Selection of an alternate cementitious mortar using ceramic tile dust waste: a hybrid MCDM approach.

Selection of a suitable alternative material from a pool of alternatives with many conflicting criteria becomes a Multi-Criteria Decision Making (MCDM) problem. In the present study, ternary blended mortars were prepared using ceramic tile dust waste (CTD), fly ash (FA), and ground granulated blast furnace slag (GGBFS) as binder components. Crusher dust (CD) was used as a fine aggregate component. Binder to aggregate ratios of 1:3 and 1:1 were prepared considering suitable flow. A total of 16 mortar mixes were cast. These mortars were tested for various conflicting criteria compressive strength, flexural strength, porosity, water absorption, bulk density, thermal conductivity, specific heat, thermal diffusivity, and thermal effusivity whose weightages obtained were 29.09%, 20.08%, 12.77%, 10.60%, 8.74%, 6.74%, 5.54%, 4.47%, and 1.97%, respectively, as per AHP analysis. Later, considering these different criteria and alternate mortars, it was observed that a 1:1 mortar with 20% CTD, 30% FA, and 50% GGBFS (RC20F30G50) is found to be the suitable mortar with the highest relative closeness coefficient of 0.861 and the highest net outranking flow of 0.316 with respect to MCDM techniques: technique for order of preference by similarity to ideal solution (TOPSIS) and preference ranking organization method for enrichment of evaluations (PROMETHEE-II), respectively. The ranking of the mortar in both methods complies with the relative weightages of the criteria and the performance of the mortars with respect to the above criteria.

MgO-based supersulfated cement with different industrial by-product gypsum: Experiments and molecular dynamics simulation.

Super sulfate cement (SSC) emerges as a sustainable alternative to ordinary Portland cement, boasting minimal carbon emissions and exceptional performance. As the quest for eco-friendly alternatives intensifies, there's a growing focus on exploring alkaline and sulfate activators conducive to SSC's environmental goals. This study delves into the viability of utilizing MgO as an alkaline activator in producing MgO-based supersulfated cement, while also investigating the impact of various industrial by-product gypsums on its performance. Findings reveal that employing MgO as an alkaline activator yields favorable hydration properties and mechanical strength in SSC. The optimized formulation comprises 15 % industrial by-product gypsum, 83 % granulated blast furnace slag (GGBFS), and 2 % MgO. Incorporating building gypsum and flue gas desulfurization (FGD) gypsum demonstrates superior unconfined compressive strength (UCS) growth compared to citric gypsum and phosphogypsum. Notably, gel-pores below 20 nm dominate the matrix, with variations in their distribution linked to the gypsum type used. The pH level and crystal structure of the industrial by-product gypsum emerge as pivotal factors dictating the hydration process. The interaction energy between hydrated building gypsum crystal planes and water molecules proves lower, contributing to the root cause of its high sulfate activating capability. Compared to traditional SSC, MgO-based supersulfated cement requires less alkaline activator content and accommodates more industrial by-product gypsums, thus reducing costs, CO2 emissions, and promoting the efficient utilization of these solid wastes.

A Study on the Shrinkage and Compressive Strength of GGBFS and Metakaolin Base Geopolymer under Different NaOH Concentrations.

