Sustainable Concrete Research Articles

Comparative environmental assessment of low and high CaO fly ash in mass concrete mixtures for enhanced sustainability: Impact of fly ash type and transportation

The effect of fly ash type on the sustainability of concrete mixtures has yet to be quantified. This study aims to assess the environmental impacts of low calcium oxide (CaO) and high CaO fly ash in mass concrete mixtures from Thailand. The study analyzed 27 concrete mixtures with varying percentages of fly ash as a cement replacement (0%, 25%, and 50%) for 30 MPa, 35 MPa, and 40 MPa compressive strengths at specified design ages of 28 and 56 days. Sources of fly ash have been located between 190 km and 600 km away from batching plants. The environmental impacts were assessed using SimaPro 9.3 software. The global warming potential of concrete is reduced by 22–30.6% and 44–51.4% when fly ash, regardless of type, is used at 25% and 50%, respectively, in comparison with pure cement concrete. High CaO fly ash has more environmental benefits than low CaO fly ash when utilized as a cement substitute. The reduction in environmental burden was most significant for the midpoint categories of mineral resource scarcity (10.2%), global warming potential (8.8%), and water consumption (8.2%) for the 40 MPa, 56-day design with 50% fly ash replacement. The longer design age (56 days) for fly ash concrete showed better environmental performance. However, long-distance transport significantly affects ionizing radiation and ecotoxicity indicators for terrestrial, marine, and freshwater environments. Furthermore, the results show that a high cement replacement level (50%) may not always have a reduced environmental impact on mass concrete when considering long-distance transportation. The critical distance calculated based on ecotoxicity indicators was shorter than those calculated using global warming potential. The results of this study can provide insights for developing policies to increase concrete sustainability using different types of fly ash.

Mechanical properties and microstructural characterization of ferrock as CO2–negative material in self-compacting concrete

The construction industry is one of the major sources of pollution and global warming, with the utilization of cement being a significant contributor. This study aimed to minimize cement usage in construction while maintaining overall strength through the development of sustainable and eco-friendly concrete. A self-compacting concrete (SCC) was created by replacing cement with eco-friendly ferrock, aggregates and superplasticizers at levels of 5%, 10%, 15%, 20% and 25%. The optimal blend was determined based on fresh and mechanical behaviour parameters. Rheological analysis of the fresh concrete was conducted using L-box, Slump cone, V-funnel equipment and visual stability index. The SCC was then cured through water immersion, CO2 exposure and a combination of both. The performance of the ferrock SCC was evaluated under different curing conditions to determine its hardened and microstructural properties. The addition of ferrock altered the properties of the concrete, and changing the curing method also influenced the behaviour of the hardened concrete. CO2 curing achieved about 40% of the concrete strength within four hours, while combined water and CO2 curing produced higher-quality concrete, as shown by UPV, SEM, and XRD results. The incorporation of ferrock almost doubled the strength of the concrete in combined curing. At an optimum replacement level of 10%, the compressive strength values of water, CO2, and combined curing increased by 21.9%, 25.9% and 32.6%, respectively, after 28 days. The bond strength also increased by 20% at this level of ferrock addition for combined curing. Comparison with normal SCC indicated that the ferrock-based SCC was physically stronger at an optimum replacement level of 10%, with a higher degree of compaction and dense matrix. These findings suggest the superiority of ferrock SCC, which offers potential for use in future construction.

Influence of red mud on the engineering and microstructural properties of sustainable ultra-high performance concrete

