Antiwashout Underwater Concrete Research Articles

Comparative Study of the Performance of Underwater Concrete between Anionic and Nonionic Anti-Washout Admixtures

An investigation was carried out to study the influence of two types of anti-washout admixtures (AWAs) on the performance of underwater concrete, specifically, workability and washout resistance. The tested AWAs were hydroxypropyl methylcellulose (HPMC) and polyacrylamide (PAM) as nonionic AWAs and carboxymethyl starch (CMS) and polyanionic cellulose (PAC) as anionic AWAs. Rheological properties (slump and slump flow), washout resistance, and compressive strength were measured to evaluate the properties of the fresh and hardened concrete. The results indicate that anionic AWAs are more effective at improving workability and strength than nonionic AWAs in anti-washout underwater concrete. When the nonionic AWA dosage exceeded 0.3% (W/C = 0.45), the fluidity and air content were negatively impacted. Additionally, nonionic AWAs more readily alter the morphological structure of cement paste, affecting cement particle hydration and underwater concrete properties. Regarding the mechanical properties, compared with those of concrete without AWAs and with nonionic AWAs, the 28-day compressive strength of concrete with anionic AWAs reached 37 MPa, an increase of 151% and 131%, respectively. Compared with nonionic AWAs, concrete with anionic AWAs is more stable.

Research on plugging treatment of flooded mine: Determination of plugging location and optimization of anti-washout underwater concrete ratio

A high-quality underground copper sulfide mine in Africa has been flooded for a long time. It is proposed to use underground plugging method and stage drainage to recover underground copper sulfide ore resources. In this paper, 3DMine software is used to establish a three-dimensional mine model, analyze the spatial relationship and connectivity between SS30 safety pillar, roadway engineering and goaf, and then determine the location of water blockage. Then, the anti-washout underwater concrete is proposed for the construction of the cut-off wall. The ratio of anti-washout underwater concrete was designed by a three-factor and three-level orthogonal test, and the optimal ratio of anti-washout underwater concrete was obtained by combining range analysis, variance analysis, SPSS multiple linear regression analysis and MATLAB three-dimensional visualization. The results show that the sealing position is more suitable near the SS30 security pillar (610L, 820L, 1120L, 1440L, 1900L, and 1930L). The optimum proportion of anti-washout underwater concrete is water-binder ratio 0.45, anti-washout content 1.5%, sand ratio 42%. The research results can provide theoretical guidance for the treatment of similar flooded mines, so that the underground flooded mineral resources can be recovered safely and economically.

Influence of seawater and sea sand on the performance of Anti-washout underwater concrete: The overlooked significance of Mg2+

Seawater and sea sand are widely used in marine concrete to overcome the shortage of freshwater and river sand. However, the effect of the various salts in seawater and sea sand on the performance of anti-washout underwater concrete (AWC) is unclear. In this study, the influence of seawater and sea sand, as well as the aggressive ions in seawater, on the anti-washout ability, mechanical performance, and microscopic structure of AWC mortar are studied systematically. The AWC mortar molded in seawater has a lower compressive strength even though its indicators of anti-washout ability perform better than that in freshwater. This is because Mg2+ in seawater chemically binds with OH– in cement to form Mg(OH)2 film absorbed by anti-washout admixture(AWA), which inhibits the release of substances in AWC while also introducing more defects in AWC. This study lays the foundation for promoting the application of seawater and sea sand AWC in marine engineering.

Influence of Seawater and Sea Sand on the Performance of Anti-Washout Underwater Concrete: The Overlooked Significance of Mg2+

Influence of Seawater and Sea Sand on the Performance of Anti-Washout Underwater Concrete: The Overlooked Significance of Mg2+

Effect of superplasticizer in anti-washout admixture on paste

Anti-washout admixture used for anti-washout underwater concrete is composed of flocculant (e.g., paste stabilizer), superplasticizer, setting retarder, strengthening agent, etc. Good compatibility among those constitutes is necessary to release the vast material potential of anti-washout admixture. In the study, effects of polycarboxylate superplasticizer on fresh cement paste mixed paste stabilizer of various ionic type were experimentally investigated. Based on the experimental results, the optimizations on the ionic type and molecular weight of paste stabilizer, regarding the compatibility with polycarboxylate superplasticizer, were hence obtained. Additionally, suitable content ranges of polycarboxylate superplasticizer, molecular weight and content of paste stabilizer have been determined through systematic tests, such as saturation point test, fluidity test, and anti-washout test.

The Mix Ratio Study of Self-Stressed Anti-Washout Underwater Concrete Used in Nondrainage Strengthening.