Geopolymers (GPs) are gaining prominence due to their low carbon emissions and sustainable attributes. However, one challenge with GPs, particularly those made with ground granulated blast furnace slag (GGBFS), is their significant shrinkage during the geopolymerization process, limiting its practical applicability. This study focuses on how the substitution ratio of metakaolin (MK) and the concentration of sodium hydroxide (NaOH) in the activator can influence the shrinkage and strength of a GGBFS-based GP. The experimental approach employed a 3 × 3 parameter matrix, which varied MK substitution ratios (0%, 50%, and 100%) and adjusted the NaOH concentration (6 M, 10 M, and 14 M). The results revealed that increasing MK substitution, particularly with 6 M NaOH activation, reduced the GP shrinkage but also diminished compressive strength, requiring higher NaOH concentrations for strength improvement. Statistical tools, including analysis of variance (ANOVA) and second-order response surface methodology (RSM), were employed for analysis. ANOVA results indicated the significant impacts of both the MK content and NaOH concentration on compressive strength, with no observable interaction. However, the shrinkage exhibited a clear interaction between MK content and NaOH concentration. The RSM model accurately predicted compressive strength and shrinkage, demonstrating a high predictive accuracy, for which the coefficients of determination (R2) were 0.99 and 0.98, respectively. The model provides a reliable method for determining the necessary compressive strength and shrinkage for GGBFS-based GP based on MK substitution and NaOH concentration. Within the optimization range, the RSM model compared with experimental results showed a 6.04% error in compressive strength and 0.77% error in shrinkage for one interpolated parameter set. This study establishes an optimized parameter range ensuring a GP performance that is comparable to or surpassing OPC, with a parameter set achieving a compressive strength of 34.9 MPa and shrinkage of 0.287% at 28 days.

Effect of SF and GGBS on Pore Structure and Transport Properties of Concrete.

Ground Granulated Blast-Furnace Slag (GGBS) and silica fume (SF) are frequently utilized in gel materials to produce environmentally sustainable concrete. The blend of the two components contributes to an enhancement in the pore structure, which, in turn, increases the mechanical strength of the material and the compactness of the pore structure and decreases the permeability, thereby improving the durability of the concrete. In this study, the pore structures of GGBS and SF blends are assessed using Nuclear Magnetic Resonance (NMR) and Mercury Intrusion Porosimetry (MIP) tests. These methodologies provide a comprehensive evaluation of the effect of GGBS and SF on the pore structure of cementitious materials. Results showed that the addition of SF and GGBS reduces the amount of micro-capillary pores (10 < d < 100 nm) and the total pore volume. The results indicate that the transport properties are related to the pore structure. The incorporation of SF reduced the permeability of the concrete by an order of magnitude. The pore distribution and pore composition had a significant effect on the gas permeability. The difference in porosity obtained using the MIP and NMR tests was large due to differences in testing techniques.

Application of various microscopy techniques to study early-age and longer-term behaviour of super sulphated cement microstructure.

Super sulphated cement (SSC) is a very promising substitute for traditional construction materials (i.e. Portland cement), due to its enhanced durability and particularly low environmental impact. This paper explores the microstructure and certain properties of SSC, focusing on the particular complexities of its microstructure and the difficulties of microanalysis of its hydrates. To do so, SSC paste samples were first cast to identify hydration products using X-ray diffraction, then observed at early age using confocal laser scanning microscopy (CLSM) and at early and late age using scanning electron microscopy. In addition, concrete cores impregnated with fluorescein in order to highlight porosity, cracking and aggregates debonding were observed under UV light using optical microscopy (OM), showing a complete absence of cracking and aggregate debonding. Both microscopy techniques (CLSM and UV light OM) have been applied to this type of binder for the first time. The results show that SSC microstructure is characterised by a sophisticated intergrowth of various phases, including ettringite and amorphous calcium-(alumina)-silicate hydrate gels. Finally, Monte-Carlo simulation of electron-matter has been provided for a better understanding of EDS analysis.

Sustainable binary/ternary blended mortars with recycled water treatment sludge using fly ash or blast slag: Characterization and environmental-economical impacts.

Water treatment sludge (WTS) is produced daily and disposed of as hazardous material. It would be advisable to use locally available waste products as supplementary cementitious materials that ensure to be disposed of without harming the environment. As a novelty, this research investigated the potential of using recycled WTS with fly ash (FA) and ground-granulated blast furnace slag (BFS) as ternary blended binders. Thus, it can provide an economical solution and alleviate the adverse environmental effects of excessive production of wastes and cement production. Within this scope, the mortars with 0-30 wt% replacement of cement with modified WTS (MWTS) were produced as binary blend, and also, they were combined with FA/BFS as ternary blended binders. Therefore, optimum utilization of waste products into the mortar in terms of rheological, mechanical, durability, microstructural properties, and environmental-economical aspects was examined. Adding 10% recycled WTS as binary caused higher strengths with lower porosity measured by the mercury intrusion porosimeter test and denser microstructure, as revealed by XRD patterns and SEM results. However, the drawbacks of using recycled WTS, in terms of rheological parameters and environmental-economical aspects, were suppressed by adding FA/BFS with comparable strength values. Specifically, cost, CO2 footprint, and embodied energy were reduced by combining 10% MWTS with FA by 8.87%, 37.88%, and 33.07%, respectively, while 90-day compressive and flexural strength were 5.1% and 5.32% lower. This study developed a feasible solution to use recycled MWTS by obtaining more eco-friendly and cost-effective cement-based materials.

