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In our earlier study, the impact resistance of slabs made up of concrete containing hybrid fibers (i.e., steel and synthetic fibers in various proportions) was evaluated through an experimental program. The test specimens, measuring 600 × 600 × 90 mm, were cast with varying amounts of fibers, while some were kept as control samples without any fibers. The high-velocity impact tests were conducted using a gas-gun system, where hemispherical steel projectiles were fired at the slabs. The craters’ sizes and penetration depths were measured. The hybrid fibers in the concrete reduced spalling and scabbing damage and reduced the size of craters. In the current study, the impact response of the hybrid fiber-reinforced concrete (HFRC) slabs was investigated numerically. LS-DYNA software was employed for this investigation, and crack sizes, areas of spalling and scabbing damages, and penetration depths were estimated. The numerical simulations provided an efficient and practical tool for analyzing the HFRC slabs’ response against impact load. The use of hybrid fibers decreased front surface damage and prevented concrete particles from flying out of the back face. The inclusion of fibers in concrete increased the perforation energy by 49%–203%. The numerical predictions of penetration depth were reasonably close, with absolute errors varying from 3.6%− 32.6%, and the error in the prediction of maximum rebar strain varied from 2.5% to 12.7%. The presented model thus has the capability to predict the local damages of various types of RC and HFRC slabs with acceptable accuracy.

This paper presents a case study of an energy efficient and cost optimized design of a light gauge steel building. The structural analyses conducted were linked to the concept of design for manufacture and assembly (DfMA) for the optimization of assembly time, quantity of labors and materials. A variety of analyses were performed on a prefabricated residential building constructed with cold formed and hot rolled steel materials for comparison which has a limited research previously. The energy optimization for the prefabricated building was carried out using Autodesk Insight 360. Several tools for structural, thermal, energy and cost analyses were adopted in this research. A Building Information Model (BIM) was developed in Revit and structural model in ETABS for structural analysis. Thermal performance was executed using Simulinks in MATLAB followed by energy simulations in DesignBuilder and EnergyPlus software packages. The material and energy costs of the designed building were estimated using CostX tool. From the analysis, the optimal window-wall ratio (WWR) was found to be 10%− 15% produced better energy and cost savings. Furthermore, the total energy consumption and greenhouse gas emissions of the building was found to be reduced by 28.7%− 31.5% with an application of insulation in its external walls in simulations. Improved bending capacity and shear force for CFS compared to RHS was observed. Finally, a framework was proposed for the automation and interoperability of building analysis tools.

This paper experimentally investigates the dowel action contribution of longitudinal reinforcement, a hybrid of steel and GFRP bars (usually adopted for avoiding corrosion of steel bars), in concrete deep beams for different reinforcement schemes. The self-consolidating concrete without and with steel fibers (0.9 % and 1.2 % by volume) was used. Sixteen simply supported deep beams of 140 × 300 (depth) × 1500 mm were tested under the two-point loads. A model is developed to predict the shear capacity of deep beams without web reinforcement, taking into consideration the dowel action contribution of longitudinal reinforcement, which is a hybrid of steel and GFRP rebars. The results showed a significant dowel action contribution of steel as well as GFRP rebars to beam shear strength. However, the use of a hybrid system of steel and GFRP bars caused a reduction in the dowel action of steel bars due to their combined action.

Glass fiber-reinforced polymer (GFRP) bars are emerging as a potential replacement for steel rebars due to their vulnerability to corrosion. However, the shear behavior of GFRP bars is not well established, especially in functionally graded self-compacting concrete (SCC) deep beams reinforced with hybrid rebars (GFRP and steel). This article experimentally explores the behavior of functionally graded high-strength SCC deep beams having a hybrid of steel and GFRP bars as tension reinforcement. A total of fourteen deep beams were prepared with varying reinforcement ratios and steel fiber volume fractions. There were three groups of deep beams: (i) plain SCC (i.e., no fibers) beams, (ii) fiber-reinforced SCC (FRSCC) beams having 0.6 % and 1.2 % steel fibers, and (iii) functionally graded deep beams. The functional grading was achieved by casting beams in two layers, with the first layer of lower two-thirds depth having steel fibers and the second layer without fibers. The beams were shear deficient and tested in flexure. The shear resistance of functionally graded deep beams was compared with beams having fibers in full depth and without fibers. The test results reveal the significance of the hybrid system of rebars, which is found to effectively improve the structural capacity of concrete beams and increase the load required to initiate cracking. In addition, the mixing of fibers in concrete enhanced the deep beam shear capacity by 15–23 % for 0.6 % fibers and 37–39 % for 1.2 % fibers. The increase in the shear resistance of concrete deep beams was not influenced by the use of hybrid rebars compared to using GFRP bars only. A model is developed for assessing the shear resistance of functionally graded fiber-reinforced concrete deep beams by incorporating the dowel action of hybrid longitudinal reinforcing bars. The study indicates that the dowel action provided by GFRP bars is comparable to the steel bars of the same area.

