Concrete Mixtures Research Articles

Predictive models for properties of hybrid blended modified sustainable concrete incorporating nano-silica, basalt fibers, and recycled aggregates: Application of advanced artificial intelligence techniques

The main objective of this work is to improve the compressive strength of concrete, specially in sustainable construction is to develop more precise predictive modeling techniques. The compressive strength prediction of basalt fiber reinforced concrete filled with nano-silica and recycled aggregates can be done using a hybrid deep learning model suggesting the use of the combination of Convolutional Neural Networks and Long Short-Term Memory networks. The CNN captures microstructural features from SEM images, while the LSTM models temporal dependencies from sequential curing data samples. To enhance the prediction accuracy, PCA was performed on feature dimensionality reduction and GA optimized hyperparameters both for the model as well as the concrete mix design for improved strength with cost effectiveness. With an R² value of 0.92–0.95, the performance results of the presented model came out better than the baseline models, as well as reducing the MAE by 20 %. Besides, there existed a 5–8 % better compressive strength in GA-optimized mix designs. Robustness comes into play with the model that shows steady strength predictions, regardless of conditions of curing under multiple conditions and at different material composition levels. Furthermore, the reutilization of recycled aggregates and nano-silica gives a real environmental benefit as less waste is produced but the material performance is maximized. This kind of outcome indicates how the proposed model can be practically applied in optimizing concrete design in terms of strength and sustainability features, thus providing an accessible instrument for decision-making in the construction field. It is an effective tool to improve the performance of concrete while minimizing environmental and material wastes.

Explainable Boosting Machine Learning for Predicting Bond Strength of FRP Rebars in Ultra High-Performance Concrete

Aiming at evaluating the bond strength of fiber-reinforced polymer (FRP) rebars in ultra-high-performance concrete (UHPC), boosting machine learning (ML) models have been developed using datasets collected from previous experiments. The considered variables in this study are rebar type and diameter, elastic modulus and tensile strength of rebars, concrete compressive strength and cover, embedment length, and test method. The dataset contains two test methods: pullout tests and beam tests. Four types of rebar, including carbon fiber-reinforced polymer (CFRP), glass fiber-reinforced polymer (GFRP), basalt, and steel rebars, were considered. The boosting ML models applied in this study include AdaBoost, CatBoost, Gradient Boosting, XGBoost, and Hist Gradient Boosting. After hyperparameter tuning, these models demonstrated significant improvements in predictive accuracy, with XGBoost achieving the highest R2 score of 0.95 and the lowest Root Mean Square Error (RMSE) of 2.21. Shapley values analysis revealed that tensile strength, elastic modulus, and embedment length are the most critical factors influencing bond strength. The findings offer valuable insights for applying ML models in predicting bond strength in FRP-reinforced UHPC, providing a practical tool for structural engineering.

Numerical simulation on structural behavior of FRP profile‐concrete hybrid beams with bolt shear connector

AbstractFRP profile‐concrete hybrid beam, composed of a FRP profile beam, a concrete slab made of normal concrete (NC) or ultra‐high‐performance‐concrete (UHPC), and shear connectors, shows significant potential for employment in large‐span bridges due to its excellent corrosion resistance, lightweight, and easy construction. The structural behavior of such hybrid beam was simulated using a three‐dimensional non‐linear finite element model (FEM) in Abaqus. The Hashin failure model and concrete damage plastic (CDP) model were employed to characterize the progressive failure of FRP, NC, and UHPC, respectively. The FEM considered partial shear connection by utilizing shear load‐slip model and the orthotropic behavior of the FRP profile. The proposed FEM was validated through comparisons with experimental data in terms of load‐midspan deflection curve, load‐end slip curve, and failure modes. A parametric study was subsequently conducted to identify the effects of various factors, including concrete strength, bolt spacing, concrete slab width, concrete slab height, FRP flange and web thickness, and shear span. Based on the results yielded from FEM analysis, the accuracy of the calculation method in Chinese standard (GB‐50608) for predicting the loading capacity of hybrid beams was evaluated and found too conservative.