This paper introduces a new application of industrial solid waste red mud to use as a cementitious material in the development of ultra-high performance concrete (UHPC) performances. In addition, utilization of red mud can reduce the environmental impact of red mud landfill. For gaining this aims, UHPC specimens were prepared with different contents of red mud and analyzed the effects of different RM contents on the fluidity, setting time, mechanical properties, durability, drying shrinkage and microstructure of the red mud-based UHPC. The results indicated that fluidity was reduced to 310 mm at 20% red mud level, but it still belongs to enormous fluidity, which is convenient for construction. In addition, it is worth noting that using red mud instead of cement can significantly shorten the setting time, providing a new method for applying the UHPC rapid-repairing process. Red mud-based UHPC mortar prepared with appropriate red mud instead of cement exhibits higher mechanical properties, better durability and reduced drying shrinkage of UHPC during curing. After curing for 28d, the highest compressive strength of UHPC samples containing 20% red mud was 129.5 MPa, the compressive strength of the UHPC samples' sulfate resistance was 136.6 MPa, and the drying shrinkage value was around 414 µm. Moreover, observed information from scanning electron microscopy (SEM) noted that red mud can fill the micro-cracks between particles of cementitious materials, make the structure more compact and form new hydrates. Finally, the two characteristics of low cost and energy consumption further promote the sustainable application of red mud-based UHPC. Therefore, replacing OPC with 20% RM is meaningful to produce a sustainable UHPC mixture and field applications.

Evaluating the use of mucilage from opuntia ficus-indica as a bio-additive in production of sustainable concrete

The global demand for a sustainable and environmentally responsible economy, has called for incorporation of aspects of sustainability into infrastructure materials. Being the most globally consumed primary construction material, concrete’s strength and durability enhancement using green approaches is pivotal to sustainability of the built environment. Production of chemical admixtures is high energy consuming and environmentally taxing, thus the need for bio-available sustainable substitutes and/or supplements. This paper presents findings of an experimental and environmental impact evaluation, conducted on Normal Strength Concrete (NSC) mixtures dosed with Opuntia ficus-indica mucilage (Ofim) by mass-replacement of the mixing water. ASTM compliant tests for consistency, strength, and durability performance were conducted at standard time intervals up to 56 days, while the Scanning Electron Microscopy (SEM) and Fourier Transform Infrared (FTIR) Spectroscopy were employed for concrete micro-characterization. The study explored the interaction between the natural bio-additive and synthetic commercial admixture. A comparative Environmental Life Cycle Assessment (E-LCA) was also conducted to assess resource use efficiency and quantify the environmental impacts of Ofim-modified concrete relative to conventional concrete. Test results showed that the use of Ofim led to slight increase in the compressive strength and elastic modulus, in addition to a pronounced impact on durability of concrete, resulting in reduced fluid ingress by up to 39%, a lowered decrease in K-values by 14%, and an increase in the freeze–thaw resistance with high retention of Relative Dynamic Modulus of Elasticity (RDME) in the Ofim-modified mix relative to the control mix. A 15% mixing-water mass-replacement resulted in an average reduction in greenhouse gas (GHG) emissions of 9.6%. Hence, even if the improvement in the mechanical performance is not substantial, a reduction in GHG emissions scales up as the concrete industry is huge and tremendously contributes to climate change through embodied carbon.

Experimental studies on durability performances of ultra-lightweight low-carbon LC3 cement composites against chloride ingression and carbonation

This study aims to experimentally evaluate the durability performances of a novel ultra-lightweight low-carbon calcined clay cement composite (ULCC-LC3) for use in sustainable concrete. The durability performances of ULCC-LC3 were characterized by conducting rapid chloride migration tests, accelerated carbonation tests, MIP and TGA tests. Results indicate that using LC3 is beneficial for improving chloride resistance of ULCC-LC3 due to refined pore structure while the carbonation resistance performance can be reduced due to less content of cement and pozzolanic reaction. The MIP tests showed the effect of using LC3 on microstructure of ULCC without carbonation was reducing the volume of porosity coarser than gel pores while increasing the volume of gel pores. The cementitious matrix of mixes with LC3 was significantly densified by carbonation. The carbon emission and energy consumption were significantly decreased by 41.9% and 26.7% respectively by replacing cement with calcined clay and limestone. However, it was noted that the use of superplasticizer increased the energy consumption especially for the mix with LC3.

