Ground Granulated Blast Furnace Slag Content Research Articles

Early performance and bonding mechanism of metakaolin (MK)- ground granulated blast furnace slag (GGBS) based geopolymer road repair mortar

ABSTRACT Metakaolin (MK) and ground granulated blast furnace slag (GGBS) based geopolymers have been utilised as materials for concrete road repair. However, their early-stage performance and bonding mechanism as rapid repairs are not well understood. This research investigated the workability, early strength development and bonding mechanism of geopolymer repair mortars with different GGBS contents. The reaction kinetics and reaction products of the geopolymer repairs were analyzed through reaction heat evolution and FTIR, and the microstructure of the bonding interface was examined using BSE-EDS. Results showed that geopolymer repair mortars with higher GGBS content exhibited shorter setting times, higher flowability, and higher compressive strength. Geopolymers demonstrated a one-dimensional rod-shaped nucleation pattern during hardening, and the crystallization rate decreased with GGBS addition. GGBS increased the formation of C-A-S-H gels and accelerated the geopolymerization process. However, excessive GGBS reduced bond strength due to the introduction of microcracks. A GGBS content of 60 wt.% is recommended in this investigation. The study also revealed that the cement substrate could absorb alkali activator, leading to the formation of high-Ca gels and strengthening the interface.

Forecasting the compressive strength of GGBFS-based geopolymer concrete via ensemble predictive models

The compressive strength (fc) of the concrete is an important parameter in the structural design. However, the assessment of fc via an experimental program is time-consuming, costly, and needs a labor force. Therefore, the forecasting of fc through different algorithms can accelerate and facilitate this process and also provide guidance for scheduling the progress of the construction. While some studies have explored the use of models for the prediction of fc of concrete, the ensemble models that can predict the fc of GPC with industrial by-products is still lacking. Within this scope, decision tree (DT), Bootstrap aggregating (Bagging), and Least-squares boosting (LSBoost) models were devised to predict fc of ground granulated blast furnace slag (GGBFS)-based geopolymer concrete (GPC). The data points collected to devise a GEP model in the previous study were used and the prediction results of the GEP model were compared with the proposed ensemble models in the current study. The age of the specimen, NaOH solution concentration, natural zeolite (NZ) content, silica fume (SF) content, and GGBFS content were used as input parameters, and fc was used as output parameter. According to ANOVA analysis, the age of the specimen was found as the most influential parameter in the determination of the fc of GGBFS-based GPC. Also, Multiple linear regression equation was proposed to estimate the fc of GGBFS-based GPC with the accuracy of 93%. The most accurate model was introduced through performance metrics and the Taylor diagram. The results proved that the highest accuracy and stable predictions were achieved by the LSBoost model with R-squared value of 98.25% followed by GEP model developed in the previous study, DT and Bagging models. However, it is worth mentioning that due to having a high coefficient of correlation values (>%80), DT and Bagging models also have an acceptable ability for predicting fc of GGBS-based GPC.

Optimisation on the Hybridisation Ratio of Pulverised Fuel Ash and Ground Granulated Blast Furnace Slag (PFA - GGBS) for the Fabrication of Geopolymer Mortar

The current cement industry has several environmental and social problems, including high greenhouse gas emissions, air pollution, water consumption, and the generation of large quantities of waste. This matter has grown into a significant concern, and there is now a pressing requirement to substitute the conventional binding material in concrete, namely Ordinary Portland Cement (OPC). This paper presents the report on the hybridisation of two industrial by-products, namely pulverised fuel ash (PFA) and ground granulated blast furnace slag (GGBS), to produce an alternative binder known as geopolymer. A set of 11 hybrid PFA-GGBS geopolymeric mortar mixes was created using the complete range of hybridisation ratios, along with different water-to-binder ratios. The freshly mixed hybrid PFA-GGBS geopolymeric mortar was put through a flow table test to examine the required water-to-binder ratio to achieve the targeted level of workability. Afterward, all the samples were allowed to cure at room temperature before undergoing a destructive test to measure their compressive strength. According to the study's findings, the highest compressive strength of 4.6 MPa was achieved with a PFA-GGBS hybridisation ratio of 60-40 in the geopolymeric mortar. However, when the content of GGBS exceeded 40 %, the compressive strength of the hybrid PFA-GGBS geopolymeric mortar produced tended to decrease. Additionally, as the replacement level of GGBS increased, the required water-to-binder ratio also increased to maintain the targeted level of workability, ranging between 0.31-0.41. The PFA-GGBS hybridisation ratios of 60/40, 50/50, 40/60, and 30/70 have shown promising properties to be further refined regarding their application in cementless concrete. Moreover, the study conducted to replace cement as a binder in concrete has the potential to make the construction industry more sustainable and reduce carbon emissions by utilising industrial waste ash that would need to be affordable, strong, durable, and widely available in order to be practical.

