Papers by Keyword: Concrete

Abstract: The housing sector accounts for a high percentage of total energy consumption in Iraq, with most energy usage on air-conditioning systems in summer to provide comfort to residents. This study simulates energy consumption for a typical 200 m², two-story, single-family building in Al Amarah city, Iraq, to compare heating, cooling, and total energy use across three different building configurations. Locally manufactured hollow concrete blocks made with 40 × 20 × 20 cm3 dimensions were adopted to improve their thermal performance by filling the cavities with Polystyrene insulation. The research examined three residential building configurations: (i) a base case built with traditional fired-clay brick, (ii) hollow concrete block walls free of insulation, and (iii) hollow concrete block walls incorporating thermal insulation. Energy simulations using eQUEST software were conducted, utilising the thermal response factor method as the primary tool to analyse the impact of external environmental conditions on cooling and heating loads. The results demonstrated significant annual energy savings for the building with hollow concrete blocks with and without insulation. However, insulated hollow concrete blocks showed reduced annual energy consumption compared to the common brick building system. Specifically, the insulated and uninsulated blocks attained energy savings by 29.4% and 16.08%, respectively, for north-facing orientation.

Abstract: ’This study investigates the mechanical performance of concrete reinforced with recycled polyethylene terephthalate (PET) fibers obtained from discarded plastic bottles, aiming to promote sustainable waste reuse in construction materials. Previous studies on PET fiber reinforced concrete have mainly examined the influence of fiber length and content separately, without considering their combined effects on mechanical properties. In this work, the interactions between fiber length, volume fraction, and mechanical behavior were systematically analyzed using a Central Composite Design (CCD) within the framework of Response Surface Methodology (RSM). Concrete incorporating recycled PET fibers was evaluated at three volume fractions (0.3%, 0.8%, and 1.3%) and three lengths (20 mm, 40 mm, and 60 mm), while maintaining a constant water-to-cement ratio. Sixty specimens were tested to assess both fresh and hardened properties. The greatest loss of workability occurred for the mix containing 1.3% fibers with a length of 60 mm, corresponding to about a 25% reduction compared with the control. Response Surface Methodology (RSM) based on a Central Composite Design (CCD) identified 0.3% fiber content and 40 mm length as the optimal combination, representing the mix that simultaneously maximized both compressive (26 MPa) and tensile strengths (3 MPa) according to the predictive model.

Abstract: Concrete, often conceptualized as an inert construction material, is fundamentally a dynamic composite that undergoes continuous physicochemical transformations throughout its service life, governed by natural degradation processes and mechanical aging. Despite its widespread utility, concrete’s quasi-brittle behavior, characterized by low tensile strength and susceptibility to abrupt failure under traction-dominated loading regimes, remains a critical limitation in structural engineering. To address these intrinsic vulnerabilities, the rehabilitation of concrete infrastructure has emerged as a pivotal research domain, with advanced retrofitting techniques focusing on enhancing tensile performance and transitioning failure modes from brittle to ductile. Among these, externally bonded reinforcement (EBR) using fiber-reinforced polymer (FRP) composites has gained prominence as a high-efficacy solution for augmenting load-bearing capacity and structural resilience. This study employs a parametric finite element analysis (FEA) framework in Abaqus/CAE to systematically evaluate the mechanical efficacy of two distinct carbon fiber-reinforced polymer (CFRP) retrofitting strategies: (1) externally bonded CFRP plates and (2) internally embedded CFRP reinforcement within the beam’s cross-section. The computational investigation quantifies the influence of reinforcement placement on critical performance metrics, including ultimate load capacity, deformation ductility, and failure mechanisms. Numerical results demonstrate that internally integrated CFRP reinforcement significantly enhances structural ductility and peak load resistance, while maintaining a marginal mass differential. These findings underscore the critical role of reinforcement topology in optimizing stress redistribution and crack mitigation, offering actionable insights for the design of next-generation retrofitting protocols that prioritize both strength and serviceability. The study advances the discourse on sustainable infrastructure rehabilitation by delineating a pathway for leveraging embedded composite systems to transcend the inherent limitations of conventional concrete matrices.

Abstract: Concrete is a widely used material for construction, playing a crucial role in infrastructural design. Recently, with the increase in threats and protection requirements, developments and investigations are continually needed in concrete for impact-resistant applications. This study investigates the ballistic performance of sixteen concrete formulations subjected to high-velocity impact using a 12.7×99 mm armour-piercing projectile fired from a single-stage gas gun at an impact velocity of 850 m/s. The experimental campaign evaluated depth of penetration (DOP), mass loss, and failure across different concrete formulations under the same test conditions. Concrete types included ordinary concrete (OC), steel- and basalt-fibre-reinforced mixes, ultra-high-performance concrete (UHPC), basalt fibre reinforced concrete (BFRC), rubber aggregate concretes (RSC), and cement-modified variants. Qualitative analysis, high-speed camera sequences, and three-dimensional (3D) scanning were employed to assess the penetration response of each configuration. Results show that UHPC formulations exhibited the best ballistic resistance, with DOP values reduced by nearly 50% compared to ordinary concrete. Steel-fibre-reinforced concretes showed a fibre-dosage-dependent improvement in DOP and material retention, with SF160 emerging as the most balanced solution. In contrast, rubber-modified mixes demonstrated higher DOP but effectively limited surface scabbing. These findings highlight the importance of material composition in optimising ballistic performance and guide the selection of concrete systems for infrastructure protection applications.

