Search

Permeable concrete is a class of materials that has long been tested and implemented to control water pollution. Its application in low-impact development practices has proved its efficiency in mitigating some of the impacts of urbanization on the environment, including urban heat islands, attenuation of flashfloods, and reduction of transportation-related noise. Additionally, several research efforts have been directed at the dissemination of these materials for controlling pollution via their use as permeable reactive barriers, as well as their use in the treatment of waste water and water purification. This work is focused on the potential use of these materials as permeable reactive barriers to remediate ground water and treat acid mine drainage. In this respect, advances in material selection and their proportions in the mix design of conventional and innovative permeable concrete are presented. An overview of the available characterization techniques to evaluate the rheology of the paste, hydraulic, mechanical, durability, and pollutant removal performances of the hardened material are presented and their features are summarized. An overview of permeable reactive barrier technology is provided, recent research on the application of permeable concrete technology is analyzed, and gaps and recommendations for future research directions in this field are identified. The optimization of the mix design of permeable reactive concrete barriers is recommended to be directed in a way that balances the performance measures and the durability of the barrier over its service life. As these materials are proposed to control water pollution, there is a need to ensure that this practice has minimal environmental impacts on the affected environment. This can be achieved by considering the analysis of the alkaline plume attenuation in the downstream environment. [ABSTRACT FROM AUTHOR]

This paper proposes a methodology for the mixture proportioning of 3D printable mortar containing recycled sand (RS), having similar fresh and hardened properties to a reference 3D printable mortar made with natural sand (NS). The methodology is based firstly on a fast and accurate characterization of the water absorption coefficient of the RS and secondly on the volume substitution of the NS by RS. This allows hardly changing the composition of the cement paste, slightly modifying the admixture dosage with a constant Weff/C ratio. The proposed methodology is applied to two different recycled sands. Results at the fresh state show that the structuration rates of recycled mortars are slightly lower than those of the reference mortar due to the slight increase in superplastizer content, but the close obtained values suggest that the Weff/C ratios are very similar in the three mortars. This result is confirmed by the porosity measurement on hardened mortars, which shows that the porosities of the cement pastes of the three mortars are almost identical. The compressive strength of recycled mortars is slightly lower than that of the reference mortar, which can be attributed to the lower intrinsic properties of RS compared to NS. This methodology enables the use of recycled sand as a sustainable alternative to natural sand in 3D printing applications. [ABSTRACT FROM AUTHOR]

Despite the robust ability of microcapsules (MIC) to break and release agent for healing/sealing efficacy, the reduction of concrete strength has been a major issue when using MIC. In this study, the optimisation of concrete mix design was initiated with employing three main parameters: MIC size (56, 93 μm), MIC dosage (0, 3, 6% by weight of cement) and water-cement (w/c) ratio (0.40, 0.50, 0.60). The used microcapsules consisted of water repellent agent core acting as a sealing agent and polyurethane as the shell material. Results confirmed the MIC dosage as the most significant factor affecting the mechanical properties, while no significant effect on the MIC size. Further, the MIC effect can be reduced by changing the concrete mix design from low to high w/c. The sealing efficiency of concrete was remarkably improved with the inclusion of MIC and a good bond between the capsules and concrete matrix was attained.

This report demonstrates how considerations across concrete material design and infrastructure design can be used together to change environmental impacts and costs by targeting appropriate constituents, materials, and system longevity. In this early-stage exploration, methods to compare concrete mixtures proportioning as they relate to environmental impacts, comparison indices based on common performance characteristics were used. This work was then built out to explore the role of steel reinforcement on reinforced concrete member environmental impacts to elucidate mechanisms to drive emissions reduction for these multi-material members. Finally, work was extended to understand how the longevity of concrete systems could influence environmental impacts associated with concrete production. Each stage of design considered was shown to have substantial effects on mitigating environmental impacts. In all cases, the primary environmental impact addressed was greenhouse gas emissions; however, this work can be extended to address other environmental impacts in future work. These methods from this work are demonstrated in this report through evaluation of mixtures in literature as well as a case study on an existing pavement overlay and potential alternative designs.View the NCST Project Webpage

This paper presents a method for designing low carbon bio-based building materials, also named bio-concretes, produced with wood wastes in shavings form (WS) and cementitious pastes. As the aggregates phase of bio-concretes is composed of plant-based particles, known as porous and high water-absorbing materials, the bio-concretes cannot be designed by using the traditional design rules used for conventional mortar or concrete. Then, the method used in the current paper is an adaptation of a previous one that has been developed in a recent paper where bio-concretes were produced with a cement matrix, three types of bio-aggregates, and a proposal of a design abacus. However, when that abacus is used for designing WBC with low cement content in the matrix, the target compressive strength is not reached. In the present paper, the method is extended to low cement content matrix (up to 70% of cement substitution) and also considering the greenhouse gas (GHG) emission of the WBC. To obtain data for proposing a new design abacus, an experimental program was carried out by producing nine workable WBCs, varying wood volumetric fractions (40–45–50%), and water-to-binder ratios. The bio-concretes produced presented adequate consistency, lightness (density between 715 and 1207 kg/m3), and compressive strength ranging from 0.64 to 12.27 MPa. In addition, the GHG emissions of the WBC were analysed through the Life Cycle Assessment methodology. From the relationships obtained between density, compressive strength, water-to-binder ratio, cement consumption, and GHG emissions of the WBC, calibration constants were proposed for developing the updated and more complete abacus regarding an integrated mix design methodology.