Developing Geopolymer Concrete by Using Ferronickel Slag and Ground-Granulated Blast-Furnace Slag

Geopolymer concrete is gaining recognition as an environmentally friendly alternative to traditional cement-based materials, offering potential solutions for reducing the carbon emissions of the construction industry. This study aims to develop GGBFS–FNS geopolymers utilising ferronickel slag (FNS) and ground-granulated blast-furnace slag (GGBFS). Ground FNS (GFNS) is a potential candidate for replacing fly ash in geopolymers. This research aims to develop for the first time a GGBFS–FNS alkali-activated concrete. Numerous trials were conducted including different GGBFS–FNS blend percentages, several chemical admixtures and varying activator concentrations to develop the optimal binder mix composition. The effects of different chemical admixtures on the properties of geopolymer pastes, mortars, and concretes were investigated. The study evaluated setting time, compressive strength, shrinkage, and physical and durability properties. The results indicate that conventional admixtures have limited impact on the setting time, while increasing the water/solid ratio and decreasing the GGBFS content could extend the initial and final setting times. The presence of FNS aggregate could improve the compressive strength of geopolymer mortars. The water absorber admixture was highly effective in reducing shrinkage and increasing chloride diffusion resistance. The geopolymer mix containing 50 wt.% GFNS and 50 wt.% GGBFS with the presence of the water absorber admixture presented high chloride diffusion resistance, non-reactivity to the alkali–silica reaction and high sulphate resistance. Overall, the GGBFS–FNS geopolymers exhibited promising potential for engineering applications as an environmentally friendly material, particularly in aggressive environments.

Experimental study on solidification/stabilisation of high-salt sludge by alkali-activated GGBS and MSWI bottom ash cementitious materials

This study utilises alkali-activated ground granulated blast furnace slag (GGBS) as the primary method for solidification/stabilisation, with municipal solid waste incineration (MSWI) bottom ash (BA) as an auxiliary precursor to assist in the solidification/stabilisation (S/S) of high-salt sludge. The results show that the alkali-activated GGBS and MSWI BA cementitious material can effectively realize the S/S of high-salt sludge. However, having early strength of the alkali-activated GGBS solidified sludge at low GGBS content is difficult. In comparison, the addition of MSWI BA enhances the unconfined compressive strength (UCS) of the alkali-activated GGBS solidified sludge to reach 6.35 MPa at 3d curing age, whereas the UCS of the alkali-activated GGBS solidified sludge with 20% GGBS achieves only 0.31 MPa at 14d curing age. The MSWI BA significantly improves the effect of S/S on high-salt sludge by alkali-activated GGBS, and the solidified high-salt sludge with 20% alkali-activated GGBS and MSWI BA cementitious material exhibits good water stability, the UCS of which retain 2.33 MPa after 28d water immersion. The analysis of the mineral composition, chemical bond transformation, thermal stability and microstructure of the solidified sludge samples indicates that the geopolymer cementitious material generated by alkali-activated GGBS and MSWI BA can effectively cement and wrap sludge particles and soluble salts, and reduce the strength loss of the solidified samples after water immersion. Moreover, the addition of MSWI BA accelerates the polymerization of alkali-activated GGBS, leading to rapid solidification/stabilisation of high-salt sludge in early curing age and reduction of the consumption of mineral resources. The heavy metal leaching concentration of the solidified sludge is much lower than that of the raw MSWI BA, and can satisfy the pollution control standard limit of landfill. The immobilization efficiency of the heavy metals of the solidified sludge is larger than 89%. By using MSWI BA as an auxiliary precursor in alkali-activated GGBS, the co-disposal of high-salt sludge and MSWI BA can be achieved, providing insights for realizing the energy conservation and environment protection purposes of solid waste reclamation and GGBS consumption reduction.