Heterogeneous temperature characteristics considering rainfall effect during construction of an integrally-poured rock-filled concrete arch dam

Integrally-poured arch dam with the material of rock-filled concrete (RFC) is a new and rapid construction technology for mass concrete structures. There is still limited literature regarding the heterogeneous temperature field of RFC, especially under special weather conditions. In this study, a novel mesoscale model of heterogeneous RFC was generated through a combination of the discrete element method (DEM), the finite element method (FEM), and the background grid mapping method (BGMM). Based on the monitoring experiments at the Longdongwan project, this study greatly enhances the simulation precision and details by incorporating a two-phase material of heterogeneous RFC model, i.e. the stochastic pre-laid rocks and layered SCC (self-compacting concrete), and refining the analysis time step to an hourly basis. The results show that: (1) An infinite heat convection coefficient on the exposed RFC surfaces was effective in simulating the rainfall effect, and the mesoscopic simulation results aligned well with the monitoring data. (2)The cold wave with rainfall can cause a notable drop of around 10 °C in the placement temperatures of both rocks and SCC, and lowered the temperature rise by about 5°C for the subsequent freshly poured RFC lift. (3) The hydration temperature rise was recorded the highest (13–14°C) in the areas near the dam abutment, due to challenges of placing rocks. These findings can provide insights and advice for similar construction scenarios.

Aggregate blending optimisation in quarries to improve of the mechanical and environmental properties of concrete

ABSTRACT In this study, concrete mix optimisation was carried out with materials provided by Catalca (Ca) and Cendere (Ce) quarries in the region of Istanbul, Turkey which produce concrete aggregate from different rock formations. Accordingly, the properties of six different concrete aggregates produced from these quarries (3 regions in Catalca quarry and 3 regions in Cendere quarry) and the amounts of CO2-e released into the atmosphere by producing these aggregates were determined. Then, these aggregates were used in different proportions in concrete mixtures and the effects of aggregate types on the mechanical properties of concrete were statistically demonstrated by the experimental design method. According to the results, the mechanical properties of concrete were statistically significantly affected by the use of aggregate in different formations. In addition, empirical approaches that can be used in estimating the compressive strength, tensile strength and elasticity modulus of concrete have been found and using these approaches, mixtures that maximise these mechanical properties of concrete have been determined. Accordingly, mechanical properties of concrete were maximised in mixtures where Ca 1st Region 25% - Ca 2nd Region 75%, Ca 1st Region 60% - Ca 3rd Region 40%, Ca 2nd Region 13% - Ca 3rd Region 87%, Ce 1st Region 10% - Ce 3rd Region 90%, Ce 1st Region 63% - Ca 2nd Region 37%, and Ca 1st Region 35% - Ca 2nd Region 5% - Ca 3rd Region 60% were used. The CO2-e values of these mixtures were calculated as 8.405, 8.248, 8.529, 8.630, 8.476, and 8.365 kg/t respectively.

Performance-Based Design of Ferronickel Slag Alkali-Activated Concrete for High Thermal Load Applications.

This study aimed to develop optimized alkali-activated concrete using ferronickel slag for high-temperature applications, focusing on minimizing environmental impact while maintaining high compressive strength and slump. A response surface methodology, specifically the mixture design of experiments, was employed to optimize five components: water, FNS-based alkali-activated binder, and three aggregate sizes. Twenty concrete mixes were tested for slump and compressive strength before and after exposure to 600 °C for two hours. The optimal mix achieved 88 MPa compressive strength before heat exposure and 34 MPa after, with a slump of 140 mm. An upscaled version with improved workability (210 mm slump) maintained similar unheated strength but showed reduced post-heating strength (23.5 MPa). Replacing limestone with olivine aggregates in the upscaled mix resulted in 65 MPa unheated and 32 MPa post-heating strengths. Life Cycle Analysis revealed that the optimized ferronickel slag alkali-activated concrete's CO2 emissions were 77% lower than those of ordinary Portland cement concrete of equivalent strength. This approach demonstrated the applicability of mixture design of experiments as an alternative design methodology for alkali activated concrete, providing a valuable performance-based design tool to advance the application of alkali-activated concrete in the construction industry, where no prescriptive standards for alkali-activated ferronickel concrete mix design exist. The study concluded that the developed ferronickel slag alkali-activated concrete, obtained through a performance-based mixture design methodology, offers a promising, environmentally friendly alternative for high-strength, high-temperature applications in construction.

Research on adaptive hydraulic drive optimization control of concrete mixing tank truck for open-pit mine.

