Ground Granulated Blast Furnace Slag Concrete Research Articles

Mock-up performance evaluation study for crack reduction of blast furnace slag powder concrete mixed with expansive and swelling admixtures

In this study, the drying shrinkage and crack reduction characteristics of blast furnace slag concrete mixed with expansive and swelling admixtures were investigated. Basic performance experiments were conducted using different mixtures of ground granulated blast-furnace slag (GGBS), with calcium sulfoaluminate as the expansive admixture and bentonite and hydroxypropyl methyl cellulose (HPMC) as swelling admixtures. Bentonite outperformed HPMC as a swelling admixture. Specimens were then prepared for mock-up tests to evaluate the drying shrinkage of blast furnace slag concrete with different combinations of bentonite, a hardening accelerator, and a self-healing agent. The addition of bentonite and calcium phosphate as a self-healing agent in small quantities reduced the drying shrinkage of the specimens, thereby reducing cracks. The cement mixture composed of 30% GGBS, 1% bentonite, and 1% calcium phosphate (30-E1-I1) showed the optimal performance among the specimens. Further, crack monitoring was performed in concrete made with ordinary Portland cement and optimal mixture 30-E1-I1. No cracks were observed for the optimal mixture. This shows that GGBS concrete can be used in practical and field applications, subject to mid- and long-term tests for cracking.

Thermal Cracking in High Volume of Fly Ash and GGBFS Concrete

Supplementary cementitious materials (SCMs) such as fly ash and ground granulated blast furnace slag (GGBFS) are found to control the maximum temperature and the accompanying thermal gradients effectively. However, SCMs also lead to low early age strength development. Thus, it is crucial to understand the cracking behaviour of SCMs-based concrete affected by the mix design parameters. In this paper, the thermal cracking resistance was evaluated using a rigid cracking frame (RCF) with a computer-controlled temperature profile. The temperature profile was determined using the software ConcreteWorks by assuming the centre point of the mass concrete. The free shrinkage frame (FSF) and match-curing oven follow the same temperature profile as RCF to measure the free total deformation and time-dependent mechanical properties of concrete, respectively. An analytical model was proposed to calculate the autogenous shrinkage and the thermal stress separately. A time-dependent cracking risk coefficient allowing to estimate the risk of early age cracking of concrete was also proposed.

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.

Experimental Study On Hardened State Properties Of Self-curing Concrete

Concrete is the mostly used construction material in the modern world. However, with the rise of urbanization, heavy use of concrete has started to threaten the humankind due to its disastrous effect on environment. Steel and concrete industries are one of the major CO2 producing industries. Statistics show that an average person uses 1 m3 of concrete in a year making it the most used material and the cement production on global scale may reach 4800 Million Metric tons by 2030 and India being the second largest producer in 2018 with 290 million metric tons. To control this a new environment- friendly structural materials should be utilized instead of ordinary concrete to cope with environmental problems. This has led to the search for alternate sustainable materials to replace Cement. With good success, mineral admixtures have been used to partially replace cement. The technical advantage of using these mineral admixtures is the improvement of many properties in the fresh and hardened phases, including enhanced durability in acidic environments and higher ultimate strength of Concrete. GGBS (Ground granulated blast furnace slag) reaction is both hydraulic and pozzolanic because of the particle shape and increased hydration, GGBS concrete has greater particle packing. Curing of concrete place a major role on strength development and durability of concrete. Improper curing can affect the concrete performance and durability easily. In conventional curing this is achieved by external curing applied after mixing, placing and finishing. Water is maximum utilized commodity and because of this the day- by-day level of the water table is going down. If water has to be purchased for construction works, the cost of construction rises much higher. Also, in case of concreting works done at heights, vertical members, sloped roofs and pavements, continuous curing is very difficult. The performance of self-curing concrete using PEG as self-curing agent with different molecular weights concluded that addition of hydrophilic chemicals in water which is mixed in concrete reduces the evaporation of water. The research identifies Durability properties of the concrete higher for mix C20G1.5P at 7, 14, and 28 days for M20 and M40 grades, However, for the M60 grade, the mix ratio C10G1P demonstrates the highest strength, suggesting the influence of concrete grade in combination with Ground Granulated Blast Furnace Slag (GGBS) and Polyethylene Glycol (PEG 400). Increasing the supplementary cementitious material and self-curing agent strength and durability of concrete increases and up to certain point and then decreases. In addition, the micro structural analyses have been carried out for specimens of optimum level using the Scanning Electron Microscopy (SEM) and X-Ray Diffraction (XRD).

