Ground Granulated Blast Furnace Slag Content Research Articles

Long-term carbon dioxide sequestration by concretes with supplementary cementitious materials under indoor and outdoor exposure: Assessment as per a standardized model

An experimental study was carried out on concretes designed with an ordinary Portland cement (CEM I 52.5 N), blended cements containing 23 wt% fly ash (CEM II/B-V 32.5 R) or 82 wt% ground granulated blast-furnace slag (CEM III/C 32.5 N), and partial substitutions of CEM I with fly ash (30 wt%) or ground granulated blast-furnace slag (30 and 75 wt%). Measurements were carried out on Ø11X22 cm specimens after 10.8 years of exposure, under indoor and outdoor exposure, to determine their carbonation rates and degrees of carbonation. The objective was to compare CO2 uptake calculated with the parameters measured experimentally to that calculated with parameters defined by a standardized model commonly used by construction engineering (EN 16757 model). The comparison showed that the model: (i) underestimates the carbonation rate (up to 61%), (ii) underestimates the degree of carbonation under indoor exposure (up to 49%) and overestimates it under outdoor exposure (up to 78%), and (iii) considerably underestimates the maximum theoretical CO2 uptake (up to 77%) for high ground granulated blast-furnace slag content. Consequently, the model underestimates the CO2 uptake under indoor exposure (up to 86%). However, the comparison showed a better correlation under outdoor exposure. Based on these results, some adjustments to the parameters defined by the standardized model were suggested to better account for effects of exposure conditions and supplementary cementitious materials, which should improve the CO2 uptake assessment.

Improvement of two-component grouts by the use of ground granulated blast furnace slag

This work investigated the impact of a partial replacement of ordinary Portland cement (OPC) by ground granulated blast-furnace slag (GGBS) in two-component grouts. Maximum GGBS content reached 50 %wt of the binder. Fluidity, open time, bleeding behaviour, gel time, compressive strength development and durability with respect to sodium sulfate were assessed. The impact of a variation of the volumetric ratio between the grout base and the accelerator (components A and B) was also considered. The results showed that increasing GGBS content led to multiple benefits of grouts behaviour. At fresh state, the bleeding was limited without decreasing the flowability. At hardened state, it increased the 28-day compressive strength, and improved the durability of the grouts in water/sodium sulfate solutions when used at 16% of the binder mass (mix designs based on jobsite trials).

Validation of slag-binder fiber-reinforced self-compacting concrete with slag aggregate under field conditions: Durability and real strength development

The environmental conditions to which a concrete may be exposed will condition its real range of use. Thus, concrete behavior must, at all times, be verified under a wide variety of environmental conditions, in order to ensure its real applicability. In this study, the real strength development and durability behavior of a fiber-reinforced self-compacting concrete is analyzed. This particular concrete incorporates 100% coarse (4/12 mm) and fine (0/4 mm) Electric Arc Furnace Slag (EAFS) as aggregate, as well as limestone fines as aggregate powder (0/1.18 mm). Furthermore, Ground Granulated Blast Furnace Slag (GGBFS) was also added as binder. Four mixtures with and without either metallic or synthetic fibers, and different GGBFS contents were designed. Real strength development was evaluated in all the mixes by comparing the strength development of both cores extracted from full-scale beams and wet-cured laboratory specimens. The durability behavior was analyzed by Mercury Intrusion Porosimetry (MIP), freeze/thaw, moist/dry, sulfate-attack, chloride-penetration, carbonation, and SO2-attack tests. On the one hand, the long-term mechanical properties of the cores (real conditions) were similar to the properties of the specimens cured in a moist chamber for 90 days in all the mixes. On the other, the increase in water content when adding fibers to maintain flowability, as well as the addition of GGBFS, resulted in an increase in MIP porosity. Therefore, the use of fibers, both metallic and synthetic, slightly worsened the durability behavior of the concrete, facilitating the entry of aggressive external agents. Nevertheless, the increased flexibility of the cementitious matrix when adding GGBFS was beneficial against moist/dry and sulfate-attack phenomena, despite the increase in porosity. Overall, the mixes complied with the regulatory requirements for use in aggressive environments, although the amounts of fibers and GGBFS should be carefully studied.

