• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.517-520
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• 2008

In this study, corrosion resistance of steel in cracked-reinforced concrete was performed according to experimental method. Mixed design is OPC, 30% PFA, 60% GGBS and 10% SF, respectively. Moreover, corrosion resistance test was measured using ultra testing machine for 0.3mm crack induction. The corrosion resistance of blended concrete shows the results following OPC > 10%SF > 30% PFA > 60% GGBS after 60days curing. In case of mass loss test, embedded reinforcement in OPC concrete surveyed the minimum corrosion and appeared better corrosion resistance than blended concrete. As a result, corrosion resistance of sound concrete is higher than cracked concrete. Moreover, corrosion resistance of binary concrete is lower than OPC.

• Journal of Ocean Engineering and Technology
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• v.26 no.3
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• pp.26-32
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• 2012

Recently, concrete using multicomponent blended cement has been required to increase the freeze-thaw and sulfate resistances of concrete structures exposed to a marine environment. Thus, the purpose of this study was to propose the use of concrete containing multicomponent blended cement as one of the alternatives for concrete structures exposed to a marine environment. For this purpose, batches of concrete containing ordinary portland cement (OPC), binary blended cement (OPC-G, G: ground granulated blast slag), ternary blended cement (OPC-GF, F: fly ash), and quaternary blended cement (OPC-GFM, M: mata-kaolin) were made using a water-binder ratio of 50%. Then, the durability levels, including thesulfate and freeze-thaw resistances, were estimated for concrete samples containing OPC, OPC-G, OPC-GF, and OPC-GFM. It was observed from the tests that the durability levels of the concrete samples containing OPC-G and OPC-GF were found to be much better than that of the concrete containing OPC. The optimum mixing proportions were a40% replacement ratio of ground granulated blast slag for the binary blended cement and a30% replacement ratio of ground granulated blast slag and 10% fly ash for the ternary blended cement.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.805-808
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• 2008

This study analyzed the basic characteristics of concretes to develop 3 ingredients high performance concrete that displaced BS and FA, and the results are as follows. As part of fresh concrete characteristics, the flow was shown more increase than OPC with increase in admixture material displacement rate, and air amount tended to decrease with increase in admixture displacement rate. As hardened concrete characteristics, compressive strength decreased below OPC at early age with increase in BS and FA displacement rate, however at age 28 days, it was similar to OPC or increased above that. Particularly, at B30F15 with age 28 days, its compressive strength was about 15% higher than OPC

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.649-652
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• 2008

In this paper, the applicability of hwangtoh, as an alternative of cement paste, is investigated for the solution of internal heat and shrinkage caused by the hydration of cement paste. Several small-sized specimens of hwangtoh and ordinary portland concrete(OPC) were compared as to compressive strength, heat of hydration, and shrinkage strain. Moreover, the applicability of mass structure was reviewed through the test of large-size specimens. The 28-day compressive strength of hwangtoh concrete(HBC), ranged 18 to 33 Mpa, can reach that of ordinary portland concrete. Not only the maximin internal temperature of HBC was read about 1/4 of OPC as it is cured, but also its drying shrinkage decreased as lower as 50% of OPC starting from 60 days. Therefore, hwangtoh binder is more favorable than cement one in the view of hydration heat and shrinkage under the construction of mass structures.

• Journal of the Korea Institute of Building Construction
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• v.19 no.6
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• pp.511-520
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• 2019

The critical chloride content of rebar embedded in concrete was experimentally evaluated according to the admixture replacement ratio and admixture type. Four types of reinforced concrete were mixed OPC 100%, OPC 70% + GGBFS 30%, OPC 40% + GGBFS 60%, and OPC 40% + GGBFS 40% + FA 20%. NaCl solution was supplied to the specimens, and the open circuit potential of the embedded rebar was monitored. The specimens determined to initiate corrosion were cut at intervals of 5mm from the NaCl solution supply surface and conducted to chlorine ion profile. Corrosion initiation time of rebar embedded in concrete was delayed as the admixture replacement ratio increased. Looking at the critical chloride content of the types of reinforced concrete, it was highest in OPC 1.46kg/㎥, followed in order by S30 0.98kg/㎥, TBC 0.74kg/㎥, and S60 0.71kg/㎥.

• Advances in concrete construction
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• v.8 no.2
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• pp.119-126
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• 2019

This paper reports an experimental investigation conducted to evaluate the durability performance of concrete mixtures prepared utilizing blends of Type I Portland cement (OPC) and natural pozzolans (NPs) obtained from three different sources in Saudi Arabia. The control concrete mixture containing OPC alone as the binder and three concrete mixtures incorporating NPs were prepared keeping water/binder ratio of 0.4 (by weight), binder content of $370kg/m^3$, and fine/total aggregate ratio of 0.38 (by weight) invariant. The compressive strength and durability properties that included depth of water penetration, depth of carbonation, chloride diffusion coefficient, and resistance to reinforcement corrosion and sulfate attack were determined. Results of this study indicate that at all ages, the compressive strength of NP-admixed concrete mixtures was slightly less than that of the concrete containing OPC alone. However, the concrete mixtures containing NP exhibited lower depth of water penetration and chloride diffusion coefficient and more resistance to reinforcement corrosion and sulfate attack as compared to OPC. NP-admixed concrete showed relatively more depth of carbonation than OPC when subjected to accelerated carbonation. The results of this investigation indicates the viability of utilizing of Saudi natural pozzolans for improving the durability characteristics of concrete subjected to chloride and sulfate exposures.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.4
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• pp.259-266
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• 2018