The non-axisymmetric problem caused by the fluid sloshing in the tank of a mining concrete mixing tank truck during driving is affected by the excitation of complex road surfaces. The fluid sloshing is coupled with the dynamics of the vehicle body due to the excitation of the complex road surface. The traditional hydraulic drive proportional integral differential (PID) control method is not effective in dealing with such problems, which can easily lead to accidents such as overturning. To improve the accuracy and stability of the hydraulic drive control system, this paper proposes an optimized particle filter PID adaptive control method based on the elastic firefly (FA) algorithm to accelerate the convergence speed of control parameter optimization, and then analyzes its hydraulic drive control characteristics and structural applications, and discusses step steering and double lane change modes are simulated under filling rates of 1.5 and 2.0, respectively. The experimental results show that compared with traditional PID control, the proposed adaptive control method can significantly reduce the average speed error of hydraulic drive control to 0.03km/h and the maximum speed error to 0.17km/h. It also improves the control tracking performance and stability. The practicality of the adaptive hydraulic drive is verified in the filling rate experiments under step steering and double-lane shifting conditions. It has important reference value for the practical application of hydraulic drive control optimization of mining concrete mixing transport tank trucks.

Evaluating the fire resistance potential of functionally graded ultra-high performance concrete

Relevant standards stipulating the concrete surface temperature less than 380 °C and the defects of UHPC prone to fire spalling both limit the direct application of UHPC in specific tunnel fire prevention occasions. In view of this, a two-layered functionally graded ultra-high performance concrete (FGUHPC) was proposed in this paper, where lightweight aggregate concrete (LWAC) serves as the fire-resistant layer and UHPC functions as the structural load-bearing layer. The results showed that LWAC can control its backfire surface temperature to meet the standard requirements under a thickness of 40 mm, and the residual mechanical properties of UHPC before 400 °C were comparable to those at ambient temperature. The straight shear test was adopted to evaluate the FGUHPC interfacial bond strength. The results showed that the interfacial strength of FGUHPC reaches 3.05 MPa at ambient temperature, which is close to or even slightly higher than that of homogenous LWAC. When FGUHPC was treated at 1200 °C for 2h, FGUHPC can still maintains its integrity with its interfacial strength 120.0 % higher than that of LWAC. Compared to the homogenous UHPC member, FGUHPC composed of 40 mm LWAC and 120 mm UHPC effectively avoided explosive spalling, and maintained the interface temperature at around 200 °C. After static loading failure of the post-fire FGUHPC member, the two layers of concrete still remained bonded without delamination, and the loss in load-bearing capacity was less than 20 %. Finally, the design method of FGUHPC members under elevated temperature was discussed.

Performance Assessment of a Novel Green Concrete Using Coffee Grounds Biochar Waste

An actual scientific problem in current concrete science is poor knowledge of the problem of modifying concrete with plant waste. At the same time, plant waste benefits from other types of waste because it is a recycled raw material. A promising technological approach to modifying concrete with plant waste is the introduction of components based on the processing of coffee production waste into concrete. This study aims to investigate the use of biochar additives from spent coffee grounds (biochar spent coffee grounds—BSCG) in the technology of cement composites and to identify rational formulations. A biochar-modifying additive was produced from waste coffee grounds by heat treatment of these wastes and additional mechanical grinding after pyrolysis. The phase composition of the manufactured BSCG additive was determined, which is characterized by the presence of phases such as quartz, cristobalite, and amorphous carbon. The results showed that the use of BSCG increases the water demand for cement pastes and reduces the cone slump of concrete mixtures. Rational dosages of BSCG have been determined to improve the properties of cement pastes and concrete. As a result of the tests, it was determined that the ideal situation is for the BSCG ratio to be at a maximum of 8% in the concrete and not to exceed this rate. For cement pastes, the most effective BSCG content was 3% for concrete (3%–4%). The compressive and flexural strengths of the cement pastes were 6.06% and 6.32%, respectively. Concrete’s compressive strength increased by 5.85%, and water absorption decreased by 6.58%. The obtained results prove the feasibility of using BSCG in cement composite technology to reduce cement consumption and solve the environmental problem of recycling plant waste.

Lifecycle Assessment Analysis of Recycled Concrete Aggregate Incorporating Fly Ash and Hemp

The critical roles of recycling are increasing depending on depleted natural resources and its devastating consequences. Concrete has been one of the most used building materials for many years to response the basic need of human beings for shelter. The studies on the recycling of concrete are crucial to minimize negative effects of both the high amount of energy consumed during the production phase and the limited recycling opportunities after destruction. Considering the amount of construction and demolition waste (CDW) after the February 6, 2023 earthquakes in Türkiye, it is clear that recycling concrete (RC) may make a positive contribution to environmental sustainability and natural resources usage. In addition, as a result of the ongoing urban transformation projects throughout Türkiye, especially in Istanbul, there is a need to recycle CDW, the majority of which consists of concrete. This paper examines the equivalent CO2 emissions of recycled concrete aggregate (RCA) incorporation of various proportion fly ash and hemp based on previous studies by applying the Excel-based GreenConcrete LCA software developed at the University of California Berkeley Campus (UC Berkeley). As a result of the investigations, it is seen that the use of RCA, which is generated in large quantities both as a result of earthquakes and urban transformation projects, reflects positively on the environmental impacts in the LCA analysis. In addition, the use of concrete mixtures that contribute to the recycling of wastes such as fly ash and hemp used as admixtures contributes to reducing the environmental damage of these wastes and improving the concrete content.

