Use Of Industrial By-products Research Articles

Machine learning prediction of the unconfined compressive strength of controlled low strength material using fly ash and pond ash.

The sustainable use of industrial byproducts in civil engineering is a global priority, especially in reducing the environmental impact of waste materials. Among these, coal ash from thermal power plants poses a significant challenge due to its high production volume and potential for environmental pollution. This study explores the use of controlled low-strength material (CLSM), a flowable fill made from coal ash, cement, aggregates, water, and admixtures, as a solution for large-scale coal ash utilization. CLSM is suitable for both structural and geotechnical applications, balancing waste management with resource conservation. This research focuses on two key CLSM properties: flowability and unconfined compressive strength (UCS) at 28days. Traditional testing methods are resource-intensive, and empirical models often fail to accurately predict UCS due to complex nonlinear relationships among variables. To address these limitations, four machine learning models-minimax probability machine regression (MPMR), multivariate adaptive regression splines (MARS), the group method of data handling (GMDH), and functional networks (FN) were employed to predict UCS. The MARS model performed best, achieving R2 values of 0.9642 in training and 0.9439 in testing, with the lowest comprehensive measure (COM) value of 1.296. Sensitivity analysis revealed that cement content was the most significant factor with obtaining R = 0.88, followed by water (R = 0.82), flowability (R = 0.79), pond ash (R = 0.78), curing period (R = 0.73), and fine content (R = 0.68), with fly ash (R = 0.55) having the least impact. These machine learning models provide superior accuracy compared to traditional methods, particularly in handling complex interactions between mix components. The proposed models offer a practical approach for predicting CLSM performance, supporting sustainable construction practices and the efficient use of industrial byproducts. The novelty of this study lies in the development of precise design equations for evaluating UCS, promoting both practical applicability and environmental sustainability.

Approach to Design Sustainable Alkali-Activated Slag Recycled Aggregate Concrete: Mechanical and Microstructural Characterization

There is a steep increase in demand for concrete as the need for infrastructure is increasing with a rapid increase in urbanization. Consequently, there has been a surging demand for cement across the globe. By using alkaline concrete activated with ground granulated blast furnace slag (GGBS), cement usage can be eliminated in concrete, which addresses the issue of CO2 emissions concerned with the cement manufacturing process and promotes the use of industrial by-products as sustainable building materials. The current study focuses on proposing a methodology to design sustainable GGBS-based alkali-activated concrete incorporated with 100% coarse recycled coarse aggregates (RCA) recovered from construction and demolition (C&D), for various strengths by optimizing the mix proportions and verifying the same through experiments. From the current study, it is evident that this mix design procedure can be adopted to design alkali-activated slag recycled aggregate concrete (AASRAC) mixes for strengths ranging from 44MPa to 85MPa. The optimum values of alkalinity factor (λ) and NaOH concentration (M) i.e., 1.5 and 12, have a significant role in the development of high strengths which is attributed to the formation of hydrotalcite. Micrographs captured using scanning electron microscope (SEM) and energy dispersive X-ray spectroscopy (EDS) studies reveal that the alkaline binders promote the development of a denser and stronger interfacial transition zone (ITZ) that enhances the strength of lower AA/B concretes at the microstructural level as Ca/Si ratio is higher for lower AA/B concretes. Global warming potential (GWP) analysis reveals that the alkali-activated concretes have significantly lower GWP compared to conventional OPC-based concrete by approximately 2.5 times. The mix-design chart proposed in this study may pave the way to designing structural grade AASRAC with enhanced performance for the desired strength, which may find its application in fast-track construction and manufacturing of prefabricated elements.

Industrial by-products (ferrous sulfate minerals and stone powder) can serve as amendments to remediate Cd-As paddy soil, alleviating Cd-As accumulation in rice