Ternary cementless composite based on red mud, ultra-fine fly ash, and GGBS: Synergistic utilization and geopolymerization mechanism

Industrial solid wastes, such as ultra-fine fly ash (RUFA) and ground granulated blast-furnace slag (GGBS), hold tremendous potential for recycling due to their abundance and excellent pozzolanic properties. However, red mud (RM), a highly alkaline waste, has not received comprehensive attention in the construction industry. Thus, this study investigates the synergistic effect and geopolymerization mechanism of industrial solid wastes in ternary cementless composites based on RM, RUFA, and GGBS. The experimental program includes macroscopic comparative analyses of water consumption, fluidity, setting time, permeability, and compressive strength of the ternary cementless composite. Additionally, SEM and EDS analyses examine the microscopic morphology and elemental distribution of the composite. The results indicate that RM prolongs the setting time while reducing fluidity and compressive strength. A 30% increase in RM content led to a substantial rise in the initial and final setting time by approximately 191.6% and 164.7%, respectively. In contrast, GGBS enhances the compressive characteristics of the composite systems but shortens the setting time and reduces fluidity. Notably, Group D4 demonstrates the highest compressive strength, reaching an impressive 47.3 MPa. Moreover, the content of GGBS influences the hydration products in the ternary cementless composite. At low GGBS content, the material contains a significant amount of N-A-S-H gels, whereas at high GGBS content, partial N-A-S-H gels are replaced by C-A-S-H gels. These findings significantly enhance our understanding of the synergistic effect and geopolymerization mechanism of RM, RUFA, and GGBS, thereby facilitating the reuse of these three industrial solid wastes.

Mechanical and durability properties of standard and high strength geopolymer concrete using particle packing theory

Aggregate packing significantly affects the characteristics of fresh and hardened concrete; aggregates having higher packing density (PD) improve these characteristics. There is a lack of research on how the PD affects the properties of geopolymer concrete (GPC). Hence, the present study includes the effect of the PD on the mechanical and durability properties of the standard and high-strength GPC. The study parameters are the binder content, the concentration of NaOH, and the fly ash to ground granulated blast furnace slag (GGBS) ratio. Six aggregate groups (like 12.5–10 mm, 10–4.75 mm, 4.75–2.36 mm, 2.36-1.18 mm, 1.18–0.6, and 0.6–0.15 mm) were investigated for the particle packing experiment, and the blended coarse:fine aggregate ratio of 55:45 which produced the highest packing density of 0.702, were used in the GPC mixes. A total of 120 cubes of size 100 mm, 30 cylinders of size 100 × 200 mm, and 30 prisms of size 100 × 100 × 500 mm were cast for 10 different mixes in the study. Sorptivity and water absorption are the tests performed for the durability studies. The result shows that GPC mixes with Particle packing theory significantly improved the compressive strength, and durability, and showed better workability. The workability of the GPC reduces by increasing the GGBS and concentration of the NaOH solution. As the GGBS proportion and the concentration of the NaOH solution increases, the concrete compressive, split, and flexural strength increases. As the binder content increases, the strength increases at first, then reduces. Increasing the GGBS content, binder content, and molarity of the NaOH accomplishes a reduction of the sorptivity coefficient and water absorption of the GPC.