Optimum Calcination Condition of Waste Stabilized Adobe for Alkali Activated High Volume Adobe-Slag Binder Cured at Room Temperature

This study aims to determine the most convenient calcination temperature and calcination duration of waste-stabilized Adobe (AB) to produce a new alkali-activated binder. Waste-stabilized Adobe mainly consists of soil, CaCO3 as a stabilizer, and straw (for strengthening). The availability of raw materials for making Adobe presents the waste-stabilized Adobe as a potential product for a new alkali-activated binder. Waste-stabilized Adobe collected from an abandoned damaged building in the village of Inonu in Northern Cyprus, ground and calcined at the following temperatures: 450, 550, 650, 750, 850, and 950°C. The calcination at each temperature was held for different durations 1, 3, 5, and 7 h. Raw and calcined waste stabilized Adobe structures were investigated using XRF, TGA-DTA, XRD, FTIR, and SEM. Considering technical and environmental views related to energy consumption, waste stabilized Adobe calcined at 750°C for 1 h presented the most promising results regarding the production of a new precursor for alkali-activated binder. This study also presents the effect of ground granulated blast furnace slag (GGBFS) usage on the fresh and hardened properties of optimum calcined AB-based alkali-activated pastes cured at room temperature. GGBFS was used to partially replace AB to form a binary composite raw material system and seven experimental groups were designed according to replacement levels of 0%, 5%, 10%, 15%, 20%, 25% and 30% (by mass). Alkali-activated high volume waste-stabilized Adobe-slag pastes prepared using Na2SiO3-to-NaOH ratio of 2 and 12 M concentration of Sodium Hydroxide. The fresh property as flowability and the hardened property as the compressive strength of the alkali-activated pastes with different GGBFS contents were investigated. The results indicated that the incorporation of GGBFS increased the flowability of fresh alkali-activated pastes. A 28-day compressive strength of 43.75 MPa can be obtained by a 30% replacement level of GGBFS.

A comparative study of normal and self-compacting geopolymer mortar and its strength prediction using tensor flow approach

One of the looming sustainable technology in the construction industry is geopolymer composites. Experimental and machine learning approach has been used for the study of fly ash – ground granulated blast furnace slag (GGBFS) based geopolymer mortar with ambient curing condition. Fresh properties of geopolymer mortar and self-compacting geopolymer mortar including setting time and workability characteristics have been studied. Harden property (compressive strength, split tensile strength, flexural strength) and durability studies (shrinkage, acid resistance, sulphate resistance, salt resistance, water absorption) are also conducted for selected geopolymer mixes. Self-compacting geopolymer mortar shows high workability and increased setting time than normal geopolymer mortar. But in the hardened property as well as in durability tests normal geopolymer mortar shows better performance.Geopolymer mortar required a standard framework for mix design due to its complexity of different parameters such as water to solid ratio, alkali activators to binder ratio, sodium silicate solution to sodium hydroxide solution ratio etc. A multilayer ANN architecture is used for an effective prediction of compressive strength. Most of the research works were based on regression algorithms. The present study utilized the tensor flow approach developed by Google for the prediction of compressive strength. For training 150 data from different journal papers were used and the data generated by the authors experimentally in the lab is used for validation. Input independent variables considered in the proposed model were fly ash and GGBFS content, the molarity of sodium hydroxide solution, sodium silicate to sodium hydroxide ratio, and alkaline solution to binder ratio, fine aggregate to binder ratio. Compressive strength was considered as the output dependent variable. Model accuracy is checked quantitatively checked and obtained 3.6 MPa as Root mean squared error, 2.6 MPa as Mean absolute error, 8.09 % as Mean absolute percentage error and 0.6 as Root mean squared error.

Influence of chloride ions on strength and microstructure of geopolymer concrete containing fly ash, and blend of fly ash-GGBS

