The development of concrete cracks will affect the durability, serviceability, and safety of civil infrastructure. This study proposes a leakage-controlled convolutional neural network long/short-term memory (LSTM) framework for static crack detection and short-term prediction of crack severity from time-ordered image sequences. The temporal task is defined as a next-step prediction of the crack severity index (CSI) derived from the image, rather than claiming complete physical crack geometry prediction from bounding box annotations. The CSI is calculated based on the ratio of crack-box and region-of-interest areas. The ResNet34 encoder extracts frame-wise spatial features, and a two-layer LSTM models the temporal dependency of structure-level sequences. Sequence construction, augmentation usage, split rules, optimisation settings, and evaluation metrics are selected to improve reproducibility and avoid temporal leakage. On the dataset, the framework achieves 93.0% classification accuracy, 88.3% mean average precision (mAP)@0.5, 0.76 mean intersection over union, 0.015 normalised mean squared error, and 89.2% F1 score. It also clarifies the practical interpretation of CSI growth, discusses detector-level benchmarking, domain shift and uncertainty estimation, and takes this method as an interpretable short-horizon monitoring framework, rather than a fully calibrated crack metrology system.
Recycling concrete is essential for reducing the environmental impact of the construction sector, yet the reuse of recycled cement fines remains limited due to challenges in separation. The Smart Crusher applies to a selective mechanical process designed to separate cement paste from natural aggregates during processing. Its performance depends strongly on the mechanical configuration, particularly the jaw angle. This study investigates two configurations of the moving jaw (90° and 85°) and their influence on the amount and composition of fines obtained from laboratory-made CEM I and CEM III concrete. Results show that the 85° jaw angle produced more fines due to stronger size reduction, but these fines presented higher SiO2, indicating increased quartz contamination and reduced selectivity. Conversely, the 90° configuration generated fewer fines, reflected by lower available SiO2 and higher CaO content, suggesting improved preservation of cement paste and reduced aggregate crushing. This result was confirmed through X-ray diffraction analysis, showing lower quartz and higher portlandite peaks for the 90° angle. Overall, the study highlights a clear trade-off: a narrower jaw angle increases yield but decreases selectivity, while the wider angle improves cement paste recovery at the expense of quantity.
The use of industrial bamboo residues as bio-aggregates in cementitious composites offers a sustainable approach to reducing the environmental impact of conventional concrete. However, there is still limited knowledge regarding the compressive behaviour of mixtures in which bamboo particles fully replace traditional coarse aggregates. This study investigates the mechanical performance of bamboo bio-concretes (BBCs) with total replacement of coarse aggregates, using bio-aggregate volume fractions of 15%, 20%, 25%, and 30%. After 28 days, compressive strength decreased from 31.5 MPa (BBC-15) to 17.9 MPa (BBC-30), while the elastic modulus declined from 15.08 GPa to 8.57 GPa. Higher bamboo contents improved post-peak ductility, with BBC-30 sustaining up to 52% of the peak load at 8000 mu epsilon, compared to 39% for BBC-15. Poisson's ratio values (0.36-0.43) indicated significantly greater lateral deformability than that of conventional concretes, and statistical analysis showed that this parameter is governed mainly by the low stiffness of bamboo particles rather than by the bio-aggregate fraction itself. Existing theoretical models (Model Code 2010 and Eurocode 5) did not accurately represent the ductile post-peak behaviour, whereas Popovics' equation produced better fits. The results highlight the distinct mechanical features of bamboo bio-concretes and support their suitability for low-load-bearing structural elements.
Recycled aggregate concrete (RAC) is rapidly emerging as a viable structural material; however, its comparatively weaker microstructure poses challenges for bond and splice behaviour, which are critical to structural safety. This review systematically analyses 38 experimental and numerical studies concerning the effects of replacement ratio, reinforcement type, and confinement systems on bond and splice behaviour. When fully replacing natural aggregate, demonstrates a bonding capacity approximately 25% lower, primarily due to the porous nature of the interfacial transition zone. Consequently, the required splice lengths under unconfined conditions are 35-40 bar diameters for steel reinforcement and 60-75 bar diameters for fibre-reinforced polymer (FRP) reinforcement. Confinement strategies, particularly transverse reinforcement and external wrapping, effectively mitigate brittle splitting failures and promote ductile behaviour. Current design codes (ACI 318; Eurocode 2), calibrated for natural-aggregate concrete, inadequately address the distinct properties of . To bridge this gap, this review proposes a recycled-aggregate reduction factor (psi(r)), analogous to the lightweight-concrete factor in existing codes. This factor provides engineers with a code-compliant methodology for the safe design of RACs, supporting the broader adoption of sustainable construction materials.