Anti-washout underwater concrete (AWC) is widely used in nondrainage strengthening; however, there still exist some problems with it, such as high strength loss and poor interfacial bond in practical engineering application. Based on the study of self-stressed concrete (SSC), a research on the mix ratio for the C30 self-stressed anti-washout underwater concrete (SSAWC) was carried out in this paper in hope of solving the above problems, specifically, by adding an expansive agent to the AWC. The parameters, such as strength, fluidity, anti-dispersity, and expansibility, were picked as target indices in determination of the mix ratio. The orthogonal test design and range analysis were used to determine the reasonable mix ratio and study the influence of various parameters on the performance of SSAWC. The experimental program conducted includes a series of strength, fluidity, anti-dispersity, and expansibility tests on 18 groups of specimens. The results show that C30 SSAWC has an excellent performance using the optimal mix ratio. Compared with AWC, the expansibility and self-stress of the SSAWC can be easily observed, and the compressive strength ratio of the SSAWC casted in water to that casted in air is much bigger. This implies that SSAWC is applicable to the nondrainage strengthening.

An Estimation on the Performance of High Fluidity Anti-Washout Underwater Concrete

The placing of anti-washout underwater concrete for the increasing construction of offshore foundations of long-span bridges at relatively deep sea is accompanied with significant loss of the quality of concrete as well as of the durability and reliability of the structure due to limitations brought by the workability of the high-pressure pump and the performance of the anti-washout agent. Therefore, the improvement of the performance of the underwater anti-washout agent and the development of high fluidity anti-washout underwater concrete exhibiting improved packing ability and fluidity should be implemented. Accordingly, this study focuses on the concrete for foundations applied in the RCD (Reverse Circulation Drill) method. The adequate mix proportions of a high fluidity anti-washout underwater concrete satisfying a design compressive strength of 35 MPa, slump flow larger than 600 mm and with less than 50 mg/ℓ of suspended solids is derived and the corresponding characteristics are evaluated.

고로슬래그 미분말을 사용한 고유동 수중불분리성 콘크리트의 최적배합비 도출

최근, 장대교량의 해상기초 구조물에 수중불분리성 콘크리트의 사용이 증가되고 있다. 그러나, 해상기초 구조물에 사용되는 수중불분리성 콘크리트의 공사기간을 단축시키기 위해서는 이전의 수중불분리성 콘크리트보다 유동성을 크게 개선시키는 고유동 수중불분리성 콘크리트의 제조가 필요하다. 따라서 본 연구의 목적은 해상기초 구조물에 사용되는 고유동 수중불분리성 콘크리트의 최적배합비를 도출하는 것이다. 이를 위하여 단위결합재량 550, 600kg/<TEX>$m^3$</TEX> 각각에 대해서 수중불분리성 혼화제 첨가량별로 고로슬래그 미분말을 혼입한 콘크리트를 제작하였다. 제작된 콘크리트의 슬럼프 플로, 응결시간, 수중분리저항성 및 압축강도 비와 같은 품질성능을 관련 규격에 따라 평가하였다. 결국, 고로슬래그 미분말을 혼입한 고유동 수중불분리성 콘크리트는 관련 규격을 만족시키는 수중불분리성 혼화제의 최소 첨가량이 필요한 것으로 나타났다. Recently, antiwashout underwater concrete has been increasingly used for marine foundations of long span bridges. However, to shorten the construction period of antiwashout underwater concrete used in marine foundations, high fluidity antiwashout underwater concrete should be manufactured largely improving fluidity than the previous one. Thus, the objective of this experimental research is to suggest optimum mix proportions of high fluidity antiwashout underwater concrete. For this purpose, concrete specimens containing ground granulated blast furnace slag were manufactured according to the dosage of antiwashout admixture for unit binder contents of 550 and 600kg/<TEX>$m^3$</TEX>, respectively. And then, their quality performances such as slump flow, setting time, underwater segregation resistance, and ratio of compressive strength were evaluated according to the related specification of Korea Concrete Institute. It was observed from the test results that the minimum dosage of antiwashout admixture was necessary to satisfy the related specification.

플라이애시를 혼입한 수중불분리성 콘크리트의 내 황산염에 관한 실험적 연구

This paper describes the effects of fly ash replacement on the sulfate resistance of antiwashout underwater concrete which was replaced cement by fly ash from 0% to 50%. and the experimental works were performed on sulfate acceleration test of 5%Na 2SO4 solution to find out the variance of length and weight of specimens. The experimental result shows that the length of specimens of antiwashout underwater concrete age at 180day was highly increased compare with normal concrete by acceleration test. but the mixture which was replaced 50% of fly ash shows reduction of the expansion, weight various, compare with normal concrete specimen. accordingly by using fly ash as admixture in antiwashout underwater concrete in sea environment, it will makes more durable for the attacks of sulfate by sea water.

