• Proceedings of the Korean Ceranic Society Conference
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• 2007.07a
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• pp.237-245
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• 2007

• Proceedings of the Korean Ceranic Society Conference
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• 2007.07a
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• pp.97-102
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• 2007

• KIEAE Journal
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• v.12 no.3
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• pp.115-122
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• 2012

Based on previous research and existing literature, this study examines the development of admixture, which increases the early concrete strength (1 and 3 day) by mixing blast furnace slag cement and concrete stimulant. The research on early strength development of concrete is necessary in dealing with the drawbacks of slow early strength concrete on site and to shorten the construction time. The study confirmed that when a high alkaline mortar mixture is mixed with blast furnace slag, the early strength of admixture exceeds that of ordinary portland cement (OPC). The use of calcium chloride ($CaCl_2$) promotes hydration of cement at low temperature and show similar strength as the blast furnace slag admixture. Although calcium chloride seems economically advantageous, it causes steel corrosion and its use in concrete should be further studied in-depth.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.11
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• pp.147-154
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• 2019

The purpose of this study is to evaluate the effect of admixtures as blast-furnace slag(BF) and fly ash(FA) on tensile and adhesive properties of polymer cement mortar(PCM) with EVA emulsion. The test specimens are prepared with five polymer-cement ratio(P/C) and five admixture contents, and tested for tensile strength and adhesion in tension. From the test results, the tensile strength and adhesion in tension could be improved by an appropriate combination of P/C and admixture contents. In particular, the maximum of tensile strength of PCM with P/C 10% and BF content of 10% is 4.70MPa which is about 1.55 times higher than that of plain mortar, and about 1.22 times that of PCM that does not contain any mixture. The ratio of adhesion in tension to tensile strength of PCM with admixtures averaged 55.8%. It is also apparent that admixture contents of 5% or 10% could be proposed for improvement of tensile strength and adhesion in tension of PCM.

• The Journal of Engineering Geology
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• v.6 no.3
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• pp.155-163
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• 1996

The current ASTM C227-90 is a prescription on the mortar-bar method. This recornrnends that mortar-bars should be made using a mixing ratio by weight of 675 grams aggregate to 300 grams cement, and their initial lengths should be measured in $24{\pm}2$ hours. This method emphasizes that the prepare sample mortar-bars and calculate expansion rates of them. This method requires constant G values (effective gauge lengths) of denominator in the calculation formula, which are fixed either at 10 inches or 250mm. This study, based on experimental approaches, reexamines the suggestions made by those two prescriptions above and important results are summarized in the following. 1. Not only alkali-aggregate reaction but also interaction of interstitial and gel water are responsible for expansion of mortar-bars. This requires partial modification of the current ASTM C227-90. 2. A mixing ratio by volume rather than by weight of aggregate to cement is recommendable for measuring the amount of expansion resulting from alkali-aggregate reaction and from interstitial water. 3. The method of when to measure initial lengths and how to calculate expansion rate suggested by ASThI C227-90 and Cl90-93a should partly be modified for more accurate results.

• Journal of the Korean Recycled Construction Resources Institute
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• v.5 no.3
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• pp.247-252
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• 2017

The aim of this research is the feasibility analysis of the reject ash premixed cement mortar with combined aggregate. Namely, for the combined aggregate with two different qualities of aggregates, a fundamental properties of cement mortar was evaluated depending on various replacing ratios of reject ash(Ri). According to the experimental results, the combined aggregate consisted with low-quality aggregate and sea sand did not change the flow value depending on the reject ash while the combined aggregates consisted with low quality aggregate and sea sand; and consisted exploded debris sand and sea sand the increasing reject ash increased the air content with increased replacing ratio of reject ash. In the case of compressive strength, as the replacing ratio of reject ash was increased, the compressive strength was increased. It is considered that when 5% of reject ash replacing ratio made similar quality of cement mortar with favorable quality aggregate, hence, it can be suggested that 5% replacement of reject ash for desirable fluidity and compressive strength of concrete.

• Journal of the Korea Academia-Industrial cooperation Society
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• v.18 no.1
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• pp.715-723
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• 2017

This study investigates the properties of a high-performance cementitious composite with partial substitution of stone dust for fine aggregate. The relationship between the properties and particle size distribution was analyzed using several analytical models. Experiments were carried out to examine the flowability, rheology, and strength of cement mortars with different stone-dust replacement ratios of 0-30 wt.%. The results showed improved flowability, lower rheological parameters (yield stress and plastic viscosity), and improved strength as the amount of stone dust increased. These results are closely related to the packing density of the solid particles in the mortar. The effect was therefore estimated by introducing an optimum particle size distribution (PSD) model for maximum packing density. The PSD with a higher amount of stone dust was closer to the optimum PSD, and the optimization was quantified using RMSE. The improvement in the PSD by the stone dust was proven to affect the flowability, strength, and plastic viscosity based on several relevant analytical models. The reduction in yield stress is related to the increase of the average particle diameter when using stone dust.

• Journal of the Korea Concrete Institute
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• v.27 no.3
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• pp.273-281
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• 2015

In this paper, the performance of alkali-activated slag cement (AASC) is assessed in terms of compressive strength and drying shrinkage, using three different types of silica sand and river sand. The sand type has an important influence on the properties of AASC mortar. Three silica sands (SS1, SS2 and SS3) and river sand (RS) were considered. Three series of blended sands have been tested. A first series (S1) with RS and SS1, a second series (S2) with RS and SS2 and third series (S3) with RS and SS3 with a different blended ratios. The result shows a very significant influence of the blended sand on the AASC mortar properties. The compressive strength and drying shrinkage related with the particle sizes and blended ratios of sands are investigated considering blended sand properties like fineness modulus (FM) and relative specific surface. The type and blended ratio of sand seems to have very significant and important consequences for the mix design of the AASC mortar.

• Explosives and Blasting
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• v.22 no.4
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• pp.7-15
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• 2004

An explosion modeling technique was developed by using the spherical discrete element code, PFC3D, which can be used to model the dynamic stress wave propagation phenomenon. The modeling technique is simply based on an idea that the explosion pressure should be applied to a PFC3D particle assembly not in the form of an external force (body force), but in the form of a contact force (surface force). According to this concept, the explosion pressure is applied to the wall particles by the scheme of radius expansion/contraction of inner-hole particles. The output wall force is compared to the input hole pressure in every time step, and a correction routine is activated to control the radius multiplier of the inner-hole particles. A comparative blast simulation far a cement mortar block of $80\times90\times80mm$ was conducted by using the conventional explosion modeling method and the new one. The results of the simulation are presented in a qualitative fashion.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.893-896
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• 2008

As this study is to test fundamental properties of cement mortars using in Metakaolin. Recently concern is increasing for concrete durability because of an increase in the concrete structure exposed to bad environments. In the event that mineral admixture Added, microstructure will be fined, so durability can be good. Also, the study for new admixture is progressing expect that admixture widely used, for example, silica fume, fly-ash, and slag, etc. Therefore this study is making an experiment on fundamental properties of diversities sample curing at water, sea water, 10% sodium sulfate solution, and magnesium sulfate solution, to compare using for metakaolin with silica fume and fly-ash.