Evaluation of Durability Performance for Chloride Ingress Considering Long-Term Aged GGBFS and FA Concrete and Analysis of the Relationship between Concrete Mixture Characteristic and Passed Charge Using Machine Learning Algorithm.

In this study, accelerated chloride diffusion tests are performed on ordinary Portland cement (OPC), ground granulated blast furnace slag (GGBFS), and fly ash (FA) concretes aged 4-6 years. Passed charge is evaluated according to ASTM-C-1202 for 12 mixtures, considering water-binder (W/B) ratios (0.37, 0.42, and 0.47), GGBFS replacement rates (0%, 30%, 50%), and FA replacement rates (0% and 30%). The effects of aged days on passed charge reduction behavior are quantified through repetitive regression analysis. Among existing machine learning (ML) models, linear, lasso, and ridge models are used to analyze the correlation of aged days and mix properties with passed charge. Passed charge analysis considering long-term age shows a significant variability decrease of passed charge by W/B ratio with increasing age and added admixtures (GGBFS and FA). Furthermore, the higher the water-binder ratio in GGBFS and FA concretes, the greater the decrease in passed charge due to aged days. The ML model-based regression analysis shows high correlation when compressive strength and independent variables are considered together. Future work includes a correlational analysis between mixture properties and chloride ingress durability performance using deep learning models based on the time series properties of evaluation data.

Concreting a sustainable future: A dataset of alkali-activated concrete and its properties.

This data article introduces a dataset comprising 1630 alkali-activated concrete (AAC) mixes, compiled from 106 literature sources. The dataset underwent extensive curation to address feature redundancy, transcription errors, and duplicate data, yielding refined data ready for further data-driven science in the field of AAC, where this effort constitutes a novelty. The carbon footprint associated with each material used in the AAC mixes, as well as the corresponding CO2 footprint of every mix, were approximated using two published articles. Serving as a foundation for future expansions and rigorous data applications, this dataset enables the characterization of AAC properties through machine learning algorithms or as a benchmark for performance comparison among different formulations. In summary, the dataset provides a resource for researchers focusing on AAC and related materials and offers insights into the environmental benefits of substituting traditional Portland concrete with AAC.

Mass GGBFS Concrete Mixed with Recycled Aggregates as Alkali-Active Substances: Workability, Temperature History and Strength.

This study provides the results of an experiment on the possibility of using high-volume ground granulated blast furnace slag (HVGGBFS)-based concrete as mass concrete. In addition to the control concrete, the total weight of the binder was 75% ground granulated blast furnace slag (GGBFS) and 25% ordinary Portland cement (OPC). For the aggregates, both natural and recycled aggregates were used. Three specimens with dimensions of 800 mm × 800 mm × 800 mm were prepared to simulate mass concrete. The workability, temperature aging and strength of the mass concrete were tested. The test results showed that utilizing HVGGBFS concrete as mass concrete can significantly reduce the heat of hydration due to the low heat of hydration of GGBFS, while the heat of hydration of GGBFS and recycled aggregate combination is 11.2% higher than normal concrete, with a slump that is 31.3% lower than that of plain concrete. The results also showed that the use of recycled aggregates in HVGGBFS concrete can significantly reduce workability. However, the compressive strength is higher than when natural aggregates are used due to the alkali activation effect caused by the recycled aggregates. The compressive strength at 7 and 28 days increased by 33.7% and 16.3%, respectively.

The Effects of Partial Replacement of Ground Granulated Blast Furnace Slag by Ground Wood Ash on Alkali-Activated Binder Systems.

