• Journal of the Korean Recycled Construction Resources Institute
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• v.4 no.4
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• pp.446-453
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• 2016

Structural capacity of water channel fabricated of concrete including blast furnace slag were investigated in this paper. An experimental study was consisted of materials test and structural test of concrete water channel. The mechanical properties of concrete including blast furnace slag were investigated. Ordinary Portland cement (OPC) was used as basic binder and the effect of the replacement of blast furnace slag for OPC was investigated. Experiments were performed to measure mechanical properties including compressive strength, elastic modulus and modulus of rupture. Test results show that the compressive strengths and modulus of ruptures of mixtures containing blast furnace slag were equivalent to those of OPC concrete. In addition, the structural capacity of concrete water channel with up to the replacement ratio of blast furnace slag of 45% was greater than the required strength in KS specification.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.1005-1008
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• 2008

The purpose of this study is to estimate basic mechanical properties of alkali-activated concretes based on GGBS(Ground Granulated Blast Furnace Slag). In this study, various mix ratios of alkali activated concretes based on sodium silicate and GGBS were set to evaluate concrete's compressive strengths and strains on the basis of results of existing alkali-activated cements and preliminary concrete tests, which were already performed by authors [Ref. 1]. Compressive strengths of concretes of ages 1, 3, 7, 28, 56 and 91 days were tested and investigated, respectively, and at early ages (< 7days) alkali-activated slag concrete (AASC) showed a high strength development, compared to that of Ordinary Portland Cement (OPC). A compressive strengths of AASC at age-3days range between 18 and 24 MPa, while those of OPC range 12 and 15 MPa. The stress-strain curve after maximum stress, on the other hand, is approximately reached at a compressive strain between 0.002 and 0.0025, which mechanical property is very similar to that of OPC.

• Journal of the Korea Institute of Building Construction
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• v.20 no.5
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• pp.409-416
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• 2020

In this paper, strength correction factors of the concretes incorporating ordinary Portland cement(OPC), fly ash(FA) and blast furnace slag(BS) with 50% of water to binder ratio due to temperature drop for standard room temperature(20±3℃) are provided. For this, strength development was done based on equivalent age method. For calculating the equivalent age, apparent activation energy was obtained with 24.69 kJ/mol in OPC, 46.59 kJ/mol in FA, 54.59 kJ/ol in BS systems. According to the estimation of strength development of the concretes, the use of FA and BS resulted in larger strength drop than that of OPC under low temperature compared to standard room temperature. Hence, strength correction factors(Tn) for OPC, FA and BS are suggested within 4~17℃ with every 3MPa levels.

• Journal of the Korea Institute of Building Construction
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• v.24 no.3
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• pp.285-295
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• 2024

This study investigated the impact of accelerated carbonation on Ordinary Portland Cement(OPC) paste that had undergone steam curing at 500℃·hr. Two carbonation environments were examined: atmospheric carbonation(1atm, 20% CO₂) and pressurized carbonation(5atm, 99% CO₂). Chemical analysis using X-ray diffraction(XRD) and Fourier-Transform Infrared spectroscopy(FT-IR) were conducted, along with physical characterization via scanning electron microscopy(SEM) and compressive strength testing. Results indicated that atmospheric carbonation with 20% CO₂ concentration significantly densified the internal microstructure of the OPC paste, leading to enhanced compressive strength. Conversely, pressurized carbonation at 5atm with 99% CO₂ concentration resulted in rapid densification of the surface structure, which hindered CO₂ diffusion into the sample. This limited the extent of carbonation and prevented the improvement of physical properties.

• Journal of the Korea Concrete Institute
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• v.15 no.1
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• pp.95-101
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• 2003

Drying shrinkage cracking which may be caused by the relatively large specific surface is a matter of grave concern for latex modified concrete(LMC) overlay and rapid-setting cement latex modified concrete(RSLMC) overlay. LMC and RSLMC were studied for field applications very actively in terms of strength and durability in Korea. However, there were no considerations in drying shrinkage. Therefore, the purpose of this dissertation was to study the drying shrinkage properties of LMC and RSLMC with the main experimental variables such as cement types(ordinary portland cement, rapid setting cement), latex contents(0, 5, 10, 15, 20%) and curing days at a same controlled environment of 60% of relative humidity and $20^{\circ}C$ of temperature. The drying shrinkage for specimens was measured with a digital dial gauge of Demec. The test results showed that the drying shrinkage of LMC and RSLMC were considerably lower than that of OPC and RSC, respectively. This might be attributed to the interlocking of hydrated cement and aggregates by a film of latex particles, water retention due to hydrophobic, and colloidal properties of the latexes resulting in reduced water evaporation.

• Advances in materials Research
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• v.4 no.1
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• pp.13-22
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• 2015

Concrete suffers strength loss when subjected to elevated temperatures during an accidental event such as fire. The loss in strength of concrete is mainly attributed to decomposition of C-S-H gel and release of chemically bound water, which begins when the temperature exceeds $500^{\circ}C$. But it is unclear about how much strength loss occurs in different stages of heating, retention and cooling regimes. This work is carried out to separate the total strength loss into losses during different stages of heating, retention and cooling. Tests were carried out on both Ordinary Portland Cement (OPC) based concrete and Ground Granulated Blast Furnace Slag (GGBFS) blended concrete for $200^{\circ}C$, $400^{\circ}C$, $600^{\circ}C$ and $800^{\circ}C$ with a retention period of 1 hour for each of these temperature levels. Furnace cooling was adopted throughout the experiment. This study reports strength loss contribution during heating, retention and cooling regimes for both OPC based and GGBFS based concretes.