Chloride attack is an important aspect in long-term mechanical and durability performance of geopolymer concrete (GPC) in marine environment. Keeping this in view, in this study, the effect of chloride ions on compressive strength at different ages were investigated, as well as the microstructural changes in terms of molar ratio and morphology of GPC mixes. Two types of GPC mixes were prepared; the first one using 100% fly ash (FAGPC), developed under elevated curing temperature at 80 °C for 48 h, and the other one using a blend of 85% fly ash and 15% ground granulated blast furnace slag (GGBS) (FASGPC), developed under ambient condition. To investigate the effect of chloride ions, sodium chloride (NaCl) was added at 0%, 1.5%, and 3.5% by mass of geopolymer solids during the preparation of GPC mixes. From the test results, it is observed that the FASGPC exhibited lower strength as compared to FAGPC at the early age (7 days) due to lower extent of geopolymerization reaction under ambient condition. However, at later age (360 days), FASGPC showed higher strength as compared to FAGPC. The chloride added GPC mixes exhibited lower strength as compared to control GPC mixes. Furthermore, the FAGPC mixes with added chloride exhibited a higher decrease in strength when compared to FASGPC mixes at both ages. The percentage increase in strength with increase in age (i.e., from 7 to 360 days) was in the range of 106.5% to 110.5%, and 45% to 70.4% for FASGPC, and FAGPC mixes respectively, at all chloride concentrations. The obtained FESEM images indicated the formation of geopolymer gels in the GPC mixes. Furthermore, the variations in strength of GPC mixes with GGBS content and age are in line with the variations in atomic Al/Si and Ca/Si ratios obtained from the EDS analysis.

Behaviour of Fly ash and GGBS based Monoblock Prestressed Geopolymer Concrete Composite sleepers

In railways, Prestressed concrete is generally adopted for the design of railway sleepers as the material behaves in a ductile manner within certain stress limits in addition to the benefits of having the reduced size of the member. Monoblock Prestressed Concrete (PSC) sleepers because of its enormous use demands a huge amount of cement and this factor is of vast economic importance in the railway infrastructure. Considering the environmental threats resulted due to the manufacturing of cement, activation of materials consisting of SiO2 and Al2O3 in an alkaline medium is considered as an interesting alternative to produce cementitious materials. The likelihood of utilizing fly ash and Ground Granulated Blast Furnace Slag (GGBS) for manufacturing Monoblock Prestressed geopolymer concrete sleepers as per the specifications of Indian Railway Standard (IRS) Specification for sleepers without using cement was explored. Four trial mixes were used by varying the fly ash and GGBS contents for example 90% and 10% (F90 G10), 80% and 20% (F80 G20), 70% and 30% (F70 G30) and 60% and 40% (F60 G40) for evaluating the strength properties like Strength under compression, Split tensile strength and strength under flexure. Through test results, it was found that strength is proportional to the quantity of GGBS used in the mixes. Two sleepers were cast using the mix F70G30 and the static bending strength tests were conducted on the pretensioned geopolymer concrete sleepers. Moment of resistance (MR) test and Moment of Failure (MF) tests were carried out for Centre Top and rail seat bottom loading conditions. From the strength tests conducted on sleepers, it can be concluded that the sleepers cast using the alkali activation process of GGBS and cement without cement can meet the requirements of IRS Specifications for Pretensioned sleepers and fly ash and GGBS could be considered as a sustainable substitute material for cement for sleepers.

Study on fresh and mechanical properties for different grades of geopolymer concrete with recycled coarse aggregate

In the construction industry, recycled coarse aggregate (RCA) and geopolymer concrete (GC) are been identified as the two main sustainable components to overcome the disposal of construction waste and by-product waste in landfills. These components are also involved to overcome the consumption of ordinary Portland cement and natural aggregates, and the use of dismantled waste in the concrete. The waste material like low calcium fly ash, ground granulated blast furnace slag (GGBS), and RCA were used to develop sustainable GC. In the present study, Natural coarse aggregate (NCA) is partially replaced with 25% RCA to study the different grades (i.e., M20, M30, M40, M50, and M60) of RCA-based geopolymer concrete (RCAGC). Based on several trials, the optimum dosage of GGBS has been replaced with LCF for developing the workability, compressive strength, splitting tensile strength, flexural strength, and compared with limiting values of conventional concrete as per IS code for each grade of RCAGC. Sodium hydroxide (NaOH) and Sodium silicate (Na2SiO3) are used as alkaline liquids to prepare RCAGC. Sodium hydroxide of 8 M, alkaline liquid to binder ratio of 0.5 were used and cured in ambient curing for 7 days and 28 days respectively. It was observed from the results that, as the amount of GGBS content increased, for each grade of RCAGC the workability gradually decreased with an increase in compressive strength. RCAGC achieved 80–85% of compressive strength within 7 days of ambient curing. Splitting tensile and flexural strength tests have been satisfactory as per Indian standards. A polynomial relationship is obtained between the mechanical properties of RCAGC and the limiting values of conventional concrete. RCAGC grades utilize by-products along with recycling coarse aggregate is an effective way in dealing with environmental crises.