In the work, the carbonation behavior and strength characteristics in cold-joint concrete are evaluated for OPC(Ordinary Portland Cement) and GGBFS(Ground Granulated Blast Furnace Slag)concrete considering three levels of curing age (28, 91 and 365 days). The compressive strength in GGBFS concrete is level of 86% of OPC concrete at the 91 days of curing period, but is level of 107% at 365 curing days due to hydration reaction. Carbonation velocities in both OPC and GGBFS concrete significantly decease after 91 curing days. The effect of cold joint on carbonation is evaluated to be small in GGBFS concrete. The increasing ratios of carbonation velocity in cold joint are 1.06 and 1.33 for 28-day and 365-day curing condition, respectively. However they decreases to 1.08 and 1.04 for GGBFS concrete for the same curing conditions.

• Journal of the Korea institute for structural maintenance and inspection
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• v.23 no.7
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• pp.113-119
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• 2019

Concrete structures built on reclaimed land are combined with chemical erosion such as chlorine and sulfate ions from seawater. Chloride attack deteriorates the performance of the structure by corroding reinforcing bars. In addition, the waste water treatment structure has a problem that the concrete is deteriorated by the sulfate generated inside. Therefore, in this study, the characteristics and chemical resistance of low heat cement concrete used in wastewater treatment structures constructed on reclaimed land were evaluated. As a result of the experiment, the target slump and air content were satisfied under all the mixing conditions. The slump of low heat cement (LHC) concrete was higher than that of ordinary portland cement (OPC) concrete, while the air content of LHC concrete was smaller than that of OPC concrete with the same mix proportion. As a result of compressive strength test, OPC concrete showed higher strength at younger age compared to 28 days. In contrast, LHC concrete exhibited higher strength than OPC concrete at the age of 56 days. As a result of chlorine ion penetration tests, LHC-B concrete showed chlorine ion penetration resistance performance of the "very low" level at the age of 56 days. As a result of chemical resistance evaluation, when the LHC concrete is applied without epoxy treatment, chemical resistance is improved by about 18% compared to OPC concrete. In testing chemical resistance, the epoxy coated concrete exhibited less than 5% strength reduction when compared to sound concrete.

• Journal of the Korea Concrete Institute
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• v.20 no.5
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• pp.549-555
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• 2008

In this paper, the applicability of Hwangtoh, as an alternative of cement paste, is investigated for the solution of internal heat and shrinkage caused by the hydration of cement paste. Several small-sized specimens of Hwangtoh and ordinary portland concrete (OPC) were compared as to compressive strength, heat of hydration, and shrinkage strain. Moreover, the applicability to the construction structures was reviewed through the test of large-size specimens. The 28-day compressive strength of Hwangtoh concrete (HBC), ranged 18 to 33 MPa, can reach that of OPC. Not only the maximun internal temperature of HBC was read about 1/4 of OPC as it is cured, but also its shrinkage decreased more than the OPC did. Therefore, Hwangtoh binder is more favorable than cement binder in terms of its hydration heat and shrinkage under the construction of concrete.

• International Journal of Concrete Structures and Materials
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• v.7 no.3
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• pp.239-249
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• 2013

In the present scenario to fulfill the demands of sustainable construction, concrete made with multi-blended cement system of OPC and different mineral admixtures, is the judicious choice for the construction industry. Silica fume (SF) and fly ash (FA) are the most commonly used mineral admixtures in ternary blend cement systems. Synergy between the contributions of both on the mechanical properties of the concrete is an important factor. This study reports the effect of replacement of OPC by fly ash (20, 30, 40 and 50 % replacement of OPC) and/or silica fume (7 and 10 %) on the mechanical properties of concrete like compressive strength and split tensile strength, with three different w/b ratio of 0.3, 0.4 and 0.45. The results indicate that, as the total replacement level of OPC in concrete using ternary blend of OPC + FA + SF increases, the strength with respect to control mix increases up to certain replacement level and thereafter decreases. If the cement content of control mixes at each w/b ratio is kept constant, then as w/b ratio decreases, higher percentage of OPC can be replaced with FA + SF to get 28 days strength comparable to the control mix. A new method was proposed to find the efficiency factor of SF and FA individually in ternary blend cement system, based on principle of modified Bolomey's equation for predicting compressive strength of concrete using binary blend cement system. Efficiency factor for SF and FA were always higher in ternary blend cement system than their respective binary blend cement system. Split tensile strength of concrete using binary and ternary cement system were higher than OPC for a given compressive strength level.