Ultra High-Performance Concrete (UHPC) has shown extraordinary performance in terms of strength and durability. However, having a cost-effective and sustainable UHPC mix design is a challenge in the construction sector. This study aims on building a predictable model that can help in determining the compressive strength of UHPC. The research focuses on applying multiple machine learning (ML) models and evaluating their performance in predicting the strength prediction of UHPC. Two reliable metrics are used to evaluate the performance of the model which are the coefficient of determination (R2) and mean squared error (MSE). The parameters that are affecting the compressive strength of UHPC are fly ash percentage levels (FA%), superplasticizer content, water to binder ratio (w/b), and curing period. A total of 54 ML models were used, consisting of Linear Regression, Support Vector Machines (SVM), Neural Networks, and Random forests algorithms. Among these models, Random Forest proved to be the most effective in capturing the relationships in UHPC’s behaviour with an R squared score of 0.8857. The Random Forest ML model is also used in this paper to conduct a parametric study that will help in obtaining the compressive strength of UHPC with higher content of FA%, which is not sufficiently studied in the literature.

Large-particle-size graded crushed stone mixtures (LPS-GCSMs) can improve the shortcomings of conventional graded crushed stone, such as low strength, high deformation, and a low modulus of resilience. At present, there is no systematic research on the gradation design and field evaluation of the LPS-GCSMs. In this study, compaction and California bearing ratio (CBR) tests and field construction conditions were combined to design six kinds of gradation of LPS-GCSM, and the optimum gradation was revealed. In order to improve the mechanical properties of LPS-GCSM, 2.5% cement was added to the mixture to prepare a low-content cement-modified LPS-GCSM (LCC-LPS-GCSM) based on the suggested gradation. The mechanical properties of the LCC-LPS-GCSM were investigated through unconfined compression strength (UCS) and compression rebound modulus (CRM) tests. Moreover, the compaction and deflection properties of LPS-GCSM and LCC-LPS-GCSM were examined through the test battery. The results showed that the optimum gradation of LPS-GCSM can be achieved with a combination of aggregate sizes of 20–40 mm, 10–20 mm, 5–10 mm, and 0–5 mm at a ratio of 44:20:10:26. The passing rates of 19 mm and 4.75 mm should be approximately at the median value of the gradation in view of field construction uniformity and a coarse aggregate interlocking effect. The UCS and CRM values of LCC-LPS-GCSM increased rapidly from 0 day to 28 days while they slowed after 28 days, which was similar to those of cement-stabilized materials. The field detection suggested that LPS-GCSM exhibited favorable compaction and that the addition of cement improved the stability of the field compaction of the mixture. Adding a subbase course of LPS-GCSM between the old pavement and the LCC-LPS-GCSM base can lead to more uniform stress on the base. The results of this study provide a reference for the gradation design of LPS-GCSM and optimization of the design indicators.

The recycling of locally collected concrete waste is being promoted toward reducing the carbon footprint. In the preparation of concrete, recycled concrete aggregates (RCA) are encouraged instead of natural aggregates (NA), as they can help reduce the consumption of virgin materials, the extraction and transportation of which can be costly and environmentally damaging. In this context, we conducted an experimental study on various concrete mixes to evaluate the effect of using RCA instead of NA on the physical and mechanical properties of fresh and hardened concrete. The main novelty of our study lies in meeting one of the principles of circular economy, i.e., reducing the carbon footprint, by recycling concrete waste collected locally. We prepared and investigated test specimens containing 0%, 20%, 40%, and 60% of fine and coarse recycled concrete aggregates. Results for fresh concrete were determined for temperature, consistency, air content, and density, while on the other side, in hardened concrete, results were determined for compressive strength, tensile splitting strength, and density. All results were determined experimentally and then compared. Our results showed that, with the use of RCA in the concrete mix, construction companies can significantly reduce their carbon footprints and help conserve natural resources. RCA can help create a more sustainable and affordable construction industry and is better suited to meet future challenges. Our study can serve as a basis for advancing the application of RCA in the preparation of concrete for sustainable construction. Doi: 10.28991/HEF-2023-04-02-03 Full Text: PDF

The main problem of our cities is the lack of treatment and final disposal of construction and demolition waste (CDW), which, accompanied by a lack of knowledge, becomes a major problem. Likewise, a city in the north of Peru (Cutervo) is not immune to the problematic reality experienced in the country and worldwide, since the lack of CDW management projects has generated the formation of informal dumps. The main objective of this research is to determine the technical and economic feasibility of using CDW for the production of pedestrian pavers, given that it includes measurements of the physical and mechanical characteristics to be analyzed. It is concluded that the use of CDW in the production of paving stones is feasible, from the economic and technical aspects, incurring a reduction in cost.

