• Geomechanics and Engineering
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• v.17 no.3
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• pp.307-316
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• 2019

Dam deformation should be strictly controlled for the construction of 300 m-high rockfill dams, so the rockfill materials need to have low porosity. A method of using composite grout is proposed to reduce the porosity of rockfill materials for the construction of high rockfill dams. The composite grout is a mixture of fly ash, cement and sand with the properties of easy flow and post-hardening. During the process of rolling compaction, the grout admixture sprinkled on the rockfill surface will gradually infiltrate into the inter-granular voids of rockfill by the exciting force of vibratory roller to reduce the porosity of rockfill. A visible flowing test was firstly designed to explore the flow characteristics of composite grout in porous media. Then, the compressibility, shear strength, permeability and suffusion susceptibility properties of composite grout-modified rockfill are studied by a series of laboratory tests. Experimental results show that the flow characteristics of composite grout are closely related to the fly ash content, the water-to-binder ratio, the maximum sand size and the content of composite grout. The filling of composite grout can effectively reduce the porosity of rockfill materials, as well as increase the compression modulus of rockfill materials, especially for loose and gap-graded rockfill materials. Composite grout-modified rockfill tends to have greater shear strength, larger suffusion erosion resistance, and smaller permeability coefficient. The composite grout mainly plays the roles of filling, lubrication and cementation in rockfill materials.

• Journal of the Architectural Institute of Korea Structure & Construction
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• v.35 no.12
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• pp.157-164
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• 2019

Superabsorbent polymers(SAPs) are powdery material that absorb water several tens or hundreds of times its own mass. It has been reported that when SAPs are incorporated into a high strength cementitious material, the autogenous shrinkage of the material is reduced. Cross-linked sodium polyacrylate type SAPs are relatively safe for human body and low in production cost. In order to apply this type of SAPs to the admixture for total(plastic+autogenous+drying) shrinkage reduction of high strength mortar, the shrinkage behavior of mortar when an expansion agent(EA) and SAPs were mixed together was analyzed. As a result, it was found that the shrinkage was reduced when an EA 5% (mass % of cement) and SAPs 0.4% were mixed together than the mortar containing only an EA 10%. The shrinkage was further reduced when EA 10% and SAPs 0.4% were incorporated into mortar.

• Advances in materials Research
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• v.11 no.4
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• pp.251-277
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• 2022

Disposal of industrial waste in cities where municipal authorities permitting higher floor area ratio coupled with increasing living standards, a lot of demolition waste is being generated. Its disposal is a challenge particularly in megacities where no landfills are available. The ever-increasing cost of building construction materials also necessitates consuming demolition wastes in a useful manner to save fresh natural raw materials. In the present work, the crushed waste glass is used in high-strength concrete as a partial replacement of fine aggregate. The control concrete of grade M60 was proportioned following BIS 10262-2009. The crushed waste glass has been used as a partial replacement with varying percentages of 10, 20, 30, and 40% by weight of fine aggregate. Experimental tests were carried on the fresh and hardened state of the concrete. The effect of crushed waste glass on the workability of the concrete has been investigated. Non-destructive tests, acid attack tests, compressive strength, split tensile strength, and X-ray diffraction analysis was carried out for the control concrete and concrete containing crushed waste glass after 7, 28, and 270 days of normal curing. The results show that for the same w/c ratio, the workability of concrete increases with increasing replaced crushed waste glass content. However, the decrease in compressive strength of the concrete after 28 days of normal curing and further after 28 days of acid attacks, up to 30% replacement level of fine aggregate by the crushed waste glass is insignificant.