Estimating the compressive strength of GGBFS-based concrete employing optimized regression analysis

Carbon dioxide is produced during the manufacture of normal Portland cement; however, this gas may be minimized by utilizing ground granulated blast furnace slag (GGBFS). When planning and constructing concrete buildings, compressive strength (fc), a crucial component of concrete mixtures, is a need. It is essential to assess this GGBFS-blended concrete property precisely and consistently. The major objective of this research is to provide a practical approach for a comprehensive evaluation of machine learning algorithms in predicting the fc of concrete containing GGBFS. The research used the Equilibrium optimizer (EO) to enhance and accelerate the performance of the radial basis function (RBF) network (REO) and support vector regression (SVR) (SEO) analytical methodologies. The novelty of this work is particularly attributed to the application of the EO, the assessment of fc including GGBFS, the comparison with other studies, and the use of a huge dataset with several input components. The combined SEO and REO systems demonstrated proficient estimation abilities, as evidenced by coefficient of determination (R2) values of 0.9946 and 0.9952 for the SEO’s training and testing components and 0.9857 and 0.9914 for the REO, respectively. The research identifies the SVR optimized with the EO algorithm as the most successful system for predicting the fc of GGBFS concrete. This finding has practical implications for the construction industry, as it offers a reliable method for estimating concrete properties and optimizing concrete mixtures.

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.

Influence of curative temperature on strength enhancement of diverse grades GGBS amalgamation

The research paper discusses the benefits of employing ground-granulated blast furnace slag (GGBS) in concrete, including affordability, toughness, and durability. Using GGBS in concrete mixtures has become rare in expressway buildings. This is thought to result from its strength developing more slowly as it ages and is cured at room temperature. To help with its use in building the expressway, M25 and M35 grades of concrete, which contain GGBS at levels 0, 35, 40, and 45%, have been studied. By measuring the strength of reprocessed waste concrete, it was investigated how curative warmth affected the strength improvement of concretes with various GGBS percentages at premature and late ages. The concrete samples have being hardened at 20, 27, 40, 50 and 60 °C. The samples were evaluated at ages 1, 4, 16, 28, and 56. This is done to determine how strong this particular GGBS concrete has become after hardening at various hardening temperatures. The experimental research demonstrates several significant effects for GGBS replacements: it fosters strength development until an ideal replacement. The refining of the gaps is mostly caused by the reaction between GGBS and calcium hydroxides, or (Ca(OH)2), which results in the C-S-H gel, also known as calcium silicate hydrates. This process increases strength.It was also noticed that up to a particular degree, such as when it reaches adiabatic temperature, strength increases as the temperature rises, but after that, it decreases. Due to the unequal distribution of hydration products, higher cure temperatures cause bigger pores in the microstructure, as indicated.

Mechanical and durability performance of sustainable concretes containing conventional and emerging supplementary cementitious materials

This paper presents a comparative study on the mechanical and durability properties of concrete mixtures containing conventional supplementary cementitious materials (SCMs) and emerging alternatives (i.e., volcanic ash, volcanic ash-limestone blend, and metakaolin-limestone blend), with an emphasis on the latter. To enable effective comparison, identical volumetric substitution levels (30%) of SCMs along with a constant binder and aggregate volumes were employed. The metakaolin-limestone concrete performs the best among all types of concretes in terms of strength development, water absorption capacity and chloride penetration resistance. The incorporation of volcanic ash though reduces the compressive strength of concrete and increases water absorption capacity considerably compared to the reference Portland cement concrete, and its chloride diffusion coefficient is only about half of that of the reference concrete. In addition, the concretes containing volcanic ash or volcanic ash-limestone show better performance in controlling the potential alkali-silica reaction-induced expansion than the reference concrete and ground granulated blast-furnace slag concrete.

