Replacement Ratio Of Blast Furnace Slag Research Articles

A study on the change in frost resistance and pore structure of concrete containing blast furnace slag under the carbonation conditions

In this study, the change in frost resistance and pore structure of concrete containing blast furnace slag with various replacement ratio due to carbonation were investigated. As a result, there is a close relationship between the carbonation speed and 28-day compressive strength in blast furnace slag concrete. The frost resistance, carbonation resistance and scaling resistance of blast furnace slag cement concrete decrease as blast furnace slag replacement ratio increases. Furthermore, due to carbonation, the frost durability of ordinary Portland cement concrete and the concrete with a low replacement ratio of blast furnace slag tends to decrease. However, the concrete with a high replacement ratio of blast furnace slag tends to increase. Under the carbonation conditions, the pore volume decreases due to carbonation of calcium hydroxide, and the pore structure will be coarsened due to carbonation of C-S-H. In addition, it is expected that permeability of concrete is raised and scaling is inhibited due to carbonation, and the surface area with a certain thickness in the carbonated concrete will be scaled due to freeze–thaw.

Effect of Ground Granulated Blast Furnace Slag Replacement Ratio on Structural Performance of Precast Concrete Beams.

This study was conducted to investigate the effect of ground granulated blast furnace slag on the structural performance of precast concrete beams, evaluating the flexural, shear and bonding performance by using the replacement ratio of the ground granulated blast furnace slag as a variable. The design strength of the concrete was set at 45 MPa in consideration of the characteristics of precast concrete products, and the replacement ratio of the ground granulated blast furnace slag to replace cement was 30 to 70%. The experimental results showed that all specimens had similar behavioral characteristics regardless of the replacement ratio of the ground granulated blast furnace slag. Comparison of the prediction results obtained by ACI 318-19 and EC 2 showed that the mean flexural strength and shear strength were higher than 1.19 and 1.43, respectively, and the mean bond strength was 1.57, satisfying the required performance. Therefore, the experimental results showed that in using the ground granulated blast furnace slag as an admixture for precast concrete, the cement replacement ratio may be increased up to 70% without causing any problems in securing the structural performance. Summarizing the results of the present study, a ground granulated blast furnace slag replacement ratio of 50% or lower may be reasonably applied.

Effect of Blast-Furnace Slag Replacement Ratio and Curing Method on Pore Structure Change after Carbonation on Cement Paste.

The frost damage resistance of blast-furnace slag (BFS) cement is affected by carbonation. Hence, this study investigates the carbonation properties of pastes incorporating BFS with different replacement ratios, such as 15%, 45%, and 65% by weight, and different curing conditions, including air and carbonation. The BFS replacement ratio properties, determined by the Ca/Si ratio of calcium silicate hydrate in the cement paste sample, were experimentally investigated using mercury intrusion porosimetry, X-ray diffraction, and thermal analysis. The experimental investigation of the pore structure revealed that total porosity decreased after carbonation. In addition, the porosity decreased at a higher rate as the BFS replacement rate increased. Results obtained from this study show that the chemical change led to the higher replacement rate of BFS, which produced a higher amount of vaterite. In addition, the lower the Ca/Si ratio, the higher the amount of calcium carbonate originating from calcium silicate hydrate rather than from calcium hydroxide. As a result of the pore structure change, the number of ink-bottle pores was remarkably reduced by carbonation. Comparing the pore structure change in air-cured and carbonation test specimens, it was found that as the replacement rate of BFS increased, the number of pores with a diameter of 100 nm or more also increased. The higher the replacement rate of BFS, the higher the amount of calcium carbonate produced compared with the amount of calcium hydroxide produced during water curing. Due to the generation of calcium carbonate and the change in pores, the overall number of pores decreased as the amount of calcium carbonate increased.

Effect of Electrolyzed Alkaline-Reduced Water on the Early Strength Development of Cement Mortar Using Blast Furnace Slag.