Agricultural waste is rising rapidly, and turning organic residues into construction materials offers a sustainable way to reduce environmental impact. This study examines concrete mixtures enhanced with mechanically treated date palm mesh () and sugarcane bagasse () fibres. Sixty samples were prepared with fibre contents of 0%, 0.4%, 0.6%, and 0.8% by mass, were tested for slump, unit weight, absorption, compressive, flexural and tensile strength, and thermal conductivity. Increasing fibre content reduced workability, with slump values dropping from 175 mm in the control mix to 10 mm in 6. Unit weight remained between 2.2 and 2.44 g/cm(3), while palm mesh helped reduce the water absorption to 5.8 kg/m & sup3;. The 8 mix achieved the highest compressive strength of 33.69 MPa, outperforming the 22.93 MPa control. Flexural and tensile strengths peaked at 6.6 and 3.22 MPa in the 6 mix. Thermal conductivity also improved, decreasing from 6.4 degrees C in the control to 5.0 degrees C in 6, indicating better insulation. Overall, adding 0.6-0.8% palm mesh fibres significantly enhanced concrete strength, durability, and thermal performance, positioning these fibres as an effective sustainable option for construction in hot climates.
Close-range photogrammetry is used as a precise measurement tool in various fields of science. Concrete structures in projects such as bridges, hydraulic structures, and dams are constantly exposed to abrasion. In abrasion tests, assessing the abrasion resistance of concrete samples depends on the accurate measurement of the volume of worn concrete over a specified time. This paper employs close-range photogrammetry to measure the volume of worn concrete in abrasion tests. Three-dimensional modelling of the sample under abrasion not only allows for precise calculation of the volume of wear cavities but also facilitates baseline profile assessments and threshold evaluations on the depth of wear cavities. In the examined sample, the accuracy of point cloud co-ordinate estimation on the feature was better than 0.22 mm. The volume of abrasion was estimated to be 12.37 cm3, with an accuracy better than 0.001 cm3. Considering the allowable abrasion volume of 15 cm3 in this test, the concrete sample passed the test; however, regarding cavity depths, with a threshold limit of 8 mm, five out of eight cavities were rejected. The results indicate that using close-range photogrammetry can enhance the accuracy of assessments compared with traditional methods at a lower cost.
This study comprehensively investigates the effect of steel fibre () level on air content, flowability, mechanical strengths, drying shrinkage, chloride ion permeability, and pore structure of ultra-high performance concrete () containing metakaolin and limestone powder () or quartz powder (). The results indicate that air content and fluidity of fresh continuously decrease with level growth. Its compressive and flexural strength generally increase with level. addition can impose a greater improving effect on the compressive strength of QP-contained compared with LP-UHPC. Conversely, the flexural strength and ductility of LP-mixed under various levels of are bigger than those of the corresponding specimen containing . A moderate dose would relieve the drying shrinkage tendency of under 50% relative humidity and water-curing regimes. Moreover, the shrinkage value and chloride ion permeability for mixtures containing various levels of under water curing are smaller than those of QP-incorporated . The late-age flexural strength of LP-contained linearly increases with reduction of air content, and a good linear regression equation is obtained for conveniently predicting the flexural strength according to air content.
This study investigates degradation mechanisms and improvement strategies for concrete incorporating manufactured granite sand under cyclic drying, sodium sulphate immersion, and freeze-thaw cycles. Three cementitious systems were compared: pure cement (G1), cement–fly ash–slag (G2), and cement–fly ash–slag–nanomaterial (G3). Evaluations included mechanical properties, durability, and microstructural analysis. Results showed G1 exhibited inferior dynamic performance, microcrack propagation, and high chloride permeability, and while G2 enhanced sulphate resistance via pozzolanic reactions, its mechanical improvements were limited. The G3 system demonstrated superior performance, achieving approximately 20% higher compressive strength, over 10% increased dynamic elastic modulus, and 40% reduced chloride permeability. Microstructural analysis revealed that carbon nanotubes and nano-CaCO3 refined hydration products through filling and nucleation effects, effectively suppressing microcracks and delaying degradation. This research provides guidance for developing high-quality manufactured sand concrete resistant to multi-environmental conditions.