Study on properties of concrete using slag as partial replacement of cement

There are numerous greenhouse gases released during cement manufacture that contribute to global warming. Researchers, therefore, concentrate on waste materials that have binding properties that can replace cement without sacrificing its strength. The current paper study's major goal is to examine the strength of the concrete when Ground Granulated Blast Furnace Slag (GGBS) is used to partially replace cement. GGBS is a finely powdered iron slag by-product of the steel-making industry. The mechanical characteristics of M40 grade concrete with partially replaced cement of 30%, 40%, and 50% by GGBS are examined in this study. All mix design specifications and material test data are carried out per IS codes, for a curing time of 7, 14, and 28 days, compression, splitting tensile, and flexural tests were performed on the cube, cylinder, and prism, respectively. The obtained test result of GGBS concrete was compared with control concrete to arrive at an optimum dosage of GGBS. The compressive and tensile strength of GGBS concrete increases up to 40% partial substitution of cement with GGBS, beyond which it begins to reduce, and in the case of flexural strength, there is a sustained growth in flexural strength.

Environmental impact assessment and potentials of material efficiency using by-products and waste materials

As sustainability is becoming a priority in the construction industry, concerns associated with the environmental impacts of the production and use of Portland cement (PC) are being raised. To respond to this challenge and among different strategies of material efficiency, the potential of by-products and recycling wastes to produce eco-friendly cement-based or cement-less construction materials is given greater emphasis. This research investigates the environmental assessment and carbon footprint of different building envelope walls using by-product and waste materials of energy-intensive processes including power plants, and steel and glass industries. Four different products that can be used in the concrete as the replacement of Portland cement including fly ash, ground granulated blast-furnace slag (GGBS), Glass powder, and mix design of these materials are compared with the regular concrete mix to be used as an envelope wall. After that, the potentials of production and consumption of these materials in the concrete are assessed in Canada. Results show that GGBS concrete with 287 kg CO2 eq per m3 has the lowest CO2 emissions compared with other by-products/waste-used concrete. The CO2 emissions of fly ash concrete are 37% higher than GGBS and glass powder concrete has 50% higher CO2 emissions compared with GGBS concrete. Also, among different environmental damages that concrete would be responsible for, damage to human health has the highest impact on the environment. Fly ash and glass powder concrete have also the highest environmental damage to human health even than regular mix. GGBS concrete has the lowest environmental impact compared with other products that can be considered as a great replacement for PC. Due to the concrete demand exist in Canada, all studied by-products and waste can be fully used in the concrete industry.

Autogenous deformation induced- stress evolution in high-volume GGBFS concrete: Macro-scale behavior and micro-scale origin

This study aims to experimentally investigate the autogenous deformation and the stress evolution in restrained high-volume ground granulated blast furnace slag (GGBFS) concrete. The Temperature Stress Testing Machine (TSTM) and Autogenous Deformation Testing Machine (ADTM) were used to study the macro-scale autogenous deformation and stress evolution of high-volume GGBFS concrete with w/b ratios of 0.35, 0.42, and 0.50. The early-age cracking (EAC) risk (quantified by stress-strength ratio) and stress relaxation were analyzed extensively based on ADTM and TSTM results. Furthermore, Environmental Scanning Electron Microscopy (ESEM), X-ray Diffraction (XRD), and Mercury Intrusion Porosimetry (MIP) were conducted to explore the micro-scale origin of the autogenous deformation of high-volume GGBFS concrete, which supports the observations on the macroscale measurement of TSTM/ ADTM tests. This study finds that the ettringite formation in the first two days results in autogenous expansion, which can delay the appearance of tensile stress. The magnitude of autogenous expansion depends on the compatibility of ettringite content and pore size. The w/b ratio of 0.42 turns out to be optimal because it produces the highest amount of ettringite and results in the highest autogenous expansion. In comparison, the w/b ratio of 0.35 introduces significant autogenous shrinkage after the expansion peak and therefore corresponds to a high early-age cracking risk.