High volume fly ash concrete (HVFAC) has been widely used, and the mix proportion of HVFAC is usually designed based on the required compressive strength. Therefore, the research of HVFAC under the condition of equal strength has more engineering application value. However, in the current mix proportion design standard, there is no special discussion on the mix proportion design method of HVFAC. In this study, the compressive strength of HVFAC affected by four factors (water-binder ratio, FA content, curing method and curing age) was systematically studied. Based on 594 sets of strength data obtained from experiments, the method to determine the key mix proportion parameters (water-binder ratio and FA content) of equal strength HVFAC was proposed through machine learning algorithms (ML). Two ML methods (i.e., a multiple linear regression (MLR) and an artificial neural networks (ANN)) were developed to predict the HVFAC compressive strength and then their performances were compared. Through comparison, it was found that the mean absolute error and root mean squared error of the ANN model were both lower than the MLR model, and the ANN model has lower error and higher accuracy. In addition, the reliability of the proposed ANN model was verified with data in other literatures, the results showed the errors between the predicted values and the measured values are lower than 25%. The weight contribution rate of each factor to the strength was calculated. Among the four factors, the curing age had the greatest impact on the compressive strength, which contributes up to 60.3%. The influence degree of FA content is greater than that of water-binder ratio. With the development of curing age, the influence degree of FA content and water-binder ratio on the strength gradually decreases while the curing method increases. Finally, according to the ANN prediction results, the key mix parameters design method for equal strength HVFAC under multi-factor conditions was proposed, which provide guidance for concrete preparation in actual engineering.

This study addresses a critical gap in concrete strength prediction by conducting a comparative analysis of three deep learning algorithms: convolutional neural networks (CNNs), gated recurrent units (GRUs), and long short-term memory (LSTM) networks. Unlike previous studies that employed various machine learning algorithms on diverse concrete types, our study focuses on mixed-design concrete and fine-tuned deep learning algorithms. The objective is to identify the optimal deep learning (DL) algorithm for predicting concrete uniaxial compressive strength, a crucial parameter in construction and structural engineering. The dataset comprises experimental records for mixed-design concrete, and models were developed and optimized for predictive accuracy. The results show that the CNN model consistently outperformed GRU and LSTM. Hyperparameter tuning and regularization techniques further improved model performance. This research offers practical solutions for material property prediction in the construction industry, potentially reducing resource burdens and enhancing efficiency and construction quality.

Concrete mixture design has been a key focus in concrete research. This study presents a new method for concrete mixture design by combining artificial neural networks (ANN), genetic algorithms (GA), and Scipy libraries for hybrid intelligent modeling. This method enables the prediction of concrete mechanical properties and the optimization of mix proportions with single or multi-objective goals. The GA is used to optimize the structure and weight parameters of ANN to improve prediction accuracy and generalization ability (R2 > 0.95, RMSE and MAE < 10). Then, the Scipy library combined with GA-ANN is used for the multi-objective optimization of concrete mix proportions to balance the compressive strength and costs of concrete. Moreover, an AI-based concrete mix proportion design system is developed, utilizing a user-friendly GUI to meet specific strength requirements and adapt to practical needs. This system enhances optimization design capabilities and sets the stage for future advancements. Overall, this study focuses on optimizing concrete mixture design using hybrid intelligent modeling and multi-objective optimization, which contributes to providing a novel and practical solution for improving the efficiency and accuracy of concrete mixture design in the construction industry. [ABSTRACT FROM AUTHOR]

Because of urbanization, demand for housing is increasing day by day in India. Traditional clay brick leads to resource scarcity and environmental pollution. To overwhelmed this problem, manufacturing of bricks was done using the waste of thermal power plants like Fly Ash along with Sand and Cement (FAS-C Brick) as key ingredients. Fly ash is an Industrial by-product of thermal power plant. An experimental study of mix-design was carried out to increase the quality of the FAS-C brick. This paper attempt to formulate the mix design of fly ash based brick by process planning. Laboratory tests were conducted to determine the compressive strength and water absorption of the bricks. The main objective of the research study was to design the Fly Ash, Sand, Cement (FAS-C) brick and find the compressive strength using different mix design methods as a part of quality improvement process. [ABSTRACT FROM AUTHOR]

