Bengin Masih Awdel Herki

The use of steel slag (SS) as partial replacement of natural fine and coarse aggregates and micro silica (MS) as partial replacement of cement was experimented with respect to engineering performance of concrete. In the present study, 0–70% of the natural sand and gravel, respectively, were replaced by fine steel slag (FSS) and coarse steel slag (CSS) as replacements on an absolute-volume basis. Also 10% MS was added to selected mixes in which 0%, 30%, 50%, and 70% SS was used. Workability, density, compressive strength, splitting tensile strength, flexural strength, sorptivity, ultrasonic pulse velocity (UPV) and performance in an adopted modified freeze–thaw exposure protocol were assessed. The SS-only mixtures showed the best compressive strength of 42.1 MPa which was obtained from the 40% SS mixture with no MS. However, when the SS replacement level increased, the compressive strength values decreased, even though the density of the concrete was increased, for example, to 70% SS, compressive strength was reduced to 31.8 MPa. The tested combinations of mixtures containing MS had 30% SS + 10% MS with the best overall combination of mechanical and durability related properties measured. The improvements observed herein are similar to those reported in literature for the filler and pozzolanic effects but were not directly ascertained in the present study by microstructural characterization, and thus specific changes in the interfacial transition zone, pore structure or C–S–H formation are not directly obtained. Likewise, the occurrence of possible volumetric instability and microcracking at high SS replacement levels are literature-supported interpretations, due to the absence of measurement of free CaO/free MgO contents and expansion. The results of the freeze-thaw test, based on the modified exposure protocol, are comparative in nature and do not represent standard performance. The results of a screening-level embodiment of carbon comparison showed that the 30% SS + 10% MS mixture has the highest calculated compressive-strength-to-embodied-carbon ratio of all the mixtures tested. The results show the engineering potential of moderate SS replacement and MS incorporation as well as the need for direct microstructural, expansion and life cycle evaluation in the future.

The research undertaken examines the impact of recycled tire steel fiber (RTSF) and waste aluminum (WAL) on the mechanical properties and freeze–thaw durability of sustainable fiber-reinforced concrete (FRC). RTSF (0.5%, 1.25%, and 2%) and WAL (10%) were added on their own and as hybrids. Findings revealed that 1.25% RTSF was the optimum content to use, as it enhanced compressive strength by 12.8% with high durability. Tensile and flexural strengths also increased for higher fiber contents with the help of good crack bridging and increased post-crack ductility; maximal gains of 52.6% and 11.8% were obtained at 2% RTSF. In contrast, the increase in porosity and the decrease in strength were demonstrated with WAL, whereas hybrid mixes delivered a balanced performance. Microstructural analysis ensured that there was an enhanced bonding between the fibers and the matrix, coupled with a refinement in the pore at the optimal fiber content. This study establishes the structural viability, durability improvement, and sustainability prospect of hybrid recycled material concrete as a construction material with eco-efficient and resilient applications.

The sustainable utilization of industrial by-products in concrete production has recently become a priority in modern construction engineering due to its global availability, environmental benefits, and potential engineering properties. The use of steel slag (SS) in fine and coarse sizes with mineral admixtures, including micro silica (MS), in concrete design must be thoroughly examined for durability and efficiency, considering several variables, including their types and contents. The combined impacts of MS and SS must also be well investigated. This article examined the mechanical and durability properties of concrete after adding SS and MS separately and in combination. In an experimentally based investigation, fine steel slag (FSS) and coarse steel slag (CSS) was substituted for natural fine and coarse aggregate, respectively in varying ratios (20% - 70%) in the same mixture with and without MS (10%) as partial cement replacement. The concrete mixtures' workability, density, compressive strength, flexural strength, splitting tensile strength, capillary water absorption rate (sorptivity), and freeze-thaw resistance were assessed. Results indicate that compressive strength increased progressively up to 40% SS replacement, achieving 42.1 MPa compared with 36.4 MPa for plain concrete. Beyond 50% replacement, strength declined despite continuous increases in density. According to the mechanical properties and durability investigated in the present study, the optimum performance was observed in the replacement of 30–40% SS along with 10% MS, which confirmed its modification. The findings provide engineers, researchers, and decision-makers in the construction industry with valuable guidance on the practical benefits and elements to consider when including SS and MS into concrete mixtures. This application maximizes resource efficiency and reduces environmental impact while enhancing the mechanical and durability properties of concrete.

