Compressive Strength Of Concrete Research Articles

Quality Control Analysis in Construction Works of 80/100 U-Ditch Channel with 15 Ton Axle Cover (Jl. Manyar Indah)

This research records experiences and findings during the Work Practice Internship (MPK) on the 80/100 U-Ditch channel construction project with 15 Ton Axle Cover on JL. Manyar Indah, Surabaya. This MPK is part of the Bachelor of Building Engineering Education curriculum at Surabaya State University and aims to provide students with insight and practical experience that cannot be obtained in the classroom. This project, which will run from April to June 2024, provides an opportunity for students to understand the difference between academic theory and practice in the field, as well as getting to know construction implementation methods directly. The main focus of this project is quality control in construction, especially in the use of precast methods for drainage channels. Effective quality control is essential to ensure that construction meets established standards, prevent wasted costs, and guarantee the quality of the final result. In this project, quality control is carried out through several methods, including Quality Control (QC) for wiremesh, Fc'30 Ready Mix concrete, and core concrete compressive strength tests (core drill test). Each stage of quality control aims to ensure that materials and construction implementation comply with established specifications. The quality of the wire mesh used is checked through measurements and structural verification to ensure durability and sturdiness. Fc'30 Ready Mix concrete is tested through a slump test and laboratory compression test to ensure its strength. Core drill testing was carried out on the completed U-Ditch structure to evaluate the strength of the installed concrete. The findings from MPK show that strict quality control and the application of precast technology can improve construction efficiency and quality. The practical experience students gain in the field not only enriches their knowledge but also strengthens the technical and professional skills required in the construction industry. In addition, this MPK helps students build relationships with professionals in the industry, expand their network, and prepare them for careers in the building engineering field. It is hoped that this experience can improve students' competence as prospective professionals in the field of building engineering. This research also highlights the importance of collaboration between universities and industry. This collaboration not only provides benefits for students in the form of practical experience but also provides opportunities for universities to strengthen relationships with industry and expand partnership networks. Thus, this MPK not only contributes to improving the quality of building engineering education but also to the development of better construction industry practices. It is hoped that this research can make a positive contribution to the development of the building engineering education curriculum and encourage increased collaboration between universities and the construction industry. Through effective quality control and the use of precast methods, this project can be used as an example in creating efficient and high-quality construction, in line with the needs and expectations of stakeholders.

Use of Machine Learning Techniques to Predict the In-situ Concrete Compressive Strength using Non-Destructive Testing

Recently, machine learning-based prediction models have gained considerable popularity in predicting the compressive strength of concrete using results from Non-Destructive Testing (NDT) methods. This research considers NDT results from Rebound Hammer (RH) and Ultrasonic Pulse Velocity (UPV) tests for concrete samples with different concrete grades. 270 test samples were considered for the analysis using different machine learning techniques such as Multi-Layer Perceptron (MLP), Long Short-Term Memory network (LSTM), and Convolutional Neural Network (CNN). Concrete compressive strength results are obtained from Destructive Test (DT) results of the same for the purpose of labelling. Each model's performance is evaluated through the computation of the Coefficient of Determination (R²), Mean Square Error (MSE), and Mean Absolute Percentage Error (MAPE). The findings of this study underscore the potential of machine learning techniques in predicting concrete compressive strength based on Non-Destructive Test (NDT) results. The analysis findings suggested that employing UPV and RH data in conjunction with a trained MLP model to be an effective approach for accurately estimating the compressive strength of concrete specimens. The outcomes of the research serve as a valuable reference for researchers and industry practitioners alike when assessing in-situ concrete compressive strength through Non-Destructive Testing (NDT) methods.