Bond durability of FRP bars and seawater–sea sand–geopolymer concrete: Coupled effects of seawater immersion and sustained load

Fibre reinforced polymer (FRP)-reinforced seawater–sea sand–geopolymer concrete (SSGC) structures combine the advantages of corrosion-free FRP bars in marine environments and the direct utilization of seawater and sea sand, fly ash, and ground granulated blast furnace slag (GGBS), which can lead to a reduction in carbon emissions and promote sustainable development in civil engineering. This study explores the combined effects of seawater immersion (laboratory condition, ∼26 °C) and sustained load (60% ultimate interface bond strength) on the durability of the interface between FRP bars and SSGC by pull-out tests. The test parameters included FRP bar type and immersion duration (60 and 180 days). River sand and freshwater geopolymer concrete (RSGC) were used for comparison. The properties of the SSGC were also studied to reveal the impact on the interface performance. The results showed that the increase in GGBS content reduced the setting time but was beneficial for improving the compressive strength of the concretes at 28 d due to the large amount of calcium ions contained in the GGBS. The increase in Na2SiO3 content increased N-A-S-H, resulting in a dense cementitious material; compressive strength increased, and the axial ultimate strain of concrete decreased. The long-term performances of SSGC and RSGC in a seawater immersion environment were similar and characterized by reduced strength and enhanced brittleness. The bonding strength between the FRP bar–concrete interface decreased due to the decreased concrete strength under seawater immersion. As the immersion time increased, the fibre fractured under the effects of sustained load, leading to an increase in the bond strength degradation. The bond–slip constitutive model was analysed based on existing models.

Compressibility Behaviour On Carbonation of Ground Granulated Blast Furnace Slag (GGBS) Treated Kaolin

With the growing worry over pollution in the environment, the necessity to comprehend this phenomenon has multiplied. Not only that, the economic gain made in the last decade, along with the fast growth of the world population, has come at a huge environmental cost. One of the never-ending issues is carbon dioxide emission and notably, the construction sector is no exception to mean to contribute through many development activities. Therefore, this study focuses on the compressibility behaviour of Ground Granulated Blast Furnace Slag (GGBS) treated kaolin clay due to carbonation. This study discusses the effect of carbonation on GGBS-treated kaolin as an effort to use sustainable materials which able to improve the geotechnical properties of soil and safe to say, help to reduce the emission of CO2. Testing program via one-dimensional consolidation test found that the compressibility characteristics improved as increased the GGBS content. Overall, the results illustrate that higher GGBS content and longer curing period gives lower compressibility characteristic. It was also found that the carbonated kaolin sample further improve the compressibility characteristics as compared to ambient condition of treated kaolin sample. In conclusion, GGBS can improve the compressibility characteristic of kaolin with carbonation consideration.

AN EXPERIMENTAL STUDY ON GEO-POLYMER CONCRETE INCORPORATING GGBS (GROUND GRANULATED BLAST FURNANCE SLAG) AND METAKAOLIN

The major problem the world is facing today is the environmental pollution. In the construction industry mainly the production of Portland cement will causes the emission of pollutants results in environmental pollution. We can reduce the pollution effect on environment, by increasing the usage of industrial by-products in our construction industry. Geo- polymer concrete is such a one and in the present study, to produce the geo-polymer concrete the Portland cement is fully replaced with GGBS (Ground granulated blast furnace slag) and Metakaolin and alkaline liquids are used for the binding of materials. The alkaline liquids used in this study for the polymerization are the solutions of Sodium hydroxide (NaOH) and sodium silicate (Na2Sio3) of A53 which consists of SiO2 = 29.4%, Na2O = 14.7%, and water = 55.9% by mass is used. 10Molar Sodium hydroxide is taken for the preparation of different mixes by varying the percentages of GGBS (Ground granulated blast furnace slag) and Metakaolin. The cube specimens are taken of size 150mm x 150mm x 150mm for compression test. The curing was done directly by placing the specimens to direct sunlight. The geo- polymer concrete specimens are tested for their compressive strength at the age of 3, 7 and 28days and compared with conventional concrete. For this study M30 concrete mix was used for experimental work. The result shows that there is an increase in the strength of Geopolymer concrete up to 40%GGBS content and then it is decreasing. Therefore it is preferable to use 40%GGBS with Metakaolin to get high strength. Metakaolin and GGBS can be used as a replacement material for cement gives an excellent result in strength aspect and quality aspect since it is better than the control concrete. Key Words: Geopolymer concrete, GGBS, Metakaolin, Alkaline solutions, curing, compressive strength.

