• Advances in materials Research
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• v.8 no.2
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• pp.103-115
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• 2019

Polypropylene (PP) fibers for making fabric which is used for packing cement have a high strength and high tear resistance. Due to these excellent properties the present study investigates the effect of PP fibers on the mechanical strength of concrete. Mechanical strength parameters such as compressive strength, splitting tensile strength and flexural strength are evaluated. Structural integrity of concrete using Ultrasonic Pulse Velocity (UPV) was also studied. Concrete containing PP fibers in percentage of 0%, 0.15%, 0.25%, 0.5% and 0.75% was developed with a characteristic compressive strength of 25 MPa. Concrete cubes, cylinder and prismatic specimens were cast and tested. It was found that the UPV values recorded for all specimens were of the similar order. Test results indicated the used of PP fibers can significantly improve the flexural and splitting tensile strengths of concrete materials whereas it resulted a decreased in compressive strength. The relative increase in split tensile and flexural strength was optimum at a fiber dosage of 0.5% and a mild decreased were observed in 28 days compressive strength. The findings in this paper suggested that PP fibers deriving from these waste cement bags are a feasible fiber option for fiber-reinforced concrete productions.

• Journal of the Korea Concrete Institute
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• v.25 no.4
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• pp.411-418
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• 2013

Recently, in order to reduce a damage of chloride attack and hydration heat in marine concrete structures, blended cement in mixing the marine concrete is widely used. Long term strength development is distinct in concrete with blended cement and it also has excellent resistance to chloride attack and reduction of hydration heat. However, blended cement has a characteristic of relatively low compressive strength in early age of 28 days. On the other hand, a high level of compressive strength is required in the Standard Specification for marine concrete mix design. Such concrete mix design satisfying Standard Specification is effective to chloride attack but disadvantageous for hydration heat reduction due to large quantity of binder. In this study, the material properties of marine concrete considering water-binder ratio and binder type are experimentally investigated. Through the research results, compressive strength in blended cement at the age of 56 days is similar although it has smaller compressive strength at the age of 28 days compared with result of OPC (ordinary portland cement). Even though blended cement has a large water-binder ratio and small unit of binder content, chloride ion diffusion coefficient is still small and hydration heat is also found to be reduced. For meeting the required compressive strength in Standard Specification for marine concrete at 28 days, the increased unit content of binder is needed but the increased hydration heat is also expected.

• Journal of Nuclear Fuel Cycle and Waste Technology(JNFCWT)
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• v.11 no.4
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• pp.271-280
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• 2013

Since the decommissioning of nuclear plants and facilities, large quantities of slightly contaminated concrete waste have been generated. In Korea, the decontamination and decommissioning of the KRR-1, 2 at the KAERI have been under way. And concrete waste was generated about 800 drums of 200 L. The conditioning of concrete waste is needed for final disposal. The concrete waste is conditioned as follows: mortar using coarse and fine aggregates is filled void space after concrete rubble pre-placement into 200 L drum. Thus, this research has developed an optimizing mixing ratio of concrete waste, water, and cement and has evaluated characteristics of a cement waste form to meet the requirements specified in disposal site specific waste acceptance criteria. The results obtained from compressive strength test, leaching test, thermal cycling test of cement waste forms conclude that the concrete waste, water, and cement have been suggested to have 75:15:10wt% as the optimized mixing ratio. Also, the compressive strength of cement waste form was satisfied that including fine powder up to maximum 40wt% in concrete debris wastes about 75%. As a result of scale-up test, the mixture of concrete waste, water, and cement is 75:10:15wt% meet the satisfied compressive strength because the free water increased with and increased in particle size.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.05a
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• pp.289-294
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• 2001

This study concerns the cement-solidification/stabilization of the waste with high concentration heavy metals. Compressive strength and leaching test of heavy metals were evaluated for ing types of cements and the effect of the additives of Hauyne clinker and slag were also cussed. Using ordinary portland cement, rapid hardening portland cement and the cement with additives solidification materials, it shows that the strength and stability of concrete is satisfactory and superiority is in the order of rapid hardening portland cement > the cement with additives > nary portland cements.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.239-244
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• 2001