The main problem of our cities is the lack of treatment and final disposal of construction and demolition waste (CDW), which, accompanied by a lack of knowledge, becomes a major problem. Likewise, a city in the north of Peru (Cutervo) is not immune to the problematic reality experienced in the country and worldwide, since the lack of CDW management projects has generated the formation of informal dumps. The main objective of this research is to determine the technical and economic feasibility of using CDW for the production of pedestrian pavers, given that it includes measurements of the physical and mechanical characteristics to be analyzed. It is concluded that the use of CDW in the production of paving stones is feasible, from the economic and technical aspects, incurring a reduction in cost. [ABSTRACT FROM AUTHOR]

Due to the demand for decarbonization of the construction sector, research on alkali-activated binders and material-minimized carbon-reinforced structures has gained momentum in recent years. Most of the research into alkali-activated binders is focused on developing market-ready alternatives, mainly using a trial-and-error approach. In this study, an attempt is made to identify and quantify the factors influencing compressive strength development. Due to their worldwide availability, investigations are being carried out into binders based on calcined clays and natural pozzolans. The goal is to develop a method to produce tailor-made AAB for continuous manufacturing methods to combine carbon reinforcement and alkali-activated materials. For this purpose, an experimental matrix with 20 variation parameters was set up, in which the activator solution and the precursor composition varied. The design of the experiments was used to minimize the number of experiments. It was shown that no single factor is responsible for the development of compressive strength but instead involves several interacting factors. It was possible to find empirical formulas for predicting the compressive strength after 2, 7, and 28 days. [ABSTRACT FROM AUTHOR]

This study comprehensively investigates the rheological properties of self-compacting concrete (SCC) and their impact on critical parameters, including the migration coefficient, penetration depth of chlorine ions, specific electrical resistance, and compressive strength. A total of 43 mix designs were meticulously examined to explore the relationships between these properties. Quantitative analysis employed a backpropagation neural network model with a single hidden layer to accurately predict the resistant and durable characteristics of self-compacting concrete. The optimal number of neurons in the hidden layer was determined using a fitting component selection method, implemented in MATLAB software(2021b). Additionally, qualitative analysis was conducted using sensitivity analysis and expert opinions to determine the priority of research additives. The main contributions of this paper lie in the exploration of SCC properties, the utilization of a neural network model for accurate prediction, and the prioritization of research additives through sensitivity analysis. The neural network model demonstrated exceptional performance in predicting test results, achieving a high accuracy rate using 14 neurons for predicting parameters such as chlorine penetration depth, compressive strength, migration coefficient, and specific electrical resistance. Sensitivity analysis revealed that xanthan gum emerged as the most influential additive, accounting for 43% of the observed effects, followed by nanomaterials at 35% and micro-silica at 21%. [ABSTRACT FROM AUTHOR]

The use of quarry by-products can enable the commercialization of a clay building material (reconstituted earth) thanks to minimal valorized and perennial stocks of materials. This study shows that quarry by-products can be used to mix design a clay-based building material for the manufacture of CEB. These soils are composed of quarry tailing and clayey muds. Proctor and dry compressive strength tests have shown that the proportion of mud that achieves the highest possible compressive strength is a balance between increasing density through the aggregate arrangement, increasing clay activity, and decreasing density through the increase in water content. These tests resulted in the formulation of materials with compressive strengths of 5.8 MPa and 8.4 MPa at densities of 2135 kg/m3 and 2178 kg/m3. The influence of mud incorporation on the material granulometry and on its characteristics was also studied. Moreover, a model allowing us to link the compressive strength, the clay activity, and the dry density is proposed for the materials composed of quarry by-products. This model enables us to facilitate the mix design and the standardization of the earth material. [ABSTRACT FROM AUTHOR]

In this study, the fluidity, setting time, and compressive strength for 40%/60% ground granulated blast furnace slag (GGBFS)/metakaolin (MK) based geopolymer synthesis were experimentally investigated. By conducting 120 groups of tests, the effects of three design parameters of the alkaline activator, including the alkaline activator concentration, modulus, and liquid–solid ratio, were systematically analyzed. The test results show that the compressive strength of the GGBFS–MK geopolymer synthesis reaches a maximum value for a modulus of 1.2 or 1.4. Furthermore, according to the experimental results obtained, a series of contour plots for the relationship between the influencing parameters and the workability and mechanical properties for GGBFS–MK geopolymer synthesis are summarized. Then, a mix design method is proposed. Appropriate combinations of the concentration and modulus that can be used to generate a target compressive strength and fluidity are identified from the contour plots for different liquid–solid ratios. This method can be used to determine the mix proportion design for GGBFS–MK geopolymer synthesis that shows a specified compressive strength and working performance. [ABSTRACT FROM AUTHOR]