A study on the mechanical properties of alkali activated ground granulated blast furnace slag and fly ash concrete

Alkali activated concrete (AAC) is one concrete which is made without cement. As sustainable construction is gaining interest, this alkali activated concrete is a better option for conventional cement concrete. Concrete is the most used commodity second only to water with a global Carbon emission of 5%. The evaluation of strength under compression of alkali activated fly ash and ground granulated blast furnace slag concrete, was carried out in this study. The evaluation of compressive strength depending on the method of curing is also studied. In this study Ground Granulated Blast Furnace Slag (GGBFS) and fly ash are used as the pre-cursor materials. These two materials are used in varying proportions and are activated using sodium hydroxide and sodium silicate solutions of varying proportions, after which the strength properties of alkali activated concrete are studied under two methods of curing i.e., water curing and ambient temperature curing. When the results obtained for water curing and curing at ambient temperature were compared the later yields good results. So, the curing at ambient temperature can be preferred over water curing. When GGBFS alone was used as a pre-cursor material the results show higher compressive strength can be achieved in comparison to the specimens having both GGBFS and Fly ash as pre-cursor materials. With increasing proportions of fly ash and decreased GGBFS content, the decrease in compressive strength was witnessed. Also, the specimens kept under water curing and the specimens cured under ambient temperature are compared and found that the later yields higher compressive strength.

Improved strength development and frost resistance of Portland cement ground-granulated blast furnace slag binary binder cured at 0 °C with the addition of calcium silicate hydrate seeds

Low ambient temperatures drastically decelerate the strength development of cementitious materials, which shortens the construction season in cold regions. The use of ground-granulated blast furnace slag (GGBFS) in concreting works is usually avoided in winter because of its slower hydration rate relative to Portland cement (PC). In this study, the impacts of calcium silicate hydrate (C-S-H) seeds on the strength development and reaction rate of PC/GGBFS binders cured at 0 °C were investigated. The results showed that the addition of C-S-H seeds can efficiently compensate for the strength loss caused by replacing PC with GGBFS, and this effect is more obvious at a lower GGBFS content (30%) than at a high content (50%). Better frost resistance was gained in the seeded binder containing 30% GGBFS than in the pure PC binder. The enhanced compressive strength and frost resistance in the seeded binary binder were attributed to the accelerated PC reaction rate, enhanced pozzolanic reaction rate and degree of GGBFS, and increased amount of pore-filling hydration products due to the nucleation effect of the C-S-H seeds.

Investigation of ANN architecture for predicting the compressive strength of concrete containing GGBFS.

An extensive simulation program is used in this study to discover the best ANN model for predicting the compressive strength of concrete containing Ground Granulated Blast Furnace Slag (GGBFS). To accomplish this purpose, an experimental database of 595 samples is compiled from the literature and utilized to find the best ANN architecture. The cement content, water content, coarse aggregate content, fine aggregate content, GGBFS content, carboxylic type hyper plasticizing content, superplasticizer content, and testing age are the eight inputs in this database. As a result, the optimal selection of the ANN design is carried out and evaluated using conventional statistical metrics. The results demonstrate that utilizing the best architecture [8–14–4–1] among the 240 investigated architectures, and the best ANN model, is a very efficient predictor of the compressive strength of concrete using GGBFS, with a maximum R2 value of 0.968 on the training part and 0.965 on the testing part. Furthermore, a sensitivity analysis is performed over 500 Monte Carlo simulations using the best ANN model to determine the reliability of ANN model in predicting the compressive strength of concrete. The findings of this research may make it easier and more efficient to apply the ANN model to many civil engineering challenges.