Our previous research has shown that industrial by-products such as ferrous sulfate mineral and stone powder as amendments can remediate Cadmium (Cd) and arsenic (As) soil. However, their role in the soil-rice system is unknown. Therefore, this article explored the effects of the combined use of industrial by-products and commercial conditioners on the accumulation of Cd-As in weakly alkaline and acidic soil-rice systems. Potted experiments shown that SL (stone powder+ferrous sulfate mineral) and SLW (stone powder+ferrous sulfate mineral+Weidikang conditioner) could reduce the availability of Cd-As in soil by adjusting soil pH and CEC, increase iron film content on the root surface, strengthening the “barrier” for fixing Cd-As. Brown rice Cd was lower than the national food safety standard of 0.20 mg kg−1 (GB2762–2022). 1 % SLW could reduce brown rice As from 1.24 mg kg−1 to 0.83 mg kg−1. The results of field experiments confirmed the conclusion of pot experiments. SL and SLW not only reduced the accumulation of Cd-As in rice but also significantly increased rice yield by 16.58 % and 11.68 %, respectively. Compared to the two types of conditioning agents sold in the market, the material costs have been reduced by 79.1 % -86.5 % and 12.4 % -43.3 %, respectively. In summary, this study demonstrates that ferrous sulfate minerals and stone powder could efficiently remediate Cd-As pollution in paddy soil under different acid-base conditions, providing an application example for the resource utilization of industrial by-products for the remediation of Cd-As pollution in paddy soil.

Evaluation of geotechnical, mineralogical and environmental properties of clayey soil stabilized with different industrial by-products: A comparative study

The utilisation of soil stabilization techniques employing binders like lime or cement enables the use of soils that are classified as disposable, thereby reducing the need for landfills and the consumption of natural resources. However, the production of lime and cement results in significant CO2 emissions. Therefore, the application of industrial by-products (IBP) for stabilizing expansive soils presents an opportunity to minimise the use of traditional binders. This study investigates the geotechnical, mechanical, mineralogical, and environmental properties of four IBP (biomass bottom ash, biomass fly ash, steel slag, and mixed recycled aggregate) combined with a silica-based nanomaterial for road layer applications. The technical feasibility of the use of IBP was demonstrated, especially in combination with nanomaterials, allowing a 66 % reduction in the percentage of added lime, obtaining significant improvements with minimal plasticity and swelling index and bearing capacity CBR values higher than 25 %, applying BBA, BFA and SS. An environmental assessment of leachate analysis was performance, showing an immobilization of heavy metals that makes the application of IBP feasible. In addition, a life cycle analysis study showed the environmental benefits of applying IBP, such as a 50 % reduction in CO2 emissions due to the reduction of lime, resulting from the use of these materials, thus promoting more sustainable economic models.

Sustainability and durability performance evaluation of geopolymer concrete with industrial effluent as alternative to conventional river sand

Due to infrastructural development activities, the need for the construction materials increases, because of which most of the naturally available natural resources are over exploited and the cost of construction materials are increased. Therefore, the present study focuses on the use of industrial by-products for the development of concrete and examines the physical, mechanical, durability and sustainable performances. Fly ash (FA) and ground granulated blast furnace slag (GGBS) were employed as binder medium and the industrial effluent sodium silicate waste was used to replace the conventional river sand in the geopolymer concrete (GPC). GGBS was employed as source material for the production of concrete to increase the polymerization reaction process and further, the developed concrete was cured in the ambient condition of temperature range 27 ± 2 °C, in the laboratory. The concentration of the sodium hydroxide (NaOH) in the present study was 12M, and the alkaline solution ratio was 1:1.5. During the production process of sodium silicate solution in the factory, the residue left at the bottom of the boiling hopper were dumped as waste in the open land. GPC gains its strength based on the alumina and silica in the source material and alkaline activator solution, therefore, this industrial waste residue was identified as potential alternative to conventional river sand. The concrete with and without effluent was subjected to two types of acid (Sulfuric acid (H2SO4) and Hydrochloric acid (HCl)) and further to examine the performance of concrete under marine condition, two types of salt solutions, namely, magnesium sulfate (MgSO4) and Sodium Chloride (NaCl) were used, the concentration of acids employed in the present study is 2% and the marine solution is 3.5%. Increase in the proportion of effluent from 0% to 100% decreases the slump value of the concrete. Contrastingly, increasing the proportion of effluent increases the strength of GPC after 28-d of room temperature curing. To examine the performance of the concrete under acidic and marine conditions, average of three concrete specimens were employed and the duration of exposure was considered in the present study starts from 28-d and continues till 360-d. After exposing to acidic environment, mass loss, strength loss and surface modification were examined; the loss in mass was found to be 1.5–3% and the strength loss was found to be 35%–45%. In the case of salt solution exposure, the loss in mass was seen to be 1–2% and whereas in the case of strength, the loss was found to be 30%–42%, respectively. Further, the sustainability aspects of the concrete with industrial effluents were examined in detail; focusing on economic value of the concrete, carbon emission and energy demand during the production of concrete.

