• International Journal of Highway Engineering
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• v.14 no.5
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• pp.93-99
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• 2012

PURPOSES: The purpose of this study is to compare the alkali-silica reactivity for mortar bar and concrete prism specimens using crushed aggregates of 5 types in Korea. And the alkali-silica reactivity for those aggregates are measured by chemical test method. METHODS: The alkali-silica reactivity for those aggregates was measured by chemical test method of KS F 2545, mortar-bar test of KS F 2546, accelerated mortar-bar test method of ASTM C 1260 and concrete prism test method of ASTM C 1293, relatively. RESULTS: The alkali-silica reactivity for those aggregates was verified by chemical test of KS F 2546 and accelerated mortar-bar test of ASTM C 1260. However, it was not by mortar-bar test of KS F 2546 and concrete prism test of ASTM C 1293. CONCLUSIONS: The above results showed that relationship among the four test methods were very low. The results from 3 types of test methods using cement-aggregate combinations appeared to be different. Because the environmental conditions of test methods for measuring the alkali-silica reactivity such as equivalent alkali content(external source), humidity, temperature, and times were different though the aggregates were same. Moreover, alkali-silica reactivity showed the biggest impact when alkalis were supplied form outside and exposed to environmental conditions. The accelerated mortar-bar test method seems to be most appropriate test method for concrete structures exposed to alkali environment.

• International Journal of Concrete Structures and Materials
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• v.4 no.2
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• pp.119-125
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• 2010

In this study, the effects of the fineness modulus of reactive aggregate on ASR expansion and ASR products have been investigated. The reactive aggregate used was metamorphic aggregate originated from Korea. ASR tests were conducted according to accelerated mortar bar test. The morphology and chemical composition of products formed in mortar bars, 5 years after the mortar bar test had been performed, were studied by scanning electron microscopy equipped with energy dispersive spectroscopy. Test results indicated that ASR expansion of mortar bars decrease in linear proportion to the fineness modulus of reactive aggregate. SEM images indicated that mortar bars showed reactive products formed in cement paste, within air voids and within cracks through particles except for the mortar bar with the fineness modulus of 3.25. The EDS analysis of the reactive products showed presence of silica, calcium and sodium, typical of ASR product composition.

• Proceedings of the Korean Institute of Building Construction Conference
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• 2013.11a
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• pp.106-107
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• 2013

The purpose of this study is to characterize the bonding properties between reinforced bar and re-emulsion polymer cement mortar through the pull off test. The properties of polymer cement mortar before and after hardening were measured. Spiral reinforced steel bar was used to control the brittleness fracture of test specimens. In addition polymer content as experimental factors, the types of reinforced bar and corrosion were considered as well. Non linear FEM analysis was carried out to expect the behavior of bonding interface under the certain load.

• Structural Engineering and Mechanics
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• v.41 no.3
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• pp.379-393
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• 2012

Of the various methods of splicing reinforcing bar in reinforced concrete structure, mortar-filled sleeve reinforcement splice offers diverse benefits, not only in terms of structural performance but also for the construction process. Consequently, after the mortar-filled sleeve splices have been developed in recent years, research and development on these splices has been actively carried out, in order to evaluate its macro structural performance, such as its strength and stiffness, with the aim of enabling this system to be applied to construction in the field as early as possible. However, to make a proper evaluation on the overall structural performance of the mortar-filled sleeve reinforcing bar splice, it is of critical importance to understand the lateral confining action of the sleeve, which is known to affect the bond strength between the embedded bar and mortar in the sleeve. Accordingly, in this study, an experiment of monotonic loading and cyclic loading was conducted with a full-sized mortar-filled sleeve splice attaching strain gauges on the sleeve surface with experimental variables such as development length of bar, etc. Based on the test results, the effect of the lateral confining action of the sleeve was analyzed and considered in terms of the bond strength between the bar and mortar in this splice.

