• Journal of the Korean Ceramic Society
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• v.27 no.7
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• pp.861-868
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• 1990

Investigation for the preparation of high strength hardened cement paste using ordinary portland cement, hydroxypropyl methyl cellulose(HPMC) with SiC powder was carried out. The cement paste was mixed with 0.1 of water cement ratio by twin roll mill and cured 60 days in humidity chamber. The hydration degree of cement paste cured with W/C=0.1 in 60 days was about 30% and most pores in the paste were found to be existed as gel pores of diameter less than 0.01㎛. The maximum flexural strength of hardened cement paste was about 960kg/㎠. When the SiC powder was added to the paste, the flexural strength was 1000∼1100kg/㎠ and the Young's modulus was 8∼9×105kg/㎠.

• Journal of the Korean Ceramic Society
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• v.27 no.8
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• pp.1034-1042
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• 1990

Investigation for the preparation of high strength hardened cement paste using ordinary portland cement, hydroxypropyl methyl cellulose(HPMC) with various admixtures was carried out. The cement paste was mixed with 0.1 of water cement ratio by twin roll mill and cured 60 days in humidity chamber. When the quartz powder or white cement was added to the paste, the flexural strength was 900∼1000kg/㎠ and the Young's modulus was 8∼9×105kg/㎠. When the silicafume was added, the flexural strength was 800kg/㎠ and the Young's modulus was 6×105kg/㎠.

• Proceedings of the Korea Concrete Institute Conference
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• 1990.10a
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• pp.131-134
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• 1990

Many papers have been published on drying shrinkage of hardened cement paste and cement mortar. The causes of drying shrinkage in cement mortar may be attributed to its mechanical properties, temperature, curing time and the evaporation of water from cement mortar. This paper deals only with drying shrinkage in cement mortar. In particular, the relationships between water evaporation and drying shrinkage are discussed.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2006.11a
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• pp.57-60
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• 2006

This study proposes the physical properties of the hardened lightweight cement using the polyethylene tube and to make the fundamental data regarding a new lightweight concrete development. The aerated concrete is displaying various effects such as lightweight, insulation characteristic and it is coming to be widely applied the slab layer of apartment as an insulating material but currently the aerated concrete has many problems. Therefore, demonstrating similar property of former aerated concrete and improving the defects, developing new hardened cement is needed. In this study, we predict adopting possibility of hollow core polyethylene tube, as a material to make cement hardening containing a lot of void. So we changed the mixing ratio, a diameter and length of the polyethylene tube and improved the compressive strength and unit capacity weight of the lightweight cement hardening body. From the test results, we judge that the aerated concrete is a developmental possibility.

• Advances in concrete construction
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• v.7 no.1
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• pp.31-37
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• 2019

This paper evaluates the workability and hardened properties of self-compacting concrete (SCC) containing silica fume as the partial replacement of cement. SCC mixtures with 0, 2, 4, 6, 8 and 10% silica fume were tested for fresh and hardened properties. Slump flow with $T_{500}$ time, L-box and V-funnel tests were performed for evaluating the workability properties of SCC mixtures. Compressive strength, splitting tensile strength and modulus of rupture were performed on hardened SCC mixtures. Experiments revealed that replacement of cement by silica fume equal to and more than 4% reduced the slump flow diameter and increased the $T_{500}$ and V-funnel time linearly. Compressive strength, splitting tensile strength and modulus of rupture increased with increasing the replacement level of cement by silica fume and were found to be maximum for SCC mixture with 10% silica fume. Further, residual hardened properties of SCC mixture yielding maximum strengths (i.e., SCC with 10% silica fume) were determined experimentally after heating the concrete samples up to 200, 400, 600 and $800^{\circ}C$. Reductions in hardened properties up to $200^{\circ}C$ were found to be very close to normal vibrated concrete (NVC). For 400 and $600^{\circ}C$ reductions in hardened properties of SCC were found to be more than NVC of the same strength. Explosive spalling occurred in concrete specimens before reaching $800^{\circ}C$.

• Journal of the Korea Institute of Building Construction
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• v.15 no.5
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• pp.451-456
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• 2015

This study aimed to evaluate of the hardened properties (mortar consistency, setting time, absorption properties, drying shrinkage, and bond strength) of the basalt powder sludge mortar recycling a basalt powder sludge occurred during the manufacture process of basalt stone as a replacing material for the sea-sand used to cement filling compound for surface preparation. The hardened mortar made of the basalt powder sludge showed an enhanced performance or similar with the properties of normal mortar used to cement filling compound for surface preparation. But, the drying shrinkage was increased more than a normal cement mortar in the hardened mortar made of the basalt powder sludge since curing 8 - 9days. And the bond strength is low in the hardened mortar used the basalt powder sludge. On the whole, properties of the hardened mortar used the basalt powder sludge correspond to the required minimum quality criterion in the KS F 4716 'cement filling compound for surface preparation'.

• Proceedings of the Korea Concrete Institute Conference
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• 1999.10a
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• pp.69-72
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• 1999

In this study, we blended 2 grades of ultra fine cement using the results of previous stud. And the cement slurry was produced by water each water/cement ratio. The slurries were observed hydration phenomena during 28 days with SEM, XRD and DSC. The specimen made by slurry were evaluated with the hardened properties such as compressive strength, flexural strength length change and water absorption. And were tested the adhesive strength of specimen made by injecting the slurry between mortar bars.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2017.11a
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• pp.113-114
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• 2017

In this study, the change of composition of cement hardened at high temperature through XRD was observed. The specimen was made of cement paste and the heating rate condition was applied at rapid thermal annealing (10.0℃ / min). The decrease of calcium hydroxide was not confirmed, but the calcium carbonate tended to be impossible or decreased after 800℃. Calcium silicate and larnite were observed to increase with increasing temperature. It is considered that silicic acid, which is a stable structure due to the decomposition of calcium silicate, is changed into a phase such as lime.

• Journal of the Korean Ceramic Society
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• v.27 no.5
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• pp.589-596
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• 1990

In this study, the freezing and thawing resistance in sea-water of hardened cement paste was investigated by adding slag, diatomaceous earth and fly ash as blending materials and air entraining agent and superplasticizer as admixtures to the cement paste. The structure of hardened cement pate was densified by potential hydraulic properties and pozzolan reactivities of materials and the freezing and thawing resistance of the paste was improved with the effect blending materials and admixtures. As the blending materials were added to the paste, the quantity of C3A was relatively reduced and the formation of expansive ettringite was suppressed to decrease the penetration of sea-water or Cl-, SO42-ion, and then freeze-thaw resistance was enhanced. Particulary, when 40% of slag was mixed, the resistance was excellent.

• Journal of the Korean Ceramic Society
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• v.25 no.5
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• pp.532-540
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• 1988

Even the finest cement as having a specific surface area of 6.000~8.500$\textrm{cm}^2$/g (Blaine) is to convert into low-porosity hardened cement paste by the use of appropriate plasticizer. In this study, tests were carried out on such a special cement mix(fineness of 6.000$\textrm{cm}^2$/g, Ca-lignosulfonate plus k2CO3 as plasticizer and W/C=0.25) in comparison with ordinary Portland cement. Owing mainly to the high fineness of the cement powder and the low water-to-cement ratio, the hardened low-porosity cement paste showed a very tight microstructure, the pore texture of which consisted of micropores and wide pores only of small radii. The consequence of such mix was hence that the low-porosity special cement had excellent properties of early-high and very high strengths as compared to ordinary Portland cement. Its volume change when dried in the air or re-wetted, exhibited superor behaviour as well.