Effect of Dry Mix Alkali Activated Slag Binder Composite Properties Cured in Ambient Condition

<p>A dry mix (solution-free) alkali-activated slag (a primary cementitious material) and/or fly ash based binder composition is developed that can be cast in-site and consequently cured at ambient temperature. Mortar specimens were cast by mixing slag and or fly ash, river sand, powder form alkaline activators (NaOH 14M, varying solids percentage of Na2SiO3) and water were thoroughly mixed in fabricated equipment. The dry density (28 days) of all specimens showed greater than 2200 kg/m3. The compressive strength (28 days) of all mixes was resulted in higher than 40 N/mm2. Among all the four mixes, a mix F103 with 90% slag, 10% fly ash, 30% Na2SiO3 and 14M NaOH at 3, 7 and 28 days curing showed overall higher compressive strength. It is due to fewer solids content of Na2SiO3. The experimental results indicated that solution free studied binder composite can be developed under ambient conditions eliminating other curing types without compromising in the strength. The studied sustainable mixes require only 12-15 percent water which is less compared to regular used mixes. Thus reduced water quantities can be achieved thereby protects the reduction in volume of water bodies, environment hazards, reduces CO2 emissions due to use of industrial by-products as main binders.</p>

Investigation on the sustainable use of different sizes of sawdust aggregates in eco-friendly foam concretes: Physico-mechanical, thermal insulation and durability characteristics

The extensive mining of natural resources, such as sand, for the construction industry, poses a hazard to the environment. To preserve the environment, the researcher must thus take into account the use of industrial byproducts rather than natural materials. The use of sawdust (SD) produced by the wood industry in foam concretes (FC) has been investigated in this study. This study examined the physical, mechanical, thermal, microstructural and durability characteristics of FC containing SD as a replacement of silica sand (SS) in the rates of 0, 25, 50 and 100 %. Two different SD sizes of 0–4 mm (SD4) and 0–1 mm (SD1) were used in the fabrication of FC mixtures. Protein-based foam agent was used to create FC mixtures. Fourteen mixtures with a 0.6 water/binder (w/b) ratio were produced at two different cement contents of 400 kg/m3 and 500 kg/m3. The fresh, mechanical, physical, and sorptivity characteristics of the FC mixtures were investigated in relation to the impacts of cement dosage, SD size, and SD replacement levels of SS. Durability of FC against high temperature, sulfate attack and freeze-thaw cycles was assessed. Costs and CO2 emissions from the blends were also assessed. The outcomes revealed that a 25 %SD1 integrated FC mixture with a cement content of 500 kg/m3 generated the highest 28-day compressive strength of 3.56 MPa with a 20 % strength loss as per the Ref.500 mixture. 17 % lower thermal conductivity was gained with the inclusion of 100 %SD4 as per the Ref.400 mixture. The mixture with 50 %SD4 and 400 kg/m3 cement dosage exhibited the best resistance to high temperature. The mixture with 25 %SD1 and 400 kg/m3 cement dosage showed the best frost resistance. SD incorporated mixtures showed better durability performance than the reference mixtures.

Assessment of flexural response of RC beams and unrestrained shrinkage of fiber-reinforced high-volume fly ash-based no-aggregate concrete and self-compacting concrete

The use of industrial byproducts as a substitute for cement in concrete production to improve its properties is becoming a widespread practice in producing sustainable concrete. Although research around the world emphasizes higher substitution levels of fly ash (FA) to accrue the benefits from the microstructure refinement, no attempt has been made to study the deflection behavior and drying shrinkage of concrete that is devoid of aggregates while supplementing 80% of cement with class F fly ash (F-FA). Two types of concrete are used to cast full-scale reinforced concrete (RC) beams of size 150×300×2200 mm. The first type is a novel no aggregate concrete (NAC) made up of 80% F-FA and 20% ordinary Portland cement (OPC). The second type is high-volume fly ash self-compacting concrete (HVFASCC), which has 60% F-FA as a cement supplement and is equivalent in compressive strength to NAC. The NAC is reinforced with polypropylene fibers (PF) in three varying volume fractions: 0.6%, 0.8%, and 1.0%. All the beams are tested under a simply supported four-point loading condition. The drying shrinkage strain and mass loss are measured for prisms of size 75×75×300 mm up to 220 days exposed at 20% relative humidity (RH) and 50 ºC temperature in a humidity oven for all the mixes. The mechanical properties are also assessed along with the water absorption (sorptivity). The results indicate that adding PF to the beams with NAC delays the formation of the first crack and improves the peak load, the ultimate load, and the ductility of the NAC beam. Additionally, the beams with PF exhibit lower mid-span deflection and ductile failure mode, improving the overall structural performance. Regarding drying shrinkage, the HVFASCC prisms record the lowest shrinkage strains of all mixes. Adding PF to NAC increases the initial and ultimate drying shrinkage strains. However, adding PF to NAC inhibits the rate of shrinkage strain over the test duration. This research enhances understanding of how PF affects no-aggregate concrete behavior, paving the way for more comprehensive construction materials.

