• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.1
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• pp.101-110
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• 2014

Expansion agent is a very effective admixture for prevention of cracking due to autogenous/drying shrinkage and this can induce internal chemical prestress to embedded reinforcement. In this paper, tension-softening and hardening in cement mortar with steel and CSA expansion agent are experimentally evaluated. Cement mortar with steel reinforcement is prepared and tensile strength test is performed for evaluation of cracking and tensile behavior. In spite of slightly reduced strength and elasticity in CSA mortar, significantly increased tension-hardening behavior is evaluated in CSA mortar with induced chemical prestress. Furthermore previous tension softening models are compared with the test results and improvement are proposed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.12 no.6
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• pp.180-192
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• 2008

The purpose of this research is to evaluate the structural performance of mortar-filled ductile cast iron sleeve splice developed for SD500 high-strength reinforcing bar under cyclic loading. The test variables adopted in this study are the development length of bar, compressive strength of mortar, bar size, sleeve types and others. In this research, it is showed that the mortar-filled sleeve splice for SD500 high-strength bar satisfied the structural performance required in ACI, AIJ code as well as domestic code. Also the results of experimental research presented in this paper provided basic engineering data for developing a reasonable design method of mortar-filled sleeve splice for SD500 high-strength reinforcing bar.

• Journal of the Korea institute for structural maintenance and inspection
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• v.18 no.3
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• pp.125-132
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• 2014

Steel fiber is a effective composite for crack resistance and improve structural performance under tensile loading. This study presents an evaluation of crack resistance and structural performance in cement mortar with steel fiber and expansion agent through internal chemical prestressing. For this work, cement mortar samples with 10% replacement of cement binder with CSA (Calcium-Sulfo-Aluminate) expansion agent and 1% volume ratio of steel fiber are prepared. Including basic mechanical properties, initial cracking load and fracture energy are evaluated in cement mortar beam with notch. Initial cracking load and fracture energy in cement mortar with CSA and steel fiber increase by 1.75 and 1.41~1.53 times compared with those in cement mortar with steel fiber. With optimum mix design for steel fiber and CSA expansive agent, the composite with chemical prestressing can be applied to various members and effectively improve crack resistance to external loading.

• Polymer(Korea)
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• v.37 no.2
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• pp.148-155
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• 2013

The purpose of this study is to clarify the effect of the emulsifier ratio on the properties of the polymer cement mortars based on styrene-butyl acrylate (S/BA) latexes, and to obtain necessary basic data to develop appropriate latexes for cement modifiers. The polymer dispersions for cement modifiers was synthesized using styrene and butyl acrylate. Polymer cement mortars based on S/BA latexes were prepared with various monomer and emulsifier ratios, and their water-cement ratio, air content, flexural and compressive strengths, water absorption and chloride ion penetration were tested. From the test results, the maximum flexural and compressive strengths of polymer cement mortars based on S/BA latexes were obtained at a bound styrene content of 60% and an emulsifier ratio of 6%. Also, the water absorption and chloride ion penetration depth are greatly affected by the polymer-cement ratio rather than the bound styrene and emulsifier content. Accordingly, it is judged that S/BA latexes can be used place of the conventional polymer dispersions of cement modifier.

• Journal of the Korea Concrete Institute
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• v.15 no.3
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• pp.386-391
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• 2003

Ready mixed mortar has been originated from lime industry of Germany and is being used widely in the world at present. In recent years, the studies of mortar with new faculty have been progressed. In this study, we used elvan instead of using sand in order to make cement mortar and investigated characteristics of elvan and mortar that used elvan. The major compositions of elvan were $SiO_2$ and $Al_2O_3$. The crystal phases of elvan were composed of quartz and sillimanite. Elvan had a lot of pore and absorption ratio was 2.09%. The compressive strength of mortar that used elvan satisfied korean industrial standards under 1:3 (mixing ratio) and water retentivity increased according to increase of elvan contents. Far infrared radiation and deodorization ratio increased and thermal conductivity decreased according to increase of elvan contents.