Predicting the compressive strength of CFRP-confined concrete using deep learning

The application of externally bonded fiber-reinforced polymers (FRP) has revolutionized structural rehabilitation, offering cost-effective and rapid solutions for damaged structures. This study presents a novel deep learning approach for predicting the compressive strength of circular carbon-FRP-confined concrete columns. Leveraging an extensive database of 664 experimental results, the model incorporates monotonicity and smoothness constraints, with hyperparameters optimization using the OPTUNA framework. The proposed model demonstrates exceptional accuracy, achieving R² = 0.93, a20-index = 0.95, and MAPE = 7.89 % on unseen test data, consistently outperforming nine benchmark models including established design guidelines. Scenario-based analysis confirms the model's ability to capture known physical behaviors, such as the effects of concrete strength, column diameter, and FRP thickness on confinement effectiveness. The integration of physical constraints enhances the model's reliability and interpretability, bridging the gap between data-driven and physics-based approaches. This research contributes to the advancement of more accurate, economical, and reliable design guidelines for FRP-strengthened structures, while also demonstrating the potential of constrained deep learning in structural engineering applications.

The Influence of Fibres on the Properties and Sustainability of Oil-Impacted Concrete

There are significant environmental and health consequences associated with oil-contaminated sand due to its toxic and persistent nature. The impacts include disrupted ecosystems with harm to plants and animals and contamination of water sources, requiring immediate and sustained remediation. Using oil-contaminated sand in construction addresses waste management and promotes sustainability by reducing waste, protecting the environment, saving energy, and driving innovation. This study investigates the impact of crude oil-contaminated sand on concrete’s physical and mechanical characteristics. It focuses on assessing the impact of incorporating four different fibres (Forta Ferro PP, ReoShore 45 PP, glass, and steel fibres) and finding the optimal quantity (0.1, 0.2, 0.3, 0.4 or 0.5%) to improve the physical and mechanical properties of concrete prepared with sand contaminated by crude oil. The impact of crude oil on the bond strength between fibres and concrete was examined. Additionally, the effect of crude oil on heat flow and cumulative heat was analysed. The results demonstrated that increasing oil content decreases concrete density and compressive strength. Nevertheless, the findings indicated that sand contaminated with 10% oil is suitable for low-strength concrete applications. Incorporating 0.1% of Forta Ferro PP, glass, and ReoShore 45 PP fibres had a negligible impact on the mechanical properties of concrete contaminated with 10% oil. Comparatively, steel fibres enhanced the concrete’s compressive strength by 30% at 0.1%, and the flexural strength improved by 9.6% at 0.5%. Concrete with a 10% crude oil content reinforced with steel fibres hinders fracture stabilisation and load transfer, making it suitable as a sustainable material for low-strength civil engineering applications.

Seismic Behavior of Composite Columns with High-Strength Concrete-Filled Steel Tube Flanges and Honeycomb Steel Webs Subjected to Freeze-Thaw Cycles

To investigate the seismic behavior of composite columns with high-strength concrete-filled steel tube flanges and honeycomb steel webs (STHHC) after being subjected to freeze-thaw cycles, 36 full-scale STHHCs were designed with the following main parameters: the shear span ratio (λs), the axial compression ratio (n0), the number of freeze-thaw cycles (Nc), the concrete cubic compression strength (fcu), and the steel ratio of the section (αs). Compared with existing experimental data, the validity of the finite element modeling method was verified. Parameter analysis was conducted on 36 full-scale STHHCs to obtain the hysteresis curve of the composite columns and to clarify the impact of the different parameters on the skeleton curve, the energy dissipation capacity, the stiffness degradation, and the ductility of the composite columns. The results showed that the hysteresis curves of all specimens after freeze-thaw cycles exhibited an ideal shuttle shape, reflecting that this kind of composite column has good energy dissipation ability and freeze-thaw resistance. The specimens’ maximum bulging deformation and maximum stress both occurred at the column base. Finally, the restoring force model of this kind of composite column is therefore established, and design recommendations based on these results are proposed.

Mechanical and Drying Shrinkage Performance Study of Ultra-High-Performance Concrete Prepared from Titanium Slag under Different Curing Conditions.