Performance evaluation of high-performance concrete mixes incorporating recycled steel scale waste as fine aggregates

In this study, steel-scale waste (SSW), a byproduct generated during the manufacturing of steel, was investigated as a potential alternative to natural fine aggregates (sand) for preparing high-performance concrete (HPC). Three grades of sand and SSW with different particle sizes were mixed in varying combinations. Three different compaction techniques (loose, tamped, vibration) were employed. The optimum packing density for both SSW and natural aggregates was achieved using the vibration compaction method. Since the combination of 50 % sand and 50 % SSW exhibited the best packing density for both materials, this bi-grade aggregate mixture was selected for the mix preparation. The mechanical tests (compressive strength, flexural strength) and durability assessment (bulk water sorptivity, rate of water absorption, chloride ion penetration) were performed to achieve the desired objectives. The specimens were exposed to two different curing regimes i.e., normal curing and heat curing at elevated temperature. A significant increase in compressive and flexural strength was observed with the increased content of SSW. A compressive strength as high as 140 MPa was obtained for the HPC mix containing SSW aggregates and steel fibers. The replacement ratio of SSW was optimized to achieve better strength and durability. Experimental results showed that heat curing was more effective than conventional curing methods in improving the performance of the concrete.

Compressive stress-strain response of freshly compressed rubberized concrete: An experimental and theoretical study

Although using crumb tire rubber concrete (CTRC) in constructing structural elements is accompanied by various environmental and economic advantages, it always comes with challenges due to a significant loss in some mechanical properties of this concrete type. To tackle this challenge, a novel technique of compressing fresh concrete was used, and its impacts on improving the mechanical features of CTRC were investigated. For this purpose, concrete specimens containing crumb tire rubber (CTR), as the fine aggregate substitute, were constructed considering the variables of the water-to-cement ratio (w/c), volume percentage of CTR, and the fresh concrete pressure level as a fraction of steel tube (mold) yielding stress. After the application of a specified short-term pressure to the fresh mix inside the steel molds and the time required for the concrete setting, the steel tubes were removed after curing, and the concrete core alone was exposed to an axial compressive load. According to the test results, the mechanical properties, weight loss resulting from compressing the fresh concrete, energy absorption, failure pattern, the concrete microstructure, water absorption, and porosity were evaluated. By applying an initial axial pressure of 25–80 MPa on the mixes containing 0 %, 15 %, and 30 % CTR replacing the fine aggregate, the compressive strength, the ultimate strain, the toughness, and the initial modulus of elasticity experienced 100–140 % increase, 130–420 % increase, 120–1140 % increase, and 66–70 % decrease, respectively, compared with the uncompressed specimen. Finally, a regression analysis was employed to propose prediction models for the compressive capacity, modulus of elasticity, peak strain, ultimate strain, and relative toughness of freshly compressed concrete containing CTR particles; these models show proper agreement with the experimental results.

Flexural cracking behavior of steel-NC-UHPC composite beam under negative bending moment

Steel-concrete structures are widely applied in bridge engineering due to their superior mechanical performance and cost-effectiveness. However, normal concrete (NC) decks often suffer cracking problems, adversely affecting their serviceability. Ultra-high performance concrete (UHPC) can be used to partially replace the top of NC decks to enhance their post-cracking behavior because UHPC shows high tensile strength, strain-hardening characteristics in tension, and strong bond strength with NC. To this end, this paper focused on the flexural behavior of steel-NC-UHPC composite beams regarding their failure mode, stiffness, strain development, cracking behavior, crack width, etc. Test results indicated that the test specimens mainly exhibited two types of failure modes: shear failure of the NC layer and local buckling of the compressive flange at the steel girder, which were mainly determined by the reinforcement ratio. Flexural stiffness was controlled by the steel girder, and the reinforcement ratio had a notable effect on the reinforcement strain and crack propagation. Additionally, cracks can be categorized into three types: through cracks, connecting cracks, and separate cracks. These cracks in the UHPC layer and NC layer would affect each other, especially those near the roughening interface. The sectional nonlinear analysis was employed to calculate the strain of reinforcement and the steel girder accurately. Finally, the prediction methods of crack width for the NC layer and UHPC layer were discussed. Formulas in NF P18–710 were verified to be feasible for the prediction of UHPC crack width. The UHPC influence factor was introduced to modify the calculation results of the NC crack width by the Chinese NC code.