The construction industry is a major source of environmental degradation as it is responsible for a significant share of global CO₂ emissions, especially from cement and aggregate consumption. This study fills the need for sustainable construction materials by developing and evaluating a low-carbon fiber-reinforced concrete (FRC) made of steel slag powder (SSP), processed recycled concrete aggregates (PRCAs), and waste steel rivet fibers (WSRFs) derived from industrial waste. The research seeks to reduce dependency on virgin materials while maintaining high values of mechanical performance and durability in structural applications. Sixteen concrete mixes were used in the experimental investigations with control, SSP, SSP+RCA, and RCA, reinforced with various fiber dosages (0%, 0.2%, 0.8%, 1.4%) by concrete volume. Workability, density, compressive strength, tensile strength, and water absorption were measured according to the appropriate standards. Compressive and tensile strength increased in all mixes and the 1.4% WSRF mix had the best performance. However, it was found that a fiber content of 0.8% was optimal, which balanced the improvement in strength, durability, and workability by sustainable reuse of recycled materials and demolition waste. It was found by failure mode analysis that the transition was from brittle to ductile behavior as the fiber content increased. The relationship between compressive, tensile strength, and fiber content was visualized as a 3D response surface in order to support these mechanical trends. It is concluded in this study that 15% SSP, 40% PRCA, and 0.8% WSRF are feasible, specific solutions to improve concrete performance and advance the circular economy.

The study looks at how adding locally sourced recycled tire steel fibers (SF) and waste aluminum (WAL) affects the strength and absorption capacities of fiber-reinforced concrete (FRC). FRC is a popular choice in sustainable construction because it improves strength, durability, and cracks resistance. However, the performance of FRC is influenced by fiber type, volume, and distribution. In this research, three SF volume fractions (0.5%, 1.25%, and 2%) and 10% WAL as a partial replacement for fine aggregate were incorporated into eight concrete mixes, including plain concrete, SF-enhanced concrete with varying fiber contents, WAL concrete, and combined SF-WAL mixes. Workability, density, compressive strength, splitting tensile strength, and water absorption were determined after 28 days by the experimental program. Mechanical properties were found to increase by 1.25% SF, but strength decreased when the SF content was raised to 2%, as it caused fiber clumping. The experiment showed that when WAL is used alone, its effect is to boost workability, but it lowers the strength in compression and tension. Still, using 1.25% SF together with 10% WAL brought about a good balance, preserving the concrete’s strength. Using a moderate amount of SF limited water absorption, but when the concrete contained WAL, water absorption went up somewhat. According to this study, adding recycled SF and WAL to concrete improves its strength and supports sustainable construction.

Construction industry is the major source of environmental degradation as it is responsible for a significant share of global CO₂ emissions, especially from cement and aggregate consumption. This study fills the need for sustainable construction materials by developing and evaluating a low-carbon fiber reinforced concrete (FRC) made of steel slag powder (SSP), processed recycled concrete aggregates (PRCA) and waste steel rivets fibers (WSRF) derived from industrial waste. The research seeks to reduce dependency on virgin materials but while maintaining high values of mechanical performance and durability in structural applications. Sixteen concrete mixes were used in the experimental investigations with control, SSP, SSP+RCA, and RCA; reinforced with various fiber dosages (0%, 0.2%, 0.8%, 1.4%) by concrete volume. Workability, density, compressive strength, tensile strength, and water absorption were conducted according to the appropriate standards. Compressive and tensile strength increased in all mixes and the 1.4% WSRF mix had the best performance. However, it was found that a fiber content of 0.8% was optimal, which balanced the improvement in strength, durability, and workability by sustainable reuse of recycled materials and demolition waste. It was found by failure mode analysis that the transition was from brittle to ductile behavior as the fiber content increases. The relationship between compressive, tensile strength and fiber content was visualized as a 3D response surface in order to support these mechanical trends. It is concluded in this study that 15% SSP, 40% PRCA, and 0.8% WSRF are feasible, specific solution to improve concrete performance and advance the circular economy.