• Advances in concrete construction
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• v.10 no.2
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• pp.127-140
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• 2020

This study explores the feasibility of granite waste aggregate (GWA) as a partial replacement of natural fine aggregate (NFA) in binary blend self-compacting concrete (SCC) prepared with fly ash. Total of nine SCC mixtures were prepared wherein one was Ordinary Portland cement (OPC) based control SCC mixture and remaining were fly ash based binary blend SCC mixtures which included the various percentages of GWA. Fresh properties tests such as slump flow, T₅₀₀, V-funnel, J-ring, L-box, U-box, segregation resistance, bleeding, fresh density, and loss of slump flow (with time) were conducted. Compressive strength and percentage of permeable voids were evaluated in the hardened state. All the SCC mixtures exhibited sufficient flowability, passing ability, and resistance to segregation. Besides, all the binary blend SCC mixtures exhibited lower fresh density and bleeding, and better residual slump (up to 50% of GWA) compared to the OPC based control SCC mixture. Binary blend SCC mixture incorporating up to 40% GWA provided higher compressive strength than binary blend control SCC mixture. The findings of this study encourage the utilization of GWA in the development of binary blend SCC mixtures with satisfactory workability characteristics as a replacement of NFA.

• Computers and Concrete
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• v.20 no.4
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• pp.461-468
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• 2017

With the increasing demand in the production of concrete, there is a need for adopting a feasible, economical and sustainable technique to fulfill practical requirements. Self-Compacting Concrete (SCC) is one such technique which addresses the concrete industry in providing eco-friendly and cost effective concrete. The objective of the present study is to develop a mix design for SCC with Crushed Rock Fines (CRF) as fine aggregate based on the plastic viscosity of the mix and validate the same for its fresh and hardened properties. Effect of plastic viscosity on the fresh and hardened properties of SCC is also addressed in the present study. SCC mixes are made with binary and ternary blends of Fly Ash (FA) and Ground Granulated Blast Slag (GGBS) with varying percentages as a partial replacement to Ordinary Portland Cement (OPC). The proposed mix design is validated successfully with the experimental investigations. The results obtained, indicated that the fresh properties are best achieved for SCC mix with ternary blend followed by binary blend with GGBS, Fly Ash and mix with pure OPC. It is also observed that the replacement of sand with 100% CRF resulted in a workable and cohesive mix.

• Advances in concrete construction
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• v.7 no.4
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• pp.263-275
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• 2019

In the present work, Granulated Blast Furnace Slag (GBFS) and Fly ash (FA) were used as partial replacement of Natural Sand (NS) and Ordinary Portland Cement (OPC) by weight. One control mix, one with GBFS, three with FA and three with GBFS-FA combined mixes were prepared. Replacements were 50% GBFS with NS and 20%, 30% and 40% FA with OPC. Preliminary investigation on development of compressive strength was carried out at 7, 28 and 90 days to ensure sustainability of waste materials in concrete matrix at room temperature. After 90days, thermo-mechanical study was performed on the specimen for a temperature regime of $200^{\circ}-1000^{\circ}C$ followed by furnace cooling. Weight loss, visual inspection along with colour change, residual compressive strength and microstructure analysis were performed to investigate the effect of replacement of GBFS and FA. Although adding waste mineral by-products enhanced the weight loss, their pozzolanicity and formation history at high temperature played a significant role in retaining higher residual compressive strength even up to $800^{\circ}C$. On detail microstructural study, it has been found that addition of FA and GBFS in concrete mix improved the density of concrete by development of extra calcium silicate gel before fire and restricts the development of micro-cracks at high temperature as well. In general, the authors are in favour of combined replacement mix in view of high volume mineral by-products utilization as fire protection.

• Journal of the Korea Concrete Institute
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• v.16 no.2 s.80
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• pp.241-248
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• 2004

The rheological properties of cement paste system mixed with mineral admixtures (MAs) used to increase the strength and improve durability and fluidity of concrete were investigated. And cement paste systems were designed as one-, two- and three-ingredients blended paste systems. The rheological properties of paste systems were assessed by Rotovisco RT 20 rheometer (Hakke inc.) having a cylindrical serrated spindle. The rheological properties of one-ingredient paste systems were improved with increasing the dosage of superplasticizer. For two-ingredients paste systems, as increasing the replacement ratio of blast furnace slag (BFS) and fly ash (FA), the yield stress and plastic viscosity were decreased compared with non-replacement. In the ordinary portland cement (OPC)-silica fume (SF) paste systems, in accordance with an increase in the replacement ratio of SF, the yield stress and plastic viscosity were increased steeply. For three-ingredients paste systems, both OPC-BFS-SF and OPC-FA-SF paste systems, the rheological properties were improved compared with the only replacement of SF. In the case of both two-and three-ingredients paste systems, the rheological properties using BFS were improved more than FA.