• Proceedings of the Korea Concrete Institute Conference
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• 2006.05b
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• pp.289-292
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• 2006

The purpose of this study was to evaluate a performance of latex-modified repair material applied to the substrate concrete. The experimental variables were latex-cement ratios (5, 10, 15%), polymer(0.5%, 1%) and admixtures. The flow, air content, compressive strength, flexural strength were tested. Test results showed that compressive and flexural strength decreased by adding hydroxyethyl cellulose and increasing water-binder ratio. The compressive and flexural strength were increased when addition of defoamer.

• Proceedings of the Korea Concrete Institute Conference
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• 2003.05a
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• pp.799-804
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• 2003

The purpose of this study was to investigate the effects of re-vibration and curing temperature onto the physical properties of latex-modified concrete with ordinary cement and rapid-setting cement, and thus to provide a guide line of re-vibration and curing conditions for good quality controls. The main experimental variables included two cement types(ordinary portland cement, rapid-setting cement), curing Temperature($10^{\circ}C$, $20^{\circ}C$, $30^{\circ}C$), re-vibration methods(continued, intermittent), and re-vibration times(initial setting, one day after mixing). The experimental results showed that the re-vibration affected little to the mechanical properties of LMC and RSLMC, while, the curing temperature a quite some. The early strength development was the highest at $20^{\circ}C$ curing temperature, and decreased at higher temperature. The permeability of concrete generally decreased with curing time. The rapid chloride permeability was a function of time and temperature. The chloride permeability of RSLMC was so small and negligible.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.769-772
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• 2004

Very-Early-Strength Latex-Modified Concrete(VESLMC) provides the repairing material with short curing time as well as excellent bond strength, flexural strength and impermeability against water and chloride. In 2001, VESLMC introduced in Korea and improved superior material through research and development on material properties and durability. In 2003, the field test progressed for study problems of VESLMC field application. This paper introduced equipment improvement for bridge deck repair save both repair time and labor, while producing quality VESLMC structures.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.445-448
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• 2004

Recently, bridge deck overlay with latex modified concrete is widely applied in domestic. the capacity of bridge deck overlay depends on bond state on the surface. factors that have an effect on bond state are clean condition on the surface, absence of surface microcracking, absence of laitance, overlay curing. In this study, it is researched that characteristic of bond strength according to moisture condition on the surface and the removal method of concrete. As a result, it shows high bond strength in dry condition when w/c is $31\%$ and in moisture condition when w/c is $38\%$ respectively. characteristic of bond strength according to the removal method of concrete shows high bond strength when using water-jets rather than jackhammers.

• Proceedings of the Korea Concrete Institute Conference
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• 2006.11a
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• pp.841-844
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• 2006

Recently, tunnels being constructed in korea with the increased construction of highways, high-speed railways and hydro structure. shotcrete and spray is one of the major processes in that construction. So general Shotcrete and spray has many problems on strength property, environmental pollution and human body noxiousness as the use of accelerater. However, In this paper using HES-LMS(High Early Strength Latex Modified Spray) without accelerater can solve problems which are mentioned above. problems that the hish early cement has can be solved by modifying material with latex. Therefore HES-LMS mortar is Classify by High performance and High ability. Analysis according to the variables such as W/C, Latex content and sand content is conducted. Studied about mechanical characteristic of material such as each parameter characteristic, and rebound characteristic is completed.

• Journal of Industrial Technology
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• v.22 no.A
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• pp.193-200
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• 2002

Drying shrinkage cracking which may be caused by the relatively large specific surface IS a matter of grave concern for latex modified concrete(LMC) overlay and rapid-setting cement latex modified concrete(RSLMC) overlay. LMC and RSLMC were studied for field applications very actively in terms of strength and durability in Korea. However, there were no considerations in drying shrinkage. Therefore, the purpose of this dissertation was to study the drying shrinkage properties of LMC and RSLMC with the main experimental variables such as cement types(ordinary portland cement, rapid setting cement), water-cement ratios and curing days at a same controlled environment of 60% of relative humidity and $20^{\circ}C$ of temperature The drying shrinkage for specimens was measured with a digital dial gauge of Demec. The test results showed that the drying shrinkage of LMC and RSLMC were considerably lower with low water-cement ratio, respectively This might be attributed to the interlocking of hydrated cement and aggregates by a film of latex particles, water retention due to hydrophobic, and colloidal properties of the latexes resulting in reduced water evaporation.