State of workability design technology for fresh concrete in Japan

As high-performance concrete and various new types of concrete, such as self-compacting concrete and anti-washout underwater concrete, have been developed and put to practical use, it has become increasingly important to optimize the consistency of fresh concrete to attain high-quality and efficient concrete construction, which is called workability design of concrete. Up to the present, many scientists from all parts of the world have performed a lot of studies on the rheological properties, test method, and flow analysis of fresh concrete for realizing the workability design under various construction conditions. This paper gives a brief outline of the current situation, problems and prospects in the art of workability design of fresh concrete in Japan.

Evaluation on steel bar corrosion embedded in antiwashout underwater concrete containing mineral admixtures

This study aims the evaluation of the corrosion of steel bar embedded in antiwashout underwater concrete, which has rather been neglected to date. To that goal, accelerated steel bar corrosion tests have been performed for three series of steel bar-reinforced antiwashout underwater concrete specimens manufactured with different admixtures and under different environments. The three series of antiwashout underwater concrete were: concrete constituted exclusively by ordinary portland cement (OPC), concrete composed by ordinary portland cement mixed with fly-ash in 20% ratio (FA20) and concrete with ground granulated blast furnace slag is mixed in 50% ratio (BFS50). And, the three different environments were: manufacture in the air, in tap water, and in artificial seawater. Measurement results using half-cell potential surveyor showed that, among all the specimens, steel bar in OPC manufactured in artificial seawater was the first one that exceeded the threshold value proposed by ASTM C 876 with a potential value below − 350 mV after 14 cycles. And, the corresponding corrosion current density and concentration of water soluble chloride were measured as 0.3 μA/cm 2 and 0.258%. On the other hand, for the other specimens that are FA20 and BFS50, potential values below − 350 mV were observed later at 18 and 20 cycles, respectively. Results confirmed the expectation that mineral admixtures may be more effective in delaying the development of steel bar corrosion in antiwashout underwater concrete.

Frost attack resistance and steel bar corrosion of antiwashout underwater concrete containing mineral admixtures

This study aims to evaluate frost durability and steel-bar corrosion in antiwashout-underwater concrete, which has been neglected to date. To achieve this goal, repeated freezing and thawing and accelerated steel-bar corrosion tests have been performed for three types of antiwashout-underwater concrete specimens. The results of repeated freezing and thawing test reveal that adding mineral admixtures has little effects on frost durability because of the large and uneven entrapped-air imprisoned by the cellulose-type antiwashout-underwater admixture. Slight improvement of frost durability was observed through the action of air-entrained (AE) agent in the case of SG50 which presented an air content of 6 ± 0.5%. Measurement results using the half-cell potential showed that, among the entire specimens, steel-bar in Control specimen manufactured under artificial seawater was the first one that exceeded the threshold value, −350 mV proposed by ASTM C 876, at 14 cycles, where the corresponding corrosion current density and concentration of water soluble chloride were measured as 0.3 μA/cm 2 and 0.258%, respectively. For the other specimens, potential values became below −350 mV later than 18 cycles.

광물질혼화재 혼합 수중불분리성 콘크리트의 물성 및 동결융해 저항성

초록·키워드 목차 오류제보하기 등록된 정보가 없습니다. ABSTRACT1. 서론2. 실험개요3. 실험결과 및 고찰4. 결론참고문헌요약

Evaluation on Steel Bar Corrosion Embedded in Antiwashout Underwater Concrete

This study aims the evaluation of the corrosion of steel bar embedded in antiwashout underwater concrete, which has rather been neglected to date. To that goal, accelerated steel bar corrosion tests have been performed on three series of steel bar-reinforced antiwashout underwater concrete specimens manufactured with different admixtures. The three series of antiwashout underwater concrete were: concrete constituted exclusively with ordinary portland cement (OPC), concrete composed of ordinary portland cement mixed with fly-ash in <TEX>$20\%$</TEX> ratio (FA20), and concrete with ground granulated blast furnace slag mixed in <TEX>$50\%$</TEX> ratio (BFS50). The environment of manufacture was in artificial seawater. Measurement results using half-cell potential surveyor showed that, among all the specimens, steel bar in OPC was the first one that exceeded the threshold value proposed by ASTM C 876 with a potential value below -350mv after 14 cycles. And, the corresponding corrosion current density and concentration of water soluble chloride were measured as <TEX>$30{\mu}A/mm^2$</TEX> and <TEX>$0.258\%$</TEX>. On the other hand, for the other specimens that are FA20 and BFS50, potential values below -350mV were observed later at 18 and 20 cycles, respectively. Results confirmed the hypothesis that mineral admixtures may be more effective on delay the development of steel bar corrosion in antiwashout underwater concrete.

