Md. Alhaz Uddin, Md. Habibur Rahman Sobuz, Md. Abu Safayet
et al.
Abstract This study presents an innovative approach to predicting the compressive strength (CS) of recycled rubberized concrete (RC) using advanced hybrid machine learning (ML) algorithms. The integration of recycled rubber in concrete offers significant environmental and sustainability benefits by reducing waste and promoting circular construction practices. Its heterogeneous nature introduces complexity in accurately estimating mechanical properties through traditional empirical models. To address this challenge, five ML models, XGB, RF, GBR, and two hybrid ensembles, XGB–RF and XGB–GBR, were developed and evaluated using a data set comprising 369 experimental samples with seven key mix-design parameters. The innovation of this work lies in the development and comparison of hybrid learning frameworks, which effectively capture nonlinear relationships among input parameters and enhance model generalization beyond conventional ML techniques. Model performance was rigorously validated using statistical metrics, such as the coefficient of determination (R 2), mean absolute error (MAE), mean absolute percentage error (MAPE), and root mean square error (RMSE). The XGB model achieved the highest predictive accuracy R 2 = 0.904, RMSE = 3.835 MPa, and MAE = 2.697, outperforming other individual and hybrid models. The XGB–GBR model achieved a high predictive accuracy of R 2 = 0.879, RMSE = 4.012 MPa, further validating the strength of hybrid ensemble approaches. To further interpret model behavior, SHAP (SHapley Additive exPlanations) and partial dependence plot (PDP) analyses were conducted, revealing that rubberized aggregate (RA) content exerts the most significant negative influence on CS, followed by notable effects from fine aggregate, superplasticizer, and water content. The study not only highlights the effectiveness of AI-driven methods in forecasting concrete strength but also identifies optimal material proportions for mix design improvement. This research demonstrates that hybrid ML techniques provide a cost-effective, rapid, and highly accurate alternative to conventional testing for RC, offering valuable insights for sustainable material optimization and decision-making in modern civil engineering.
Systems of building construction. Including fireproof construction, concrete construction
Shashwati Soumya Pradhan, Mahmoud Elkady, Muhammad Akbar
et al.
Abstract Efforts to enrich concrete performance and reduce environmental impact drive the development of alkali-activated concrete (AAC), which eliminates the need for cement. This study investigates the effect of fly ash (FA) and rice husk ash (RHA) on ground granulated blast furnace slag (GGBS) based AAC to produce sustainable concrete. Different AAC mixes were developed using a constant amount of GGBS (50%), with the remaining 50% replaced by FA (50% to 0%) and RHA (0% to 50%) using a 12 M NaOH solution. The test results show that fresh AAC achieves a higher slump using lower RHA with higher FA content. The unit weight of AAC is reduced when using a higher RHA with lower FA content. The research shows that using 40% FA with 10% RHA exhibits superior mechanical properties. Linear regression analysis examines the correlation between compressive strength and both destructive and non-destructive parameters. Analysis of variance (ANOVA) was used to assess the influence of selected variables (binder and curing age) on the mechanical strength of ternary blend AAC. Microstructural analysis (SEM and FTIR) reveals mechanisms that enhance the strength of the ternary blend AAC. This study also emphasizes the cost-effectiveness and eco-friendliness of ternary blend AAC, utilizing industrial and agricultural waste, and assesses its environmental impact.
Systems of building construction. Including fireproof construction, concrete construction
Abstract To study the uniaxial dynamic tensile constitutive model of concrete under freeze–thaw conditions, the temperature field of concrete is modeled using finite element analysis software. The results are then imported into the thermal stress field as a predefined field for sequential coupled thermal stress analysis. Subsequently, a numerical simulation analysis of a dynamic tensile test under a freeze–thaw environment was conducted to ascertain the evolution of concrete damage. The constitutive model was established by correcting the concrete damage evolution parameters in the uniaxial stress–strain relationship of concrete as outlined in the Code for Design of Concrete Structures. The uniaxial tensile behavior of concrete under the action of freeze–thaw cycles was simulated using the modified intrinsic model and the damage plasticity model included in the software, taking into account the influence of the damage factor. The results demonstrate that the modified constitutive model aligns well with the actual experimental results. The research findings can be utilized in numerical simulations and concrete-related engineering applications.