Effects of waste glass sand on the thermal behavior and strength of fly ash and GGBS based alkali activated mortar exposed to elevated temperature

This study investigated the thermal behavior of a series of alkali activated mortars (AAm) based on blends of fly ash (FA) and ground granulated blast furnace slag (GGBS) precursors with waste glass (WG) and natural sand (NS) as fine aggregate. Results revealed that with increasing GGBS content, the AAms deteriorate after exposure to elevated temperature owing to dehydration causing mass loss, and weakening binder- aggregate bonding, which in turn decreased residual compressive strength. The efficacy of WG on the thermal behavior and mechanical strength depends on the binder type as well as on the temperature to which the AAms were exposed. In FA rich AAms, increasing WG showed good resistance to elevated temperature (200 –800 °C). Increasing WG in GGBS rich AAms, only showed acceptable performance for AAms exposed to 600 °C and 800 °C as the melted WG formed strong bonds with the matrix. However, for samples with 100 wt% WG and 100 wt% GGBS, surface spalling occurred at 200 °C, 400 °C and 600 °C and explosive spalling at 800 °C mainly caused by the high stresses induced on the expansion of both WG and matrix during exposure to elevated temperature.

Compressive Strength of Ternary Blended Geopolymer Concrete Composites

Use of industrial wastes as supplementary concreting materials in the manufacturing of concrete is very vital at present to obtain a sustainable environmental solution. Some of the commonly used pozzolanic materials are Fly ash, Ground Granulated Blast Furnace Slag (GGBS), Silica Fume and Rice Husk Ash (RHA) etc. In the present experimental investigation, the compressive strength property of ternary blended geopolymer concrete has been studied by considering Fly ash, Ground Granulated blast furnace slag (GGBS) and Rice Hush Ash (RHA) in various percentages as source materials for geopolymerisation. The source materials were activated with alkaline activators consisting of a combination of Sodium Hydroxide (NaOH) & Sodium Silicate (Na2SiO3) solutions with the concentration of NaOH being 10 molarity (10M). For various combinations of Fly ash, Rice Husk ash and GGBS the compressive strength for 7 days and 28 days were determined experimentally. From the test results, it has been found that as the GGBS content increases, the compressive strength of the concrete also increases whereas, as the content of RHA increases, the density and compressive strength of the concrete decreases. The optimum combination was found to be F60 G30 R10 and F70 G20 R10 for which the compressive strength of the concrete is 34.67 MPa and 24.87 MPa which can be used in applications where M30 and M20 grades of concrete are required. The density of F60 G30 R10 GPC is 2320 kg/m3 which is lesser than conventional concrete. It is also found that usage of 90% of rice husk ash in geopolymer concrete is not at all effective. The obtained compressive strengths are in the range of 10 MPa to 34.0 MPa which depends on the ratio of GGBS to RHA. Proper consumption of the RHA contributes in solving the environmental pollution and also to improve the environmental friendliness of concrete to make it suitable as a green building material.

GGBS Use in Concrete as Cement Constituent: Strength Development and Sustainability Effects – Part 1

This study, third in the series, following from ground limestone and Class F fly ash, evaluates, as a cement constituent, the effect of using ground granulated blast furnace slag (GGBS) on the strength development of concrete, and consequently its embodied carbon dioxide (CO2e). The paper has been built from systematically analysing, evaluating and modelling the extensive data-matrix developed, having 85,099 data points, from the information sourced from 663 studies published in English, during 1974 to 2020, by 1,672 authors, working in 718 institutions in 49 countries, globally. It is shown that, at a given water/cement ratio, in comparison to Portland cement (PC), the use of GGBS results in a reduction in 28-day concrete strength, which increases with GGBS content, at a rate determined by the strength of concrete, GGBS fineness, and curing of concrete. It is also shown that, as to achieve a 28-day design strength, a lower water/cement ratio is required with a PC/GGBS blended cement than PC, this will reduce the actual CO2e savings that can be realised with the use of GGBS as cement constituent in manufacturing concrete. Finally, it is shown that GGBS is more effective in lowering CO2e of concrete than FA and GLS.