This review explores the use of biochar as a sustainable additive in concrete and its potential to reduce the environmental impact of construction materials. It begins by outlining the environmental challenges associated with conventional concrete production, particularly its high carbon emissions, and highlights the growing interest in biochar as a low-carbon alternative. A scientometric analysis is conducted to examine publication trends, leading researchers, influential institutions, and key research themes within this field. The review then discusses the fundamental properties of biochar, including its sources, feedstocks, and production methods, as well as the factors that influence its quality and performance. Its influence on the fresh, mechanical, and durability properties of concrete is evaluated, together with its role in long-term carbon sequestration. The paper further explains the interaction between biochar and cementitious matrices through mechanisms such as pozzolanic reactions, water retention capacity, and microstructural refinement. Finally, environmental and economic implications are considered through life-cycle and cost assessments, and key research gaps and future directions are identified to support broader implementation.
This study investigated the feasibility of partially replacing fine aggregates with crumb rubber () in fly ash bricks and examines the influence of sodium hydroxide (NaOH) treatment on their performance. Fly ash bricks were produced with 3-25% replacement by volume, using both untreated () and NaOH-treated () rubber. Mechanical, durability, and microstructural properties were assessed through compressive and flexural strength tests, water absorption (), initial rate of water absorption (), efflorescence testing, scanning electron microscopy (), and X-ray diffraction () analysis. Results indicate that up to 12% replacement caused no significant loss in compressive or flexural strength, with bricks consistently outperforming bricks. NaOH treatment slightly reduced (0.65-2%) and marginally improved values, although revealed more voids in specimens at higher contents. analysis confirmed no major crystalline phase changes between and bricks. Limited difference is observed in cost and global warming potential relative to conventional clay bricks. The findings suggest that NaOH-treated can be used in fly ash bricks at replacement levels up to 12% without compromising mechanical performance, offering a viable and sustainable alternative for masonry applications.
Natural fibres such as sisal and coir are used as reinforcements in concrete to enhance its mechanical properties. In this investigation, pre-treatment techniques of these fibres were studied to enhance their performance in concrete applications. Chemical treatments using sodium bicarbonate and sodium hydroxide solutions have been adopted to modify the surface texture of sisal and coir fibres. Fourier transform infrared spectroscopy of treated and untreated sisal fibre shows there is removal of the hemicellulose part of the fibre. analysis indicated that the removal of the outer layer of cellulose from the fibre leaves behind a rougher surface that enhances the bonding capacity with the cement matrix. A change in morphology is seen after chemical treatment, as shown by the analysis through SEM, which depicts an improved roughness on the surface; also the cost comparison between the synthetic fibre and pre-processed natural fibre is observed. This results in better load transfer and, thus more durable concrete structure.
The construction sector is under increasing pressure to reduce its environmental footprint caused by conventional materials such as fired clay bricks and cement, which contribute significantly to greenhouse gas emissions and natural resource depletion. This study investigates the development of eco-friendly solid and hollow mortar bricks by incorporating pine needles into a standard 1:4 cement-to-sand mortar mix. Pine needles, a forest biomass waste that contributes to wildfire hazards, were used at dosages of 1.0%, 1.5%, and 2.0% by weight of cement in a 1:4 cement-sand mortar mix. The prepared bricks were evaluated for compressive strength, water absorption, and density under both normal and accelerated curing conditions. Results indicated that bricks with 1.5-2.0% pine needle incorporation demonstrated enhanced strength and reduced weight, with hollow bricks achieving a maximum compressive strength of 18.62 MPa after 28 days of accelerated curing. To demonstrate practical applicability, a pilot-scale constructed wetland was designed using the hollow bricks, enabling natural wastewater treatment through a decentralised system. This innovative application demonstrated the effective integration of eco-friendly bricks into sustainable infrastructure. The study highlights a dual-benefit approach transforming pine needle waste into a value-added construction material while reducing wildfire risks and advancing green wastewater treatment solutions.
