• Geomechanics and Engineering
• /
• v.29 no.4
• /
• pp.391-405
• /
• 2022

A newly proposed grouting simulation method, the sequential diffusion solidification method was introduced into the numerical simulation of combined bi-borehole grouting. The traditional, critical and difficult numerical problem for the temporal and spatial variation simulation of the slurry is solved. Thus, numerical simulation of grouting and blocking of flowing water in karst conduits is realized and the mechanism understanding of the combined bi-borehole technology is promoted. The sensitivity analysis of the influence factors of combined bi-borehole grouting was investigated. Through orthogonal experiment, the influences of proximal and distal slurry properties, the initial flow velocity of the conduit and the proximal and distal slurry injection rate on the blocking efficiency are compared. The velocity variation, pressure variation and slurry deposition phenomenon were monitored, and the flow field characteristics and slurry outflow behavior were analyzed. The interaction mechanism between the proximal and distal slurries in the combined bi-borehole grouting is revealed. The results show that, under the orthogonal experiment conditions, the slurry injection rate has the greatest impact on blocking. With a constant slurry injection rate, the blocking efficiency can be increased by more than 30% when using slurry with weak time-dependent viscosity behavior in the distal borehole and slurry with strong time-dependent viscosity behavior in the proximal borehole respectively. According to the results of numerical simulation, the grouting scheme of "intercept the flow from the proximal borehole by quick-setting slurry, and grout cement slurry from the distal borehole" is put forward and successfully applied to the water inflow treatment project of China Resources Cement (Pingnan) Limestone Mine.

• Journal of Digital Convergence
• /
• v.19 no.3
• /
• pp.245-251
• /
• 2021

This study was to investigate the effect of the new surface treatment method of zirconia on the shear bond strength with resin cement. The zirconia specimens were classified according to the surface treatment. CON: non-treatment, HF: 10 minutes exposure to 9% HF, ZS15: Apply 15% ZrO2 slurry, ZS30: Apply 30% ZrO2 slurry, ZS50: Apply 50% ZrO2 slurry. The resin cement was layered on the surface treated zirconia, and the shear bond strength between the zirconia and the resin cement was measured after thermo-cycling. The statistical methods for shear bond strength were Kruskal-Wallis test, Mann-Whitney U test, and Bonferroni correction(α=.05/10=.005). ZS15, ZS30, and ZS50 groups treated with zirconia slurry showed higher shear bond strength than CON and HF groups(p<.05/10=.005). Within the limits of this study, the surface treatment using zirconia slurry increased the shear bond strength with resin cement. The new surface treatment method complements and improves the limitations of the adhesion of zirconia, so that various clinical applications of zirconia can be expected.

• Cement Symposium
• /
• no.27
• /
• pp.54-60
• /
• 2000

As conventional grouting materials for the sheath such as cement slurry or cement-mortar are mixed and pumped in site, those harden with bleeding or shrinkage and meets low compressive strength. Also the materials haven''t always same cements, sand size d

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.05a
• /
• pp.301-306
• /
• 2001

This study was _ performed of rheological properities for slurry of ultra fine cement using admixtures. An experimental parameter is W/B and superplasticizier ratio and different water-soluble polymers. As a results, it's strongly appeared to rheological properties of slurry as particles ratio, it's know that rheological properities affected by admixtures.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1996.10a
• /
• pp.175-182
• /
• 1996

This paper deals with the properties of water permeability and porosity of cement mortar substrate coated with siliceous slurry coating under the exposure environment. Conditions of exposure enviornment are four kinds of in constant temperature water and humidity box, in indoor and outdoor exposure. Coated mortar substrate was expected continually increase in water and humidity condition, but was not in dry condition. Watertightness effect of siliceous coating was better in the condition of humidity then the dry condition, and the pore volume was decreased in that condition.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2000.10b
• /
• pp.1205-1210
• /
• 2000

In this research we made the mean cement particle size 4 $\mu\textrm{m}$ which can penetrate even minor cracks based on the theory of J.K. Michel who reported particles can penetrate the crack of width up to 3 times of maximum particle size. The cement slurries were produced by adding super plasticizer. The slurries were tested with slurry characterization methods and its rheological properties were characterized. The early hydrated phenomena of ultra fine cement were observed by SEM, XRD and DSC during 24 hours. Mechanical properties of hardened slurry with JIS molds were also tested in 3, 7 and 28 days. The cracked specimens which were repaired with slurries produced various conditions were tested after 3, 7 and 28 days curing in the air and adhesion properties were characterized.