Effect of various powder content on the properties of sustainable self-compacting concrete

This research goal is to evaluate the characteristics of glass powder (GP), quartz powder (QP), and limestone powder (LP) as Supplementary Cementitious Materials (SCMs) to replace cement content in terms of fresh and hardened properties of Self-Compacting Concrete (SCC) for sustainable building construction. Moreover, the obtained results were modeled using a soft computing approach. This investigation created ten mixtures incorporating varying percentages of GP, QP, and LP by replacing cement at about 0 %, 10 %, 20 %, and 30 %, respectively. The slump flow and J-ring tests were done to observe how SCMs affected the properties in fresh condition. In addition, the mechanical properties and pore structure configuration of the specimens were investigated. It was observed that GP and LP positively affected the fresh properties, increasing the mixes flowability by up to 8 %. Moreover, 20 % GP was able to enhance the compressive strength by 7 % by improving the pore structure of the cement matrix, which was confirmed by the mercury intrusion porosimetry analysis. Finally, the built machine learning models indicated good accord with test outcomes for Artificial Neural Network (R2 = 0.95) and could be applied to calculate the compressive strength of concrete containing GP, QP and LP for construction housing sector.

Concrete Sustainability: A Future Perspective

Abstract Concrete and cement are among the most widely used building materials worldwide. Concrete is a versatile material with strong potential as a sustainable material. The increased use of mineral additions to lower the clinker component is a feasible option. Adequate recycled material quality monitoring and mix designs enable a wide use of concrete recycled aggregates for the built environment. In addition, new performance-based durability tests that better simulate the real field exposure with the combined environmental actions will promote more resilient, durable, and sustainable reinforced concrete infrastructures.

A systematic review of the mechanical and durability properties of sustainable bacterial concrete

In response to escalating ecological concerns, there is an unprecedented surge in demand for sustainable construction materials. These materials should necessitate minimal energy usage and generate the least possible carbon emissions. As a result, the construction industry has witnessed the emergence of modified concretes, incorporating industrial waste as a substitute for traditional concrete. This manuscript delves into innovative methodologies, promoting autogenous self-healing within concrete structures. This process is achieved through the clever integration of specific bacterial strains. Furthermore, the study explores the effects of incorporating various kinds of industrial waste, including fly ash, slag, and crystalline additives, on the concrete's overall performance. However, it has been observed that the enhanced fracture closure ensuing from the stimulated autogenous self-healing mechanisms doesn't invariably correlate with superior mechanical qualities or increased durability of the cracked samples. Therefore, it is imperative to implement performance-based evaluations while assessing cement-based materials. The paper also investigates the potential role of biological approaches in crafting sustainable construction materials. It discusses the impact of bio-based agents and bacterial solutions on numerous concrete parameters, shedding light on the determinants influencing the selection of bacteria. This burgeoning field of green biotechnology holds considerable promise. It offers an environmentally benign alternative to conventional remediation methods in diverse arenas, thereby providing a viable solution to mitigate a range of environmental issues.

A New Approach for Producing Sustainable Concrete by Incorporating Treated Waste Rubber

A New Approach for Producing Sustainable Concrete by Incorporating Treated Waste Rubber

The Role of Hybrid Machine Learning for Predicting Strength Behavior of Sustainable Concrete

The Role of Hybrid Machine Learning for Predicting Strength Behavior of Sustainable Concrete

Effect of superplasticizer types and dosage on the flow characteristics of GGBFS based self-compacting geopolymer concrete

Self-compacting geopolymer concrete (SCGC) is produced from waste materials that act as binders or precursors promoting sustainable concrete. Among all components of the SCGC mix, the superplasticizer dosage primarily controls the workability of concrete along with mechanical strength. An attempt is made in this current study to find the best suitable type of superplasticizer and its dosage through given fresh property investigation. For the accomplishment of the project objective, four types of superplasticizers are considered in the SCGC mix preparation and are polycarboxylate ether-based, modified naphthalene-based, lignosulphonate-based, and mother liquor-type superplasticizers. The superplasticizer dosage considered in each is 4%, 6%, and 8%. In the absence of a suitable design standard SCGC mix designs are prepared and concrete is produced with characterized material components. Twelve M25 SCGC mix designs are prepared with some constant parameters like 12 M concentration of sodium hydroxide, the ratio of sodium silicate to sodium hydroxide as 2.5, and 24% extra water addition. The freshly prepared concrete has undergone various workability tests to examine the filling ability (FA) (slump flow, T50cm slump flow, V-funnel); passing ability (PA) (L-box, J-ring); and segregation resistance (SR) (V-funnel at T5minutes). The 6% naphtha (NP)-based superplasticizer is regarded as the superior superplasticizer from the fresh property consideration in the GGBFS-based SCGC.