Cement production contributes significantly to carbon dioxide emissions. Alkali-activated materials offer an environmentally friendly alternative due to their comparable strength, durability and low-carbon emissions while utilizing wastes and industrial by-products. Wood ash is a waste material that shows promising results as a partial replacement for Portland cement and precursors in alkali-activated systems. The aim of this study was to examine the effect of ground wood ash on the mechanical properties of alkali-activated mortars. Wood ash was incorporated as a 0 wt%, 10 wt% and 20 wt% partial replacement for ground granulated blast furnace slag (GGBFS). The wood ashes were ground in a planetary ball mill for 10 and 20 min. Sodium silicate (Na2SiO3), sodium carbonate (Na2CO3), and sodium hydroxide (NaOH) were used as alkali activators. The results demonstrated that ground wood ash improved the mechanical properties of alkali-activated systems compared to untreated wood ash. However, the incorporation of wood ash increased the porosity of the binder matrix.

The Influence of Blast Furnace Slag on Cement Concrete Road by Microstructure Characterization and Assessment of Physical-Mechanical Resistances at 150/480 Days.

The results presented in this paper on the appropriateness of using of blast furnace slag (BFS) in the composition of roads make an original contribution to the development of sustainable materials with the aim to reduce the carbon footprint and the consumption of natural resources. The novelty of this work consists of determining the optimal percentage of BSF in road concrete, in order to: increase mechanical resistances, reduce contractions in the hardening process, and ensure increased corrosion resistances, even superior to classic cement-based mixtures. Thus, the physical-mechanical characteristics and the microstructure of some road concretes were studied in the laboratory for three different recipes. We kept the same amount of ground granulated blast furnace slag (GGBS) as a substitute for Portland cement, respectively three percentages of 20%, 40%, 60% air-cooled blast furnace slag (ACBFS) and crushed as sand substitute from now on called S54/20, S54/40, S54/60. Drying shrinkage, mechanical resistances, carbonation-induced corrosion, microstructure characterization of hardened concretes, and degree of crystallinity by SEM and XRD measurements were analyzed after a longer curing period of 150/480 days. The obtained results on the three BSF mixtures indicated a reduction of drying shrinkage and implicitly increased the tensile resistance by bending to 150 days well above the level of the blank composition. The degree of crystallinity and the content of the majority phases of the mineralogical compounds, albites, quartz, and tobermorite out of the three BSF samples justifies the increase in the compressive strengths at the age of 480 days in comparison with the test samples. Scanning electron microscope (SEM) and X-ray diffraction measurements showed the highest compactness and lowest portlandite crystal content for the S54/20 slag composite. Future research concerns are the realization of experimental sections in situ, the study of the influence of BFS on the elasticity module of road concrete, and the opportunity to use other green materials that can contribute to the reduction of the carbon footprint, keeping the physical and mechanical properties of road concrete at a high level.

A Comprehensive Study on Non-Proprietary Ultra-High-Performance Concrete Containing Supplementary Cementitious Materials.

Ultra-high performance concrete (UHPC) is a novel cement-based material with exceptional mechanical and durability properties. Silica fume, the primary supplementary cementitious material (SCM) in UHPC, is expensive in North America, so it is often substituted with inexpensive class F fly ash. However, future availability of fly ash is uncertain as the energy industry moves toward renewable energy, which creates an urgent need to find cost-effective and environmentally friendly alternatives to fly ash. This study investigated replacing cement, fly ash, and silica fume in UHPC mixtures with ground granulated blast-furnace slag (GGBFS), metakaolin, and a natural pozzolan (pumicite). To identify acceptable UHPC mixtures (28-day compressive strength greater than 120 MPa), workability, compression, and flexural tests were conducted on all mixtures. Then, durability properties including shrinkage, frost resistance, and chloride ion permeability (rapid chloride permeability and surface resistivity tests) were evaluated for the acceptable UHPC mixtures. Results showed that 75, 100, and 40% of fly ash in the control mixture could be replaced with pumicite, metakaolin, and GGBFS, respectively, while still producing acceptable strengths. Flexural strengths were greater than 14.20 MPa for all mixtures. For durability, UHPC mixtures had shrinkage strains no greater than 406 µstrain, durability factors of at least 105, and "very low" susceptibility to chloride ion penetration, indicating that these SCMs are suitable candidates to completely replace fly ash and partially replace silica fume in non-proprietary UHPC.