The potential of solid waste as a viable replacement for quartz sand in the ultra-high performance concrete: a comprehensive review

ABSTRACT Ultra-high performance concrete (UHPC) is renowned for its dense structure and exceptional mechanical properties, including durability. However, its widespread adoption is hindered by the high costs of essential fine aggregates like quartz sand and the associated environmental impact. Additionally, using industrial solid waste raises pollution concerns, contradicting global sustainability goals. Numerous studies have shown that it is feasible to produce eco-friendly UHPC with excellent performance by solid waste. This comprehensive review thoroughly investigates the workability, mechanical properties (including compressive strength, flexural strength and tensile strength), microstructure (encompassing pore structure and interfacial transition zone) and durability of UHPC incorporating solid waste in its production. The paper emphasizes the critical influence of factors, such as the solid waste substitution rate and the physical and chemical properties of solid waste. The paper also outlines the current application of UHPC with solid waste in pavement engineering and highlights the urgent need to address challenges such as high production costs, the lack of design standards and construction technique deficiencies, thereby emphasising the urgency surrounding the design and advancement of solid waste-incorporated UHPC in pavement engineering as it can reduce the environmental impact of traditional UHPC and improve the efficient use of solid waste.

Exploring Current Techniques for Improving the Properties of New Concrete

In modern construction, the properties of new concrete are crucial for building quality and structural performance. Recent technological advancements have led to significant progress in enhancing the properties of new concrete. This study employs theoretical and experimental methods to explore the connection among shear stress and shear strain rate under vibration, the impact of aggregate substitution on concrete performance, and the rheological properties of moist shotcrete. The findings suggest that adjusting mix proportions and using additives can significantly improve concrete's strength, durability, and workability. This research provides engineers with a theoretical foundation for optimizing concrete mixtures and construction techniques, thereby improving overall building quality and construction efficiency. The findings suggest that sustainable materials can be used without compromising structural integrity, making the construction process more environmentally friendly while maintaining high performance standards. Furthermore, this study highlights the importance of understanding concrete behavior under various conditions to develop more resilient and long-lasting structures.

Investigation of Performance Specifications for Marshall Mixes Using Performance-Based Mix Design Methodology

This paper presents a comprehensive study for developing the performance specifications for the Marshall mixes using the performance-based mix design (PMD) methodology. The specification describes the desired levels of fundamental engineering properties for predicting performance during mix design or quality assurance checks at the time of construction. In this study, the bituminous concrete mixture was designed through complementing volumetric criteria with performance tests such as dynamic creep and the indirect tensile asphalt cracking test for evaluating resistance against rutting and fatigue cracking, respectively. This study considers different factors such as five different types of design aggregate gradations (mid-gradation, fine-coarse gradation, coarse gradation, coarse-fine gradation, and fine gradation), three binder types (VG-30, VG-40, and PMB-40), and five levels of compactive efforts (35, 50, 75, 90, and 110 blows on each face). The study finds the effect of design aggregate gradation, binder type, and compactive effort on the rutting and cracking resistance of bituminous mixes. The research study also comprehends the influence of volumetric properties on the performance parameters. Further, it establishes the initial performance criteria for rutting and cracking for Marshall mixes. The performance space diagram (PSD) has also been plotted, portraying the overall performance (acceptable, desirable, or unsatisfactory performance regions) of bituminous mixtures based on rutting resistance and cracking resistance. This paper highlights and advocates the integration of these performance-based specifications into the Marshall mix design specifications for improving pavement characteristics and extending overall service life.