Sustainable production of eco-friendly roofing tile using methyl ester residue as the alternative binder – A preliminary study

Making full use of industrial by-products is an effort to achieve ‘zero waste’ and promote greener development. Methyl ester residue (MER) is a waste commonly found in oleochemical manufacturers, such as palm oil mills. Contrary to conventional cement and clay, MER was employed as an alternative binder to fabricate a novel eco-friendly roofing tile, henceforth referred to as MER-RT. Parameters tested were transverse strength, water absorption, sulfate resistance, and fire resistance. During the optimization phase, a range of 6–11% of MER was mixed with a fixed composition of fly ash and fine sand, compacted and cured at 190° C for 12–48 hours. Considering the electrical energy consumption, the optimal curing duration chosen was 24 hours as this MER-RT achieved a dry transverse strength of 4112 N whereas curing for an additional 18 hours further contributed to only 16% strength gain. The optimal MER-RT was found to contain 10% MER as it showed the highest dry transverse strength (6410 N), the highest wet transverse strength (3681 N) and the lowest water absorption percentage (2.67%), meeting the American Society for Testing and Materials (ASTM) standards. Besides exhibiting minimal corrosion under the sodium sulfate test, the optimal MER-RT was non-flammable and did not undergo structural changes when exposed to fire. The study reveals the potential of both MER and fly ash as green binders and fillers for roof tiles, despite their origins as industrial waste.

Optimization of production variables for metakaolin and rice husk ash-based geopolymer cement

Geopolymer concrete has emerged as an eco-friendly alternative to conventional Portland cement-based concrete, boasting superior mechanical performance and a significantly reduced carbon footprint. This research delves into the effects of incorporating rice husk (RH) and metakaolin (MK) as supplementary materials in geopolymer concrete, with the goal of enhancing its properties and sustainability while making productive use of industrial by-products. The research commences with a comprehensive characterization of the raw materials, including rice husk ash (RHA) and metakaolin, via physical, chemical, and mineralogical analyses. Different combinations of RH and MK are then blended with an alkali activator solution to formulate geopolymer paste mixtures. The findings of this study reveal that the incorporation of RH and MK as partial substitutes for conventional materials in geopolymer concrete yields positive effects on its performance. The utilization of rice husk ash enhances workability and reduces the alkaline activation time of the geopolymer paste, leading to improved early-age strength development. This study demonstrates that the synergistic use of rice husk and metakaolin in geopolymer concrete promotes a more sustainable construction material with a diminished environmental impact. It offers valuable potential to guide engineers, researchers, and industry professionals in adopting sustainable and cost-effective strategies for enhancing the properties of geopolymer concrete, thus fostering its wider adoption in the construction sector.

Limestone and yellow gypsum can reduce cadmium accumulation in groundnut (Arachis hypogaea): A study from a three-decade old landfill site