This research investigates the effects of various curing regimes, the incorporation of titanium slag, and the utilization of quartz sand on the strength properties and shrinkage behavior of ultra-high-performance concrete (UHPC). By using low-heat silicate cement to prepare UHPC, this study conducted standard curing and steam curing, and comprehensively analyzed the macro and micro performance of UHPC under different curing conditions. The findings indicate that the application of steam curing markedly enhances the mechanical attributes of UHPC while efficiently decreasing its drying shrinkage. In the comparative tests, we found that the compressive strength of concrete that had undergone 2 days of steam curing was 9.15% higher than that of concrete cured for 28 days under standard conditions. In addition, under the same curing conditions, titanium slag sand had higher mechanical properties than quartz sand. Under standard curing conditions, the 28-day compressive strength of UHPC using titaniferous slag aggregate was 12.64% higher than that of UHPC using standard sand. Through the data analysis of XRD, TG, and MIP, we found that the content of Ca(OH)2 in the hydration products after steam curing was reduced compared to the standard curing conditions, and the pore structure had been optimized. The UHPC prepared with titanium slag sand has greater advantages in mechanical properties and drying shrinkage, and has a smaller pore structure than the UHPC prepared with quartz sand. Moreover, the use of titanium slag sand offers ecological and economic benefits, making it a more sustainable and cost-effective option for high-performance construction applications.

Flexural capacity design model of reinforced concrete beams strengthened with hybrid bonded CFRP

In order to improve the calculation methodology for the flexural capacity of RC (Reinforced Concrete) beams strengthened with HB-CFRP (Hybrid Bonded-Carbon Fiber Reinforced Polymer), three-point bending tests were conducted in this study. The experimental setup involved 9 HB-CFRP strengthened T-shaped beams and 1 unstrengthened beam for comparison. The effects of anchor spacing, anchor pressure, CFRP thickness, and anchor distribution pattern on the flexural performance of strengthened beams were investigated. Additionally, the development of the full range load-deflection curves of the HB-CFRP strengthened specimens was analyzed. Two bond strength models (the Wu model and Liu model) were modified. Six parameters were considered in the modified model, namely, the CFRP elastic modulus, CFRP thickness, number of mechanical fasteners in the shear span, CFRP-concrete width ratio, concrete cylinder compressive strength and normal pressure applied to the mechanical fasteners. The accuracy of the modified models was compared on the basis of three specifications. Results indicated a notable enhancement in the flexural capacity of the strengthened beams, ranging from 61.1 % to 158.1 % compared to the unstrengthened beam. Taking the ACI specification as an example, the mean value and coefficient of variation (COV) of the flexural capacity obtained by directly using the Wu model were 1.187 and 0.169, respectively; the results obtained by using the modified Wu model based on the measured FRP strain were 1.038 and 0.125, respectively; and the results obtained by using the modified Wu model based on the ACI reversed-calculated strain were 1.012 and 0.106, respectively. After the strengthened beam reached the peak load, the load then decreased abruptly to the vicinity of the moment mid-span deflection curve of the reference beam. As the loading continued, the resistance improved by 27.4 %∼79.3 % due to the increase in interface friction in the mechanical fasteners and concrete.

The structural assessment for concrete structure on the onset of cracking with respect to steel corrosion

The present study concerns structural behaviour of a marine bridge in terms of cracking exposed to a seawater environment under the risk of chloride-induced corrosion with the axial loading. In the modelling process, the corrosion propagation was expressed into the rust formation on the steel surface, while the axial load was given 5–30 % to the compressive strength of concrete. The interfacial gap between steel and concrete was taken 10 µm, imposing the buffering capacity against a build-up of the rust at the steel-concrete interface. As a result, it was found that the tensile damage produced the cracking on the surface of concrete with a minimal corrosion of steel, which was further developed into the inner concrete depth with increasing corrosion formation. Also, an increase in the axial load resulted in an increase in the surface cracking at a given rust formation. At the steel-concrete interface, the cracking was much affected by the compressive deformation arising from a build-up of rust, as being limited in the vicinity in the interfacial zone, presumably due to the limited rust formation. A combination of steel corrosion and axial loading imposes the accelerated cracking of concrete structure then to rapidly deteriorate its serviceability.

