• Advances in nano research
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• v.5 no.2
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• pp.99-111
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• 2017

Nano particles have been gaining increasing attention and applied in many fields to fabricate new materials with novel functions due to their unique physical and chemical properties. In the present study two nano materials, namely nano silica (NS) and nano clay metakaolin (NMK) were partially replaced with ordinary Portland cement (OPC). The replacement level was varied from 0.5 to 2.0% in OPC and blended in cement mortar with a water cement ratio of 0.40. Mechanical property studies and durability experiments such as compressive strength, tensile strength, water absorption, depth of chloride penetration test. Nano silica was synthesized from rice husk ash and analyze the size using particle size analyzer. The results indicate that the compressive and tensile strength of the cement mortars containing nano materials were higher strength compared to the plain mortar with the same water cement ratio.

• Journal of the Korea institute for structural maintenance and inspection
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• v.11 no.4
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• pp.152-158
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• 2007

This is a fundamental research to utilize alkali activated cement(AAC) in concrete. The compressive strength of AAC concrete were measured for the various mixing ratios of activator/fly ash, and the mixing ratios of water glass, NaOH, and water among the activators. The mixing ratio of fine and coarse aggregates was maintained constantly. The relationships between the compressive strength and mixing ratios were analyzed to find the optimal mixing ratio of AAC concrete. As the results, the optimal mixing ratio of activator/fly ash in AAC concrete was 0.7, and that of water glass, NaOH, water among the activator was 4.0:1.0:2.5 for the maximum compressive strength.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.10a
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• pp.385-390
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• 2002

Autogenous shrinkage of concrete has been defined as decrease in volume due to hydration cement, not due to other causes such as evaporation, temperature change and external load and so on. For ordinary concretes, autogenous shrinkage is so little compared to the other deformations that it has been dignored. It has recently been proved, however, that autogenous shrinkage considerably increase with decrease in water to cement ratio. And it has been reported that cracking can be caused by autogenous shrinkage, when high- strength concretes were used. In this study, we propose an analytical system to represent autogenous shrinkage in cement paste in order to control crack due to autogenous shrinkage. The system is composed with the hydration model and pore structure model. Contrary to the usual assumption of uniform properties in the hydration progress, the hydration model to refine Tomosawa's represents the situation that inner and outer products are made in cement paste. The pore structure model is based upon the physical phenomenon of ion diffusion in cement paste and chemical phenomenon of hydration in cement particle. The proposed model can predict the pore volume ratio and the pore structure in cement paste under variable environmental conditions satisfactorily The autogenous shrinkage prdiction system with regard to pore structure development and hydration at early ages for different mix-proportions shows a reasonable agreement with the experimental data.

• Journal of the Korea Institute of Building Construction
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• v.12 no.2
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• pp.194-202
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• 2012

This paper predicts the cementing efficiency of fly-ash(FA) based on mortar test considering binder-water ratio and FA replacement ratio as experimental variables. The cementing efficiency prediction model proposed by statistical analysis enables us to estimate the value according to the binder-water ratio and FA replacement ratio of matrix. When FA replacement ratio is the same, the lower the binder-water ratio, the higher the estimated cementing efficiency. There are significant differences in the values according to binder-water ratio at FA replacement ratios of 15% or less, but there are almost no differences when FA replacement ratio is more than 15%. As the binder-water ratio increases, the variations in the values according to FA replacement ratio are great at FA replacement ratios of 15% or less. As the FA replacement ratios increase, the values increase for FA replacement ratios of 15% or less, but decrease for more than 15%. The values range from -0.71 to 1.24 at binder-water ratio of 1.67-2.86 and FA replacement ratio of 0-70%. The RMSE of the 28-day compressive strength predicted by modified water-cement ratio is 2.2 MPa. The values can be trusted, as there is good agreement between predicted strength and experimental strength.