Systems of building construction. Including fireproof construction, concrete construction
Abstract The utilisation of industrial by-products and waste materials as supplementary materials in cement-based composites offers a sustainable approach towards reducing environmental impact and optimising resource utilisation in construction. This study investigates the potential use of ferronickel slag (FNS) aggregates in cement mortar, focusing on their influence on alkali silica reactivity (ASR) and mechanical properties. The compressive strength of mortar mixes was evaluated at different water to cement ratio, with varying proportions of FNS as a replacement for natural sand. The results revealed that a 50% replacement of standard sand with FNS aggregates yielded the highest compressive strength, reaching a maximum of 59.49 MPa. Full replacement with FNS aggregates ASR expansion tests indicated that FNS aggregates are highly reactive in NaOH solutions, with expansion levels exceeding ASTM limits. However, innocuous expansion was observed in water and Ca(OH)₂ environments, highlighting their stabilizing effect. Regression analysis showed that use of FNS aggregates present challenges in strongly alkaline environments, they hold significant potential for enhancing the mechanical properties of cement mortar, particularly when used in balanced proportions.
Systems of building construction. Including fireproof construction, concrete construction
Melaku N. Seifu, Jemal Kedir Adem, Hammad R. Khalid
et al.
Abstract Enhancing the performance and sustainability of concrete is critical in modern construction, and in-situ carbonation offers a promising approach by introducing CO2 directly during mixing. This study investigates the influence of CO2 dosage on the workability, durability, and strength of concrete with varying water-to-binder ratios. Gaseous CO2 was injected during mixing, leading to the immediate formation of amorphous calcium carbonate and a noticeable reduction in slump within 10 min. Experimental results showed that CO2 addition improved pore structure and chloride resistance, with reductions of up to 18% in total charge and 13% in migration coefficient. However, a decrease in 28-day compressive strength was observed, varying with mix design. These findings highlight the importance of carefully balancing CO2 dosage and water-to-binder ratio to enhance durability without compromising long-term strength.
Systems of building construction. Including fireproof construction, concrete construction
Yeokyeong Lee, Yeonju Chun, Venkatesh Kodur
et al.
Abstract This study evaluates the material behavior of heated concrete with varying supplementary cementitious material (SCM) contents and quantifies its effect on the post-fire performance of reinforced concrete (RC) columns. The novelty of this research lies in examining the influence of SCM content on the residual behavior of heated concrete and its application to RC columns exposed to fire. Concrete specimens were prepared with different mix ratios of fly ash and slag ranging from 0% to 30% of the total binder weight. Residual stress–strain responses were obtained by testing the specimens after exposure to elevated temperatures. These material properties were then incorporated into finite element (FE) models of full-scale RC columns. Thermo-mechanical coupled analyses and structural analyses were sequentially performed to predict the post-fire performance of the columns. The results indicate that the load-bearing capacity of fire-damaged columns cannot be explained solely by the material behaviors of concrete. Notably, the column containing concrete with 10% fly ash and 10% slag demonstrated greater residual load capacity than other models, despite having strength and elasticity not always higher compared to other concrete mixtures. Nonetheless, the residual strength ratio of the columns correlates with that of concrete in general. A comparison between structural and material behaviors indicates that the residual strength ratios of the columns align with those of concrete heated to 400–500 ℃.
Systems of building construction. Including fireproof construction, concrete construction
Remilekun A. Shittu, Akram AlFantazi, Ahmed K. Alkaabi
et al.
Abstract This paper investigates the significance of thermal diffusion on chloride diffusion in concrete under high ambient temperature in arid climates. Of particular interest is to study the effects of silica fume (SF) and ground granulated blast furnace slag (GGBS) on chloride penetration into concrete subjected to temperature gradient conditions. This was achieved by making three sets of concrete samples—the control samples, the samples containing 5% SF, and the samples containing 5% SF and 50% GGBS. These samples were exposed to a NaCl environment under isothermal and thermal gradient conditions. The total and free chloride contents of the exposed samples were determined via potentiometric titration. The total chloride concentration of the samples exposed to thermal gradient conditions could be 1.3–6 times higher than those exposed to isothermal conditions at the same temperature. The addition of SF and GGBS yielded significantly lower total and free chloride contents than the control samples under isothermal and thermal gradient conditions. While thermal gradient significantly reduces the chloride binding capacity, adding SF and GGBS increases this ability. SEM analysis revealed microstructural changes in concrete due to high temperature and thermal gradients, with larger and deeper pores in samples exposed to thermal gradient. Numerical estimation of chloride concentration and the corrosion initiation time of a reactor containment building was also performed using the modified chloride diffusion equation, including the effects of mass- and thermo-diffusion.