Cadmium (Cd) toxicity has cropped up as an important menace in the soil-plant system. The use of industrial by-products to immobilise Cd in situ in polluted soils is an interesting remediation strategy. In the current investigation, two immobilizing amendments of Cd viz., Limestone (traditionally used) and Yellow gypsum (industrial by-product) have been used through a green-house pot culture experiment. Soil samples were collected from four locations based on four graded levels of DTPA extractable Cd as Site 1 (0.43 mg kg−1), Site 2 (0.92 mg kg−1), Site 3 (1.77 mg kg−1) and Site 4 (4.48 mg kg−1). The experiment was laid out in a thrice replicated Factorial Complete Randomized Design, with one factor as limestone (0, 250, 500 mg kg−1) and the other being yellow gypsum (0, 250, 500 mg kg−1) on the collected soils and groundnut was grown as a test crop. Results revealed that the DTPA-extractable Cd content in soil and Cd concentration in plants decreased significantly with the increasing doses of amendments irrespective of initial soil available Cd and types of amendment used. The effect of amendment was soil specific and in case of Site 1 (low initial Cd) the effect was more prominent. The reduction in DTPA-extractable Cd in combined application of limestone and yellow gypsum @500 mg kg−1 over the absolute control in soil under groundnut for the sites was by far the highest with the values of 83.72%, 77.17%, 48.59% and 40.63% respectively. With the combined application, Target Cancer Risk (TCR) of Cd was also reduced. Hence, combined application of limestone and yellow gypsum can be beneficial in the long run for mitigating Cd pollution.

Productive Management of Garbage: A Case of Rawalpindi Waste Management Company (RWMC)

This study quantifies the role and importance of Rawalpindi Waste Management Company, the whole processes that take place in it, and the policies on which they work. Urbanization has led to the increasing use of industrial by-products. Industries influence the environment in two folds one is creating waste during the manufacturing process and the second is products make more waste after they are used. Waste is managed by using (R-3) Reuse, Recycle, and Restore. Waste composition varied from time to time and region to region. RWMC’s target is Clean and Green Rawalpindi. Waste from Households, Hospitals, industries, and others is properly discarded by fulfilling the National Environmental Quality Standards. In this regard, the main concern is to focus on ‘’Sustainable Development’’ to secure our environment for the next generations.

Alkali activation of fly ash in self-consolidating concrete at low molar concentration

As a means of minimising the negative effects on the environment, the use of industrial byproducts in the building industry is becoming more popular. Recently, alkali activation of precursors has boomed in the market since activation of precursors improves mechanical properties and reduces the carbon footprint. However, one risk factor in alkali activation is molar concentration. This is because the increase in the molar concentration of sodium hydroxide/sodium silicate and the release of volatile substances from those acids is more harmful to the environment. Therefore, the present study investigates the activation of the precursor at low molar concentration, thereby equalising performance through the dosage of superplasticisers. In this regard, fly ash was activated at 5 M sodium hydroxide (NaOH) and replaced cement at varying percentages in the range of 0–30% by weight. The performance of self-consolidating concrete (SCC) was evaluated through fresh and hardened characteristics and microstructural analysis. The blended mixtures of SCC, activated fly ash (AFA) at 5 M sodium hydroxide, 0.89% of superplasticisers and 15% of replacement performed better than the control SCC. The outcome of the present study will provide a platform for activating a precursor at low molar concentration through the influence of superplasticisers.

Strategies to Assess the Impact of Sustainable Functional Food Ingredients on Gut Microbiota.

Nowadays, it is evident that food ingredients have different roles and distinct health benefits to the consumer. Over the past years, the interest in functional foods, especially those targeting gut health, has grown significantly. The use of industrial byproducts as a source of new functional and sustainable ingredients as a response to such demands has raised interest. However, the properties of these ingredients can be affected once incorporated into different food matrices. Therefore, when searching for the least costly and most suitable, beneficial, and sustainable formulations, it is necessary to understand how such ingredients perform when supplemented in different food matrices and how they impact the host's health. As proposed in this manuscript, the ingredients' properties can be first evaluated using in vitro gastrointestinal tract (GIT) simulation models prior to validation through human clinical trials. In vitro models are powerful tools that mimic the physicochemical and physiological conditions of the GIT, enabling prediction of the potentials of functional ingredients per se and when incorporated into a food matrix. Understanding how newly developed ingredients from undervalued agro-industrial sources behave as supplements supports the development of new and more sustainable functional foods while scientifically backing up health-benefits claims.

Commercial and recycled carbon-based fillers and fibers for self-sensing cement-based composites: Comparison of mechanical strength, durability, and piezoresistive behavior

The possible use of industrial by-products as carbon-based fillers and/or fibers to produce Multifunctional Cement-based Composites (MCC) with piezoresistive behavior for Structural Health Monitoring (SHM) was investigated. As fillers, Used Foundry Sand (UFS) and Gasification Char (GCH) were compared with commercial Graphene Nanoplatelets (GNP). As fibers, 6 mm-long recycled carbon fibers (RCF) were compared with virgin ones. Mortars were tested in terms of mechanical strength, water absorption, microstructure, and piezoresistive behavior. UFS and GCH are more effective than GNP in decreasing the mortar electrical resistivity (−30%), total porosity (−11%), water absorption (−27%) and in increasing the compressive strength (+10%). The combination of UFS with RCF in mortars provides the best results in terms of fluidity, strength, water absorption, and piezoresistive parameters. Generally, a lower mortar resistivity, even if with lower piezoresistivity properties, allows the use of cheaper instrumentation for SHM, thanks to the lower full scale and the better correlation strength between the change in resistivity with strain.