Sustainability-driven application of waste steel and tyre rubber fibres as reinforcement in concrete: An optimization study using response surface methodology

Innovative use of waste materials has proven to be effective for improving concrete’s technical properties while eliminating the threat of environmental pollution. There is paucity of research regarding the combined use of Waste Steel Fibres (WSFs) and Waste Tire Rubber Fibres (WTRFs) in concrete. Thus, this study aimed to investigate the influence of WSFs and WTRFs as reinforcement in concrete and determine their optimal fractions for enhancing the concrete strength properties using Response Surface Methodology (RSM). WSFs of 0.3-1.5% with a 0.6% increment and WTRFs of 0.3-1.5% with a 0.6% increment by concrete volume as reinforcement in concrete with water-to-cement ratio (W/C) of 0.25–0.65 with 0.2 increment were designed using the Box-Behnken Design of RSM. A total of fourteen (14) concrete mixes with a design strength of 25 N/mm2 were prepared. The fresh and hardened properties (slump, density, water absorption, 7- and 28-day compressive and split tensile strengths) of concrete were determined using standard procedures. The RSM was used to evaluate the interaction between the concrete variables and identify their optimum combination which gave the peak values of responses. Furthermore, the characteristics and sustainability of the concrete under optimum variables were compared with that of the conventional concrete. The outcomes revealed that the inclusion of WSFs and WTRFs yielded concretes with maximum slump, density, water absorption and 28-day compressive and split tensile strengths of 25 mm, 2633 kg/m3, 5%, 41 N/mm2 and 4.54 N/mm2, respectively. The optimization technique showed the optimal variables combination which yielded the peak response values of WSFs (1.40%), WTRFs (0.66%) and W/C (0.54). The nominal variance with the absolute percent error of less than (9%) between the actual experimental verified results and predicted results for all the responses validates the predictability of the model. The split tensile strength and compressive strength increased by 28.33% and 48.85%, respectively at the optimum setpoint of variable with respect to the reference concrete. In addition, the WSFs and WTRFs-reinforced concrete exhibited lower embodied CO2 emission but the embodied energy and cost are slightly higher relative to conventional concrete. Nevertheless, the embodied energy of the concrete was significantly lesser than that of concrete that used individual fibers for reinforcement. Thus, the enhancement of concrete strength properties with the prospect for sustainable fibre-reinforced concrete production through the use of waste steel and tyre rubber fibres is feasible.

Research on cyclic behavior of precast bridge piers with ECC-socket connections

Precast bridge piers with socket connections (SCPs) have been widely studied and certainly applied in recent years. To reduce the punching failure of socket connections, decrease their construction difficulty, and improve their application in complex environment areas, the embedment depth of SCPs needs to be decreased and the cyclic behavior of SCPs needs to be improved. In this study, engineered cementitious composite (ECC) was firstly introduced to the SCPs, a novel precast bridge piers with ECC-socket connections (SCEs) were proposed. Subsequently, 3D finite element models (FEMs) were established and validated against experimental results. Then, a detailed parametric study was conducted to investigate the cyclic behaviors of SCEs, including the embedment depth, ECC height, axial compression ratio, reinforcement ratio, and concrete compressive strength. Finally, a simplified calculation model was proposed to evaluate the bearing capacity and failure mode of SCEs. The results show that the shear damage of the embedded section is more severe for traditional shallow socket connections. Compared to traditional SCPs, the cyclic behavior of SCEs is better and influenced by ECC height and embedment depth, as well as axial compression ratio, reinforcement ratio, and concrete compressive strength. The simplified calculation model is suitable to evaluate the bearing capacity and failure mode of SCEs.