Abstract: The article is devoted to the determination of the main physical and mechanical characteristics of compressed concrete at different strain rates of its. A method for predicting the main strength and deformation characteristics of compressed concrete in the widest range of its loading rates is proposed: from instantaneous dynamic to long-term with the maximum possible development of creep deformations. This method is based on the well-known law of conservation of potential energy of material deformation (up to its destruction) and the general patterns of change of the known integral characteristic of concrete - the factor of elasticity-plasticity. The functional interdependence of the levels of strength and deformability of compressed concrete for its different strain rates was established.

Abstract: The use of light concretes on porous aggregates in various areas of construction has an interest in many countries. The volume of concrete produced can be increased and the cost can be reduced by using a multicomponent binder, which includes Portland cement, quicklime, fly ash and chemical additives. Comprehensive consideration of the physical and technical properties of light concretes on porous aggregates makes it possible to reasonably identify rational areas of its application in products and structures. The selection of compositions and the study of the properties of structural light concretes was carried out by calculation and experimental method. The data were processed using experimental and statistical modeling, which made it possible to assess the degree of influence of the selected factors to the strength and deformation properties of light concretes.

Abstract: With the continuous development of novel concrete formulations incorporating various materials, a prevalent issue is their susceptibility to deterioration, which often results in the formation of cracks within the internal structure. This study mainly explores the impact of liquid concrete deep-penetration sealer (CDPS) on the durability of concrete. The evaluation of durability included compressive strength tests, abrasion resistance tests, permeability tests, and rapid chloride ion penetration tests. Although compressive strength and permeability are conventionally regarded as the primary metrics for assessing concrete performance in the industry, abrasion resistance is often overlooked. To address this gap, this study incorporated abrasion resistance testing to ascertain the sealer's efficacy in mitigating surface wear. This barrier mitigates the ingress of deleterious external agents, thereby enhancing the overall durability of the concrete. Furthermore, the results highlight the potential of such treatments to significantly improve critical performance parameters, particularly in terms of wear resistance and resistance to chloride ion penetration, which are essential for prolonging the lifespan of concrete structures.

Abstract: Incorporating steel binding wire waste into concrete offers a sustainable solution that aligns with green construction practices. This study aims to explore the feasibility of using untreated steel binding wire (SBW) waste as a material in concrete production. This research examines the mechanical properties of concrete containing SBW as a partial replacement for sand to improve the concrete’s structural performance by addressing its inherent weakness in tension. Two different shapes of SBW (powder and fiber) and three ratios of replacement of sand by SBW (10%, 15%, and 20%) were considered. The obtained results demonstrate that incorporating SBW wastes enhances the fresh concrete workability. The increasement ranged from 15% to 35% for powder and fiber of SBW, respectively compared to the ordinary concrete (OC). When fiber SBW is added, the concrete density increases from 3.62% to 5.9% for 10% and 20% of SBW, respectively compared to OC. Whereas for powder SBW incorporation, it decreases from 1.7% to 0.37% for 10% and 20%, respectively. The addition of SBW fiber improves compressive strength (CS), which increases as the replacement ratio increases by 73% and 104%, for replacement ratios of 10% and 20%, respectively. However, a low ratio of SBW powder increases the compressive strength by 49%, while higher ratio results in a decrease in CS and the gain drops to 2%. Both SBW fiber and powder addition concrete demonstrate similar behavior in tensile strength (TS) as observed in compression. The study concludes that adding up to 20% SBW fiber and less than 10% SBW powder significantly enhances the mechanical properties of concrete, providing a practical method for waste utilization and material performance improvement.

Abstract: Over the years, plastic production has increased in direct proportion to the amount of plastic waste generated globally. Single-use plastics such as low-density polyethylene (LDPE), linear low-density polyethylene (LLDPE) and polypropylene (PP) have increased significantly. Therefore, they can be used as aggregates in the production of concrete to reduce the generation of plastic waste in the environment. LDPE, LLDPE and PP were the plastic types used, with 25% and 50% of plastic aggregate replacing sand. The tests included Fourier-transform infrared spectroscopy (FTIR) analysis of the plastic granulate, density, and compression tests of the concrete specimens. The type of granulate used follows the type of plastic tested from the results of the FTIR characterization. It was found that the compressive strength of concrete containing 25% of plastic aggregates was higher than that of concrete containing 50% of plastic aggregates. The compressive strength of the LLDPE concrete specimens is 31.4 MPa, whereas the compressive strength of the LDPE concrete specimens is only 26.3 MPa and that of the PP concrete specimens is 30.4 MPa. Further research will be carried out to determine the optimum strength of concrete with plastic aggregates.

Abstract: This paper deals with the experimental determination of the freezing and thawing resistance of concrete using an innovative approach to evaluating the signal obtained by the ultrasonic pulse velocity test. Test specimens made of two types of concrete were used for the experiment. They were concrete mixtures of similar composition - the same components were used for their production. The only major difference was their level of resistance to freezing and thawing. The test specimens were prisms produced in the laboratory using plastic moulds and cylinders obtained by core drilling from the experimental pillar. The core-drilled test specimens were exposed to 100 freeze-thaw cycles and the test prisms with as many as 200 freeze-thaw cycles. After every 25th cycle, the non-destructive parameters were determined using the ultrasonic pulse velocity test as well as the resonance method. It was found that more advanced parameters of the ultrasonic signal than just its velocity were useful for evaluating the freezing and thawing resistance of concrete.