CARBONATION PERFORMANCE OF KAOLIN TREATED WITH GROUND GRANULATED BLAST FURNACE SLAG

This study is prompted by the fact that currently available information, regarding carbon dioxide (CO2) and ground improvement, is rather limited, as the emphasis in this area, is mainly directed at health and environmental issues. This includes efforts to counter climate change, by reducing the level of carbon dioxide levels in the atmosphere. Nonetheless, several geotechnical researchers have delved into CO2 sequestration, through magnesium-rich materials. Among such materials is ground granulated blast furnace slag (GGBS). This waste material, which contains between 5% to 9% magnesium, and roughly 35% calcium, appears to be a favourable option for CO2 sequestration. The purpose of this study, is to determine the appropriate optimal amount of GGBS (based on the strength value recommended by the Public Works Department), and its effect in terms of durability, for the treatment of kaolin clay, under ambient and carbonated conditions, with a 24-hour carbonation period, subjected to a CO2 pressure of 200 kPa. Compaction, unconfined compressive strength (UCS), and durability (wetting and drying) tests were performed, with various GGBS contents (5%, 15% and 25%), and curing periods (7, 14, 28 and 60 days). The test results indicate an increase in strength of almost 20 times, for kaolin clay treated with 25% GGBS, with a curing period of 60 days (ambient condition). An additional 22.86% increase in strength was registered, for carbonated conditions. The wetting and drying test, also demonstrated that GGBS-treated kaolin was improved in terms of durability, while retaining its strength under wet and dry conditions. Thus, it can be concluded that with an appropriate amount and curing period, GGBS has the potential to stabilize kaolin clay, and contribute towards the realisation of a more sustainable environment, by curbing the amount of CO2 released into the atmosphere.

Mechanical properties and microstructure of engineered cementitious composites with high volume steel slag and GGBFS

Engineered cementitious composites (ECC) achieve exceptional ductility and durability, but the heavy reliance on cement has notable environmental impacts. In this work, the steel slag (SS) and ground granulated blast furnace slag (GGBFS) are introduced into ECC by largely substituting cement. The impact of SS and GGBFS content on ECC’s mechanical performance is analyzed at macro and micro scales in terms of fiber dispersion, mechanical properties, cracking patterns, cement hydration, and microstructure. The results demonstrate that SS can enhance fiber dispersion due to the low water demand and the strong electronic double layer formed on the surface of SS particles. While ECC with a high volume of SS alone (60 wt% SS) lacks the necessary strength for structural applications, the combination of GGBFS and SS exhibits favorable hydration properties and can effectively refine the pore structure. Thus, ECC with GGBFS and SS attains ideal toughness. ASTM C 1018 based toughness indices reveal that the Imax of ECC with 30 wt% GGBFS and 30 wt% SS is 2.30 times that of OPC based ECC. A sustainability analysis demonstrates that substituting 30 wt% SS and 30 wt% GGBFS for cement leads to a 33% reduction in energy consumption and a 53% decrease in CO2 emissions of ECC.

Desert sand-high calcium fly ash-based alkali-activated mortar: Flowability, mechanical properties, and microscopic analysis

In this study, the reaction mechanism of desert sand-high calcium fly ash-based alkali-activated mortar under different influencing factors has been investigated. Different properties of the developed desert sand-high calcium fly ash-based alkali-activated mortar, such as flowability, compressive and flexural resistance, micro-morphological attributes, and reaction mechanism, were studied for alkali admixture (Na2O/b), sodium silicate modulus, and ground granulated blast-furnace slag (GGBS) content. The results indicate that too low and too high Na2O/b (2%, 10%) and sodium silicate modulus (0.4, 2.0) lead to poor flowability and compressive strength. The compressive strength of the specimens could reach more than 70 MPa for Na2O/b and sodium silicate modulus in the range of 5%–8% and 1.0–1.5, respectively. With the increase in GGBS content, the flowability of the fresh paste continued to decrease, whereas the compressive strength increased. Under the effect of alkali activation, the desert sand was partially dissolved, promoting the formation of C(N)-A-S-H gel to some extent. It is also found in this study that the iron ions in the high calcium fly ash partially dissolved and formed a rice-grain iron-rich gel, effectively filling the matrix pores.