• Journal of the Korea Concrete Institute
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• v.18 no.2 s.92
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• pp.205-211
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• 2006

The objective of this study was to evaluate the durability of low shrinkage high performance concrete(LSHPC), which was combined with expansive additives and shrinkage reducing admixtures. We tested for not only LSHPC but also high performance concrete(HPC) and normal concrete(NC) to be compared with the durability of LSHPC. HPC was made in the same water-binder ratio of LSHPC without expansive additives and shrinkage reducing admixture. As a result, it was found that LSHPC had higher compressive and tensile strength than that of HPC. LSHPC showed more excellent performance than HPC and NC in the case of resistance to chloride ion penetration and resistance to carbonation and also showed nearly 100 durability factor in the freeze-thawing test with 500 cycles. From the examination about the watertightness and the pore distribution, it was found that the durability of LSHPC was improved because its hardened cement paste is organized closer. So we can conclude that when LSHPC is applied to structures in field, it is possible to reduce the shrinkage and crack in concrete and improve the durability.

• Journal of the Korean Recycled Construction Resources Institute
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• v.6 no.2
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• pp.94-99
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• 2018

The purpose of this study is to investigate the effect of combinations of different accelerators mixed on the early age strength development of concrete of 21 to 27MPa in the curing temperature of $10^{\circ}C$ compared with existing early strength agent. The present study was assessed the early strength development of combinations of three different accelerating admixtures with early strength type agent comparing to single accelerating admixture with early strength type agent. As a result of this study, the effect of $CaBr_2+NaSCN+DEA$ combination on strength development showed better than $CaBr_2$ or NaSCN alone with early strength type agent. Therefore, we observed that concrete using $CaBr_2+NaSCN+DEA$ combination with early strength agent was achieved 5MPa 12hours earlier than use of $CaBr_2$ or NaSCN alone.

• Journal of the Korea institute for structural maintenance and inspection
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• v.8 no.2
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• pp.185-194
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• 2004

In recent years, construction company makes inroads into the world construction market, and receives the order of extra-large concrete structure under marine environment in south-east asia specially. At this point of time, to enhance the quality of concrete, we research the High Strength Concrete (HSC) containing mineral admixtures. In this study, therefore, HSC with various combination of ordinary portland cement(OPC), blast-furnace slag(SG), silica fume(SF), and expansion admixture(SS) are cured 23 and $35^{\circ}C$ considering the site weather, and are cured in water for 3, 7 or 56 days respectively. Test results show that the HSC cured at $35^{\circ}C$ gains higher early-age strength but eventually gains lower later-age strength compare with the HSC cured at $23^{\circ}C$. Especially, HSC with combination of OPC+SG+SF+SS or OPC+SG+SF show very excellent resistance of chloride penetration. The permeability of HSC was therefore enhanced as because of containing the proper content of SG, SF, and SS and making dense micro-structure of HSC.

• Magazine of the Korean Society of Agricultural Engineers
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• v.16 no.3
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• pp.3472-3476
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• 1974

This test was attempted to investigate the effects of some mix designs of concreteon the compressive strengths and corrosive rates when exposed to sea water of the West Sea. In this test, concrete mixes consisted of an ordinary concrete, a pozzolan concrete and concretes with different admixtures such as fly ash, pozzolith and vinsol resin. Compressive strengths of the concrete were measured at ages of 1-year and 2-years when exposed to both sea water and fresh water. Corrosive rate was tested at ages of 1-year and 2-years when exposed to sea water only. The results obtained from the test may be summarized as follows: (1) When all of concretes were exposed to fresh water, compressive strength of an ordinary concrete was the lowest at all mixes of concretes, and all of them showed higher strength as the exposing age is longer. It was evidance that the uses of pozsolan cement, fly ash, pozzolith and vinsol resin in mix design of concrete had an effect on increasing compressive strength and that fresh water also had an effect on curing concretes even though at a long-time age. (2) When concretes were exposed sea water, a concrete with fly ash was the highest in compressive strength and its strength was increasing as the exposing age is longer, but the other concretes were decreased at 2-year exposure. It was found that a concrete with fly ash was the most effective on compressive strength of all concrete, but the other concretes were attacked by action of the sea water. (3) The use of vinsol resin admixture was the most resistant to corrosion by sea water, while the use of pozzolith was the most serious at corrosion and the others were corroded to almost same extent. (4) The relationship between corrosions and compressive strengths of concretes was not clearly correlated yet. It was known that the corrosive rate of concretes could not affect to compressive strengths by 2-year exposure of the sea water. (5) Pozzolan concrete was the most effective in compressive strength when exposed to fresh water only, However, the use of a fly ash admixture was available for compressive strength when exposing to both fresh water and sea water. It was also noticed that the use of vinsol resin was not available for strengths of concrete but for resistance to corrosion when exposed to sea water. (6) It was found that the use of pozzolith was so defective in compressive strengths and corrosiive resistance when exposing to sea water that it was only available for fresh water.