Development of sustainable concrete using recycled polyethylene terephthalate (PET) granules as fine aggregate

Solid waste management has become a significant environmental challenge globally. This study aims to examine the performance of sustainable concrete incorporating polyethylene terephthalate (PET) granules as partial (0%, 10%, 30%, and 50%) volumetric replacement of sand. The mechanical properties including compressive strength, tensile strength and elastic modulus were examined. The flexural and cracking performance of the reinforced concrete (RC) beams, as well as bond behaviour of concrete mixes with steel reinforcement were investigated. Incorporating 10% PET granules demonstrated positive impact on the mechanical properties, flexural strength and cracking behaviour of RC beam, as well as bond strength. A theoretical model was proposed for predicting bond strength of concrete containing PET granules and the results corresponded well with both experimental and previous research findings. The American and Australian standards conservatively predicted cracking and flexural moments of the RC beams. Finite element modelling was conducted on the RC beams and the results corresponded well with the experimental findings.

A Study on Effect of Mustard Husk Ash on Properties of Porous Concrete

Abstract: Mustard Husk Ash (MHA), a by-product of the mustard oil extraction process, has gained attention as a potential supplementary cementitious material in the construction industry. The incorporation of MHA in porous concrete offers the dual benefits of waste management and sustainable construction practices. The environmental advantages of utilizing MHA, such as reducing landfill waste and conserving natural resources. The review paper synthesizes the findings from various research studies that have investigated the influence of RHA on the properties of porous concrete. The impact of different percentages of Rice Husk Ash (RHA) as a partial replacement for cement is analysed. The fresh and hardened properties of porous concrete, including workability, compressive strength, water absorption, and porosity, are examined in light of the incorporation of RHA. The review paper identifies key trends and observations from the existing literature. It discusses the influence of water content and size of coarse aggregates on the performance of RHA-based porous concrete. It also addresses the challenges and limitations associated with the use of RHA, such as its effect on the water demand and workability of concrete mixes. By synthesizing the collective findings, the review paper provides valuable insights into the effectiveness and feasibility of RHA as a sustainable alternative in porous concrete production. It identifies knowledge gaps and areas for further research, emphasizing the need for long-term durability studies and performance assessments on MHA based on porous concrete under different environmental conditions. In conclusion, this review paper contributes to the understanding of the effect of mustard husk ash on the properties of porous concrete. It underscores the potential of MHA as a viable option for enhancing the sustainability and performance of porous concrete. The comprehensive analysis serves as a valuable resource for researchers, engineers, and practitioners seeking to explore the application of MHA in porous concrete and promote environmentally friendly construction practices.

Partial Replacement of Cement with Different Wastes - A Review

Abstract: The production of sustainable concrete, the adoption of sustainable practices, and the exploration and utilization of supplementary cementitious materials (SCM) have gained popularity worldwide. The traditional concrete practices and their environmental impact, such as greenhouse gas emissions resulting from cement production, make researchers and industries look for alternative cementitious materials. This paper reviews the SCM Bamboo leaves ash, coconut shell ash, eggshell powder, fly ash, GGBS (ground granulated blast furnace slag), paper sludge ash, waste glass powder, rice husk ash, silica fume, steel slag, sugarcane bagasse ash, water hyacinth, and wheat straw ash, their performance to improve strength and durability properties, as well as their impact on the concrete mix. The main purpose of this review paper is to study and evaluate the possibilities of cement replacement material in the production of sustainable concrete. This review article gives information about SCM and how these materials can help reduce the environmental impact of conventional concrete and promote the development of sustainable concrete and environmentally friendly construction practices.