Increasing demand for concrete construction and the consequent increase in the production of conventional Portland cement is thwarting efforts towards sustainable construction practices. This is seen in the carbon dioxide footprint caused by cement manufacturing as well as natural resources consumption. Therefore, the so-called geopolymer or alkali-activated composites using byproduct or natural materials are seen as a potential substitute for cement-based binders. Similarly, recycled rubber recovered from shredded tires has been used in concrete mixes, which in addition to the environmental benefit, offers desirable properties, e.g., improved deformability and energy dissipation capacity. Therefore, this paper investigates the influence of introducing recycled rubber in metakaolin-based geopolymer mixes on the workability, compressive behavior (stress–strain components and failure mode), flexural strength, unit weight, air content, and water absorption percentage. Seven mixes were employed for this purpose with two main variables comprising rubber size (fine, coarse, or combination of both) and replacement percentage (0%, 20%, and 40%). Recycled rubber was observed to reduce the mix workability by 4%–52.5% and 40%–62.5% when fine or coarse rubber particles were added to concrete mixes, respectively. Average compressive strength of 14.3–37.7 MPa was achieved when fine and/or coarse rubber particles replaced 20% or 40% of the conventional fine and/or coarse aggregates. Furthermore, rubberized geopolymer concrete showed more deformability than plain mixes coupled with lightweight characteristics, which are desirable in many construction applications. This indicates the suitability of the rubberized geopolymer concrete for developing low to moderate-strength concrete for non-structural and structural applications.

The emission of CO2 from the construction and concrete industry poses a serious threat to human health and drastically impacts the environment. Therefore, there is an urge towards green or CO2 free concreting and construction by the United Nations by 2050. Researchers around the globe are exploring the best sustainable and alternative materials for cement and concrete with minimum to net zero CO2 emissions. Despite this, the research on zero-carbon concrete is still in the earlier stages with some interesting and prospective sustainable concrete solutions have been developed. The current paper presents a comprehensive review of the research carried out so far for achieving concrete technology with minimum to zero-carbon emissions. The main objectives of this review are to highlight the research directions for future research in the field of zero-carbon technology. Various search engines such as SCOPUS predominantly, Google Scholar, Engineering Village, Web of Science were adopted to explore the articles on zero-carbon concrete. The selected articles for review were divided into three key sections in this paper, i.e., 1) Formulations and microstructure of the sustainable concrete, 2) Durability of sustainable concrete, 3) Structural applications of sustainable concrete. The gaps and future research directions are elicited and presented in this paper. Finally, the key conclusions and recommendations are provided at the end of this paper.

Damage induced by fire is considered a serious threat to reinforced concrete structures during their useful lifetime. While concrete is a non-flammable material, its exposure to fire affects its stress-strain characteristics and durability. Given that a full replacement and/or demolition option is economically inefficient for fire-damaged structures, a better alternative for lengthening their service life involves repair or strengthening the damaged members. The current testing program primarily investigated the influence of strengthening by glass fiber reinforced polymer (GFRP) sheets on the behavior of heat-damaged plain and fiber-reinforced normal and high strength concretes. Strengthening was considered for concrete cylinders after being exposed to 400 °C and 600 °C temperature and left to cool by air cooling or water quenching. Fiber-reinforced concrete (FRC) mixes were cast with steel, polypropylene, or a hybrid of steel and polypropylene fibers. For plain and various fiber-reinforced normal strength concretes exposed to 400 °C and cooled by ambient air cooling or water quenching, the compressive strength of GFRP confined concrete increased by 39% to 48% and 42% to 56%, respectively (in comparison to the unheated specimens). However, this enhancement was observed to be higher for concretes heated at 600 °C.

Effect of steam curing regimes on high-performance green concrete (HPGC) has been studied. The concrete was steam cured under three different steam curing regimes with temperatures of 50 °C, 65 °C, and 80 °C and durations of 6, 11, and 16 h. In addition, the replacement level of palm oil fuel ash (U-POFA), which was an experimental variable, was 0%, 20%, 40%, and 60% by weight of cement. The compressive strength (CS), initial surface absorption, porosity, water absorption, gas permeability, and water permeability were tested at 3, 7, 28, 90, 180, and 360 days. The results of the study showed that the utilization of U-POFA in HGPC led to a reduction at the early age CS of the HPGC up to 3 days. However, concrete mixes made with U-POFA showed higher CS at 28–360 days. U-POFA incorporation improved the transport properties of the concrete, with U-POFA60 mix exhibiting the most significant improvement. While application of higher curing temperature tends to impair the properties of the HPGC, longer steam curing period appears to provide a positive effect than shorter duration. The use of U-POFA lessens the negative impact of steam curing on the long-term transport properties of the HPGC. The use of U-POFA at 60% of the weight of the cement achieved CS of 115.8 and 116.9 MPa at 360 days under normal and steam curing, respectively. At the same time, the water absorption was 3.13% and 2.29% under normal and steam curing, respectively.