This study investigates the use of sea sand (SS) and coral aggregate (CA) as substitutes for river sand and natural coarse aggregate in the production of seawater sea sand coral aggregate concrete (SSCAC). The inherently porous structure of CA increases interfacial friction between the cement paste, SS, and CA, thereby influencing the workability of SSCAC. To address this issue, the rheological properties of SSCAC were optimised by partially replacing cement with limestone powder (LS), incorporating crushed coral aggregate (CCA), and adjusting the superplasticiser (SP) dosage to improve the wet packing density (WPD). A total of 45 SSCAC mixtures were prepared with varying contents of LS, CA, CCA, and SP. These mixtures were evaluated for flowability, L-box passing ability (PL), segregation index, WPD, and compressive strength at 28 and 91 days. The results demonstrated that the inclusion of LS and CCA effectively enhanced the WPD of SSCAC, thereby improving segregation resistance, flowability, and PL. A strong positive correlation was identified among flowability, PL, and WPD, confirming the critical role of particle packing in optimising SSCAC rheology.
This study investigates the effects of sugarcane fibre (SCF), an agricultural waste fibre, and polypropylene fibre (PPF), a synthetic fibre, on concrete’s mechanical and durability properties. Experimental tests were conducted on concrete incorporating SCF and PPF in different proportions (0.5%, 1%, and 1.5% by weight of binder), along with a hybrid combination (SCPP-FRC) containing a maximum of 1.5% fibres. Results indicate that both fibres, used individually or in hybrid form, significantly improve the concrete’s performance. Individually, SCF and PPF increased compressive strength by 7–17% at 1% fibre content, beyond which strength declined due to fibre clumping. The optimal hybrid mix (SCF 0.75% + PPF 0.75%) achieved the highest strength. Tensile and flexural strengths improved by 23% and 28%, respectively. SCF-based concrete exhibited higher water absorption (5.58%) compared to control and PP-FRC due to SCF’s hydrophilic nature, while hybrid SCPP-FRC showed moderate absorption. Acid resistance tests revealed that SCPP-FRC had lower strength loss (18%) than control concrete after 56 days of acid exposure. Scanning electron microscopy analysis confirmed fibre bridging effects, enhancing the interfacial transition zone, resulting in denser concrete. The study concludes that a 1% fibre content or (0.75% SCF + 0.75% PPF hybrid) optimally improves concrete’s mechanical and durability properties.
The construction industry's rising emphasis on sustainability and durability has encouraged innovation in concrete materials. This study develops a one-part alkali-activated self-compacting concrete that utilises coal mine overburden (CMO) as a viable substitute for natural fine aggregate. The one-part alkali activation method increases practical application by using solid precursors rather than liquid activators, which removes the need to handle corrosive solutions. The primary precursor, ground granulated blast furnace slag, was combined with solid sodium metasilicate as the dry activator. The raw material properties of the CMO were studied to determine its suitability as a fine aggregate. Several mix design trials were conducted to achieve sufficient paste volume, consistent aggregate distribution, and workability. The developed concrete satisfied the requirements for M30 grade concrete with 28th-day compressive, split tensile, and flexural strengths of 39.55, 4.75, and 4.65 MPa, respectively. In addition, it showed low chloride ion permeability, minimal drying shrinkage (0.037%), and reduced thermal conductivity (1.20 W/mK). These results indicate that CMO can be successfully added to one-part alkali-activated SCC as a fine aggregate substitute, offering a technically viable and sustainable solution.
This study investigates the efficient design of ground granulated blast furnace slag (GGBFS)-based ambient-cured alkali-activated reactive powder concrete (AARPC) by examining the effects of mix proportions and alkali activators, including alkali-activator to binder (Al/Bi) ratio, silicate modulus (SiO2/Na2O), and binder to aggregate (Bi/Agg) ratio, on workability and compressive strength. Microstructural analyses, including X-ray diffraction, scanning electron microscopy with energy-dispersive spectroscopy, and Fourier transform infrared spectroscopy, were performed to reveal phase changes and reaction products. A total of 27 mix combinations were evaluated. The flow diameter ranged from 100 to 242 mm, and compressive strength ranged from 65.8 to 106.0 MPa at 7 days and 72.3 to 124.4 MPa at 28 days. Lower Al/Bi ratios with lower silicate modulus enhanced workability through better dissolution of slag particles, whereas higher Al/Bi ratios with higher modulus improved flow by way of binder dispersion. Compressive strength increased with a higher Al/Bi ratio for Bi/Agg = 0.9 and 1.0, whereas a higher silicate modulus reduced strength due to insufficient dissolution. Denser microstructures were observed at lower Al/Bi ratios, whereas micro-cracks and unreacted slag were more prevalent at higher silicate modulus. Overall, this study provides significant insights into the efficient design of practical ambient-cured GGBFS-based AARPC.