Effects of binder proportion and curing condition on the mechanical characteristics of volcanic ash- and slag-based geopolymer mortars; machine learning integrated experimental study

Contradicting natures of volcanic ash (VA)- and ground granulated blast furnace slag (GGBFS)- based geopolymers with regard to their need for being exposed to a heating source for conducting alkali-reactions make meaningful differences in the strength and flowability of mortars. To address the impacts of types of the geoploymerizing agent, their proportions, and different curing regimes on their strength and shrinkage behavior, three different curing scenarios including curing at room temperature, RT curing; resting under room temperature for various curing periods, and then hydrothermally curing at an elevated temperature for one day, RO curing; and curing in the oven for one day and then resting at the room temperature, for various curing periods, OR curing, are considered. Based on the flowability, setting time, unconfined compressive strength (UCS), and drying shrinkage tests on eight different mixtures, the effects of binder proportion and curing conditions are evaluated. It was observed that with the substitution of 30% VA with GGBFS, specimens cured at RT condition outperformed OR specimens. This threshold was 45% while comparing RT and RO specimens and with higher slag content, RT specimens gain higher UCS. Also, for GGBFS proportion less than 45%, specimens cured at RO conditions showed higher long-term UCS compared to the OR specimens, and this behavior was reversed for higher GGBFS content. Scanning electron microscopy test results indicated that N-A-S-(H) type gel is the dominant geopolymeric gel in VA-based specimens, and as the amount of slag increases, the gels formed change to N-(C)-A-S-H and with further addition of GGBFS, C-A-S-H type gel is the dominant gel which results in strength development in GGBFS-based specimens. Based on the results of 80 UCS and 140 drying shrinkage tests, different machine learning (ML) algorithms and an evolutionary model were employed to present accurate and cost-effective predictive models as useful and capable methods for practitioners and researchers for the preliminary design stages of projects. A comparative study revealed the superior prediction efficiency of the gradient boosting (GB) model with the R2 score of 95% among 8 different ML algorithms and advanced ensemble models. In addition, evolutionary models with the coefficients of determination of 92% and 95% are, respectively, proposed for the drying shrinkage and the UCS. This study advances the field by assessing VA-GGBFS blend and curing effects on geopolymer mortars and developing ML-based models for compressive strength and drying shrinkage, facilitating efficient optimization in practical applications.

Damage evolution, brittleness and solidification mechanism of cement soil and alkali-activated slag soil

Alkali-activated materials are environmentally friendly gelling agents that have been intensively studied in soil solidification over a long period of time. Currently, there is little research on the deformation and damage laws of solidified soils during compression failure. This study investigates the energy dissipation mechanism and plastic damage model of Weibull distribution to explore solidified soil under different curing ages, moduli, and cement, ground granulated blast furnace slag (GGBS), and alkali-activator contents to further explore the damage evolution law and elastic-plastic state of alkali-activated slag soil. The destruction of solidified soil is accompanied by energy dissipation, and the damage to a specimen under load can be expressed as the amount of dissipated energy. In this paper, the change rules of the damage variable (D), total dissipation energy (U), elastic strain energy (Ue), and dissipation energy (Ud) of solidified soil during compression are described in detail, and the damage to the solidified soil is characterized using the dissipation energy ratio (Ud/U) and damage variable. Based on the energy dissipation mechanism, a brittleness index (BI) is established considering the pre-peak elastic-plastic state and post-peak load-bearing capacity loss states. The U, Ue, and BI increase with a decrease in the modulus and increase in the curing age and cement, GGBS, and alkali-activator contents, whereas Ud/U and D decrease. D is linearly proportional to Ud/U. The BI and Ud/U demonstrated an exponential correlation. Finally, the influence of the cement, GGBS, and alkali-activator contents are shown to increase through X-ray diffraction (XRD), thermogravimetry (TG/DTG) and nuclear magnetic resonance (NMR) tests. Additionally, the effects of the cement, GGBS, and alkali-activator contents and alkali-activator modulus on the damage variable and brittleness index are explained from a microscopic point of view. The relationships between porosity and Ud/U, D, and BI are established. This study provides a reference value for the characterization of mechanical properties of solidified soil and the relationship between the pore structure and mechanical indexes.

