• Journal of the Korea Academia-Industrial cooperation Society
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• v.19 no.12
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• pp.279-286
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• 2018

The grouting method is to reinforce the ground by injecting the chemical solution for the strengthening of the ground. Cement grouting material has usually used portland cement for centuries ago, but the cement particle size is large and the injection effect is limited. This study analyzes the effect of ultrafine cement grouting in rock ground using 3S-1 grouting in rock ground and ordinary Portland cement (OPC). The results of tests were compared and analyzed from the Lugeon test, bore loading test (P.M.T.), and injection (P-Q) test. The use of ultrafine cement (3S-1) had a higher effect (K, 10-6cm/sec) than OPC. The reinforcement effect of 3S-1 was also confirmed. Ultrafine cement (3S-1) was 4~9 times more injectable than OPC. Therefore, it is more advantageous to use ultrafine cement (3S-1) than OPC.

• Journal of Industrial Technology
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• v.24 no.A
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• pp.165-171
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• 2004

Latex modification of concrete provides the material with higher flexural strength, as well as high bond strength and reduced water permeability. However, If the thermal expansion properties of overlay concrete (latex-modified concretes) are big different from that of substrate (ordinary portland cement concrete), these would cause a big interfacial stresses and result in premature failure. Therefore, the purposes of this study were to investigate thermal expansion characteristics of latex-modified concrete with cement types. The result of thermal expansion showed the coefficient of thermal expansion of concretes increased with latex inclusion. The coefficient of thermal expansion of RSLMC was a little smaller than that of LMC, which might be due to the finer cement grain, compacter internal, and stiffer properties of concrete. However, the coefficients of LMC and RSLMC were quite similar to that of ordinary cement concrete. Thus, this would not cause an interfacial stresses and will enable to ensure long-term performance of concrete bridge deck overlays.

• Journal of the Korean Ceramic Society
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• v.47 no.5
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• pp.387-393
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• 2010

To improve concrete quality one of the most widely used chemical admixtures is polycarboxylate type superplasticizer. Unlike lignosulfonate and naphthalene-sulfonate, it has high dispersion property and excellent sustainable dispersion property for cement and concrete. Thus, polycarboxylate type superplasticizer has been widely used as a high-performance water reducing admixture together with silica fume in high-performance concrete and other applications for the dispersion of high-strength concrete over 100 MPa. However, even though there have been many studied on the dispersion of concrete by the structure of polycarboxylate type superplasticizer, there have a few studied that clarified the relationships between its rheological properties and microstructure properties in the early hydration behavior of ordinary portland cement. To investigate the correlations between the rheological properties and microstructure of cementitious materials with polycarboxylate type superplasticizer, this study experimented on the rheology, pore structure, heat evolution, and consistency in early hydration as well as on the compressive strength by early dispersion characteristics.

• Transactions of the Korean Society of Mechanical Engineers A
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• v.31 no.12
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• pp.1214-1220
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• 2007

The vertical roller mill, which performs the grinding and partly blending of raw material, is the one of the important machine to produce ordinary portland cement. It has been reported that an unexpected fatigue failure occurred in a table liner in the course of grinding portland cement. The life of table liner is estimated to $4{\times}10^7$ cycles in the design stage, but at the field, when its operating time reaches to $2{\times}10^6{\sim}8{\times}10^6$ cycles, the fracture of table liner begins to be found. The fracture of table liner is initiated from the outside edge of grinding path contacting with the grinding roller. Its maintenance normally take 30 % of the total maintenance costs of the roller mill. Therefore, this study shows the clarification of the reasons occurring the fatal destruction of the table liner by fatigue fracture analysis utilizing fracture mechanics and by the finite element method. And, the results from Goodman diagram illustrate relationship of including information on the transition between tensile and bending fatigue strength in the fatigue characterization of table liner.

• Journal of the Korean Ceramic Society
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• v.36 no.2
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• pp.130-135
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• 1999

The enhanced slag fineness and the batch water of low water-to-cement ratio(W/C) were employed in order to improve the early strength of blast-furnace slag blended cement at low temperature. A grinding aid was used to grind the blast-furnace slag into the fineness of 6,280$\textrm{cm}^2$/g (Blaine), and this fine slag was then homogeneously mixed with the ordinary Portland cement to produce the blast-furnace slag blended cement containing 40% slag by weight composition. On the other hand, the batch water could be reduced from W/C=0.50 (KS L 5105) to W/C=0.33 through a commercial, naphthalene type superplasticizer. Through the method mentioned above, the early strength of the blast-furnace slag blended cement at low temperature could be enhanced even somewhat higher than the Portland cement strength. And the microsturcture of the cement was studied by both the pore structure analysis and the A.C. impedance measurement.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.13 no.3
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• pp.13-24
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• 1993