This experimental study aims to examine the effectiveness of shear stirrups and carbon fiber-reinforced polymer (CFRP) strengthening scheme in enhancing the deep beams’ shear strength. For this purpose, a total of six deep beam specimens of 150 mm × 300 mm (depth) × 1000 mm with an effective span of 750 mm, classified into three groups of two specimens each, were prepared. The beams of the first group were of normal concrete (NC). The beams of the second group were prepared using ultra-high-performance fiber-reinforced concrete (UHPFRC). In the third group, the UHPFRC deep beams were strengthened using CFRP strips. Each group had two beams – one with no shear stirrups and another with shear stirrups. All deep beams were tested under four-point loading until failure. According to the experimental results, shear stirrups effectively contributed to enhancing shear strength, ultimate load, and deformation capacity for NC deep beam. By utilizing the UHPFRC mix, the deep beams’ shear strength was upgraded significantly compared with the NC deep beams, but the deformation capacity was reduced. The implemented strengthening scheme was effective in the enhancement of deep beams’ shear strength and deformation capacity. The improvement in the shear strength of strengthened UHPFRC deep beams was moderate (16%); however, a considerable increase was observed in the deformation capacity as the displacement and energy ductility indices were enhanced by 49% and 185%, respectively.

Ultra-high-performance concrete (UHPC) is a form of cementitious composite that has been the most innovative product in concrete technology over the last three decades. Ultra-high-performance concrete has been broadly employed for the design of numerous forms of construction owing to its excellent mechanical characteristics and durability, and studies on its behavior have grown fast in the last decades. While the utilization of ultra-high-performance concrete in bridge engineering (BE) is limited owing to its high costs, little is recognized about the utilization of UHPC in various BE elements. As a result of these issues, a comprehensive review of the current UHPC development trends should be conducted to determine its present state and perspective. This study presents a review of the state-of-the-art UHPC applications in BE. This review also discusses the current status, limitations, challenges, and areas for the further investigation of UHPC in BE. The aim of this research to help various construction stakeholders understand the distinctive characteristics, benefits, and barriers to the broad utilization of ultra-high-performance concrete applications. The understanding of UHPC will aid in increasing its entire market share in both the national and worldwide building sectors.

Ordinary Portland cement (OPC) is commonly adopted as an effective binder in the production of concrete and cementitious mortars. The metakaolin (MK) based geopolymer (GP) binder offers a sustainable alternative to the OPC due to its essential environmental and technical benefits in reducing the carbon footprint. In the present study, two conventional and six GP repair mortars were used. Three GP mortars were plain (without fibers), and the remaining three were produced by mixing Polyvinyl-alcohol (PVA) fibers. The GP mixes were produced by varying sand content, alkaline solids to MK, and sodium silicate to NaOH ratios, resulting in different molar ratios. The test specimens were prepared by overlaying a 5 mm thick layer of repair mortar on a concrete substrate for conducting pull-off strength tests. This research was undertaken to investigate the effect of exposure to elevated temperatures on the performance of bond strength of GP mortar used as a repair material. The test specimens were subjected to ambient temperature and elevated temperatures of 200 and 400 °C for a duration of 3 h before conducting pull-off tests. The test results revealed that the selected GP mixes could be a promising alternative repair material for structures due to their good bond strength performance. The addition of fibers in stable mixes of GP mortars enhanced the bond strength at ambient as well as when exposed to 200 °C, through crack control mechanism.

The formulas available in the literature for predicting the projectile impact response of reinforced concrete (RC) targets are generally developed based on the results of impact tests. Recently, however, in order to avoid performing involved and challenging projectile impact tests, the impact response of RC targets was predicted using the quasi-static punching response of RC slabs. In this paper, the concept is extended to concrete slabs strengthened with textile-reinforced mortar (TRM) or carbon fiber-reinforced polymer (CFRP) sheets externally bonded to the concrete surface. In 16 groups, 96 slabs of 600 × 600 × 90 mm size were cast and tested under quasi-static and impact loads. The slabs were reinforced with two types of reinforcement: ϕ8@100 mm and ϕ4@25 mm. The singly and doubly reinforced concrete slabs with rebar spacing of 100 mm were strengthened using externally bonded CFRP and TRM on the back side of the slab specimens. Two mixes of concrete, representing normal and high-strength concretes, were used. The results of the present study reveal that the CFRP and TRM strengthening of RC slabs enhanced the energy absorption in punching by 57–130% and 20–59%, respectively. The use of WWM in singly and doubly reinforced slabs also resulted in a 30–42% and 41–63% increase in energy absorption in punching, respectively. An earlier proposed model was modified to incorporate the influence of strengthening (CFRP and TRM) in the estimation of the projectile perforation energy of the strengthened RC slabs with the help of energy absorbed in their quasi-static punching. This perforation energy was then employed for predicting the ballistic limit of CFRP- and TRM-strengthened slabs. The predictions show good agreement with the experimentally observed ballistic limits.