Geopolymer Concrete (GPC) has emerged as an alternative to cement concrete due to its reduced carbon footprint and excellent mechanical properties. However, not much emphasis is made on the development of mix designs using industrial waste. The current study focuses on the mix-design considerations for GPC using fly ash and Ground Granulated Blast Furnace Slag (GGBS). The mix design of GPC involves in selecting materials to produce the desired strength. In this investigation, Water Glass (WG) is used as an activator for the activation of the polymerization reaction. The mix design of GPC is the optimization of a group of various parameters, such as the activator to binder ratio, aggregate to binder ratio, coarse aggregate to fine aggregate ratio, activator concentration, and amount of binder content. The activator to binder ratio affects workability and strength, while the activator concentration influences the polymerization reaction and final strength development. The selection of suitable aggregates plays a vital role in achieving a dense and durable GPC matrix. The mix design for GPC requires a holistic approach that considers the selection of appropriate binders, activators, and aggregates. Proper optimization of these factors can result in excellent strength and durability of the GPC and a reduced carbon footprint. Further research is needed to explore alternative binders, evaluate long-term performance, and establish standardized mix design guidelines for the widespread adoption of GPC in construction. [ABSTRACT FROM AUTHOR]

In order to solve the global problem of bridge head jumping caused by the insufficient compaction of the roadbed in the transition section of highways and bridges, a desulfurization gypsum–fly ash flowable lightweight soil without vibration, capable of self-compaction, low bulk density, and economic and environmental protection, has been developed. This study selected low-grade cement, industrial waste (fly ash and desulfurization gypsum), and Yellow River silt as the raw materials for the design of the mix ratio of a desulfurization gypsum–fly ash flow-state lightweight soil mix. Through multiple indoor experiments, the influence of cement content, silt content, and the fly ash/desulfurization gypsum quality ratio on its fluidity and mechanical properties was systematically studied. The stress–strain relationship under uniaxial compression was analyzed and the strength formation mechanism was revealed through scanning electron microscopy (SEM). The results show that the mechanical properties of the prepared desulfurization gypsum–fly ash flowable lightweight soil meet the engineering requirements. Increasing both the cement and fly ash content results in the decreased fluidity of the desulfurization gypsum and fluidized fly ash. However, as the mass ratio of fly ash to desulfurization gypsum increases, the fluidity reaches its maximum when the mass ratio of fly ash to desulfurization gypsum is 2:1. Based on the stress–strain relationship test results, a uniaxial compressive constitutive model of the desulfurization gypsum–fly ash flowable lightweight soil was proposed. The model was fitted and analyzed with the test results, and the correlation was greater than 0.96. The high degree of agreement showed that desulfurization gypsum can promote the disintegration of fly ash, thereby increasing the specific surface area. This provides more contact points, promotes the hardening process, and enhances the interlocking force between particles and the formation of cementitious substances, further enhancing strength. [ABSTRACT FROM AUTHOR]

This research paper systematically investigates the combined influence of fly ash, cementitious capillary crystalline waterproofing (CCCW) materials, and polypropylene fibers on the mechanical properties and impermeability of concrete through comprehensive orthogonal tests. Microscopic morphological changes in the concrete induced by different composite materials are examined via scanning electron microscopy (SEM) and X-ray diffraction (XRD) testing. The objective is to facilitate a beneficial synergetic interaction among these materials to develop highly permeable, crack-resistant concrete. Key findings of this study are: (1) The study unveils the impact of the concentration of three additive materials on the concrete's compressive strength, tensile strength, and penetration height, thereby outlining their significant influence on the mechanical properties and impermeability of the concrete; (2) An integrated scoring method determined the optimal composite dosage of three materials: 15% fly ash, 2% CCCW, and polypropylene fibers at 1.5 kg/m3. This combination increased the concrete's compressive strength by 12.5%, tensile strength by 48.4%, and decreased the average permeability height by 63.6%; (3) The collective introduction of these three materials notably augments the hydration reaction of the cement, resulting in denser concrete microstructure, enhanced bonding between fibers and matrix, and improved concrete strength and durability. [ABSTRACT FROM AUTHOR]

Three-dimensional concrete printing (3DCP) is a sustainable and green approach for rapid construction with the ability to create complex shapes to preserve the intended aesthetic appearance for an affordable cost. Even after a decade of attempts, there are many limitations and challenges to applying this technology for constructions without borders. The lack of guidelines for mix designs, quality control procedures during extrusion, printing and building phases, compatibility of material with extruder, standard testing, and guidelines to verify suitability of mixture with respect to the application and exposure conditions and limited machine capacity are several areas to be addressed for applications without borders. The development of 3DCP applications as a sustainable and green technology is another challenging task due to high Portland cement consumption in 3DCP. However, reducing the high usage of ordinary Portland cement (OPC) with pozzolanic waste materials replacement and environmentally friendly cement indicates the direction of moving 3DCP into a sustainable pathway. The authors reviewed more than 200 refereed articles published on materials and techniques in 3DCP. Inconsistency in disseminating knowledge in research articles has hindered the creation of a monolithically connected chain of research efforts and findings in accelerating the development and adoption of this technology. This paper summarizes the common approach to developing 3DCP mix designs and identifies the key areas for the future development of materials and techniques and challenges to be addressed for the global adoption of 3DCP. The current progress and challenges in the context of Australia’s construction industry and future trends for the acceptance of 3DCP are also reviewed.