Optimisation and environmental impact analysis of green dry mix mortar paving block incorporating high volume recycled waste glass and ground granulated blast furnace slag.

This research incorporates sustainable materials such as ground granulated blast furnace slag (GGBS) and recycled waste glass (RWG) as cement and fine aggregate replacement respectively to produce green dry mix mortar paving blocks. The GGBS and RWG contents in the mortar paving block were optimised using the response surface methodology (RSM), considering the performances of the ultrasonic pulse velocity (UPV), flexural and compressive strengths, water absorption, and Cantabro loss. Life cycle assessment (LCA) was also conducted to evaluate the environmental impact of the optimised green mortar paving blocks. The RSM suggested that the paving block with optimum GGBS and RWG contents of 26.5% and 91.3%, respectively, could exhibit compressive strength of 36.5 MPa, which complied with the requirement for concrete segmental paving units (MA20). Excluding the mixes not fulfilling the MA20 requirement, the mix with 40% GGBS and 100% RWG exhibited the lowest values for the acidification potential (AP), global warming potential (GWP), photochemical oxidation (POCP), abiotic depletion potential for fossil fuel (ADPF), and water scarcity/strength ratio. Whereas, for eutrophication potential (EP) and abiotic depletion for elements (ADP (elements))/strength ratio, the mix with 100% RWG exhibited the lowest value. The optimised mix from RSM showed a similar performance as the two mixes.

In-situ remediation of phosphogypsum in a cement-free pathway: Utilization of ground granulated blast furnace slag and NaOH pretreatment.

In-situ remediating phosphogypsum (PG) for cemented paste backfill (CPB) in the contaminated site is economic management for promoting sustainable developments in the phosphate industry. This study concerns the combined use of NaOH pretreatment and ground-granulated blast furnace slag (GGBFS) additives to promote the solidification/stabilization of PG with a lower carbon footprint pathway. According to physico-chemical analyses, the NaOH pretreatment effectively removed approximately 95% of F within the PG, which may originally be present as sparingly soluble fluorides or coexisting with silicates. The micro mineralogical characterization illustrates that the pretreatment can accelerate the early age hydration, with more hydration products observed, including calcium silicate hydrates and ettringite, effective F and P retention candidates. Whereas the incorporation of GGBFS plays an essential role in promoting the generation of additional cement hydrates at the following stages. The macro mechanical performance analysis indicates that the mixtures of pretreated-PG-OPC-GGBFS exhibit an excellent mechanical performance satisfying the design criteria. Subsequent elemental mapping and toxicity characteristic leaching procedures demonstrate that this combined approach has a competitive F and P immobilization ability compared to the typical OPC binder and individual GGBFS addition. The newly formed phases effectively controlled the concentration of F and P through adsorption, incorporation, or encapsulation. Objectively, the proposed methodology can be a promising candidate pathway for extrapolating the in-situ immobilization of PG. This study opens up new perspectives for synergetically recycling PG and GGBFS in a profitable and low carbon footprint way.

Production of sustainable self-consolidating mortar with low environmental impact.

