• Journal of the Korea Concrete Institute
• /
• v.13 no.4
• /
• pp.336-345
• /
• 2001

The construction of underwater structures has been increased, but underwater concrete hassome problems of quality deterioration and contamination around in-situ of civil and architecture; therefore, new materials and methods for them are demanded. In this paper in-situ application of underwater antiwashout concrete which is manufactured for trio purpose of not only decreasing suspended solids and the heat of hydration but also increasing long term strength was studied. In the case of mock-up test(Ⅰ), when underwater antiwashout concrete, whose slump flow was 58 cm, was placed in the mock-up test at a speed of 24 ㎥/hr, it took about a minute to flow to the side wall, and the surface was maintained at horizontal level. In this case, compressive strength of the core specimens in each section was higher than the standard design compressive strength of 240 kgf/㎠. In the case of mock-up test(II), pH value and suspended solids of high strength underwater antiwashout concrete were 10.0∼11.0 and 51 mg/ℓ at 30 minutes later, initial and final setting time were about 30, 37 hr, and the slump flow of that was 53$\pm$2 cm. In the placement at a speed of 27 ㎥/hr, there was no large difference in flowing velocity, with or without reinforcement and flowing slope was maintained at horizontal level. In this case, compressive strength and elastic modulus of the core specimens somewhat decreased as flowing distance was far : however, those of central area showed the highest value.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2005.05b
• /
• pp.401-404
• /
• 2005

Because the underwater structures are subjected to the deterioration according to use environment, it is necessary to repair and reinforce when the durable performance are considered in structures. Epoxy mortar in the underwater used to the repair and reinforcement for durability. Epoxy mortar in the underwater-harding maked epoxy and filler. Filler is divided aggregate and powder system. Because aggregate take a matter too seriously to supply that alternation material is used to rapidly chilled steel slag. As result of study, it is possible that rapidly chilled steel slag can be applied for replacement materials about aggregate in epoxy mortar because the strength is not different.

• Journal of the Korea Institute of Building Construction
• /
• v.3 no.1
• /
• pp.123-129
• /
• 2003

The production accounts of domestic by-product is increased after 1990's. It is worried about the life reduction of dump land, as dump land's capacity have reached to limitation and the amount of construction industrial wastes is going higher. Recently, recycling aggregates could be gained from the reconstruction works using recycle process, and the study research of recycle concretes developed concrete application methods. It could put some outcome of studies to practical use for concrete products. The methods of crushing waste concrete are going diverse. In this study. the fundamental experiments and recycling application is investigated and analyzed with use of recycling aggregate which made of mechanical crush and underwater electrical impact crush, and the difference between underwater electrical impact crush, mechanical crush and natural aggregates is studied.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2002.10a
• /
• pp.829-834
• /
• 2002

Recently, research and development for a number of repairing material like an epoxy-based material and polymer-cementitious material as well as anti-washout underwater concrete have been carried out. But, the study on tile materials for the concrete structure exposed to a wetted condition is at a standstill and there are not any suitable reference data at a repairing work for the concrete structure at a splash as well as a structure under severe moisture condition. In this study, the material, called as “ceramic metal”, with an excellent mobility and plasticity as well as with a high bond strength and durability of freezing-thawing resistant properties under any environmental conditions was developed. And, the experimental evaluations for the utility wert widely performed.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.1077-1080
• /
• 2003

High reactivity metakaolin (HRM) is a manufactured pozzolan produced by thermal processing of purified kaolinitic clay. Field performance and laboratory research of concrete containing HRM have demonstrated its value for bridge decks, bridge deck overlays, high-strength concrete and masonry products. This paper discusses laboratory evaluations to assess the physical properties of antiwashout underwater concrete (AWC) containing HRM, such as pH value, suspended solids, slump flow, and compressive strength. There were not much variations of pH value with the changing HRM contents, but suspended solid test showed that the amount of suspended solids of AWC with 10 and 20% of HRM were reduced in comparison with plain. Due to the fast hydration and reaction property of HRM, slump flow was decreased with increasing HRM contents. According to the results of compressive strength test, AWC with 10 and 20% of HRM showed higher strength characteristic than plain at all curing ages.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2006.05b
• /
• pp.301-304
• /
• 2006

The purpose of this study is to evaluate bonding properties of PMMA mortars using EPS with silane coupling agent. PMMA mortars are prepared with various silane coupling agent, and tested for flexural strength test, adhesion test in flexure and tensile strength in underwater and air. It is estimated that the application of silane coupling agent to PMMA mortar is more effective in underwater than air.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1998.04a
• /
• pp.261-266
• /
• 1998

The purpose of this study is to present the reference data on the development of undispersed underwater mortar for augered pile under various replacement ratio of fly-ash. According to the experimental results, when 10% of fly-ash is mixed under mix proportion of 1:1.5(c:s), as strength and shrinkage decrease slightly, whereas fluidity increase, high quality mortar for augered pile can be achieve in case above condition is applied.

• Magazine of the Korea Concrete Institute
• /
• v.11 no.2
• /
• pp.231-239
• /
• 1999

When the concrete is cast at the sea, there are lots of restrictions in the working process being different from in land, and the concrete is suffered from the physical and chemical action in terms of marine environment. The compressive strength was measured after antiwash out underwater concrete mixed with fly ash had been cast and cured in order to produce the endurable high performance concrete, and then its characteristic was discussed by comparing one cured in air with in fresh water, and the effect of fly ash usage under the properly controled sea water temperature of $15{\pm}3^{\circ}C$ was also covered. The present work showed that the proper usage of fly ash was obtained at the condition of around 10% of substituted binder weight under the structure required the early age strength, and at the condition of over 40% if considering its durability and economy.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2010.05a
• /
• pp.345-346
• /
• 2010

The overall quality of underwater concrete will ultimately be affected by factors such as performance of antiwashout admixture and mix proportions of concrete. Of these, performance of antiwashout admixture may significantly influence quality of underwater concrete. Thus, objectives of this experimental research are to evaluate the performance such as slump flow, setting time, compressive strength, and water segregation of the concrete containing antiwashout admixture. It was observed from the test results that concrete containing antiwashout admixture was found to improve quality of concrete such as fluidity, compressive strength, and antiwashout compared to plain concrete.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.11a
• /
• pp.427-432
• /
• 2001

In this study, crushed sand is blended with river sand and sea sand, to investigate the quality change of antiwashout underwater concrete with variation of blend ratio of crushed sand(0%, 20%, 40%, 60%, 80%, 100%). To see experiment conclusion, the more blend ratio of crushed sand increases, the more unit weight increases. Because the for that specific gravity of crushed sand is higher comparatively than that of river sand and sea sand. Higher compressive strength is measured following the order of river sand, crushed sand, sea sand regardless of age and casting-curing condition. Except for case of using river sand, blend ratio of 40% is appeared on most compressive strength. So the optimum blend ratio of crushed sand is 40% from the view point of compressive strength.