• Journal of the Korean Recycled Construction Resources Institute
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• v.8 no.3
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• pp.365-371
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• 2020

In this study, in order to recycle the stems of opuntia cactus discarded after harvesting the fruit, the cactus stems were powdered and applied as a cement-based admixture. The powder of cactus stem was mixed into the mortar, and its effect on the fresh properties and strength of the mortar was studied. The results were compared with the properties of mortars produced by mixing with a retarder sugar and a viscosity agent methyl-cellulose, which are conventional saccharide-based admixtures. Based on the test results, the cactus stem powder did not clearly show the effect as a retarding agent, whereas the flow and the air content were similar to those of the mortar mixed with methyl-cellulose. This indicated that the cactus stem powder can be used as a viscosity agent. It was found that the strength of the mortar tended to increase when the mixing ratio of the cactus stem powder was lower than 0.3%.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.04a
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• pp.749-752
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• 2008

This experimental study compared polymer cement mortar with inorganic polymer binder mortar for physical properties by Si/Al mol ratio change of inorganic polymer binder. As the result of this experiment, We found that when Si/Al mol ratio goes up flexural strength and compressive strength increases but workability becomes worse. And according to the keeping them for 28 days we found that physcal property becomes worse when Si/Al mol ratio is larger than 2.61. When Si/Al mol ratio of inorganic polymer binder is from 2.43 to 2.61 compressive strength increases than over 32% after keeping for 7 days and over12 % for 28 days

• Polymer(Korea)
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• v.33 no.4
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• pp.342-346
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• 2009

The effects of the monomer ratios on the typical properties of polymer modified mortars that contain styrene and butyl acrylate latexes was investigated. Basic data was also obtained that is necessary for the development of appropriate latexes for cement modifiers. Polymer modified mortars that contain styrene and butyl acrylate latexes polymerized with various monomer ratios were prepared for different polymer-cement ratios. They were then tested to obtain the particle size of the polymer latexes, air contents, water-cement ratios, flexural and compressive strengths, water absorption, and chloride-ion penetration. From the test results, the polymer modified mortars that have styrene and butyl acrylate latexes (with the mix proportions of synthesis having monomer ratios of between 40:60 to 60:40 for the appropriate mix proportions) could be recommended for practical applications. The basic properties of the polymer modified mortars were more affected by the polymer-cement ratio than by the monomer ratio, and were improved over unmodified mortar.

• Magazine of the Korea Concrete Institute
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• v.10 no.4
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• pp.145-151
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• 1998

The vertical tensile stress, ${\sigma}_y$, in the contact zone between the overlay (mortar layer) and substratum (base concrete) can be the main cause of the failure phenomenon of overlaid concrete structures. The development of tensile stress, ${\sigma}_y$, due to external rainy condition was analytically investigated using finite element method. Rainfall intensity $(n_R\;=\;1/a,\;t_R\;=\;10min,\;60min)$, thickness of overlay (do=1,2,4,10 cm) and overlay material (CM,ECM,EM) were the main variables in the analyses. An equation was suggested with which the development of vertical tensile stress, ${\sigma}_y$, in the rainy condition could be determined. Using this equation, it is possible to select proper material properties and overlay thicknesses to prevent failure in the contact zone due to thermally transient condition caused by rainfall.

• Journal of the Korea Institute of Building Construction
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• v.17 no.3
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• pp.219-225
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• 2017

The durability factors of concrete has been researched by many researchers. Among the chemical ingression by acid, alkali, or salt, specially the ingression by sulfate has been actively studied and reported. Generally, for the oil type chemical, it is reported to cause the excessive expansion of cement mortar and further to cause the collapse, while there was no enough research on influence of oil type, relationship with microstructure of mortar, and collapse pattern. Therefore, in this research, using the various oils from general market, the degradation properties of the mortar mixtures with various mix designs were evaluated. according to the experiment, Bio diesel damaged worst and the mix design with less cement content showed the worst damage against oils.