Systems of building construction. Including fireproof construction, concrete construction
Despite the great potential and flexibility of smart contract-enabled blockchains, building privacy-preserving applications using these platforms remains an open question. Existing solutions fall short since they ask end users to coordinate and perform the computation off-chain themselves. While such an approach reduces the burden of the miners of the system, it largely limits the ability of lightweight users to enjoy privacy since performing the actual computation on their own and attesting to its correctness is expensive even with state-of-the-art proof systems.To address this limitation, we propose smartFHE, a framework to support private smart contracts using fully homomorphic encryption (FHE). To the best of our knowledge, smartFHE is the first to use FHE in the blockchain model; moreover, it is the first to support arbitrary privacy-preserving applications for lightweight users under the same computation-on-demand model pioneered by Ethereum. smartFHE does not overload the user since miners are instead responsible for performing the private computation. This is achieved by employing FHE so miners can compute over encrypted data and account balances. Users are only responsible for proving well-formedness of their private inputs using efficient zero-knowledge proof systems (ZKPs). We formulate a notion for a privacy-preserving smart contract (PPSC) scheme and show a concrete instantiation of our smartFHE framework. We address challenges resulting from using FHE in the blockchain setting—including concurrency and dealing with leveled schemes. We also show how to choose suitable FHE and ZKP schemes to instantiate our framework, since naively choosing these will lead to poor performance in practice. We formally prove correctness and security of our construction. Finally, we conduct experiments to evaluate its efficiency, including comparisons with a state-of-the-art scheme and testing several private smart contract applications. We have open-sourced our (highly optimized) ZKP library, which could be of independent interest.
Abstract With the development of recycled aggregate concrete (RAC), the recovery rate of construction waste is improved, and the pollution problem is alleviated. In particular, RAC beams strengthened with prestressed carbon fiber reinforced plastics (CFRP) can exhibit improved mechanical properties, expanding RAC application. Four groups of reinforced RAC beam specimens contained 0%, 40%, 70%, and 100% recycled coarse aggregate, respectively. Each group of beams was first pre-cracked and then strengthened by prestressed CFRP with one layer and two layers respectively. Finally, the bearing capacity tests were performed for these beams. The test results show that as the recycled coarse aggregate content increases, the cracking moment and ultimate load capacity of the beam decrease, while its crack width increases. As the CFRP layer increases, the deformation and crack width of the beam decreases, while the number of cracks increases. The prestressed CFRP also exhibited tensile and peeling failure. A beam deflection calculation model was established by introducing a coefficient k representing the interaction between recycled aggregate and CFRP. The influence coefficient of concrete elongation on the crack width and average crack spacing of the beam was modified, and the crack width analysis model of the beam was established. The calculated results are in good agreement with the experimental observations. It can provide reference for the application and design of recycled concrete beams strengthened with prestressed CFRP.
Systems of building construction. Including fireproof construction, concrete construction
Abstract In recent years, constructing natural aggregates as a base layer for the roads has increased. Natural resources will run out as long as human consumption of them continues. Recycled concrete aggregate (RC) has thus emerged as a substitute material for the building of road base layers. Additionally, RC can be utilized to create interior city highways. The base layer for roads must have sufficient strength to support the working load on the pavement surface without damage deforming. As a result, the focus of this paper is on enhancing the structural performance of sandy soil reinforced with various RC percentages. The three key factors are relative soil density (Dr = 83 and 97%), recycled concrete aggregate reinforcing levels (RC = 0,5,10,15,20,25,30,40,50 and 100%), and reinforcement layer thickness (Rd = 0.0B, 0.5B, B, and 2B where B is the footing model width). Numerous laboratory experiments were conducted in order to examine the impact of important parameters on the properties of the mixtures. The plate bearing tests were carried out using a footing model (250 × 250 mm) inside a tank (1500 × 1500x1000 mm) to ascertain the stress–strain response, bearing capacity ratio (BCR), ultimate bearing capacity, and modulus of elasticity of the tested mixtures. It is clear that raising the RC has no effect on the diameters of the grains. It was found that as RC increased, the mixture's bulk density increased but specific gravity decreased. Maximum dry density rose as RC rose, whereas water content fell. It was noted that BCR unquestionably increased as RC increased for all RC levels and all values of settlement ratios. The appropriate reinforcing layer thickness is suggested to be no more than 2B. As the RC concentration in the sand and Rd increased, the difference between two pressure-settlement curves of densities 83% and 97% significantly decreased. Furthermore, when RC reaches 50%, two curves are roughly comparable. At RC = 50%, it is advised that the relative density of 83% is sufficient to produce the same behavior as the relative density of 97%. It was found that as RC and Rd grew, the tested mixtures' ultimate bearing capacity and elasticity modulus increased as well. A novel proposed formulas are developed to compute bearing capacity ratio, ultimate bearing capacity, and elasticity modulus of the tested mixtures taking into account the influence of RC, reinforcement layer depth, settlement ratio, and the relative density, and its results agree with the experimental results.