Reusing industrial by-products and agricultural waste as supplementary cementitious materials for producing sustainable concrete is one of the most promising ways to reduce cement production and the detrimental effects of concrete constructions on the environment. However, when it comes to preparing self-consolidating concrete (SCC) and mortar (SCMO) containing such materials in high volume, bleeding, and segregation of their fresh mixture are the crucial factors hindering their large-scale application. In this regard, the main aim of this study is to address such issues by designing sustainable SCMO using ground granulated blast furnace slag (GGBS) in high volume and rice husk ash (RHA) with comparatively lower environmental impact and high quality. To achieve this goal, the workability of fresh mixture and all its three main characteristics, including segregation resistance, passing ability, and filling ability, were evaluated with recently developed empirical apparatuses. For this purpose, 12 mixtures with different compositions were prepared to investigate the fresh properties, compressive strength, setting time, and environmental impact index. The results indicate that there are inextricable links between mixing proportions, strength, and carbon emissions of the mixture. Sustainable SCMO with an embodied-CO2 index lower than 4.5 kg/MPa.m3, good workability, and compressive strength of 49.7 MPa was designed by optimizing cementitious content, while the e-CO2 index of the control mixture was around 8 kg/MPa.m3. The addition of GGBFS and RHA not only decreased the e-CO2 index but also increased the unit cement strength contribution index. The results also indicated that by increasing GGBFS, the fluidity and segregation of the mixture increased while adding RHA increased viscosity and modified bleeding and the segregation index. Moreover, the growth rate of the compressive strength in mixtures containing GGBFS was much higher than that of the control mix at the same age. The promising results of this experimental study indicate that utilization of GGBFS and RHA in SCMO mixture can provide a practical way to reduce the environmental effects of cement production and pave the way for friendly disposal of slag and waste products.

Experimental Study on the Application of Cementless Material with Industrial By-Products to Steam-Cured Precast Concrete Products.

The purpose of this study was to apply a cementless binder using industrial by-products (fly ash, ground-granulated blast furnace slag, and silica fume) to precast concrete products. In this binder, calcium hydroxide was included as an alkali stimulant but Portland cement was not included. Experiments on the compressive strength and durability of this type of material were conducted and its applicability to precast concrete products was investigated using full-scale specimens. The experiments proved that high-temperature steam curing is effective at obtaining strength development and that compressive strength can be expressed as a linear function of the binder-water ratio. Experimental results of chloride ion diffusion coefficient and sulfuric acid resistance suggested that the proposed material has higher resistances than conventional cement concrete against these deterioration factors. It was also demonstrated that full-scale specimens of a box culvert and a centrifugally compacted pipe using this type of material have almost the same load-bearing capacity and deformation performance as those using conventional cement concrete. It is believed that the proposed material could be used as a construction material instead of cement concrete, contribute to reducing CO2 emission, and increase the reuse of industrial by-products.

Reduction, stabilization, and solidification of Cr(VI) in contaminated soils with a sustainable by-product-based binder.

This study evaluated the use of a sustainable GFD binder for the stabilization/solidification (S/S) of chromium VI (Cr(VI))-contaminated soil. The GFD binder was composed of ground granulated blast furnace slag (GGBFS), fly ash and desulfurization ash, named after the initials of the three materials. The effects of curing time and binder dosage on soil unconfined compressive strength (UCS), Cr leachability, soil pH, and reduction ratio of Cr (VI) were tested. The immobilization mechanisms of Cr(VI) in contaminated soil were further explored using X-ray diffraction (XRD), scanning electron microscopy (SEM), and sequential extraction procedure (SEP). The results showed that the UCS and pH of the soil increased substantially after the GFD binder was added. After 28 days of curing with a 20% binder dosage, the leached total Cr concentration decreased from 34.4 mg/L in the contaminated soil to 1.44 mg/L in the treated soil, and the leached Cr(VI) concentration decreased from 28.0 mg/L to 0.45 mg/L. A Cr(VI) reduction ratio of 96.2% was achieved, indicating the strong reducibility of GGBFS. XRD revealed that the main hydration products of the GFD binder were hydrated calcium silicate (C-S-H) and ettringite. SEM results showed that the formation of hydration products and Cr-bearing precipitates filled the soil pores, resulting in a dense soil structure. The SEP results demonstrated that the levels of the unstable fraction F1 decreased considerably, and that the levels of the stable fractions F3 and F5 increased after treatment. Encapsulation by C-S-H, reduction by sulfides, adsorption of C-S-H, and precipitation of Cr-bearing hydroxides were the main mechanisms involved in Cr immobilization using the GFD binder.

Effect of Magnesium Salt (MgCl2 and MgSO4) on the Microstructures and Properties of Ground Granulated Blast Furnace Slag (GGBFS)-Based Geopolymer.