• Polymer(Korea)
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• v.37 no.2
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• pp.148-155
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• 2013

The purpose of this study is to clarify the effect of the emulsifier ratio on the properties of the polymer cement mortars based on styrene-butyl acrylate (S/BA) latexes, and to obtain necessary basic data to develop appropriate latexes for cement modifiers. The polymer dispersions for cement modifiers was synthesized using styrene and butyl acrylate. Polymer cement mortars based on S/BA latexes were prepared with various monomer and emulsifier ratios, and their water-cement ratio, air content, flexural and compressive strengths, water absorption and chloride ion penetration were tested. From the test results, the maximum flexural and compressive strengths of polymer cement mortars based on S/BA latexes were obtained at a bound styrene content of 60% and an emulsifier ratio of 6%. Also, the water absorption and chloride ion penetration depth are greatly affected by the polymer-cement ratio rather than the bound styrene and emulsifier content. Accordingly, it is judged that S/BA latexes can be used place of the conventional polymer dispersions of cement modifier.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.123-128
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• 2001

The Purpose of this study is to clarify the effect of the monomer ratio on properties of the polymer-modified mortars using methyl methacrylate-butyl acrylate latexes, and to obtain basic data necessary to develop appropriate latexes for cement modifiers. This paper deals with the effect of the monomer ratio on the typical properties of polymer-modified mortars with methyl methacrylate-butyl acrylate latexes. The polymer latex-modified mortars are prepared with 5, 10, IS and 20% of polymer cement ratio respectively, and properties of modified mortars such as water absorption, compressive and flexural strengths, chloride-ion penetration depth are tested. The test results indicate that the monomer ratio is very important factors to characterize the strength properties of polymer-modified mortars, but the water absorption and chloride-ion penetration depth are influenced by polymer-cement ratio rather than monomer ratios.

• Proceedings of the Korean Society of Agricultural Engineers Conference
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• 2000.10a
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• pp.266-271
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• 2000

This study was performed to find out how much water the cement hydration reaction need. It is real situation that it is difficult to find out the amount of chemical combined water with stoichiometric chemical reaction form. Because several variation occurred during hydration reaction it's not easy to divide water which used at cement paste mixture. In this study high temperature(105$^{\circ}C$) dry method was used to divide evaporable water and non-evaporable water. The last is combined water chemically and some free water absorbed to products of hydration physically. The test was processed with variation of water cement ratio from 10% to 45% with 5% intervals. The weight of cement paste specimens were measured after dry for 72hours at each checking time(0.5, 1, 3, 5, 10, 24, 48, 72, 168hour). In this study some conclusions such as follows were derived. Firstly, Pure combined water contents required at cement hydration result in 23.3percent of the weight of cement. Secondly, The sufficient mixing water needed to fully hydrated cement result in about 40∼45percent of weight of cement. That is, gel pores water could be about 16.7∼21.7percent of weight of cement.

• Journal of the Korean Society for Railway
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• v.5 no.2
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• pp.61-69
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• 2002

Recycling of dredged soils as construction materials is experimently discussed in this paper. The strength of light-weighted soils(LWS) consisting of expanded polystyrene(EPS), dredged soils and cement is characterized by uniaxial and triaxial compression tests with varying initial water contents of dredged soils, the EPS volume and cement contents, and expanded ratio of EPS. Test results show that the strength of light-weighted soils increases with adding cement contents, whereas the strength increases with decreasing initial water contents of dredged soils and expanded ratio of EPS. It was, however, found that increasing the EPS volume makes a lower the strength of light-weighted soils.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.691-694
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• 2004

The effects of polymer-cement ratio and antifoamer content on the setting time and durability of high-fluidity polymer-modified mortars using redispersible polymer powder are examined. As a result, the setting time of the polymer-modified mortars using redispersible polymer powder tend to delayed with increasing polymer-cement ratio, regardless of the antifoamer content. The water absorption and chloride ion penetration depth of the high-fluidity polymer-modified mortars using redispersible polymer powder decrease with increasing polymer-cement ratio and antifoamer content. The water absorption and chloride ion penetration improvement is attributed to the improved bond between cement hydrates and aggregates because of the incorporation of redispersible polymer powder.

• Journal of the Korean Ceramic Society
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• v.44 no.9
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• pp.496-501
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• 2007

The properties of the polymer-modified mortars are influenced by the polymer film, cement hydrates and the combined structure between the organic and inorganic phases. Also, this quality of polymer modified cement strongly depend on weather condition. To overcome this problem, polymer-modified cement based on rapid setting cement mortars were prepared by varying polymer/cement mass ratio (P/C) with a constant water/cement mass ratio of 0.5. The effect of polymer on the hydration of this polymer cement is studied on different curing temperature. The results showed that the polymer mortar which is modified with rapid setting cement have superior physical strength properties on independent curing temperature. In addition the PIC ratio, the compressive strength, flexural strength, tensile strength and adhesion strength of mortar is enhances and polymer-modified cement based on rapid setting cement is more beneficial to the improvement of the mortar properties in jobsite.