficacy by the photocatalyst system technique was nearly identical. In summary, the photocatalytic system demonstrated superior degradation and mineralization; hence, its application in dairy wastewater treatment is compelling.

Sawdust industrial residue could be hazardous to the environment, but it becomes pozzolanic when incinerated. Thus, harnessing sawdust ash (SDA) and lateritic soil as road construction materials for low-cost roads is apt. However, modeling and prediction of the properties of soils treated with SDA have received very little attention. This study predicted the compressive strength of lateritic soil treated with cement and SDA using an Artificial Neural Network (ANN). The soil was found to belong to A-2-4(0) in the AASHTO rating and clayey sand (SC) in the Unified Soil Classification System. The soil minerals composition was conducted using an x-ray diffraction technique, which comprises non-clay minerals such as quartz, albite, orthoclase, goethite, and muscovite, as well as clay minerals like clinochlore. The tests carried out on the treated soil were compaction tests, California Bearing Ratio (CBR), unconfined compressive strength (UCS), and durability tests. The maximum dry density of the reinforced soil was reduced, whereas the optimum moisture content increased with an increase in SDA content. At the addition of cement and SDA of up to 8% and 30%, respectively, the strength properties like the CBR and UCS at 7 days of curing increased by up to 1965.46% and 989.25%, respectively. Also, the reinforced soil satisfied the durability requirements. The treated soil could be used as the sub-base of road pavement structures. The ANN modeling dependably predicted the unconfined compressive strength at 7 days of curing of the reinforced soil with coefficients of correlation of 0.989 and 0.996 for training and testing, respectively.

Ecological implications posed by the cement industry, biomass ashes, and agricultural waste are growing with emerging concerns. Hence, this paper analyzes and evaluates the characterization of Iraqi date palm frond waste ash (PFWA) and its potential impact on the performance of cement-based mortar. PFWA was utilized to substitute 10, 20, and 30% of the partial weight of cement. The
experimental program consists of three main parts: Firstly, the preliminary
physicochemical and microanalysis characterization of PFWA powder was
investigated and corresponded with the limits of ASTMC-618. Secondly, the
compressive and flexural strength, dry density, and water absorption capacity of
the fabricated cement-based mortar with the adopted replacement percentages
were observed. Finally, the cost analysis of the final products was conducted to
obtain a cost-effective evaluation. Generally, the results proved that incorporating
10% PFWA boosts the hardened characteristics. Alternatively, further upgrading
of the PFWA content adversely affects the investigated properties. After 28 and
90 days, 10% PFWA boosted the compressive strength by around 15% compared
with the control mixture. The cost analysis proves a reduction in the total cost of
the mortar by 8.1, 16.1, and 24.1% by replacing 10%, 20%, and 30% of OPC with
PFWA. Therefore, using PFWA as SCM in cement-based composites could be a
promoted alternative that would benefit the management, recycling, and reusing
rate of agricultural waste and support the advancement of sustainability through
the construction sector with cost-effective advantages

Ductility is an important mechanical property of concrete structures, in tensile members, as it is the property that allows the structural member to deform plastically long before the failure point. To increase the deformation period of the beams, i.e., the ductility of failure. In the current paper, four reinforced concrete beams were modeled and compared using nonlinear finite element analysis. Reinforced concrete beams are developed and analyzed by using ABAQUS commercial software. Nonlinear material behavior, as it relates to steel reinforcing bars and plain concrete, is simulated. The effect of the change of the concrete compressive strength in the upper one-third of the beams on the ductility, the ultimate strengths, and the mode of failure of beams are investigated. One of the beam specimens was used as a reference. The change in the compressive strengths in the compressive zone was in the range of 27, 31, 37, and 42 MPa. The results of the analysis of the modeled beams were validated and compared with beams tested experimentally by previous researchers. It was found that load-deflection curves of the FE modeling of the beams match the same findings in the experiments. Furthermore, to investigate different techniques in strengthening the upper third of the beams for enhancing ultimate strength and ductility behavior, a parametric study was performed by modeling beam specimens consisting of two groups, among them using a hybrid of Carbon nanotubes (CNTs) & steel fiber, which was added to the concrete mixture of the upper third of a beam specimen and was used as strengthening layer stuck to the top layer of the compression zone of another beam. It was found that the beam that was strengthened in the compression zone by the layer of the concrete containing the mixture of the CNTs & steel fibers increased the beams' strength and ductility; hence, the ultimate load and deflection were increased by 63%, and 40%, respective