Development of optimized binary ceramic tile and concrete wastes geopolymer binders for in-situ applications

This study explored the development of an optimized binary geopolymer system of ceramic tile waste (CTW) and concrete waste (CW) for more sustainable use in in-situ applications. The geopolymer binders were synthesized based on a physico-chemical method of different CTW and CW combinations, between 20% and 80%, predetermined liquid-to-solid (L/S) and chemical parameters of SiO2/Al2O3 and Na2O/SiO2 ratios, while using curing at room temperature. The flow spread diameters, setting times, compressive strengths and microstructural investigations of binary compositions were performed at various CTW and CW contents and preselected oxide values. Meanwhile, the effect of short-term elevated temperatures on the optimum strength combinations was also considered under 50 °C, 75 °C, and 100 °C. Moreover, further optimization was tried at ambient curing by incorporating supplementary cementitious materials (SCM) in ternary CTW-CW-SCM compositions including 15%, 30% and 45% of metakaolin (MK), ground granulated blast furnace slag (GGBS), Class C fly ash (FC) and Class F fly ash (FF). X-ray diffraction (XRD), scanning electron microscopy (SEM) and Fourier transformed infrared spectroscopy (FTIR) were performed to investigate the effect of the mentioned parameters on geopolymer formations. The results indicate that the optimum binary CTW + CW composition can be reached at 40% CTW + 60% CW and SiO2/Al2O3 and Na2O/SiO2 of 12.3 and 0.18, respectively. Adding 45% GGBS content in ternary mixtures helped attain very high strength binders of more than 100 MPa at normal conditions. Along with the designed physical and chemical ratios, the amount of Ca2+ played a dominant role in enhancing the degree of geopolymerization and the properties of C-A-S-H/C-S-H and N-A-S-H reaction products.

Microstructure and shrinkage behavior of high-performance concrete containing supplementary cementitious materials

This paper investigated the influence of supplementary cementitious materials (SCM, including fly ash (FA), ground granulated blast-furnace slag (GGBS), metakaolin (MK)) on the microstructure and shrinkage behavior of high-performance concrete (HPC). The prediction accuracy of some typical shrinkage models and the correction factor kSCM were evaluated with statistical parameters RE and R2new. After analysis of shrinkage models, the kSCM*B4 model and kSCM*CEB were more suitable for the drying shrinkage and autogenous shrinkage of HPC, respectively. Although the activities of FA, GGBS, and MK were different, SCM were helpful to form a dense interfacial transition zone (ITZ) microstructure. To analyze comprehensively the effect of single or binary addition of SCM on its shrinkage properties, XRD, SEM, slump and compressive strength experiments of HPC were carried out. The diffraction peaks of Ca(OH)2 decreased with the content of FA and GGBS. The setting time of HPC was prolonged with the content of SCM. Both the decrease of FA and the increase of GGBS and MK could enhance the compressive strength of HPC. Drying shrinkage decreased with the content of FA, GGBS, and MK thanks to the refined microstructure with SCM. Autogenous shrinkage decreased remarkably with the content of FA and GGBS, however, that of MK was opposite. For the same total content of SCM, effects of binary addition of FA and MK, FA, and GGBS on the shrinkage behavior of HPC were more markedly than that of single FA. The drying shrinkage of HPC with single MK was slightly less than that with single GGBS, however, the autogenous shrinkage of HPC with single MK was significantly more than that with single GGBS.

Utilization of Blast-Furnace Slag as a Standalone Stabilizer for High Sulfate-Bearing Soils

This paper presents experimental results and analysis of sulfate-bearing soils treated with ground granulated blast-furnace slag (GGBS). The experiments involve the unconfined compression strength test, shrinkage, free swelling, suction measurements, and microstructural examination. Short- and long-term swelling tests were conducted to inspect the durability of GGBS stabilization against the sulfate-induced heave. The concept of the shrinkage curve was employed to elucidate how GGBS stabilization alleviates soil shrinkage behavior and alters the pore size distribution. The results manifested that 7% GGBS was sufficiently adequate to improve the 28-day strength of the tested sulfate-bearing soils about five times. The GGBS treatment mainly results in the decline of calcium sulfate content and the formation of calcium silicate hydrate, ettringite, and calcite. The results of long-term swelling tests indicated a delayed sulfate-induced heave that started beyond a month from the time of exposing the treated soils to water. The delayed heave was still not significant as compared with that of the untreated control soil specimens. Accordingly, it is recommended that the treated sulfate-bearing soils are tested with the selected GGBS content for any delayed swelling before application in the field. The GGBS treatment has significantly escalated suction magnitude during curing mainly due to the consumption of water in the hydration process and the formation of ettringite.