Strength evaluation sustainable concrete with waste ingredients at elevated temperature by employing interpretable algorithms: Optimization and hyper tuning

Mix proportions of the component materials employed significantly affects the concrete's compressive strength (CS) at elevated temperatures. Predicting the CS of concrete under elevated temperatures is complicated and requires the application of reliable and effective algorithms. In the present study, machine learning methods using distinct learners and combined learners, such as bagging and boosting, are used to estimate the CS of concrete at elevated temperatures. This is achieved by the utilization of Anaconda software using Python. The combined learner boosting (Adaboost and Xgboost), bagging, and modified bagging algorithms are utilized in constructing a robust ensemble learner by integrating an individual learner. These ensemble algorithms were incorporated with decision tree (DT), support vector regression (SVR), and multilayer perception neural network (MLPNN) techniques to enhance the robustness of the models. The database used to develop the models comprised 207 data points with nine input parameters: water, temperature, silica fume, cement, fly ash, superplasticizer, sand, Nano silica, and gravels and CS as output. The optimization was performed to achieve the maximum R2 by training the data in 20 sub-models for each boosting and bagging technique. The data is verified by using a K-fold cross-validation approach. In addition, various statistical measures such as MAE, RMSE, NSE, and MSE are employed for cross-validation of the data. Based on the findings, it appears that making use of bagging and boosting learners results in improved particular model performance. In more general terms, RF and DT with bagging produce the most accurate results among the developed models, with a higher R2 value of 0.94 and lesser error values. When it comes to machine learning, having an ensemble model would often improve the model's overall accuracy.

Effect of recycled of recycled glass aggregates on mechanical and physical properties of structural concrete

The exponential expansion in concrete use has put the environment under immense pressure to supply cement, aggregates, and water. Natural resource consumption impacts the environment and undermines the concrete industry. A swift shift towards sustainable concrete is required considering the emergency triggered by human activity on the climate. Glass concrete (GC) has sparked the curiosity of the construction industry owing to its environmentally friendly approach. The study uses recycled glass aggregates (RGA) to partially replace natural aggregates (NA) to produce sustainable structural concrete with superior mechanical properties. 20% glass concrete outperformed all others in fresh and hardened concrete. Only 75% glass blend demonstrated a slight decrease in compressive strength due to drop in density. Glass concrete showed a lower water absorption capacity. However, glass has triggered an alkali-silica (ASR) reaction, reducing the durability of the concrete significantly.

Research on a sustainable concrete synergistic reinforced with carbon fiber and carbon nanofiber: Mechanical properties, durability and environmental evaluation

A sustainable concrete was developed by incorporating carbon fiber (CF) and carbon nanofiber (CNF), where the synergistic modification effect of micro-scale and nano-scale of fibers was exploited and the mechanical properties and durability of concrete were improved. The mechanical test, shrinkage test, freeze-thaw cycle test, water permeability test and carbonation test were conducted on carbon fiber/carbon nanofiber reinforced concrete (CF/CNFRC) with different mix proportions. The results show that, when the content ratio of CF to CNF is 1:3, the compressive strength, splitting tensile strength and flexural strength are increased by 14.12%, 21.46% and 18.05% compared with plain concrete (PC). At the same time, the shrinkage rate at 180-day age, relative permeability coefficient, compressive strength loss rate at 200 freeze-thaw cycles and carbonation depth at carbonation age of 28 days are reduced by 30.57%, 66.56%, 37.72% and 34.09% respectively, at which time CF and CNF have the best synergistic modification effect. Durability value was further introduced to quantitatively evaluate the durability of CF/CNFRC, showing that the durability value of CF/CNFRC01 was the largest and increases by 57% compared with PC. Through MIP and SEM tests, the microstructure of CF/CNFRC was analyzed, and the multiscale synergistic modification mechanism of CF and CNF was further explored. Compared with the single CNF, appropriate amounts of CF and CNF can exert a positive multiscale synergistic effect, which further optimizes the pore structure through fiber bridging and filling, inhibits crack propagation, improves the compactness and integrity, and thus improves the mechanical properties and durability of concrete. In addition, the economic and environmental benefits of CN/CNFRC were discussed by calculating the cost-benefit ratio and CE-benefit ratio (the ratio of CO2 emissions to durability benefits). The calculation results show that CN/CNFRC has the best economic and environmental benefits when the content ratio of CF to CNF is 1:3, where the environmental benefits are 31% higher than that of PC.