광물질 혼화재료를 첨가한 수중불분리성 콘크리트의 특성에 관한 연구

초록·키워드 목차 오류제보하기 등록된 정보가 없습니다. ABSTRACT1. 서론2. 사용재료 및 실험3. 공시체 제작 및 시험방법4. 실험결과 및 고찰5. 결론참고문헌요약

In-Situ Application of High-Strength Antiwashout Underwater Concrete

Recently, the construction of underwater structures has been gradually increased, but underwater concrete got some problems of quality deterioration and water contamination around cast-in-situ of construction. In addition, massive underwater structures such as LNG tank, underwater concrete structures of large and continuous high- strength subterranean wall under water are being demanded lower heat of hydration. In this paper, the mechanical properties of high-strength antiwashout underwater concrete (HAWC) containing with two kinds of mineral admixtures respectively were investigated. On the basis of these results, the pH value and suspended solids of HAWC manufactured in the mock-up test were 10.0<TEX>$\Box$</TEX>11.0 and 51 mg/<TEX>${\iota}$</TEX> at 30 minutes later, respectively, initial and final setting time were about 30,37 hours, and the slump flow was 530<TEX>$\pm$</TEX>20Tm. In the placement at a speed of <TEX>$27 m^3/hr$</TEX>, there was no large difference in flowing velocity with or without reinforcing bar, and flowing slope was maintained at horizontal level. Compressive strength and elastic modulus of the cored specimen somewhat decreased as flowing distance was far; however, those of central area showed the highest value.

광물질 혼화재를 혼합한 수중불분리성 콘크리트의 물성 향상을 위한 연구

초록·키워드 목차 오류제보하기 등록된 정보가 없습니다. ABSTRACT1. 서론2. 실험개요3. 수중불분리성 콘크리트의 기초물성에 대한 실험결과 및 고찰4. 수중불분리성 콘크리트의 약품저항성에 대한 고찰5. 결론참고문헌요약

セルロースエーテルを添加したコンクリートの材料分離特性に関する材料設計法

The nonionic cellulose ether, a kind of water-soluble polymer, is used for several cement matrices such as plastering mortar, ceramic tile mortar, self smoothing flooring compound, high fluidity concrete, antiwashout underwater concrete, shot concrete and cement extrusion molding e. t. c.. The purpose of this study was to clarify the influence of the moIecuIar weight and the concentration of cellulose ether on characteristic in three kind of concrete (high fluidity concrete, antiwashout underwater concrete and shot concrete) containing cellulose ether. The results obtained were as follows. 1) Characteristics of concrete (such as the resistance of segregation e. t. c.), as well as mortar and cement paste was previously reported, were affected by the molecular weight and the concentration of cellulose ether. 2) Characteristic factors were able to be expressed by the following function of the molecular weight and the oncentration on material design method. Characteristic factors ∝ M^α×C^β where M : moIecuIar weight of cellulose ether, C : concentration, α, β : (0.67, 1.0) or (-0.67, -1.0)

水中不分離性コンクリートの沈埋函基礎充填への適用

Instead of bentonite mortar used a lot of filling materials, the authors considered the use of anti-washout underwater concrete satisfying the quality requirements for filling 50-cm thick confined spaces in water between crushed stone foundations and the bottoms of immersed tunnel elements. The concrete is required to have high fluidity to permit filling of thin and extensive spaces, adequate segregation resistance and excellent pumpability over a long distance. The authors investigated the performance of anti-washout underwater concretes by adjusting the mixture proportions with the aim of reducing the dosage of viscosity agent. The placeability and filling capability of the selected concrete was then confirmed by pumping tests and mock-up tests. The concrete was proven to have stable properties by the quality tests in actual production, retaining its placeability throughout the transportation and placing processes.

EFFECTS OF ADMIXTURES ON ANTIWASHOUT UNDERWATER CONCRETE

Antiwashout underwater concrete needs large amount of unit water-content than that of conventional concrete, because of developing an appropriate fluidity according to the condition of a site. As the excessive water content in a concrete mixture is not desierable to control thermal cracks and to make economic concrete, superplastisizer are used in the antiwashout underwater concrete to reduce unit water content. In some case, mineral admixtures such as blastfurnace slag and fly ash are used too. However, lime stone powder is not used so far. This paper reports the fluidity, setting, strength development, permeability, chloride penetration effected by lime stone powder used in the antiwashout underwater concrete.