This study evaluated the use of electrolyzed alkaline-reduced water instead of an alkaline activator for the production of a strong cement matrix with a large blast furnace slag replacement ratio. The flexural and compressive strength measurements, X-ray diffraction analysis, and scanning electron microscopy images of the cement matrices produced using electrolyzed alkaline-reduced water and regular tap water, and with blast furnace slag replacement ratios of 30 and 50% were compared to a normal cement matrix. The cement matrix produced using electrolyzed alkaline-reduced water and blast furnace slag exhibited an improved early age strength, where hydrate formation increased on the particle surface. The cement matrix produced using electrolyzed alkaline-reduced water exhibited a high strength development rate of over 90% of ordinary Portland cement (OPC) in BFS30. Therefore, the use of electrolyzed alkaline-reduced water in the place of an alkaline activator allowed for the formation of a very strong cement matrix in the early stages of aging when a large blast furnace slag replacement ratio was used.

Experimental Investigation of Material Properties and Self-Healing Ability in A Blended Cement Mortar with Blast Furnace Slag.

This paper presents the results of an experimental investigation on the material properties and self-healing ability of a blended cement mortar incorporating blast furnace slag (BFS). The effect of different types and Blaine fineness of BFS on the material properties and self-healing was investigated. Thirteen cement mixtures with BFS of different types and degrees of Blaine fineness are tested to evaluate the mechanical properties, namely compressive strength, bending strength, freeze–thaw, and accelerated carbonation. The pore structure is examined by means of mercury intrusion porosimetry. Seven blended mortar mixtures incorporating BFS for cement are used to evaluate the mechanical properties after applying freeze–thaw cycles until the relative dynamic modulus of elasticity reached 60%. The experimental results reveal that incorporating BFS improves the mechanical properties and self-healing ability. In the investigation of self-healing, smaller particle and high replacement ratios of BFS contribute to increasing the relative dynamic modulus of elasticity and decreasing the carbonation coefficient in the mortar after re-water curing. Moreover, BFS’s larger particles and high replacement ratio are found to provide better self-healing ability. A regression equation is created to predict the relative dynamic modulus of elasticity in mortar considering the Blaine fineness, BFS replacement ratio, and curing conditions.

Fly ash based geopolymer stabilisation of silty clay/blast furnace slag for subgrade applications

The mechanical and microstructural properties of problematic silty clay (SC) stabilised with fly ash (FA) based geopolymer and blast furnace slag (BFS) replacement are presented in this research. The influence factors evaluated included FA:BFS replacement ratio, NaOH concentration, and curing temperature. A series of geotechnical laboratory tests and microstructural analyses were also undertaken. The strength of the stabilised material was found to be governed by interparticle forces, mainly from the contribution of the chemical bonding strength. The results indicated that the unconfined compression strength (UCS) values of FA based geopolymers stabilised with SC/BFS blends increased with increasing NaOH concentration, at the various FA:BFS replacement ratios when cured at various temperatures (25, 50 and 80°C). The high concentration of NaOH could dissolve FA particles to leach silica and alumina which reacted with NaOH to produce a geopolymerization (N-A-S-H gel) process, which resulted in high UCS results. The decrease in FA:BFS ratio however reduced the specific area of particles to be welded by FA geopolymerization products and reduces the geopolymer gel due to the reduction in quantity of FA precursor. As such, the interparticle forces increased as the FA:BFS reduced up to the optimum value and then decreased as the FA:BFS reduced. The optimal FA:BFS ratio was found to be 20:10. An elevated curing temperature accelerated the geopolymerization reaction, leading to the higher UCS at higher temperature. The use of waste by-products BFS and FA to stabilise problematic soil in civil engineering applications will contribute to a significant reduction in construction costs and the sustainable development of the project life cycles.

Optimization of alkali-activated mortar utilizing ground granulated blast-furnace slag and natural pozzolan from Germany with the dynamic approach of the Taguchi method

This paper presents an investigation into the applicability of the dynamic approach of the Taguchi method to optimize alkali-activated mortar utilizing ground granulated blast-furnace slag and natural pozzolan from Germany called trass (hereafter, AAGT). The volume ratio of powder to alkaline activating solution (Vp/Vaas) was chosen as an input signal, while flow value and flexural and compressive strengths were considered as output values. The concentration of sodium hydroxide solution, mass ratio of sodium silicate to sodium hydroxide solution, ground granulated blast-furnace slag replacement ratio, mixing regime, mixing time, curing temperature, and cumulative temperature in heat curing were taken into account as design parameters. Based on the experiments conducted using an L18 orthogonal array and the calculated results of signal to noise (SN) ratios and sensitivities, input–output relationships between Vp/Vaas and the output values were optimized. Long-term tests on the optimized specimens revealed the applicability of AAGT as a construction material; however, expansion cracks due to a gypsum formation were noticed after long-term immersion in a 10% sulfuric acid solution.