The influence of the bubble structure and strength characteristics on the freeze-thaw resistance of high strength concrete is investigated by the laboratory experiment. The test conditions are formed in the manner that water is continueusly supplied externally and the specimens were received severe weather actions from ordinary to significantly low temperatures. The experiments are performed in two stages. In the first stage, the relation between the durability to frost action and the bubble structure is analyzed especially with respect to the water-cement ratio and the amount of air. The AE and non-AE concrete specimens made of ordinary portland cement are used in the test. In the second stage, the non-AE concrete specimens using vibratory compaction to improve the durability to frost action, and the high watertight specimens of rapid hardening portland cement to increase their initial strength are produced and tested. The degree of watertightness of the specimens is determined by measuring the permeability of the specimens and the bubble structure of the high watertight concrete is also estimated.

• Journal of the Korean GEO-environmental Society
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• v.23 no.11
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• pp.5-11
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• 2022

The objective of this study is to evaluate the mechanical properties of high-flowable retaining wall material (RWM) incorporated with ground granulated blast-furnace slag (SG) and steel fiber (SF) based on a comparison with those of ordinary portland cement (OPC). To produce the specimens of RWM, some chemical agents such as superplasticizer (SP), air-entrained agent (AEA) and viscosity modifying agent (VMA) are added in the fresh RWM. The compressive, split tensile and flexural strength measurements were performed on the hardened RWM specimens. Additionally, surface electric resistivity and absorption tests according to ASTM standards were carried out at predetermined periods after water curing. It was found that the mechanical properties of slag cement concrete (SGC) RWM mix are better than those ordinary portland cement concrete (OPC) RWM mix. The effect of SF is remarkable to improve the mechanical properties of RWM mixes. It is noted that the usage of SG shows a beneficial effect to resist water penetration as well as long-term strength development of RWM mixes.

• Journal of Korean Society of Environmental Engineers
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• v.29 no.7
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• pp.801-809
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• 2007

Fly ash and blast furnace slag are an industrial by-product that can be alkali-activated to yield adhesive and cementitious materials, whose production is less energy-intensive and emits less $CO_2$ than ordinary Portland cement manufacture. A laboratory investigation was carried out to evaluate the effect of alkali-activating conditions on compressive strength of fly ash/slag cement and the acid corrosion resistance of this cement. Two alkali activator solution, NaOH and waterglass + NaOH solutions, were used. Waterglass concentration was the factor that gave the highest compressive strength in all tests. The next significant factor was the NaOH concentration, followed by curing temperature. Acid corrosion resistance of FC(fly ash cement) and FSC(fly ash/slag cement), such as sulfuric$(H_2SO_4)$ and hydrochloric acid(HCl), was for better than Portland cement(PC).

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.161-166
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• 1994

Production of high strength concrete requires a low water-cement ratio and this leads to the high cement content. Mineral admixture like fly ash(FA) is often cheaper than ordinary portland cement(OPC) and this factor in combination with possible improvement in workability and moderation of the heat evolution of the cement-rich mixes tends to encourage its use. The other mineral admixture that its use has been widly advocated is silica fume that increases compressive strength due to its pozzolanic reaction. The objective of this study is to assess the contribution of mineral admixtures(FA, SF) to the workability and the strength of concrete with low water-binder ratios. In this experimental study that investigates and analyzes the properties of fresh concrete, it is presented that using admixtures like flysh and silica fume as binding material increases properties of high strength flowing concrete having very low water cementitious ratios of 0.25 and 0.30.

• Proceedings of the Korea Concrete Institute Conference
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• 1995.04a
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• pp.72-77
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• 1995

Blast-furnace slag cement has been used widely as a structural material due to the latent hydraulicity of granulated ground blast furnace slag(GGBS)for a long time as The wall as ordinary portland cement. In this study, based on the fundamental investigation on the high strength and high durable concrete using the high fineness GGBS the following remarks can be made. 1) The average desired strenth of concrete is Or=600~800kg/$\textrm{cm}^2$. 2) The above high strength concrete using the high fineness GGBS is more workable than those using only OPC. 3) The adiabatic temperature and drying shringkage decrease, so the density and resistance to sea water attack increase as results. 4)The unit cement content and unit air entrained admixture at the same desired strength of concrete decrease, so the economical high strength concrete can be manufactured from using the high fineness GGBS.