Mechanical and microstructural properties of municipal solid waste incinerator bottom ash (MSWIBA) concrete exposed to salt erosion and drying-wetting cycles

In cold and saline soil areas, concretes usually experience multi-factor erosions, such as freezing-thawing cycles (FTCs), drying-wetting cycles (D-Ws), and salt erosion. To promote green and sustainable development of the construction industry, municipal solid waste incinerator bottom ash (MSWIBA) was adopted as a partial replacement for conventional fine aggregates in concretes. In this study, the coupled effects of the D-Ws and salt erosion (i.e., 5 % NaCl solution and 5 % Na2SO4 solution) were experimentally conducted to investigate the mechanical and microstructural properties of ordinary and MSWIBA concretes. The results showed that D-Ws had a negative effect on the mechanical properties of concretes. The depth and width of cracks in concretes increased with the D-Ws raised. During the D-Ws, the influence of salt solution on concretes could be divided into two stages. Initially, the filling effect of salt crystals was beneficial to the development of concrete strength. Subsequently, salt crystals accumulated in concretes caused cracks, and accelerated the deterioration of concrete specimens. Meanwhile, sodium sulphate reacted with hydration products in concretes to produce some expansive substances, the evident diffraction peaks of expansive substances (e.g., gypsum and ettringite) had been clearly observed after D-Ws. Thus, the damage effect of 5 % Na2SO4 solution (SS) to concrete structure was more serious than that of water (WT) and 5 % NaCl solution (CS). Furthermore, the total porosity of the concrete specimens generally decreased with the MSWIBA substitution rate increased. There was an optimal MSWIBA content for concretes to obtain the excellent mechanical and microstructural properties. In detail, when the substitution rate of MSWIBA was between 0 % and 33.0 %, it had an excellent effect on improving the pore structure of concretes. Specifically, the compressive strength of concretes was larger than 35.0 MPa when the substitution rate of MSWIBA with natural river sand was between 24.8 % and 57.8 %, whereas the substitution rate of MSWIBA should not exceed 33.0 % exposed to D-Ws. This study could provide a significant reference for the sustainable development of concretes in cold and saline soil areas, as well optimization and innovation usage of MSWIBA.

Pengaruh Penggunaan Limbah Ampas Tebu Merah Sebagai Pengganti Semen terhadap Kuat Tekan Beton

The aim of this research is to determine the effect of red sugar cane bagasse waste as a cement substitute on the compressive strength of concrete and to determine the compressive strength value of concrete after adding red sugar bagasse waste as a cement substitute. This research is experimental research which begins with preparation of tools and materials, aggregate inspection, slump test, job mix design, making test objects, caring for test objects, testing concrete volume weight and ends with testing concrete compressive strength. The research results show that the addition of red sugar cane bagasse powder as a cement substitute in making concrete has an effect on the mechanical properties of concrete such as: slump value, concrete volume weight and concrete compressive strength. The average compressive strength value of concrete produced after adding 2.5% red sugar cane bagasse waste; 5%; 7.5% and 10% at 28 days are 20.95 MPa respectively; 17.15 MPa; 14.79 MPa and 11.87 MPa. Thus, red sugar bagasse waste is not recommended to be used as a cement substitute because the compressive strength value of the planned concrete is very far from normal concrete.

Influence of fibers and bubble structure on thermal conductivity and mechanical performances of foam concrete

This study aims to effects of fibers and bubble structure on thermal conductivity and mechanical performances of foam concrete. The factors of fiber type, length, fiber dosage, and silica fume dosage were considered. The workability and compressive strength tests were carried out. The bubble structure was observed. Numerical simulation of thermal conductivity was performed. The results indicated that the influence of a single factor on the strength of foam concrete is slight. The addition of silica fume significantly reduces the workability of foam concrete. The synergistic effect of silica fume and PP fiber can improve the compressive strength of foam concrete. The compressive strength of foam concrete with good performance is 7.2 MPa, and the dry density is 827 kg/m3. The pore diameter of about 400 μm is the main pore diameter that affects the strength of foam concrete. The thermal conductivity of foam concrete with the same porosity but different pore size distribution is similar when the pores are closed. The defects on the hole wall, small aperture and uniform distribution are still conducive to improving the strength. When the profile of the same temperature passes through the pore, the curve is concave and convex first, and the larger the pore size, the more obvious this phenomenon is. The holes in the foam concrete play a role in dissipating energy during heat transfer.