Durability, mechanical properties and rebar corrosion of slag-based cement concrete modified with graphene oxide

The application of nanomaterial to concrete is an innovative approach to enhancing mechanical properties and durability. In fthis work, the combined additions of graphene oxide nano-platelets (GO) to concrete mix formulated to use ground granulated blast furnace slag (GGBFS) as a substitute for Portland cement (PC) for use in salt-rich environments is studied. The need arises in both off-shore structures and also places coming to contact with brine due to de-icing of road structures or the geological peculiarities specific to saline terrain. The physical, mechanical, chloride, and water permeability and electrical conductivity tests on the developed concrete are compared with those of ordinary concrete under conditions of varying temperature and water pressure. The addition of GGBFS is known to improve the mechanical properties of concrete specimens. Results from the present work show that the addition of no more than 0.1 wt% GO to 50 wt% GGBFS substituted concrete increases the after-curing compressive strength by 40 %, and flexural strength by 60 %. The electrical conductivity of the 90-day cured samples as a measure of chloride permeability dropped from nearly 4000 Coulombs in ordinary concrete to roughly 1100 Coulombs for the modified concrete indicating a nearly 70 % reduction. Accelerated CSH gelation, followed by Ca(OH)2 crystallization after GO addition, combined with altered pore structure from the addition of finely milled slag. The nucleation mechanism is affected such that the average pore diameter falls to 6.2 nm from 11.4 nm in the PC concrete. The low porosity thus established is reflected in the measured improvements in strength, resistance to water absorption, chloride permeability, and the overall enhanced corrosion performance. Calorimetric conductivity, thermogravimetric analysis (TGA), and differential thermogravimetric (DTG) analysis under nitrogen from 105 to 1000 ◦C, total porosity and pore size distribution using Mercury Intrusion Porosimetry (MIP) with a maximum pressure of 200 MPa, X-ray diffraction, linear polarization and electrochemical impedance spectroscopy (EIS) corrosion test results further corroborate that the addition of 0.1 % by weight of GO improved the physical, durability, and corrosion resistance properties of GGBFS concrete.

Using Artificial Intelligence and Machine Learning Model for Prediction of Uniaxial Compressive Strength of GGBS Concrete

Ground Granulated Blast-furnace Slag (GGBS) concrete is sustainable and also proven to show enhanced properties such as reduced heat of hydration, refinement of pore structure and increased resistance to corrosion and chemical attacks when compared with Ordinary Portland Cement concrete. Uniaxial compressive strength (UCS) and enhanced properties of the GGBS concrete are dependent on the proportions of GGBS and other elements in the mix. It is essential to accurately predict the UCS of the blended mix. Developments in computer hardware and the easy availability of research data made artificial intelligence and machine learning (AI & ML) prediction techniques feasible. In this study AI & ML techniques namely, linear regression, lasso regression and ridge regression are used to predict the UCS of GGBS concrete. Algorithms are trained using data collected from various standard publications. All data points are cleaned and then normalized with standard scalar function to avoid biased predictions. Root Mean Squared Error, Mean Squared Error, Mean Absolute Error and Coefficient of Determination for all three techniques are found to be almost identical. The above-mentioned AI & ML models have high prediction accuracy. Hence, based on the results AI & ML algorithms specified above can be reliably used in the above-mentioned GGBS concrete.

Salt-scaling resistance of highly durable RC slabs utilizing GGBS concrete with expansive additive

In recent years, the utilization expansive additive for ground granulated blast furnace slag (GGBS) concrete has been confirmed to be indispensable to reduce the early-age thermal tensile stress, which results in successful crack mitigation in several highly durable reinforced concrete (RC) slabs in Japan. However, various investigations have cited that the application of large amounts of expansive additive might reduce the salt-scaling resistance of durable RC slabs. This study experimentally investigates the salt-scaling resistance on the top surface of highly durable RC deck slab specimens by utilizing GGBS concrete with applicable dosages of expansive additive. Test results revealed that the proposed salt-scaling method modified based on ASTM C672 with a 6 h cycle and with more severe scaling temperatures at a minimum and maximum of ± 35 °C can reasonably reduce the experimental duration and effort for practical purposes. Moreover, although the salt-scaling resistance of the highly durable RC slab specimens decreased as the dosage of the expansive additive increased, acceptable salt-scaling resistance was obtained in the specimens with 20 and 25 kg/m3 expansive additive dosages.