Microbial‑induced carbonate precipitation (MICP) technology: a review on the fundamentals and engineering applications.

The microbial‑induced carbonate precipitation (MICP), as an emerging biomineralization technology mediated by specific bacteria, has been a popular research focus for scientists and engineers through the previous two decades as an interdisciplinary approach. It provides cutting-edge solutions for various engineering problems emerging in the context of frequent and intense human activities. This paper is aimed at reviewing the fundaments and engineering applications of the MICP technology through existing studies, covering realistic need in geotechnical engineering, construction materials, hydraulic engineering, geological engineering, and environmental engineering. It adds a new perspective on the feasibility and difficulty for field practice. Analysis and discussion within different parts are generally carried out based on specific considerations in each field. MICP may bring comprehensive improvement of static and dynamic characteristics of geomaterials, thus enhancing their bearing capacity and resisting liquefication. It helps produce eco-friendly and durable building materials. MICP is a promising and cost-efficient technology in preserving water resources and subsurface fluid leakage. Piping, internal erosion and surface erosion could also be addressed by this technology. MICP has been proved suitable for stabilizing soils and shows promise in dealing with problematic soils like bentonite and expansive soils. It is also envisaged that this technology may be used to mitigate against impacts of geological hazards such as liquefaction associated with earthquakes. Moreover, global environment issues including fugitive dust, contaminated soil and climate change problems are assumed to be palliated or even removed via the positive effects of this technology. Bioaugmentation, biostimulation, and enzymatic approach are three feasible paths for MICP. Decision makers should choose a compatible, efficient and economical way among them and develop an on-site solution based on engineering conditions. To further decrease the cost and energy consumption of the MICP technology, it is reasonable to make full use of industrial by-products or wastes and non-sterilized media. The prospective direction of this technology is to make construction more intelligent without human intervention, such as autogenous healing. To reach this destination, MICP could be coupled with other techniques like encapsulation and ductile fibers. MICP is undoubtfully a mainstream engineering technology for the future, while ecological balance, environmental impact and industrial applicability should still be cautiously treated in its real practice.

Fly ash, GGBS, and silica fume based geopolymer concrete with recycled aggregates: Properties and environmental impacts

Recycled coarse aggregates (RA) are sustainable alternatives to natural aggregate (NA) in concrete; however, their mechanical performance has not been competent to the later. The partial replacement of Ordinary Portland Cement (OPC) with the use of industrial by-products for preparation of geopolymer concrete (GPC) has also harnessed great research interest. The objective of the current study is to investigate the technoenvironmental feasibility of using fly ash (FA), ground granulated blast furnace slag (GGBS), and silica fume (SF) in GPC to support the use of 100 % RAs in concrete. This study aims to optimize the proportion of GGBS, FA, and SF in the design mix for the best mechanical performance and eco-efficiency of GPC concrete as compared to conventional OPC concrete. Results indicated positive synergistic effect between FA, GGBS, and SF causing improved mechanical, and microstructural performance of RA based GPCs as compared to OPC concrete with RA. The highest compressive (52.15 MPa), flexural (5.81 MPa), and split tensile strength (5.23 MPa) were exhibited by GPC-MG15 with a cement substitution ratio of FA: GGBS: SF – 35:50:15 which were 18–34 % and 7–10 % higher than that of OPC concrete with NA and RA, compensating the effects of RA addition. The microstructural, and mineralogical properties analysed through SEM and XRD results depicted the densification of the matrix and formation of C-S-H, C-A-S-H, and N-A-S-H gels which could be the possible reasons for the improved performance of GPCs. The environmental performance of optimized GPCs analysed through Life cycle assessment (LCA) reported a 50–60 % reduction in the environmental impacts as compared to OPC concrete with NA. Although GPC-FG50 (GGBS: FA – 50:50) was also environmentally competent, GPC-MG15 was the most sustainable concrete mix which was environmentally superior while not compromising on the functional properties.