• Journal of the Korea Concrete Institute
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• v.21 no.4
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• pp.531-537
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• 2009

In this study alkali reactivity of crushed stone was conducted according to the ASTM C 227 that is traditional mortar bar test, and C 1260 that is accelerated mortar bar test method. The morphology and chemical composition of products formed in mortar bar, 3 years after the mortar bar tests had been performed, were examined using scanning electron microscopy (SEM) with secondary electron imaging (SEI) and electron probe microanalysis (EPMA) with backscattered electron imaging (BSEI). The crushed stone used in this study was not identified as being reactive by ASTM C 227. However, mortar bars exceeded the limit for deleterious expansion in accelerated mortar bar test used KOH solution. The result of SEM (SEI) analysis, after the ASTM C 227 mortar bar test, confirmed that there were no reactive products and evidence of reaction between aggregate particles and cement paste. However, mortar bars exposed to alkali solution (KOH) indicated that crystallized products having rosette morphology were observed in the interior wall of pores. EPMA results of mortar bar by ASTM C 227 indicated that white dots were observed on the surface of particles and these products were identified as Al-ASR gels. It can be considered that the mortar bar by ASTM C 227 started to appear sign of alkali-silica reaction in normal condition. EPMA results of the mortar bar by ASTM C 1260 showed the gel accumulated in the pores and diffused in to the cement matrix through cracks, and gel in the pores were found to be richer in calcium compared to gel in cracks within aggregate particles. In this experimental study, damages to mortar bars due to alkali-silica reaction (ASR) were observed. Due to the increasing needs of crushed stones, it is considered that specifications and guidelines to prevent ASR in new concrete should be developed.

• Journal of the Korea institute for structural maintenance and inspection
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• v.16 no.4
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• pp.79-88
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• 2012

The purpose of this study is to evaluate the stiffness of the mechanical sleeve reinforcement splices filling high-strength mortar under monotonic loading. For this objective, we analyzed and compared the previous test data of 189 actual-sized mortar-filled sleeve bar splices specimens, including the reinforcing bar splices prepared and tested by the author. The paper results indicated that the minimum values of compressive strength of mortar($f_g$) multiplied by the ratio of reinforcement development length to bar diameter(L/d) were suggested for holding the stiffness of the mortar-filled sleeve reinforcement splices required in AIJ code.

• The Journal of Engineering Geology
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• v.18 no.2
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• pp.227-232
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• 2008

In this study, the pull out resistance characteristics of an anchor bar to support a spillway installed in a slope are investigated by field tests. The injection materials were a cement mortar and cement milk. Unconfined compression strengths of those materials under several conditions were measured. As the result of compression test, the unconfined compression strengths of the cement mortar and the cement milk have positive proportional relation-ship with the water-cement ratio. They also have negative proportional relationship with increasing the curing time. In the same condition of water-cement ratio and curing time, the unconfined compression strength of cement milk is larger than that of cement mortar. In order to reduce the eccentricity in anchor bar during pull-out test in the field, the installation apparatus was improved by inserting a nut type of steel fixing coupling into the anchor bar. As the result of the pull-out test, the strength modification of cement milk was increased steeply at the early curing time. However, that of cement mortar was increased gradually with passing the curing time. Therefore, the cement milk has to use as the injection material for a prompt construction of anchor bar because the strength modification of cement milk is occurred at the early curing time.

• Proceedings of the Korea Concrete Institute Conference
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• 1994.10a
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• pp.447-450
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• 1994

The chemical method and mortar-bar method for identification of the susceptibility to Alkali-Aggregate Reaction (AAR) was established as KS method by referencing the ASTM methods. However, the chemical method requires skilled chemical engineers and aggregates are tested in very severe condition, and on the other hand, the mortar-bar method needs a long time of 3 or 6 months. Judging from this circumstance that the use of crushed stones are increased due to the shortage of natural aggregates, the development and standardization of a new rapid test method is considered essential. The purpose of this paper is to research for the possibility to apply the rapid method, instead of the chemical method and the mortar-bar method with using the several domestic crushed stones.

• 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 of Building Construction
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• v.11 no.2
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• pp.181-188
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• 2011

Spalling must be considered when designing high-strength concrete to cope with fire. This study investigates the temperature rise of steel bar in high-strength concrete coated with fireproof mortar using gypsum exposed to fire. It was found that fireproof mortar using gypsum is more effective in constraining the temperature rise of steel bar in the high strength concrete than fireproof mortar using cement, and that the thinner the cover depth of the fireproof mortar, the more significant the influence of the gypsum. In addition, while there was no difference between ${\alpha}$-hemihydrate mortar and ${\beta}$-hemihydrate mortar on the temperature rise of steel bar, the compressive strength of ${\alpha}$-hemihydrate mortar is higher than that of ${\beta}$-hemihydrate mortar.