Experimental investigation on static/dynamic response and γ/n shielding of different sustainable concrete mixtures

Concrete has an influential role in the construction industry as it is a prominent building element that affects the present infrastructure and the construction industry's economy. There is a considerable consumption of raw materials needed for concrete production since crushed stone production was increased in the last decades. Thus alternatives for aggregates are highly recommended solutions for such problems. Steel slag and mill scale are considered sustainable contenders for natural resources of structural materials.Nuclear bombs accompanied with radiations and dynamic loads are considered one of the major disasters that threaten human lives and structures. Therefore, this research investigates the effect of utilizing by-product materials as coarse and fine aggregates to manufacture sustainable concrete, probably with novel static and dynamic performance and radiation attenuation capability. This issue could be done by substituting crushed stone aggregates by steel slag and silica sand by mill scale in concrete production. Fresh and hardened properties of concrete were experimentally explored. Workability, compressive, tensile and flexural strength, impact resistance, and linear attenuation capability were the major evaluated characteristics in this research work. The achievements of this study showed that a superior static and dynamic performance by up to 81.67% and 178.39% compared to normal concrete, respectively, could be achieved by utilizing steel slag and mill scale in concrete fabrication besides its considerable environmental benefits and economic affordability. Also, the radiation attenuation capability was enhanced by up to 84.1% with prepared sustainable concrete mixtures, which makes it a good candidate for radiation shielding. Thus, producing novel structures such as radiation shielding facilities probably with superior dynamic performance.

Durability and microstructure study on concrete made with sewage sludge ash: A review (Part Ⅱ)

Abstract The quantity of carbon dioxide gas released during the manufacturing and acquisition of raw ingredients determines the sustainability of concrete. Industrial garbage dumping is a critical difficulty that humanity is experiencing because of globalization and the increasing population. Through the efficient use of industrial by products, efforts are being undertaken to lower carbon discharges in the concreting process. It has been recommended by sustainable development goals and standards to use byproducts that have lower embodied energy and carbon emissions. Ash from sewage sludge demonstrates its suitability for use in concrete. However, a compressive assessment is needed to determine the past, present, and future research aspects of using sewage sludge ash (SSA) as a construction material. Therefore, this research is carried out on using SSA as a construction material. All the essential properties such as the physical and chemical properties of SSA, its effect on durability properties, and morphology structure study are the main aspect of this review (Part II). The analysis also highlights the research gap for upcoming exploration which further improved its performance.

Efficacy of Fire Protection Techniques on Impact Resistance of Self-Compacting Concrete

The present research investigates the behaviour of sustainable Self-Compacting Concrete (SCC) when subjected to high temperatures, focusing on workability, post-fire impact resistance, and the effects of fire protection coatings. To develop environmentally friendly SCC mixes, Supplementary Cementitious Materials (SCM) such as Fly Ash (FA), Ground Granulated Blast Furnace Slag (GGBFS), and Expanded Perlite Aggregate (EPA) were used. Fifty-six cubes and ninety-six impact SCC specimens were cast and cured for testing. Fire-resistant Cement Perlite Plaster (CPP) coatings were applied to the protected specimens, a passive protection coating rarely studied. SCC (unprotected and protected) specimens, i.e., protected and unprotected samples, were heated following the ISO standard fire curve. An extensive comparative study has been conducted on utilising different SCMs for developing SCC. Workability behaviour, post-fire impact resistance, and the influence of fire protection coatings on sustainable SCC subjected to high temperatures are the significant parameters examined in the present research, including physical observations and failure patterns. The test results noted that after 30 min of exposure, the unprotected specimen exhibited a significant decrease in failure impact energy, ranging from 80% to 90%. Furthermore, as the heating duration increased, there was a gradual rise in the loss of failure impact energy. However, when considering the protected CPP specimens, it was observed that they effectively mitigated the loss of strength when subjected to elevated temperature. Therefore, the findings of this research may have practical implications for the construction industry and contribute to the development of sustainable and fire-resistant SCC materials.