Geopolymer Concrete (GPC) has emerged as an alternative to cement concrete due to its reduced carbon footprint and excellent mechanical properties. However, not much emphasis is made on the development of mix designs using industrial waste. The current study focuses on the mix-design considerations for GPC using fly ash and Ground Granulated Blast Furnace Slag (GGBS). The mix design of GPC involves in selecting materials to produce the desired strength. In this investigation, Water Glass (WG) is used as an activator for the activation of the polymerization reaction. The mix design of GPC is the optimization of a group of various parameters, such as the activator to binder ratio, aggregate to binder ratio, coarse aggregate to fine aggregate ratio, activator concentration, and amount of binder content. The activator to binder ratio affects workability and strength, while the activator concentration influences the polymerization reaction and final strength development. The selection of suitable aggregates plays a vital role in achieving a dense and durable GPC matrix. The mix design for GPC requires a holistic approach that considers the selection of appropriate binders, activators, and aggregates. Proper optimization of these factors can result in excellent strength and durability of the GPC and a reduced carbon footprint. Further research is needed to explore alternative binders, evaluate long-term performance, and establish standardized mix design guidelines for the widespread adoption of GPC in construction.

Abstract Concrete presents complex behavior, being a difficult material to define the ideal proportion of its constituents. To overcome this challenge, many mix design methods have been developed over time. However, most of these methods do not consider durability parameters during the procedure. Thus, the objective of this article is to present a mix design method for concrete, with properties of workability (slump rating from 50 mm to 220 mm), axial compressive strength (class of 25MPa to 55MPa), and durability as response parameters. From the application of the proposed method, it was possible to create mix design and performance diagrams. It was noticed that all concretes fell into the pre-established consistency class and presented axial compressive strength results close to the predetermined values. Moreover, it was possible to obtain indications of the material's durability.

Microsurfacing asphalt mixtures are a preventive maintenance technology comprising the application of a slurry (produced with a modified asphalt emulsion), aggregate, filler, and water on top of an existing pavement at ambient temperature. Although it is a widely used technology, further studies on the mix design procedures are necessary to ensure an adequate composition. Thus, this study contributes to developing an improved mix design procedure for microsurfacing asphalt mixtures. Different mixtures were prepared, and the influence of the type and amount of asphalt emulsion and the amount of added water and filler (cement) on the characteristics of the mixture were evaluated. Two preliminary tests, referred to as the "pizza test" and the "ball test", were proposed to determine the initial proportions of added water and cement in the mixture, respectively. Then, consistency, cohesion, and shaking abrasion tests were performed to determine the optimum content of each component and evaluate their influence on the mixture characteristics. The results showed that these tests are essential to optimize the mix composition, even though it was found that the mix design of microsurfacings is a complex task because the mixture is a system with chemical interactions strongly influenced by its composition. [ABSTRACT FROM AUTHOR]

Three-dimensional (3D) concrete printing (3DCP) is one of the digital construction techniques that demands the fulfilment of particular material properties. One of the most important requirements for 3DCP is the material's rheology. This article provides a comprehensive analysis of the rheology of Portland cement-based materials used in extrusion-based 3DCP. The first sections of the article focused on the influence of mix design on the rheology required for 3DCP in both fibre reinforced and non-fibre reinforced mixtures, followed by the role of various chemical admixtures in tailoring the time dependent rheology. The research points out the lack of rheology benchmarking, implying a strong need for novel or standard printable mix designs that use sustainable materials to improve the structural build-up of mixtures. The review also shows a strong need for active rheology control of cementitious materials for large scale printing application. [ABSTRACT FROM AUTHOR]

The field of 3D printing is in rapid evolution. The 3D printing technology applied to civil engineering is a promising advancement. From equipment and mixture design to testing methods, new developments are popping up to respond to specific demands either for the fresh or hardened state. Standardizing methods are still at an early age. For this reason, there is a multitude of 3D printers with different capabilities to print cementitious materials. In addition, norms are not applicable in 3D printing material science. Advances are being made to create new methods of testing. The key parameters of this new 3D printing process based on stratification, multiple uses of binders, and measurement at fresh and hardened states are being perfected to achieve an industrial application. This article gives an overview of how 3D-printed structures are made along with critical parameters that influence their performances. Our review suggests that the quality of the 3D prints is determined by the printing method, key printing parameters, and the mix design. We list different tests to help characterize these 3D-printed cementitious materials at the fresh state and to assess their performances at the hardened state. We aim throughout this work to give a state-of-the-art of recent advances in 3D printing technology. This could help for a better understanding of cementitious materials 3D printing for current and future related research work. [ABSTRACT FROM AUTHOR]