Enabling sustainable rapid construction with high volume GGBS concrete through elevated temperature curing and maturity testing

Nowadays, low carbon footprint concrete for construction relies heavily on ground granulated blast-furnace slag (GGBS) as a partial cement replacement material (CRM) in places where other CRMs are in short supply. However, it is relatively well-known that the low early-age strengths of GGBS concretes discourage the maximisation of cement replacement in most applications; a constraint which can be potentially overcome through exploitation of hydration acceleration under elevated temperature curing. Concrete and mortar mixes of 47 MPa 28-day target mean cube strength were developed and investigated in this study with various percentages of GGBS (0, 20, 35, 50 and 70%) and cured under isothermal and non-isothermal regimes (20, 30, 40 and 50 °C and adiabatic). Higher temperatures appeared to significantly accelerate the strength gain of GGBS concretes, particularly those containing high GGBS percentages. In-situ strength development may be estimated through maturity functions which were initially developed for neat Portland cement concretes. The accuracy of several maturity functions, such as the Nurse-Saul, Arrhenius, Weighted Maturity, Weaver-Sadgrove and Rastrup ones, were examined together with two strength-maturity/time correlations. It was found that although maturity methods can be used to optimise a concrete mix in terms of GGBS content and depending on the application, it is not possible to obtain consistently reliable estimates for GGBS concretes from the current functions. Nonetheless, from the current models considered, the Arrhenius, Weighted Maturity and Rastrup functions appear as more appropriate for higher replacement levels of cement with GGBS. Overall, the present study highlighted a need for further improving maturity functions to account for the strength development of GGBS concrete.

Autogenous shrinkage of fly ash and ground granulated blast furnace slag concrete

Supplementary cementitious materials (SCMs) are widely used to reduce the cement content to achieve economic and environmental objectives. As a result, understanding the shrinkage of blended cement-based concrete is essential. In total, 21 concrete mixes were produced with type general purpose cement and with cement replacements of 30% by fly ash, 40% and 60% by ground granulated blast furnace slag (GGBFS). The concrete compressive strength ranged from 25 MPa to 100 MPa. Experimental results were also compared with the predictions by models. Additional tests on pastes with the same SCM content were conducted to investigate both autogenous and chemical shrinkage in relation to their time-dependent pore structure refinement. For concretes with strength below 50 MPa, no significant difference in autogenous shrinkage could be observed between the different blends up to 28 days. However, the autogenous shrinkage of GGBFS concrete increased significantly after 28 days, being about 50% higher than all other concretes at 100 days. This late increase in autogenous shrinkage between 28 and 100 days can be attributed to pore refinement processes. No clear difference was observed for GGBFS concretes with strength greater than 50 MPa. Autogenous shrinkage of fly ash concretes was overall equivalent to that of reference concretes.

Modeling blended cement concrete tensile creep for standard ring test application

AbstractThe tensile creep of concrete with supplementary cementitious materials (SCMs) such as fly ash (FA) and ground granulated blast furnace slag (GGBFS) is investigated in this paper. A total of 21 series of tensile creep tests using dog‐bone specimens under uniaxial tensile loading have been carried out. The cement replacement rates considered were 30% fly ash, 40% and 60% GGBFS. The characteristic compressive strength of concrete was ranging from 25 to 100 MPa. The tests were conducted from the age of 2 days until 28 days. It is observed that the tensile creep of fly ash concretes was slightly lower than that of the reference mixtures without SCM. For GGBFS concrete, the higher the GGBFS content, the higher the tensile creep. Existing creep models, originally developed for creep in compression, could not predict the experimental tensile creep results. Thus, a new tensile creep model was proposed including creep prediction for concrete with fly ash and GGBFS. The new model was calibrated only for controlled environmental conditions (23°C and 50% RH) and has been validated by analyzing the development of concrete tensile stress in the restrained ring test.