Utilization of Corn Cob Ash as Fine Aggregate and Ground Granulated Blast Furnace Slag as Cementitious Material in Concrete

Cementitious and recycled materials that have the potential to improve various properties of concrete have attracted the attention of many researchers recently. Different types of cementitious and recycled materials seem to possess certain unique properties to change cement concrete. This experimental study aims to investigate the impact of ground granulated blast furnace slag (GGBFS) and corn cob ash (CCA) as a partial replacement material for Portland cement (PC) and fine aggregate (FA), respectively, on fresh and hardened concrete properties, as well as the embodied carbon of concrete. The concrete mix was blended with 5–20% of GGBFS and 10–40% of corn cob ash, both individually and combined. A total of 300 concrete specimens were made to achieve the targeted strength of 25 MPa at a 0.50 water/cement ratio and cured at 28 days. It is observed that the workability of fresh concrete is lowered as the dosages of GGBFS and CCA increase in the mixture. Moreover, the compressive and split tensile strengths are augmented by 10.94% and 9.15%, respectively, at 10% of GGBFS by the weight of PC at 28 days. Similarly, the compressive and split tensile strengths are augmented by 11.62% and 10.56%, respectively, at 30% of CCA by the weight of FA at 28 days. Moreover, the combined use of 10% of GGBFS as a cementitious ingredient along with 30% of fine aggregate replaced with CCA in concrete provides the highest compressive and splitting tensile strength, with 16.98% and 13.38% at 28 days, respectively. Furthermore, the density and water absorption of concrete were reduced with increasing dosages of GGBFS and FA in concrete at 28 days. In addition, the embodied carbon and energy were also reduced as the replacement content of GGBFS along with CCA increased in concrete. It is concluded that 10% of GGBFS and 30% of CCA are the optimum percentages for structural applications to reduce the use of cement as well as the cost of the project.

Carbonated ground granulated blast furnace slag stabilising brown kaolin.

Proposals have been made by several researchers to conduct the sequestration of carbon dioxide (CO2) through calcium and magnesium-rich materials. From these materials, ground granulated blast furnace slag (GGBS) containing 5% magnesium and 45% calcium is seen to be a good candidate and is available to sequester CO2. This study intends to ascertain the ability to absorb CO2, sequester it, and increase treated kaolin strength with different content of GGBS under various carbonation periods with varying CO2 pressure. The impacts of carbonated GGBS on the mechanical attributes of soil were examined by conducting the unconfined compressive strength (UCS) test, and microstructure analysis was conducted to identify the changes in the structure and Crestline phase. Stationary carbonation in a triaxial test with pure CO2 was conducted to accelerate the carbonation process. The outcome indicates that the strength rises as the carbonation period rises. Likewise, UCS rises as the CO2 pressure rises from 100 to 200 kPa. It could be concluded that augmentation of the strength is because of carbonated calcium and magnesium products which stuff the soil voids. Changes occur on the microstructure level due to carbonation as well.

Effect of GGBFS on Workability and Strength of Alkali-activated Geopolymer Concrete

This paper focuses on the development of a concrete material by utilizing fly ash and blast furnace slag in conjunction with coarse and fine aggregates with an aim to reduce pollution and eliminate the use of energy extensive binding material like cement. Alternative binding materials have been tried with an aim to get rather an improved concrete material. Alkali-Activated Solution (AAS) made of the hydroxide and silicate solutions of sodium was adopted as the liquid binder whereas, Class F” fly ash and Ground Granulated Blast Furnace Slag (GGBFS) mixed in dry state were used as the Geopolymer Solid Binder (GSB). The liquid binder was used to synthesize the solid binder by thermal curing. The paper investigates the use, influence and relative quantities of the liquid and solid binders in the development of the alkali-activated GGBFS based Geopolymer Concrete (GPC). Varying ratios of AAS to GSB were taken to assess their optimum content. Further, different percentages of GGBFS were used as a partial replacement of Class F fly ash to determine the optimum replacement of GGBFS in the GPC. In order to assess their effects on various properties test samples of cubes, cylinders and beams were cast and tested at 3, 7, and 28 days. Thermal curing of GPC has also resorted for favorable results. It was found that AAS to GSB ratio of 0.5 and GGBFS content of 80% yielded the maximum strength with a little unfavorable effect on workability. The overall results indicated that AAS and GGBFS offer good geopolymer concrete which will find its applicability in water scarce areas. Doi: 10.28991/cej-2021-03091708 Full Text: PDF