Objective: The aim of this study was to examine supervisees' perspectives about the contribution of two predefined aspects of supervision, supervisory bond (SB) and didactic input of supervisor (DI), to their ascribed outcome of therapy. Method: Supervisees anonymously assessed the SB, supervisors' DI and their contribution to therapy outcome. Assessment was quantitative and qualitative. The supervisory aspects were assessed using a questionnaire constructed for this study. Perceived contribution was evaluated by two scaled questions, and themes generated by an open question. Supervisees (n = 111) evaluated 16 supervisors and supervision's contribution to psychotherapy outcomes of 111 clients. Findings: Hierarchical regression showed that supervisees' age, supervisors' status and frequency of supervision accounted for 24% of the variance ascribed to outcome. SB and DI accounted for 51% of the variance. These values, which are higher than reported in the literature, may be attributed to the assessment of predefined aspects of supervision by the same assessor. Thematic analysis of the didactic input produced more themes than for the supervisory bond. Conclusion: Sociodemographic variables and supervisory relationship variables determine supervisees' evaluations of supervision's contribution to outcome. Implications for practice: Training and supervision may benefit from information obtained from quantitative and qualitative measures regarding these and other predefined variables related to supervision. The in‐depth look at views and experiences shared by supervisees may advance training, practice and research. [ABSTRACT FROM AUTHOR]

Aiming at the shield muck in the mudstone stratum of Chengdu area, using cement as the solidification agent, fly ash as the active reinforcement material, and fine sand as the grading material, the mudstone muck unburned brick was prepared by pressing and molding, and was cured for 14 days in a concrete standard curing room. Using the compressive strength as an indicator, the effect of different mixing ratios on the compressive strength of the unburned brick was studied. The results show that the ratio of cement to fine sand has a positive linear relationship with the compressive strength of unburned bricks; Fly ash cannot be replaced with cement in an equal amount to improve compressive strength; When the mix design is 58% slag soil, 22% cement, 15% fine sand, and 5% fly ash, the compressive strength and softening coefficient of unburned bricks meet the MU15 grade requirements of JC/T422--2007 "Non fired Rubbish Gangue Bricks", and the appearance quality basically meets the specification re¬quirements. [ABSTRACT FROM AUTHOR]

Scientists and researchers worldwide are developing sustainable and greener alternatives to cement concrete for years now. One such alternative material is low calcium fly ash-based geopolymer concrete (FA-GPC), which constitutes fly ash (as binder material), sodium silicate (Na2Sio3), sodium hydroxide (NaOH), alkaline activator solution, aggregates, and superplasticizers. Considerable efforts across the world (especially in India due to its abundance), in recent years, have been made in developing low calcium fly ash-based geopolymer concrete mix design guidelines for achieving desired results, but still, there is a lack of appropriate mix design guidelines. In the present study, efforts have been made to develop low calcium fly ash-based geopolymer concrete (FA-GPC) mix design guidelines using experimental findings. The mix design guidelines will help in the production of low calcium FA-GPC that can achieve early strength and be utilized in precast concrete engineering applications such as kerb stone, paver block, etc. The alkaline activator solution (a mixture of Na2Sio3 and NaOH) is utilized to activate fly ash which serves as a binder material. The key variables taken into account in this investigation were activator (alkaline) solution to binder ratio (0.5, 0.55, 0.6), Na2Sio3/NaOH ratio (2, 2.5, 3), change in sodium hydroxide molarity (13 M, 14 M, 15 M), curing temperature (60 °C, 70 °C, 80 °C), the dosage of superplasticizer (2.5%, 3%, 3.5%), change in the cooling period of alkaline activator solution (1 h, 6 h, 12 h, 24 h) and change in total aggregate content (66%, 67% and, 68%) for various combinations. The findings showed that the most significant influences on the workability and compressive strength of low calcium FA-GPC were the alkaline activator solution to binder ratio, the change in sodium hydroxide molarity, the curing temperature, and the change in the cooling period of alkaline activator solution. Based on the experimental investigation findings, the ratio of Na2Sio3 and NaOH was selected as 2.5, the molarity of the NaOH solution was kept 14 M, to gain quick strength the oven curing (80 °C) regime is employed, and the total aggregate content was taken as 67%. The proposed mix design guidelines have been substantiated by examples of different grades of concrete. [ABSTRACT FROM AUTHOR]