• Proceedings of the Korea Concrete Institute Conference
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• 2001.11a
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• pp.1029-1034
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• 2001

The purpose of this research is to develop rapid setting cement latex modified concrete (RSLMC) which will be used to overlay bridge deck for maintaining and repairing. The main experimental variables were the types of rapid setting cement and variation of latex and antifoam agent contents were selected as admixture factor, then the properties of workability and strength development and durability properties were investigated. The results of this study show that latex content give increment of a slump due to surface tension in polymer particles and reduce unit weight of water for preservation of workability. In addition, When no and 1.6~3.2% antifoam agent were mixed, 8%, 2.0~3.8% were respectively obtained. An increasing the amount of latex produced concrete with increased flexural strength, but with slightly lower compressive strength. Rapid chloride permeability and freezing-thawing test carried out. As a results, according to increment of containing ratio antifoamer, strength of RSLMC increase, permeability showed lower value than ignorable 100 coulombs. Also, in the case of more than antifoamer 1.6%, the relativity dynamic modulus is mantained more than 90%, but in case of 0, 5%, it decrease. In consequence, with the view of strength and workability of RSLMC, it is considered that appropriate content ratio of antifoam agent and latex solid are respectively 1.6% by latex weight, 15% by cement weight.

• Proceedings of the Korea Concrete Institute Conference
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• 2002.05a
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• pp.355-360
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• 2002

The purpose of this study was to remove the excessive air foaming which was produced in mixing the RSLMC(latex-modified concrete with rapid- setting cement) by choosing the best antifoam agent type and the optimized quantity for performance improved RSLMC. A series of RSLMM(latex-modified mortar with rapid-setting cement) experiments were carried out as the basic for RSLMC with the main experimental variables such as antifiamer types(A, B, C, D), antifoamer contents(0, 1, 2, 3%). Air content test and compressive, flexural tests were carried out to measure the improved properties of RSLMM and RSLMC. Chloride ion permeability test was carried out to estimate water permeability resistance. The results of RSLMM showed that the decrease of 50% air content was obtained by admixturing a antifoam agent by 1%. The compressive strength and flexural strength at 3 hours after RSLMC placement were 235kgf/cm$^2$ and 49kgf/cm$^2$, respectively, which exceeded the flexural strength criterion of 45kgf/cm$^2$ in order to open the RSLMC placed to traffic. The chloride permeability using A and C antifoamer at 28 days were below 100 coulombs, which was the permeability rating of negligible according to ASTM.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.11a
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• pp.269-272
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• 2004

After concrete casts, temperature decent and shrinkage bring volume changes of concrete pavement. Microcracking and cracking in concrete pavement are caused by these volume changes. As a result, durability of concrete pavement is deteriorated. Recently, Very-Early Strength Latex Modified concrete(below:VESLMC) from the beginning of High-Way is used as urgent repair material for bridge deck. The advantage of VESLMC is that compressive and flexural strength at 3 hours age are 4.5MPa and 21MPa respectively. It allows the traffic to open in 3 hours. But, this material has the problem which is early-age shrinkage cracking caused by water self-dissipation with rapid hydration reaction and water evaporation with body dry. Unfortunately, until now, the research about early-age shrinkage of VESLMC leaves something to be desired. Therefore, the purpose of this study is to present the early-age shrinkage of VESLMC respect to latex contents and shrinkage ratio to maximum length change that can help field engineers' skill. Latex contents of 0, 5, 10, 15, $20\%$ in standard of same workability in VESLMC are selected by experimental variables. After initial set, shrinkage value was measured with 10mm LVDT for 3 days. The results of maximum shrinkage ratio were 0.019, 0.017, 0.023, $0.027\%$ respectively.

• Journal of Industrial Technology
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• v.22 no.A
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• pp.161-168
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• 2002

Latex modified concrete is governed by both cement hydration and polymer film formation processes in its binder phase. Such the reactions are expected to improve the polymer-cement co-matrixes themselves and the bond between the cement hydrates and aggregates, and to improve the properties of hardened latex-modified concrete. The purpose of this study was to study the strength and chemical resistance of Rapid-setting latex modified concrete(RSLMC) with the main experimental variables such as latex content(0, 5, 10, 15, 20%) and water-cement ratio(36, 38, 40%) at latex content 15%. Water absorption test was earned out to estimate water permeability resistance. Chemical resistance test was carried out to measure the weight change and to observe the appearance of RSLMC immersion in hydrochloric acid, sulfuric acid, and calcium choloride.