Systems of building construction. Including fireproof construction, concrete construction
Ahmet Can Altunişik, Yunus Emrahan Akbulut, Süleyman Adanur
et al.
Abstract The past two decades have witnessed rapid advances in the use of fiber-reinforced polymer (FRP) composites in different engineering fields. Advantages such as high strength-to-weight ratio, corrosion resistance, and tailority have led to immense interest in the use of FRPs in wide spectrum repair and strengthening of structures. Despite their many advantages, FRPs are highly sensitive to high temperatures, which pose a major concern for fire potential structures such as buildings. Applying proper thermal insulation can enhance the fire performance of FRP and reduce the possible fire damage to the FRP strengthened element. This study set out to experimentally investigate the effectiveness of two insulation systems, “FIRECOAT” and “REALROCK” on fire performance of CFRP and GFRP strengthened concrete specimens. Various configurations and exposure durations were considered to evaluate the effectiveness of insulating materials. To perform the experiments, cylindrical concrete specimens were fabricated and strengthened using CFRP or GFRP. After insulating the specimens, they were exposed to a standard fire curve for two different durations of 30 and 60 min. The results indicate that less than 30 min of fire, both insulation systems can provide the required protection. During long exposure duration of 60 min, only REALROCK can provide the required thermal resistance for FRP-strengthened concrete. Within the tested materials, Fire Set 60 outperformed other insulating materials. It was observed that implementing Fire Set 60 in the innermost layer of thermal insulations has crucial importance in preventing the fire induced reductions in strength of FRP-strengthened concrete elements.
Systems of building construction. Including fireproof construction, concrete construction
Abstract Sand-bentonite-cement are commonly used as cut-off walls to isolate polluted soils or in ground improvement technologies and as retaining structures as secant pile wall. In this research, a laboratory program consisted from 105 sample were prepared and tested between different tests, such as hydraulic conductivity, porosity, and compressive strength to monitor the mechanical behavior of sand-bentonite-cement at different ages. Based on the experimental relationships between hydraulic conductivity coefficient and samples age; there were reduction due to added bentonite to mixture reach about 35.0% at 7 days. Moreover, the average reduction in the compressive strength of plastic concrete samples with bentonite was lower by average range about 51.0% than the compressive strength of plastic concrete samples without bentonite at 7 days. In this study, proposed formulas were derived to estimate the splitting tensile strength based on the compressive strength and the hydraulic conductivity in terms of the bentonite/cement ratio and testing age. The predicted values showed well agreement with the experimental records for samples of sand-bentonite-cement mixtures where the standard deviation and coefficient of variation were 0.02, and 0.94%, respectively.
Systems of building construction. Including fireproof construction, concrete construction
Wael Mohamed Montaser, Ibrahim Galal Shaaban, Joseph P. Rizzuto
et al.
Abstract Previous investigations carried out on reinforced self-compacted concrete (SCC) beams have reported contradictory results on reinforcement bond behaviour occurring in the zones defined for good bond conditions according to Eurocode2. Cantilevered SCC beams’ critical upper tension reinforcement bond behaviour has previously had limited reporting. In this study, the bond behaviour in normally vibrated concrete (NVC) and self-compacted concrete (SCC) in poor conditions zones are compared and the differences are highlighted. The effect of four parameters, including (i) concrete type (SCC and NVC), (ii) characteristic strength of SCC, (iii) lap splice length, and (iv) depth of concrete cover for the reinforcement is investigated. It was found that for the studied beams, increasing splice length improved the energy absorption and changed the failure mode to a more ductile manner even at the poor bond conditions zones. The maximum measured steel strains in SCC beams in the lap splice zones, were higher than those for NVC specimens. The mean bond stress values, for SCC beams with 25–50% lap splice lengths, were higher than those of NVC beams, with the same lap splice lengths, by 16–13%, respectively. The results of the current study showed that the empirical equations from the literature overestimated the bond strength of the splice lap length for cantilever upper steel in SCC beams with long splices which agrees with the state of the art as these equations were developed originally for short anchorage lengths.
Systems of building construction. Including fireproof construction, concrete construction