As a non-biodegradable material and a major environmental hazard due to its discharge into the environment, by-products like steel production steel slag (SS) are disposed of in open spaces, agricultural lands, and close to residential areas. This by-product is now considered to have qualities that make it a potential substitute for cement and natural aggregates in the manufacturing of concrete or clinker in the cement manufacturing sector. The effects of using a novel type of SS made in an induction furnace (IF) in place of Portland cement and natural coarse aggregate in concrete were investigated experimentally. Steel slag powder (SSP), low-density steel slag (LDSS) aggregate, and high-density steel slag (HDSS) aggregate were all physically and chemically examined in this study. Each of these three replacement materials was added to concrete in weight proportions of 20%, 40%, and so on. The performance of the resultant mixtures was compared to that of the plain concrete, and the mechanical properties such as split tensile strength, flexural strength, and compressive strength were examined, along with the durability properties of water absorption (WA) and freeze–thaw, and the non-destructive testing of ultrasonic pulse velocity (UPV) of the concrete mixtures were also evaluated. The results indicated that adding HDSS to the concrete increased its mechanical and durability properties, while adding LDSS and SSP resulted in a small and a significant drop in mechanical properties, respectively, when compared to the plain concrete. The increase in compressive strength and the decrease in water absorption at the standard age of 28 days reached 5.2% and 2.1%, respectively. The percentage decrease in compressive strength (8.95–21.74%) of SS concrete mixtures after freeze–thaw cycles was greater than that of the control concrete. Additionally, a concrete mixture containing 40% HDSS yielded the best results.

Durable building materials are essential for sustainability in construction projects, aiming to reduce environmental damage from the start to the end of a building’s life. Reducing the use of Portland cement in concrete production is essential because of the significant CO₂ emissions generated globally during its production process. This study investigates the workability, compressive strength, and water absorption of concrete when Portland cement is partially substituted with waste glass powder (WGP) and recycled concrete powder (RCP). These two waste powders can be used to partially substitute Portland cement in order to produce environmentally friendly concrete. The activity of the particles in concrete made from these two waste powders is mostly determined by the type and rate of the powders, as well as the curing methods. Therefore, the current research examines how different curing conditions impact the workability, compressive strength, and water absorption characteristics of this innovative eco-friendly concrete that includes the abovementioned waste powders. According to the experimental results obtained, adequate strength can be achieved using an appropriate replacement level of the powders and curing methods. Therefore, the application of these two recycled mineral admixtures in concrete can save Portland cement and has certain environmental and economic benefits.

The quality of concrete and serviceability for three old buildings utilizing non-destructive testing(NDT) method of rebound hammer (RH) and ultrasonic pulse velocity (UPV) was assessed in the presentstudy. Identification, classification and evaluation of in-situ concrete have helped us to decide whether thesethree buildings need to be repaired and in result extent their service life or it is not acceptable for its intendedusage and they need to be demolished. To evaluate the level of deterioration in historical and fire-damagedbuildings or infrastructures, non-destructive testing (NDT) methods can be used. In fact, NDT methodemploys inspection techniques to evaluate engineering properties to see if it is acceptable for its intendedusage that does not need specimens to be crushed like the destructive testing method. The NDT method ofrebound hammer (RH) and ultrasonic pulse velocity (UPV) in combination with conventional methods suchas internal and external visual inspection and concrete color change to locate deterioration was used toevaluate the quality of concrete structures for three old buildings. According to the results obtained the RHand UPV can be used as reliable tools to predict the mechanical properties of concrete structures subjectedto fire and/or weathering deterioration. In addition, combining the two NDTs decreased inaccuracies causedby utilizing one method alone to evaluate concrete quality.

The improper curing of concrete can seriously affect its hardened properties. However, a large quantity of water is required to cure concrete after casting. Water is a valuable resource and its availability is posing a particular challenge in the Middle East including the Kurdistan region of Iraq. Self-curing concrete may be considered a novel curing method in that the water inside the concrete mix is retained so that hydration can continue without the supply of additional water after casting. Therefore, the aim of this study was to include a self-curing agent, named Polyethylene glycol-400 (PEG-400), as one of the concrete mix constituents in order to save water that is normally required after casting. Six concrete mixes were cast with a constant W/C ratio of 0.5; two of them were ordinary concrete mixes whereas the other mixes contained 0.5%, 1%, 1.5%, and 2% of PEG-400 by weight of cement. All concrete ingredients, except the PEG-400, were provided locally. Three different curing regimes were employed: air curing under ambient laboratory conditions, water curing, and self-curing using different dosages of PEG-400. Testing included compressive strength, ultrasonic pulse velocity (UPV), and water absorption. The results showed that 1% of PEG-400 is the optimum dosage to be used for self-cured concrete.