Opens the construction market recently, the construction industry of Korea has faced up to the barrier of globalism, and has been enforced to follow the various global standards in many aspects. Accordingly, it is expected that the test method related to the cement and concrete will be changed to conform to the international standards in Korea. Therefore, in this study, the strength tests are executed for the cement mortars, made by KS and ISO standards respectively, and then obtains such results. 1) The flow of the cement mortar according to ISO is about 8% higher ,than that of KS. 2) The flexural strength of the cement mortar according to ISO is about 10~20% higher than that of KS, and the compressive strength is about 30% higher. 3) The compressive strength relation between the cement mortars of KS and ISO may be expressed in the first-order recurrence formula as follows: Y = 1.33X - 8 In which X is the compressive strength(kgf/$\textrm{cm}^2$) of the mortar according to KS and Y is the compressive strength(kgf/$\textrm{cm}^2$) of the mortar according to ISO.

• Journal of the Korea Concrete Institute
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• v.16 no.1 s.79
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• pp.130-138
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• 2004

The primary factors that affecting concrete sulfate resistance are the chemistry of the Portland cement and the chemistryandreplacementlevelofmineraladmixtures. In order to investigate the effect of those on the sulfate attack the testing program involved the testing of several different mortar mixes using the standardized test, ASTM C 1012. four different cements were evaluated including one Type I cement, two Type I-II cements, and one Type V cement. Mortar mixes were also made with mineral admixtures as each cement was combined with three different types of mineral admixtures. One Class F fly ash and one Class C fly ash was added in various percent volumetric replacement levels. The expansion measurements of mortar bars were taken and compared with expansion criteria recommended from past experience to investigate the effect of each factor.

• Journal of the Korean Ceramic Society
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• v.46 no.4
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• pp.365-371
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• 2009

It is well known that the properties of concrete such as the compressive strength, water permeability, water tightness and durability are affected by micro-structure in hardened cement paste. Especially, for durability of concrete, watertightness of cementitious materials is the most critical property among various properties. Recently, many types of materials as organic and/or inorganic materials are used for watertightness of concrete. In this study, The effect of Stearic Acid at $0.5\;wt%{\sim}3.0\;wt%$ adding ratios on the hydration and watertightness property of cement were investigated. And we also discussed the changing of microstructure in hardened cement paste by addition of Stearic Acid. Cement paste with Stearic Acid showed improvement of watertightness by reducing of cement total pore volume and decomposition of Stearic Acid.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.323-326
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• 1999

The purpose of this study is to examine the properties of cement mortar with PVA(Poy Vinyl Alcohol) and MC(Methyl Cellulos). In this paper, Water-soluble polymer cement motar using PVA and MC with water-cement ratio of 50%, polymer-cement ratio of 1.0%, 0.8% and a ratio of cement to fine aggregate (size: #5, #7) 2:3 are prepared, and tested for compressive strength, shear bond strength, flow test, penetration and dry-shirinkage.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.216-219
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• 2004

Due to the recent amazing achievements in nano technology. preparation of cement nano particles by mechanical method are examined to improve their properties. The experimental results show that the particle size after 3 hr milling were about 500nm. The SEM photographs of specimens also reveal that average sizes of cement particles are gradually decreased by milling time. And in the TG/DSC, influence of the alcohol is showed strongly. The value of TG of the crushed cement was larger than that of the non-crushed cement. That is also judged to be cause the alcohol.

• Proceedings of the Korea Concrete Institute Conference
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• 1996.04a
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• pp.166-171
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• 1996

This study examines whether the raw diatomaceous rock, after thermally activated for converting into a pozzolanic form, can improve cement quality(i.e., compressive strength) of the cement-mortar. The diatomaceous rock, heat-treated at 75$0^{\circ}C$ for 30minutes as an optimum pozzolanic form was mixed with OPC(Ordinary Portland Cement) on a weight basis from 0, 2.5, 5.0, 10, 20, 40%. The cement quality was then assessed by the compressive strength and analysis of XRD(S-Ray Diffraction) and SEM(Scanning Electron Microscope).