The use of seawater to prepare geopolymers has attracted significant research attention; however, the ions in seawater considerably influence the properties of the resulting geopolymers. This study investigated the effects of magnesium salts and alkaline solutions on the microstructure and properties of ground-granulated-blast-furnace-slag-based geopolymers. The magnesium salt-free Na2SiO4-activatied geopolymer exhibited a much higher 28 d compressive strength (63.5 MPa) than the salt-free NaOH-activatied geopolymer (31.4 MPa), with the former mainly containing an amorphous phase (C-(A)-S-H gel) and the latter containing numerous crystals. MgCl2·6H2O addition prolonged the setting times and induced halite and Cl-hydrotalcite formation. Moreover, mercury intrusion porosimetry and scanning electron microscopy revealed that the Na2SiO4-activated geopolymer containing 8.5 wt% MgCl2·6H2O exhibited a higher critical pore size (1624 nm) and consequently, a lower 28 d compressive strength (30.1 MPa) and a more loosely bound geopolymer matrix than the salt-free geopolymer. In contrast, MgSO4 addition had less pronounced effects on the setting time, mineral phase, and morphology. The Na2SiO4-activated geopolymer with 9.0 wt% MgSO4 exhibited a compressive strength of 42.8 MPa, also lower than that of the salt-free geopolymer. The results indicate that Cl- is more harmful to the GGBFS-based geopolymer properties and microstructure than SO42- is.

Effects of Admixtures on Energy Consumption in the Process of Ready-Mixed Concrete Mixing.

The production and utilization of concrete and concrete-based products have drastically increased with the surge of construction activities over the last decade, especially in countries such as China and India. Consequently, this has resulted in a corresponding increase in the energy used for the production of ready-mixed concrete. One approach to reduce the cost of concrete manufacturing is to reduce the energy required for the manufacturing process. The main hypothesis of this study is that the power required for mixing the concrete can be reduced through the use of mineral admixtures in the mix design. Optimization of energy consumption during mixing using admixtures in concrete manufacturing is the predominant focus of this article. To achieve this objective, power consumption data were measured and analyzed throughout the concrete mixing process. The power consumption curve is the only source to distinguish the behavior of the different materials used in the concrete in a closed chamber. In the current research, fly ash and ground granulated blast-furnace slag (GGBS) were used as mineral admixtures to produce ready-mixed concrete. The experimental study focused on the influence of GGBS and fly ash on power consumption during concrete mixing. The results indicated that the use of a higher content of GGBS is more beneficial in comparison to the use of fly ash in the mix due to the lower mixing time required to achieve homogeneity in the mixing process. It was found that the amount of energy required for mixing is directly related to the mixing time for the mix to achieve homogeneity.

Nano-Modified Vibrocentrifuged Concrete with Granulated Blast Slag: The Relationship between Mechanical Properties and Micro-Structural Analysis.

Currently, in civil engineering, the relevant direction is to minimize the cost of the manufacture of the hollow structures of annular sections, as well as their construction and installation efficiency. To optimize the costs associated with building products and structures, it is proposed to apply the technology of vibrocentrifugation, to reconsider and comprehensively approach the raw materials for the manufacture of such products and structures. The purpose of this study is a theoretical substantiation and experimental verification with analytical numerical confirmation of the possibility of creating improved variotropic structures of vibrocentrifuged concrete nano-modified with ground granulated blast-furnace slag. The study used the methods of electron microscopy, laser granulometry, and X-ray diffraction. Slag activation was carried out in a planetary ball mill; samples were prepared on a special installation developed by the authors-a vibrocentrifuge. The optimal and effective prescription-technological factors were experimentally derived and confirmed at the microlevel using structural analysis. The mathematical dependencies among the composition, macrostructure, microstructure, and final properties of vibrocentrifuged concrete nano-modified by slag are determined. Empirical relationships were identified to express the variation of some mechanical parameters and identify the relationship between them and the composition of the mixture. The optimal dosage of slag was determined, which is 40%. Increases in strength indicators ranged from 16% to 27, density-3%.