Influence of industrial by-product sulfur powder on properties of cement-based composites for sustainable infrastructures

The use of industrial by-products has attracted much attention globally in recent years because of the improved durability and sustainability of cement-based composites. To promote the application of sulfur powder (SP) in cement-based composites, a new hydrophilic modified sulfur powder (MSP) was prepared in this paper. The effects of unmodified sulfur powder (NSP) and MSP on workability, strength, permeability, dry shrinkage, and frost resistance of cement-based composites were thoroughly studied. Based on microstructural evolution, hydration heat, hydration product composition, and pore structure, the modification mechanism of NSP and MSP on cement-based composites were investigated. The results show that adding NSP improves the fluidity of cement-based composites while adding MSP has the opposite effect. An appropriate amount of MSP and NSP improves the durability of cement-based composites. However, both NSP and MSP reduce the 28d strength of cement-based composites. Compared with NSP, the incorporation of MSP reduces the hydration release rate, refines the pore structure, and improves the interface bond with the cement matrix. This study deepens our understanding of the influence of SP on the fundamental properties of cement-based composites, which also provides new perspectives on creating a sustainable built environment.

Mechanical and microstructural properties of lightweight CaO-activated fly ash composites in the presence of magnesium nitrate

The use of industrial by-products is required to replace cement to reduce carbon emission, and it is necessary to secure the strength of cementless binder to satisfy the required mechanical performance. The purpose of this study is to develop a new binder system composed of activated fly ash (FA) with CaO by adding magnesium nitrate ((Mg(NO3)2) as a new additive. To reveal the mechanism of strength enhancement, the influence of the dosage of Mg(NO3)2 on compressive strength, reaction products, and pore characteristics was observed. In addition, expanded perlite (EP) and expanded vermiculite (EV) were mixed in selected samples to develop a lightweight cementless composite. The results showed that adding Mg(NO3)2 significantly increased strength of CaO-activated FA system. In the reaction process, Mg(NO3)2 promoted the solubility of quicklime (CaO) to form more C-(A)-S-H and Ca–Mg–Al-(OH)-NO3-AFm phase and increased the initial concentration of silicon (Si) and aluminum (Al) from FA. The dense C-(A)-S-H formation enhanced mechanical strength by reducing porosity in binder matrix. When EP and EV were mixed in the selected binder, even if the strength decreased as the amount of EP and EV increased, the requirements for the strength and specific gravity of commercial autoclave aerated concrete (AAC) were satisfied.

Effect of Ordinary Portland Cement on Mechanical Properties and Microstructures of Metakaolin-Based Geopolymers.

Geopolymers have been considered a sustainable alternative to ordinary Portland cement (CEM I) for its lower embodied carbon and ability to make use of industrial by-products. Additionally, its excellent engineering properties of high strength, low permeability, good chemical resistance, and excellent fire resistance also strike a chord in the minds of researchers. The goal of this study is to clarify the effect of calcium sources on the mechanical properties and microstructures of the geopolymers. CEM I was chosen as the sole calcium source, while metakaolin was used as the source material. Five distinct geopolymers were prepared, having various ratio of CEM I: 0%, 5%, 10%, 20%, and 30%. The alkali-activator was a mixture of 12 M sodium hydroxide (NaOH) and sodium silicate (Na2SiO3), utilizing compressive strength and flexural strength to evaluate the changes of the geopolymers' mechanical properties. SEM, XRD, and FTIR were used to examine microscopic features, evaluate internal morphology, and analyze changes in components of the geopolymers containing different amounts of CEM I. The experimental results indicated that the optimal incorporation of CEM I was 5%. Under this dosage, the compressive strength and flexural strength of the geopolymers can reach 71.1 MPa and 6.75 MPa, respectively. With the incorporation of CEM I, the heat released by cement hydration can accelerate the geopolymerization reaction between silica-alumina materials and alkaline solutions. Additionally, the coexistence of N-A-S-H gel from components of an aluminosilicate mix and C-S-H gel from the CEM I promoted a more densified microstructure of the geopolymers and improved the geopolymer's strength. However, as the amount of CEM I in the mixture increased, the geopolymer matrix was unable to provide enough water for the CEM I to hydrate, which prevented excessive CEM I from forming hydration products, weakening the workability of the matrix and eventually hindering the development of geopolymer strength.