Impact of hydration stoppage on quantification of the GGBS content in ternary limestone cements using the PONKCS method

Most supplementary cementitious materials (SCMs) are predominantly poorly-crystalline or amorphous. Their reactivity is routinely evaluated through SEM image analysis (SEM/IA), which is a laborious and resource intensive technique. Quantitative X-ray diffraction (QXRD) provides an alternative, facilitating simultaneous evaluation of reaction kinetics and phase assemblages. However, QXRD requires relevant model structures, which are lacking for amorphous phases. In this study, we use the Phases of No Known Crystal Structures (PONKCS) method to model and calibrate ground granulated blast furnace slag (GGBS) and assess robustness in quantifying the GGBS content in synthetic and hydrated ternary blended CEM I-GGBS-limestone cements. Implications of sample preparation, in particular hydration stopping methods on the quantification was measured via the external standard method. Subsequently, the results are compared with SEM/IA calculations, based on backscattered images and magnesium maps. Robustness of the calibrated PONKCS phase is demonstrate with and without hydration stopping. However, X-ray absorption by the cements must be accounted in the attenuation co-efficient calculation. Freeze-drying destroyed water-rich phase assemblages and led to overestimation of the calibrated GGBS phase contents.

An Experimental Study on Partial Replacement of GGBS with Cement and Utilizing Demolished Coarse Aggregate in Concrete

bstract: The majority of municipal solid wastes are made up of debris from construction and demolition projects, including recycled construction aggregate (RCA). This paper presents the findings of an experimental and analytical examination of the creation of environmentally friendly concrete. It is a good idea to replace natural material with aggregate from old, demolished structures to reduce debris and preserve the environment. To reduce consumption, recycled aggregate can be utilized in place of natural aggregate. To address these issues, an attempt is undertaken in the current experimental work to substitute GGBS in varied proportions for cement. The purpose of this research is to demonstrate the findings of an investigation into the applicability of GGBS in the manufacturing of concrete by using construction and demolition debris as a recycled resource. Ground granulated blast furnace slag (GGBS) and recycled concrete aggregates are the recycled materials employed in this study. A concrete mix of grade M25 was created through the mix design process. GGBS was partially replaced with wastedestroyed aggregate in the amounts of 0, 10, 20, 30, and 40% to create the mixes. Cubes of 150x150x150mm3 were poured. The compressive strength of the concrete cube specimens was measured by smashing the cube after 7, 14, 28, 60, and 90 days of curing for various curing intervals. The compression test results on the cubes show that strength increases with the amount of slag added up to the maximum value. Compressive strength was seen to grow when GGBS content increased up to 30%, but after the replacement level was above 30%, strength began to deteriorate. The outcomes of GGBS with conventional concrete and concrete made entirely of demolished aggregate without GGBS are compared to the outcomes of GGBS with concrete containing demolished aggregate

Effects of incorporating polynary SCMs on sulfate resistance and chloride impermeability of concrete considering capillary action in dry-wet cycling environment