Recent studies on geopolymers often focus on single-factor effects, such as alkali concentration or curing temperature, neglecting their synergistic influence on mechanical performance and statistical reliability. Existing literature rarely correlates strength results with experimental variability or statistical significance, complicating mix optimisation. This study addresses these gaps by experimentally evaluating metakaolin-fly ash geopolymers under varied curing temperatures (25 degrees C and 50 degrees C), sodium hydroxide molarities (6, 8, and 10 M), and sodium silicate-to-sodium hydroxide ratios (1:1 and 2:1). Mechanical properties were assessed at 7 and 28 days, and phase transformations via X-ray diffraction (XRD). Results were statistically validated using t-tests and ANOVA to confirm the significance of processing parameters. Findings show that elevated curing temperature (50 degrees C) markedly increases compressive strength (maximum achieved by G-82-50), while flexural strength responds more modestly. XRD confirmed that thermal activation promotes mullite dissolution and the formation of a denser geopolymer gel. The integration of statistical and microstructural analysis provides deeper insight into mix sensitivity compared with conventional reporting. This study offers a multiparameter evaluation and statistical significance approach to geopolymer mix design, providing a reliable pathway for high-performance, sustainable cement alternatives.
Geopolymerisation of geopolymer concrete often relies on heat or steam curing to improve mechanical properties and durability. However, heat curing can be challenging for field applications. This study focuses on creating fly ash-based geopolymers without external heat, using high-calcium fly ash and ordinary Portland cement to accelerate curing at ambient temperatures Terminalia chebula (TC) and honey. The optimal percentage of bio-additives should be determined to achieve the desired mechanical properties, such as compressive and tensile strengths. Durability can be assessed through tests, such as sorptivity and acid attack. In this research, two bio-additives were added at varying weight percentages to aluminosilicate minerals, and the samples were cured under winter conditions of 12 ± 4°C and 60% relative humidity. Experimental results indicated that 0.75% of the TC and 0.75% enhanced compressive strength by 18.05% and splitting tensile strength by 5.68% compared with control specimens cured for 28 days. Durability analysis revealed a 40% lower sorptivity coefficient, a 26.69% reduction in compressive strength loss, and a 39.23% decrease in mass loss due to acid attack compared with the control specimens.
Pervious concrete (PC) is an environmentally friendly construction material with an interconnected void structure that regulates stormwater runoff, reduces urban heat islands, and promotes groundwater recharge. This review study employs scientometric tools to examine nearly 30 years of PC research based on Scopus-indexed publications. Extensive research has been conducted on PC production methods and performance; this paper conducts a systematic review of its applications using Preferred Reporting Items for Systematic Reviews and Meta-Analyses and enhanced by VOSviewer's bibliometric mapping of keyword clusters, international co-authorship, and citation trends. Studies show that there is a growing interest in PC research for achieving sustainable urban development. However, the review identifies a lack of emphasis on the scientific rigour of the underlying research, such as experimental methodology consistency, sample size adequacy, and statistical significance. This review study also inspects different developments in PC material configuration, mix designs, mechanical and structural characteristics, and the relationship between porosity, permeability, and load-bearing capacity. The addition of supplementary cementitious materials, like as fly ash, silica fume, and so on, increases PC performance and also helps to recycle the industrial wastes. The combination of bibliometric insights and technical evaluations can strengthen PC's contribution to sustainable infrastructure development.
The possibility of improving the engineering properties of a silty clay from Calgary, Alberta, Canada, was assessed. Specimens made of silty clay soil (S), silty clay-plus-cement (SC), and silty clay-plus-cement-plus-Duraflex admixture (SCD) were tested for either unconfined compressive strength (UCS) or splitting tensile strength (STS). Two curing conditions were used (100% RH and the laboratory) for different curing durations (7, 14, 28 days, and 10 months). Lab-cured 10-month specimens with Duraflex admixture (DFI) were 10-25% statistically stronger than SC specimens and more than twice the strength of soil alone. Small but significant variations in STS/UCS ratios ranging from 0.10 to 0.27 were observed for different curing durations and conditions. However, when the same type of specimens were cured under identical conditions and duration, no statistically significant variation occurred. Brunauer-Emmett-Teller (BET-N2) analysis resulted in a notable reduction in micro- and mesopores, pore surface area, and pore volume through the addition of DFI, suggesting the addition of that admixture filled more pores with cementitious material. In addition, matric suction analysis through the filter paper method confirmed that SCD resulted in higher suction strength than SC and S, implying lower porosity and thereby statistically higher UCS and STS values.