• Proceedings of the Korea Concrete Institute Conference
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• 2008.11a
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• pp.641-644
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• 2008

This paper investigated the plant and raw material of the ready-mixed concrete company which could supply to the second Lotte World on Pusan. the results were summarized as following. Almost plants were mainly using Twin shaft mixer which was 210m$^3$/hr and horizontal type. There was different the number of admixture silos at each plants, and they were separated by types. The mixtures mainly consisted of the ordinary portland cement, fly ash and blast furnace slag. For favorable quality control, each materials had to carry from same factories, and the monitering standard for quality control should be prepared. The coarse aggregates were used with many different producing districts, so they were only used from Y caused by exclusion of quality difference. The crushed, washed and river sands were generally used as fine aggregates, so the fine aggregates which could be possible to supply stable quality were chosen. This study used Poly Carbonic Acid Admixture which was developed to satisfy maintenance of performance till 2 hours and 10MPa at 15 hours.

• KSCE Journal of Civil and Environmental Engineering Research
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• v.30 no.5A
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• pp.433-442
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• 2010

A control of chloride diffusion coefficient is very essential for service life of reinforced concrete (RC) structures exposed to chloride attack so that much studies have been focused on this work. The purpose of this study is to derive the intended diffusion coefficient which satisfies intended service life and propose a technique for optimum concrete mixture through genetic algorithm(GA). For this study, 30 data with mixture proportions and related diffusion coefficients are analyzed. Utilizing 27 data, fitness function for diffusion coefficient is obtained with variables of water to binder ratio(W/B), weight of cement, mineral admixture(slag, flay ash, and silica fume), sand, and coarse aggregate. 3 data are used for verification of the results from GA. Average error from fitness function is observed to 18.7% for 27 data for diffusion coefficient with 16.0% of coefficient of variance. For the verification using 3 data, a range of error for mixture proportions through GA is evaluated to 0.3~9.3% in 3 given diffusion coefficients. Assuming the durability design parameters like intended service life, cover depth, surface chloride content, and replacement ratio of mineral admixture, target diffusion coefficient, where exterior conditions like relative humidity(R.H.) and temperature, is derived and optimum design mixtures for concrete are proposed. In this paper, applicability of GA is attempted for durability mixture design and the proposed technique would be improved with enhancement of comprehensive data set including wider range of diffusion coefficients.

• Computers and Concrete
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• v.26 no.4
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• pp.309-316
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• 2020

The application of multi-variable adaptive regression spline (MARS) in predicting he long-term compressive strength of a concrete with various admixtures has been investigated in this study. The compressive strength of concrete specimens, which were made based on 24 different mix designs using various mineral and chemical admixtures in different curing ages have been obtained. First, The values of fly ash (FA), micro-silica (MS), water-reducing admixture (WRA), coarse and fine aggregates, cement, water, age of samples and compressive strength were defined as inputs to the model, and MARS analysis was used to model the compressive strength of concrete and to evaluate the most important parameters affecting the estimation of compressive strength of the concrete. Next, the proposed equation by the MARS method using particle swarm optimization (PSO) algorithm has been optimized to have more efficient equation from the economical point of view. The proposed model in this study predicted the compressive strength of the concrete with various admixtures with a correlation coefficient of R=0.958 rather than the measured compressive strengths within the laboratory. The final model reduced the production cost and provided compressive strength by reducing the WRA and increasing the FA and curing days, simultaneously. It was also found that due to the use of the liquid membrane-forming compounds (LMFC) for its lower cost than water spraying method (SWM) and also for the longer operating time of the LMFC having positive mechanical effects on the final concrete, the final product had lower cost and better mechanical properties.