The incorporation of supplementary cementitious materials (SCMs) in concrete can improve the properties of concrete partially immersed in salt solution. However, the current partial immersion environment only considers the capillary action above the still water level, does not consider the capillary action above the fluctuating water level in dry-wet cycling environment. In this paper, a series ofindoor exposure experiments were carried out to investigate the effects of incorporating polynary SCMs including fly ash (FA), ground granulated blast furnace slag (GGBFS) and silica fume (SF) on the sulfate resistance and chloride impermeability of concrete considering the capillary action above the fluctuating water level in dry-wet cycling environment. A total of 15 groups of concrete with different mix proportions (total 150 concrete specimens) were designed to study the effects of different replacement levels of polynary SCMs on concrete properties. The effects of incorporating polynary SCMs on the chloride impermeability of concrete above and in the fluctuating water level zone were investigated. The scanning electron microscope (SEM), x-ray diffraction (XRD) and mercury intrusion porosimetry (MIP) tests were used to analyze the microstructure of concrete. The results indicate that when concrete is incorporated with polynary SCMs and subjected to capillary action above the fluctuating water level, the compressive strength and chloride impermeability first increase and then decrease with the increase of FA content; the compressive strength and chloride impermeability decrease with the increase of GGBFS content; the compressive strength first increase and then decrease with the increase of SF content, and the chloride impermeability increase with that. The transport process of chloride in concrete above the fluctuating water level zone includes the longitudinal transport under capillary action and the transverse transport under concentration gradient action. The combined effects of both cause the higher chloride concentration in concrete above the fluctuating water level zone. Comprehensively considering the influence of different mix proportions on the sulfate resistance and chloride impermeability of concrete, it is determined that 20% FA + 5% SF is the optimal replacement level with the excellent performance considering the capillary action above the fluctuating water level in dry-wet cycling environment.

Municipal woody biomass waste ash-based cold-bonded artificial lightweight aggregate produced by one-part alkali-activation method

The rapid industrialization process has resulted in the overconsumption of natural aggregates, leading to significant environmental concerns. Additionally, the disposal of municipal woody biomass ash (MWBA) has caused the depletion of land and further environmental pollution. Hence, production of artificial aggregate using MWBA is of great interest, as it reduces the consumption of natural aggregates and landfill area while recycling the MWBA. The main objective of this study is to determine the optimal mix design that can produce artificial aggregates with satisfactory strength and lightweight properties while maximizing the utilization of MWBA. Following that, the effects of different alkaline contents (9%, 12%, 15%) and ground granulated blast-furnace slag (GGBS) contents (0%, 10%, 20%, 30%) on the physical properties of the MWBA-based AAAs were investigated. Additionally, the pore distribution, phase and elemental compositions of the aggregates were examined to ascertain the mechanism of alkali-activation and strength development of the MWBA-based AAAs. The main result showed that at 15% Na2SiO3·5H2O content, increasing the GGBS content from 0% to 30% resulted in an increase in the loose bulk density and crushing strength of MWBA-based AAAs from 817 kg/m3 to 950 kg/m3 and from 0.84 MPa to 2.25 MPa, respectively, while decreasing the water absorption from 24.0% to 12.5%. This is due to the denser matrix observed, attributed to the GGBS addition, which enhances the effect of alkali-activation. Additionally, a new amorphous phase, namely C-A-S-H, was identified. The Si/Al ratio decreased with the GGBS content, resulting in more C-A-S-H gel formation and a denser microstructure with better performance for the AAAs. The novelty of this study is to demonstrate the feasibility of using MWBA in producing AAAs through a cold-bonded one-part alkali activation method. This method presents an alternative to natural aggregates that can be utilized in concrete.

Carbonation resistance of calcined clay-ground granulated blast furnace slag alkali-activated mortar

Alkali-activated materials are obtained from the alkaline activation of a precursor rich in SiO2 and Al2O3, which can be derived from by-products or industrial residues. Calcined clay is a potential candidate as a precursor for this type of material. Large amounts of suitable clays for alkali-activated materials are available around the world. This paper evaluated the performance of different alkaline-activated mortars using calcined clays (low grade) and ground-granulated blast-furnace slag (GGBFS), including physical and mechanical performance, reaction products phases, microstructure, and resistance to accelerated carbonation. The results indicate that the increase in GGBFS content up to 60% has a significant effect on the properties of the mortars, due to the effect of Ca-rich phases such as C-(A)-S-H/C-(N)-A-S-H, promoting the densification of the microstructure, and an increase in pH from 11.91 to 12.78 for specimens with 100% calcined clay and 60% GGBFS respectively, leading to a better carbonation resistance. On the other hand, adding GGBFS leads to a reduction in concrete initial and final setting time and lowers thermal stability compared to the reference calcined clay material. The increase in the modulus ratio of the activator from 1 to 1.5 also improves the mechanical properties and resistance to carbonation of geopolymer mortars with various binder compositions.