An Experimental Study on Banana Fibre Reinforced GGBS Concrete

Fibres have been used to reinforce concrete over the last few decades because fibre has significant influence on concrete’s static and dynamic properties.Fibre reinforcement into concrete can provide a timely, workableand inexpensiveprocedure for reducingcracking and similar type of deficiencies.Industrial wastes like fly ash,Ground Granulated Blast Furnace Slag (GGBS) etc.,can be utilized as substitution of cement. At the same time, the usage of GGBS as partial substitution of cement will lower the concreterate and helps to decrease cement consumption rate. This paper describes the experimental function on the usage of banana fibre and Ground Granulated Blast Furnace Slag (GGBS) to make better strength and applications of concrete. Banana fibres are extensivelyobtainableeven as agricultural scrap from Banana cultivation. Theyhavekey characteristics like low density, light weight, cheap, high tensile strength, water andfire resistant. They are eco-friendly,inexpensive (zero cost)with chemicals free. The adding of bananafibres considerably improved many attributes of the concrete such as compressive strength, tensile strength and flexural strength. It also increased the potential to withstandrupturing and collapsing of concrete.In this study,banana fibres of four different percentage (0%, 2.5%, 5%, and 7.5%) having length of 40mm and constant percentage of GGBS (2.5%) were used. The banana fibre reinforced GGBS concrete were tested for compressive strength,tensile strength at different ages.

Stress evolution in restrained GGBFS concrete due to autogenous deformation: bayesian optimization of aging creep

Stress evolution of restrained concrete is a significant direct index in early-age cracking (EAC) analysis of concrete. This study presents experiments and numerical modelling of the early-age stress evolution of Ground granulated blast furnace slag (GGBFS) concrete, considering the development of autogenous deformation and creep. Temperature Stress Testing Machine (TSTM) tests were conducted to obtain the autogenous deformation and stress evolution of restrained GGBFS concrete. By a self-defined material subroutine based on the Rate-type creep law, the FEM model for simulating the stress evolution in TSTM tests was established. By characterizing the creep compliance function with a 13-units continuous Kelvin chain, forward modelling was firstly conducted to predict the stress development. Then inverse modelling was conducted by Bayesian Optimization to efficiently modify the arbitrary assumption of the codes on the aging creep. The major findings of this study are as follows: 1) the high autogenous expansion of GGBFS induces compressive stress at first hours, but its value is low because of high relaxation and low elastic modulus; 2) The codes highly underestimated the early-age creep of GGBFS concrete. They performed well in prediction of stress after 200 h, but showed significant gaps in predictions of early-age stress evolution; 3) The proposed inverse modelling method with Bayesian Optimization can efficiently adjusted the aging terms which produced best modelling results. The adjusted creep compliance function of GGBFS showed a much faster aging speed at early ages than the one proposed by original codes.

Mechanical and Durability Properties of Cementless Concretes Made Using Three Types of CaO-Activated GGBFS Binders.

This study examined the mechanical and durability properties of CaO-activated ground-granulated blast-furnace slag (GGBFS) concretes made with three different additives (CaCl2, Ca(HCOO)2, and Ca(NO3)2) and compared their properties to the concrete made with 100% Ordinary Portland Cement (OPC). All concrete mixtures satisfied targeted air content and slump ranges but exhibited significantly different mechanical and durability properties. The CaO-activated GGBFS concretes showed different strength levels, depending on the type of additive. The added CaCl2 was the most effective, but Ca(NO3)2 was the least effective at increasing mechanical strength in the CaO-activated GGBFS system. The OPC concrete showed the most excellent freezing–thawing resistance in the durability test, but only the CaO-activated GGBFS concrete with CaCl2 exhibited relatively similar resistance. In addition, the chemical resistance was significantly dependent on the type of acid solution and the type of binder. The OPC concrete had the best resistance in the HCl solution, while all CaO-activated GGBFS concretes had relatively low resistances. However, in the H2SO4 solution, all CaO-activated GGBFS concretes had better resistance than the OPC concrete. All concrete with sulfate ions had ettringite before immersion. However, when they were immersed in HCl solution, ettringite tended to decrease, and gypsum was generated. Meanwhile, the CaO-activated GGBFS concrete with CaCl2 did not change the type of reaction product, possibly due to the absence of ettringite and Ca(OH)2. When immersed in an H2SO4 solution, ettringite decreased, and gypsum increased in all concrete. In addition, the CaO-activated concrete with CaCl2 had a considerable amount of gypsum; it seemed that the dissolved C-S-H and calcite, due to the low pH, likely produced Ca2+ ions, and gypsum formed from the reaction between Ca2+ and H2SO4.