Performance of concrete beams strengthened with FRP rods: A review

Ductility is a critical property in structural engineering, ensuring that beams can undergo significant deformation before failure, thereby giving plenty of notice before disastrous collapse. This study investigates the ductility properties of constructions that have been reinforced using FRP rods, which are increasingly popular due to their corrosion resistance, superior strength with low mass, and durability. Traditional steel reinforcement has well-documented ductility properties, but FRP bars, due to their brittle nature, pose challenges in achieving the desired ductility levels in structural applications. This research evaluates various factors influencing FRP-reinforced beams' ductility, including the type of FRP material, the hybridization of FRP with other reinforcing materials, and the effect of utilizing fibres in the mixtures to enhance the mechanical characterstics of concrete. Studies have indicated that the ductility of beams can be enhanced using hybrid rebar systems, which integrate steel and fibre reinforced polymer. However, complex and expensive production methods limit their practical application. Using steel bars with FRP bars can significantly incresese seriviceability requiremts such as crack width and deflection, but they also lower corrosion resistance, especially in aggressive environments. The beams' overall ductile behavior is primarily determined by the concrete's characteristics. Fibres greatly increase the mechanical characteristics, toughness, and ductility of the concrete mix, strengthening the bond between bars and the concrete and improving the overall performance of the beam.

Out-of-plane performance of BFRP reinforced UHPC thin panel: experiment and numerical analysis

In this study, the out-of-plane performance of ultra-high performance concrete (UHPC) thin panels reinforced with basalt fiber reinforced polymer (BFRP) bars was investigated. Eight panels were tested under four-point load, with the investigating parameters including panel thickness, reinforcement ratio, and the presence of steel fibers. The failure mode, crack pattern, load vs. mid-span displacement, and reinforcement strain relationships were studied. Test results revealed that panels with a higher thickness (70 mm) exhibited 178.6% higher initial stiffness, 34.5% higher cracking loads, and 88.7% higher peak loads compared to those with a lower thickness (50 mm). The effects of a larger reinforcement ratio and the presence of steel fibers became more pronounced after concrete cracking, leading to 21.2% and 22.1% higher post-cracking stiffness, respectively. Adding steel fibers helped control the development of diagonal cracks and shifted the panel failure mode from shear to flexural failure. Based on the comparison of test results with design codes, the expressions in CAN/CSA-S806-12 were recommended for predicting the load-carrying capacity of the specimens. Furthermore, a two-dimensional finite element (FE) model was developed to reproduce the test results, which validates the adopted CDP model for UHPC and the bond-slip behaviors between UHPC and BFRP bars.

Carbonation and chloride penetration performance of self-compacting concrete with masonry and concrete wastes

In this research, masonry and concrete construction and demolition wastes (CDWs) were used as supplementary cementitious material (25% vol. residue of masonry, RM) and recycled coarse aggregate (RCA) in increasing levels (0%, 50% and 100% vol. residue of concrete), respectively, in the development of self-compacting concrete (SCC). The performance of SCC mixtures was evaluated in terms of fresh properties, compressive strength, resistance to both accelerated (1% CO2, 65% R.H. and 23 °C temperature) and natural carbonation as well as chloride penetration. Experimental results showed a monotonic workability reduction associated to the incorporation of increasing levels of RCA. In compressive strength, the SCC with RCA showed the greatest increase in this mechanical property after 28 days of accelerated exposure in the carbonation chamber, when compared to its water-cured counterpart. Yet, at 360 days of accelerated carbonation exposure, all SCCs showed compressive strength reductions compared to their water-cured counterparts. On the other hand, the chloride permeability resistance of the SCCs was low and very low at the ages evaluated. Thus, the findings of this study indicate that the use of CDW can generate SCCs with adequate fresh properties, compressive strength and carbonation and chloride penetration performance, which offers benefits for the environment.

A novel approach to assess internal pore structure and quantify tortuosity of clogged pervious concrete through image analysis techniques

ABSTRACT The major objective of this research was to develop an innovative approach to characterise the pore structure of pervious concrete (PC) mixtures and quantify tortuosity in pre- and post-clogged conditions through 2D and 3D image analysis. Four different types of PC mixtures were prepared and subjected to computed tomography (CT) scanning to retrieve morphological information covering over 1900 images, followed by tortuosity quantification of each of 200 interconnected pore paths using vascular modelling toolkit (VMTK). The porosity of PC obtained from laboratory-based tests was 10–25% lower than image analyses. Further, along the depth of PC, a significant decrease in the number of pores in the top 60–80 mm was observed due to clogging, which revealed that maintenance be adopted only in the top 80 mm. Control and clogged PC with smaller sized aggregates and lower w/c ratio were more tortuous compared to higher w/c ratio while opposite for larger sized aggregates, ascribed to the occurrence of shorter interconnected pore paths comprising larger pore diameter, remarking that permeability will depend on both tortuosity and path diameter. CT scanning was used in predicting tortuosity and pore interconnectivity of PC through VMTK approach extensively used in medical science and seldom used in engineering.