HSC-RSW with laterally installed XADAS dampers: Seismic performance

This study investigates the seismic behavior of high-strength concrete (HSC) rocking shear walls (RSW) equipped with X-shape Adding Damping and Stiffness (XADAS) dampers installed perpendicular to the wall via brackets. Unlike previous studies where dampers are integrated along the wall length, this research leverages the advantages of HSC to minimize sectional dimensions while employing laterally installed XADAS dampers to enhance the cyclic response, yielding flag-shaped hysteresis curves. The alignment angle of the XADAS dampers is also considered a crucial variable in assessing the overall seismic performance of the proposed HSC-RSW system. A novel constructional approach using brackets to install lateral XADAS dampers is implemented. Post-tensioning (PT) forces are applied as consistent axial strains in cables, achieved through predefined cable support displacements. A macro-FEM model is developed to validate the chosen experimental reference test and is subsequently used for further parametric studies. The parametric studies indicate that increasing concrete compressive strength (CCS) enhances the self-centering capability by reducing RSW strains and facilitating rocking. Additionally, incorporating XADAS dampers into the system improves energy dissipation, with a zero-degree alignment angle identified as optimal. Notably, the modeled HSC-RSW systems exhibit limited drift capacity (less than 2 %) compared to normal strength concrete (NSC)-RSW systems, where wall toes are conventionally prone to crushing.

Combined effect of silica fume and various fibers on fresh and hardened properties of concrete incorporating HDPE aggregates

Recycling of waste plastics has become essential to mitigate their detrimental impact on the environment. However, it can be used in the construction sector to fulfill construction needs and conserve natural resources. Previous research has demonstrated that incorporating plastic aggregate reduces the strength properties of concrete; hence, there is a need to improve its strength properties. In this study, high-density polyethylene (HDPE) plastic is incorporated in aggregate form, as a partial substitute for natural coarse aggregates (NCA) at volumetric ratios of 10 %, 30 %, and 50 %. Various strength enhancement techniques, including the addition of macro synthetic fibers (MSF), steel fibers (SF), and substituting 20 % of cement with silica fume, were employed. The results indicated that workability of concrete is improved with an increase in the content of HDPE coarse aggregates (HCA). Furthermore, concrete containing 30 % HCA performed better in terms of strength compared to concrete with 10 % and 50 % HCA. The findings demonstrate that concrete containing fibers performs better than concrete without fibers. The utilization of 0.75 % MSF and 1 % SF dosage leads to a 93 % improvement in splitting tensile strength, a 72 % improvement in flexural strength, and a 48 % improvement in compressive strength for concrete containing 30 % HCA. Using scanning electron microscopy, it was found that incorporating HCA weakens the internal matrix. However, the addition of a precise amount of fibers and pozzolanic materials resulted in improvements in microstructure. The significance of this research lies in the utilization of HDPE waste materials in concrete by simultaneous usage of different fibers.

The Influence of Nano Silica and Micro Silica on the Compressive Strength of Hybrid Fiber-Reinforced Concrete

The Influence of Nano Silica and Micro Silica on the Compressive Strength of Hybrid Fiber-Reinforced Concrete

Research on Impact Compression Strength and Explosion Resistance of Layered Gradient Rubber Concrete in Underground Engineering

Research on Impact Compression Strength and Explosion Resistance of Layered Gradient Rubber Concrete in Underground Engineering

Leveraging a Hybrid Machine Learning Approach for Compressive Strength Estimation of Roller-Compacted Concrete with Recycled Aggregates