To reduce the harm caused by industrial solid waste to the environment, and solve the problem of excavated soil disposal in buried pipeline management projects, this study proposes a method to produce soil-based controlled low strength materials (CLSM) by using industrial solid wastes (including fly ash and red mud) as partial replacements for cement. The properties of CLSM were characterized in terms of flowability, unconfined compressive strength, phase composition and microstructure. The test results showed that fly ash could significantly improve the flowability of CLSM, while red mud had more advantages for the strength development. When 20% fly ash and 30% red mud were combined to replace cement, the fluidity of CLSM was 248 mm, and the unconfined compressive strength (UCS) at 3, 7 and 28 days was 1.08, 1.49 and 3.77 MPa, respectively. The hydration products of CLSM were mainly calcium silicate hydrate gels, ettringite and calcite. Fly ash provided nucleation sites for cement hydration, while the alkali excitation of red mud promoted the dissolution of SiO2 and Al2O3 in fly ash. The filling and gelation of hydration products make the microstructure dense, which improves the mechanical properties of the mixture. [ABSTRACT FROM AUTHOR]

Historically, rubberized and non-rubberized open-graded friction courses (OGFCs) have been placed to provide three benefits: to increase traffic safety, to reduce urban highway noise, and to preserve the surface of the main pavement structural section. However, stringent environmental regulations on stormwater runoff management enacted recently have forced transportation agencies with limited right of ways in urban areas to search for creative methods to treat runoff and receive credits for preventing pollution from highways. This literature review was undertaken to explore ways to optimize current RHMA-O mix designs to provide multifunctional benefits, including water quality treatment. The literature review showed that permeability measurement is an essential parameter that influences a wide range of OG (both rubberized and non-rubberized) pavements’ performance. Further, current Caltrans aggregate gradations contain a larger fraction of fine aggregate sizes and this may also influence the permeability and functional performance of RHMA-O pavements. Part of this literature review includes an action plan recommending that the next phase of this work include optimizing current Caltrans mix designs and the mix design procedure in the laboratory and undertaking subsequent field investigations.

More than 90 percent of the road and highway network in the United States is paved with asphalt concrete. Maintenance and periodic rehabilitation require a continuous supply of aggregates and asphalt binder, both of which are becoming increasingly scarce and expensive. Recycling and reusing these resources can reduce costs and improve sustainability. The most common recyclable material used in road construction is reclaimed asphalt pavement (RAP), which is milled asphalt surface layers that have been removed from existing pavements before new asphalt overlay is placed. Reclaimed asphalt roofing shingles (RAS) are another potential source of asphalt binder.There is growing interest in allowing significantly higher percentages of RAP and RAS in asphalt mixes used on state and local roadways. However, making this change has raised concerns regarding how these composite binders may influence the performance and durability of asphalt mixes, depending on the blends of different virgin and reused binders. Researchers at the UC Pavement Research Center investigated the use of higher percentages of RAP and RAS as a partial replacement for the virgin binder in new asphalt mixes and their effect on pavement performance in California. This research brief summarizes findings from that study.View the NCST Project Webpage

The marble industry produces large amount of waste at almost every stage of marble processing. This waste is always uncontrollably discharged into open areas. Therefore, the consumption of Waste Marble Powder (WMP) in concrete is very important and will provide both an economic gain for concrete industries and an opportunity to achieve eco‐efficient concrete production. Self‐Compacting Concrete (SCC) is mostly preferred concrete type which uses the WMP as powdered material. Thus, to increase WMP usage in the production of eco‐efficient SCC, it is aimed in this study to develop a model that can predict WMP demand. To develop this model, Artificial Neural Network (ANN), an artificial intelligence method, was preferred. An ANN model was developed using a comprehensive dataset that included eco‐efficient SCC mixture compositions, workability measurements, and compressive strengths. The ANN model with seven inputs and one output as WMP was successfully trained and managed to produce the correct outputs to both validation and test datasets. Mix design of SCC with aimed properties can be a long process compared to conventional concrete. The proposed ANN model could reduce time loss in the production process. ANN's success is expected to facilitate the production of eco‐efficient SCC with WMP. [ABSTRACT FROM AUTHOR]

Copyright of Journal of Fuzhou University is the property of Journal of Fuzhou University, Editorial Department and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

3D concrete printing is an avant-garde building process with the potential to revolutionise the construction industry by automating construction procedures, reducing material consumption, lowering form-work costs, and optimising structural elements. The current study proposes a methodology for developing plain and fibered 3D printable concrete mixes using locally available binders (cement, silica fume, fly ash, and limestone powder), fine aggregate, water, admixtures, polypropylene fibers, and steel fibers. The study presents the results of 24 trials conducted to develop mixes for concrete 3D printing. According to the present studies, the recommended flow for the mix to be extrudable, printable, and buildable is between 19–21 cm and the open time is 45–60 min. The printed specimens under bending failed monolithically with a single dominant crack. The plain and fibered 3D printed specimens possessed greater flexural strength than the in-situ cast specimens. The increase in flexure capacity is found to be in the range of 07–22%. [ABSTRACT FROM AUTHOR]