• Journal of the Korea Concrete Institute
• /
• v.18 no.5 s.95
• /
• pp.703-708
• /
• 2006

The slurry infiltrated fiber concrete(SIFCON) is recognized as one of the most promising new construction materials. Compressive and direct tensile tests are performed to investigate the mechanical property of SIFCON. Hooked-end steel fibers are used in the mix with fiber volume fraction varied from 4% to 10%. The water/cement ratio is kept constant at 0.4. The amount of silica fume added is 10% by weight of cement and 0.5% of water reducing agent is added to improve the workability of the slurry. The test results in this study show that the compressive strength of SIFCON is about 1.59 to 2.68 times in comparison with the cement paste. Tensile strength is showed the enhancement of about 2.51 to 8.77 times. It is also observed that the toughness and ductility of SIFCON are increased significantly with the increasing in fiber volume fraction.

• Journal of the Korea Concrete Institute
• /
• v.13 no.4
• /
• pp.346-353
• /
• 2001

This research investigates the mixture proportioning of waste newsprint paper fiber for thin-cement product. Waste newsprint paper fibers obtained through shredded mechanically by a dry process. Waste newsprint paper fiber reinforced cement composites was manufacted by slurry-dewatering method. The waste newsprint paper fiber reinforcement conditions (fiber mass fraction, level of substitution of virgin fibers, level of fiber beating) and processing variables (pressed, unpressed) are optimized through experimental studies and statistical analyses based on factorial design of experiments and analyses of variance. The optimized recycled waste newsprint paper fiber reinforced cement composites were technically evaluated. The results are shown to possess acceptable properties and strong potentials of the recycling of waste newsprint paper of the reinforcement of thin-cement products.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1993.04a
• /
• pp.89-92
• /
• 1993

This paper deals with the effect of siliceous slurry coatings on mortar microstructure under a damp environment. For estimation on effect of siliceous slurry coating, microstructure of coated mortar was observed through SEM. Crystal production in mivrosturcture of coated mortar was periodically increased, and more produced in mortar of high water-cement ratios. And they were generated mainly in mortar ranging from the surface to the inside about 2.5 or 3mm deep.

• Journal of the Korea Institute of Building Construction
• /
• v.8 no.3
• /
• pp.93-99
• /
• 2008

The purpose of this study is to evaluate the bond strength and corrosion resistance of coated reinforcing bar using hybrid-type polymer cement slurry(PCS). PCS coated steels, which is made from two types of polymer dispersions such as St/BA and EVA are prepared, and tested for bond strength and various corrosion resistances such as autoclaved cure, carbonation and H2SO4 solution. From the test results, the bond strength of PCS coated reinforcing bar using ordinary portland cement at 1-5, 2-1 and 4-5 of mixes is higher than that of uncoated regular steel. However, bond strength of almost PCS coated reinforcing bars using ultra rapid high strength cement is higher than that of epoxy coated bar, is also in ranges of 102% to 123% compared to that of uncoated regular steel. In autoclaved accelerating test, the ratio of corrosion of uncoated regular steel is increased with the increase in NaCl content, but the corrosion of PCS coated steel was very small. In the acceleration test for carbonation, increasing the amount of NaCl the corrosion of coated steel did not produce. The corrosion of uncoated regular steel is increased with the increase in the amount of NaCl. It can be seen that the NaCl following the acceleration test for carbonation can lower the corrosion resistance of concrete. As a result, the corrosion of steel largely is affected by the acceleration curing, chloride ion penetration and carbonation and shown more severe corrosion by applying complex factors. These corrosions of steel can be suppressed by the coating of PCS.