In recent years, the use of recycled aggregate (RA) in roller-compacted concrete (RCC) for pavement construction has been increasingly attractive due to various environmental and economic benefits. Early determination of the compressive strength (CS) is crucial for the construction and maintenance of pavement. This paper presents the idea of combining metaheuristics and an advanced gradient boosting regressor for estimating the compressive strength of roller-compacted concrete containing RA. A dataset, including 270 samples, has been collected from previous experimental works. Recycled aggregates of construction demolition waste, reclaimed asphalt pavement, and industrial slag waste are considered in this dataset. The extreme gradient boosting machine (XGBoost) is employed to generalize a functional mapping between the CS and its influencing factors. A recently proposed gradient-based optimizer (GBO) is used to fine-tune the training phase of XGBoost in a data-driven manner. Experimental results show that the hybrid GBO-XGBoost model achieves outstanding prediction accuracy with a root mean square error of 2.64 and a mean absolute percentage error less than 8%. The proposed method is capable of explaining up to 94% of the variation in the CS. Additionally, an asymmetric loss function is implemented with GBO-XGBoost to mitigate the overestimation of CS values. It was found that the proposed model trained with the asymmetric loss function helped reduce overestimated cases by 17%. Hence, the newly developed GBO-XGBoost can be a robust and reliable approach for predicting the CS of RCC using RA.

Dynamic mechanical properties and energy dissipation analysis of rubber-modified aggregate concrete based on SHPB tests

The fluctuation of the waveform curves in the Split Hopkinson Pressure Bar (SHPB) test can provide a more intuitive reflection of the material's dynamic deformation process, with different strain rates resulting in varying damage states and σ-ε curves. A Φ120×100 mm size SHPB experiment was conducted to study the dynamic mechanical properties of new rubber-modified aggregate concrete (RAC). Based on the different characteristics of waveform and σ-ε curves, combined with high-speed photography technology, the typical failure modes and dynamic compressive strength of rubber-modified aggregate concrete under different loading rates were analyzed. Furthermore, the energy dissipation capacity and mechanism of rubber-modified aggregate concrete at different stages was discussed. The reflected wave of RAC shows a "double-peak" trend of "first high and then low" instead of "first low and then high" of normal concrete due to its exceptional capacity of energy absorption and dissipation. As strain rate increases, a plateau period appears in the reflected wave before first peak. The evolution process is dominated by the energy storage mechanism until it hits the limit, then by the energy dissipation mechanism. These findings can help us design and use RAC materials under dynamic stress.

Assessing the compressive strength of eco-friendly concrete made with rice husk ash: A hybrid artificial intelligence-aided technique

Providing an eco-friendly replacement for cement in cementitious materials mitigates not only its consumption but also the environmental effects such as extraction of natural resources and greenhouse gas emissions resulting from its production. In light of this, the utilization of rice husk as a by-product of rice fields in the form of rice husk ash (RHA) as a partial substitute for cement, in addition to solving the problem of its disposal due to its silica content and high pozzolanic reaction, has been considered in the construction of sustainable concretes. This study seeks to move from the traditional laboratory-based methods for the examination of compressive strength (fc′) of concretes containing RHA towards artificial intelligence-based techniques by developing a novel hybrid model by integrating biogeography-based optimization (BBO) technique with artificial neural network (ANN). Besides, the performance of the hybrid ANN-BBO model was assessed with the single ANN model. To this end, the models were developed on an extensive dataset including 1276 data records collected from the literature. The efficiency of the models was evaluated by performance criteria and error histogram, and also cross-validation was utilized to avoid overfitting problems and generalize the models. Results demonstrated that the hybrid ANN-BBO model outperformed the single ANN model with high accuracy and minimum error values. Error histograms revealed that over 90 % of errors in the ANN-BBO model occurred in the range (−4 MPa, 4 MPa], while this range for the ANN model fell within (−6 MPa, 6 MPa]. Analyzing the influence of input parameters showed that more than 70 % of the contribution rate in the fc′ of RHA concrete belonged to four influential parameters of specimen age, cement, rice husk ash, and water, respectively. Eventually, to validate the proposed ANN-BBO model, a comparison was made with recent studies, in which the performance criteria revealed that the proposed model based on a more extensive dataset outperformed the models in previous studies.