Durability of Seawater Mixed Concrete with Different Replacement Ratio of BFS (Blast Furnace Slag) and FA (Fly Ash)

Durability of Seawater Mixed Concrete with Different Replacement Ratio of BFS (Blast Furnace Slag) and FA (Fly Ash)

Apparent Activation Energy for Predicting Compressive Strength of Concrete Using Blast Furnace Slag

Concrete with blast furnace slag (BFS) shows varied strength development properties under general temperature conditions. Therefore, a precise prediction of compressive strength using a full maturity model is desired. The purpose of this study is to predict the compressive strength of concrete with BFS by calculating the apparent activation energy (Ea) for each BFS replacement ratio, applying this activation energy to the equivalent age model, and then using the Carino model. For BFS replacement ratios of 0%, 10%, 30%, and 50%, Ea is calculated as 33.475 kJ/mol, 37.325 kJ/mol, 41.958 kJ/mol and 45.541 kJ/mol respectively. Finally, the compressive strength of concrete with BFS is predicted.

Genetic expression programming for prediction of heat of hydration of the blended cements

This study presents a new approach based on Genetic Expression Programming (GEP) for modeling of variation of heat of hydration of Portland and blended cements. For that purpose, two different GEP models were developed to generate two mathematical equations. In the GEP Model 1, six input parameters such as the ground blast furnace slag replacement ratio (GBFS), ground basaltic pumice replacement ratio (GBP), clinker and gypsum ratio (CG), cement fineness (CF), grinding type (GT) and time (T) were used. In GEP Model 2, three input parameters such as cement fineness (CF), grinding type (GT) and time (T) were used. The results were highly promising in terms of training performances and prediction accuracies and revealed that the proposed GEP models can be used in the prediction of heat of hydration of blended cements. Key words: Cement, heat of hydration, genetic expression programming.

고로슬래그 분말도가 시멘트 페이스트의 유동특성에 미치는 영향

In this study, the rheological properties of cement pastes containing blastfurnace slag of different fineness were investigated. The fluidity of cement pastes with low Blaine value blastfurnace slag was increased with decreasing the plastic viscosity and the yield stress of pastes. And the optimum dosage of polycarboxylate type superplasticizer to the cement pastes was confirmed according to the fineness and the replacement ratio of blastfurnace slag. All cement pastes showed the thixotropy behavior. And also it was formed that the segregation range of cement pastes was occurred below 10 D/㎠ of the yield stress and below 350 cPs of the plastic viscosity by the coaxial cylinder viscometer.

建設材料特集 高ビーライトセメントおよび高ビーライト系混合セメントを用いたコンクリートの諸特性

Recently in Japan, the demand for low heat cement to prevent thermal cracks is growing higher because of scaling up of concrete structures. Usually, moderate heat portland cement and binary or ternary blended cement in which ground blast-furnace slag and fly ash were admixed have been used as low heat cement. However, such blended cements have several problems. For examples, the heat of hydration of moderate heat cement is not sufficiently low. The quality of blended cement is not stable and it is very difficult to control and stabilize its quality because of incorporating industrial by-products, and the rate of carbonation is quite fast. Therefore, belite-rich cement is expected much as low heat cement which is more durable and effective to prevent thermal cracks.In this study, the effect of the content of belite in cement on the property of concrete was investigated by using four kinds of belite cements in order to make the characteristics of belite-rich cement clear. The relations between the replacement ratio of blast-furnace slag and adiabatic temperature rise or strength were also investigated using belite-rich cement containing about 60% of C2S, under the condition that the replacement ratio of fly ash was kept 30% constant.