• 대한건축학회연합논문집
• /
• 제21권5호
• /
• pp.117-124
• /
• 2019

When manufacturing concrete, several mineral admixture is added to improve the basic physical property and durability and to make economical concrete. Such mineral admixture includes fly ash, granulated blast furnace slag, silica fume, etc., and not only the studies about mixing these mineral admixtures but also the studies for the development of new materials have been steadily in progress. Recently, some researchers have found, as a part of the development of new materials, the rice straw ash can also be used as a pozzolanic material for concrete considering similar chemical properties of rice straw ash to that of rice husk ash. But there has been insufficient amount of study about it. So, this study was to investigate the possibility as mineral admixture of agriculture by-product, by analyzing properties of concretes using rice straw ash with replacement ratio in comparison with other mineral admixture. In order to measure amount of SiO2 of rice straw ash, XRF(X-ray fluorescence) analysis was tested. For the measure pozzolanic reaction of rice straw ash, pH change and color change was tested according to curing day. Also to evaluate properties of concrete using rice straw ash, slump test, air contents test and compressive strength was tested.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2001년도 가을 학술발표회 논문집
• /
• pp.73-78
• /
• 2001

Portland cement concrete is made with coarse aggregate, fine aggregate, portland cement, water and, in some cases, selected chemical admixtures such as air-entraining agents, water reducer, superplasticizer, and so on, and mineral admixtures such as fly ash, silica fume, slags, etc. Typically, in the concrete, the coarse aggregate and fine aggregate will occupy approximately 80 percent of the total volume of the final mix. Therefore, the coarse and fine aggregates affect to the properties of the portland cement concrete. As the natural sands are drained, it is necessary and economical to utilize crushed sands(manufactured fine aggregate). It is reported that crushed sands differ from natural sands in gradation, particle shape and texture, and the micro fines in the crushed sands affect to the quality of the portland cement concrete. Therefore, the purpose of this paper is to investigate the characteristics of fresh and hardened concrete with high content of micro fines. This study provides firm data for the use of crushed sands with higher micro fines.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2002년도 봄 학술발표회 논문집
• /
• pp.207-212
• /
• 2002

Reportedly, the use of mineral admixtures make concrete more durable and tighten against water. But, it is needed to study more about the relationship between the admixtures and the chloride ion diffusion. When concrete is mixed with fly-ash, pozzolanic reaction occur to time. So we should consider the factors that can evaluate inner structure of concrete in order to evaluate the chloride diffusion of the concrete more accurately. Therefore, in this study, we analyzed the correlation between chloride ion diffusion and physical properties such as compressive strength, void ratio, air permeability of the concrete, and tried to use them as fundamental data for analyzing chloride ion diffusion mechanism of the concrete mixed with fly-ash.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2006년도 춘계 학술발표회 논문집(II)
• /
• pp.489-492
• /
• 2006

A chloride is an important deteriorating factor which governs the durability of the reinforced-concrete structures under marine environments. Also, the main penetration mechanism of chloride ion into concrete is a diffusion phenomenon and numerous methods have been proposed to determine the diffusion coefficient of chloride ion quickly. In this study, electrically accelerated experiments were carried out in order to evaluate diffusion coefficient of the chloride ion into concrete. The methods were diffusion cell test method in which the voltage of 15V(DC) was applied. The type of cement is blended cement in which the admixtures of blast-furnace slag and fly ash were used. In conclusion, the diffusion coefficient of chloride ion is much affected according to mineral admixtures and the diffusion coefficient of ternary blended cement showed very low values. it is presumably said that this result is due to highly densified pore structures by the aid of slag substitution and pozzolanic activity of fly ash.

• 한국건축시공학회:학술대회논문집
• /
• 한국건축시공학회 2007년도 춘계학술논문 발표대회
• /
• pp.147-150
• /
• 2007

As recent buildings often use low-quality concrete materials, are constructed defectively, and are put in extreme environmental conditions, many of them show the shortening of life resulting from the corrosion of reinforcing rods by salt damage, carbonization, freezing and thawing, cracking. This in turn raises the cost of repair and maintenance, so it is required to extend the life of structures through enhancing the durability of concrete. In response to the demand, researches on high-durability concrete are being made actively focused on the maximum water-cement ratio, the maximum unit quantity, the minimum cover thickness, the addition of mineral admixtures, etc. With this background, the present study examined the basic physical properties of concrete containing admixtures for enhancing the durability of concrete.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2005년도 봄학술 발표회 논문집(II)
• /
• pp.193-196
• /
• 2005

In this study, the purpose is to suggest the data on mixing ratio which effects on the carbonation of concrete by replacing various admixture such as silica fume, fly ash, slag powder. Thus, we have experimented the accelerated test on the carbonation related to hardened body of the concrete which was admixed by slag powder, silica fume, fly ash and it was cured for 4 weeks in carbonation accelerator after 28 days curing water. The result of this experiment showed that carbonation speed increased highly when admixtures be used to replacing by growing of admixture ratio. especially, the test sample which was replaced with silica fume 15$\%$ and slag powder 40$\%$, was promoted highly to carbonation.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2004년도 추계 학술발표회 제16권2호
• /
• pp.297-300
• /
• 2004

The purpose of this study reutilization of waste fine tailing as admixture for cement. We observe tailing's basic properties such as shape, physical and chemical basic features. Also, various admixtures were made of 2 Types of tailings, OPC, fly-ash and blast furnace slag. The basic properties of the cement mortars incorporation with these admixtures were examined and analyzed under a verity of experimental conditions. This work showed that the tailing separated coarse materials could be effectively utilized as replacement materials of cement without any decrease in the strength if we can control the blaine of materials like OPC, slag and fly ash.

• Computers and Concrete
• /
• 제13권1호
• /
• pp.97-115
• /
• 2014

Silica fume is a by-product of induction arc furnaces and has long been used as a mineral admixture to produce high-strength, high-performance concrete. Due to the pozzolanic reaction between calcium hydroxide and silica fume, compared with that of Portland cement, the hydration of concrete containing silica fume is much more complex. In this paper, by considering the production of calcium hydroxide in cement hydration and its consumption in the pozzolanic reaction, a numerical model is proposed to simulate the hydration of concrete containing silica fume. The heat evolution rate of silica fume concrete is determined from the contribution of cement hydration and the pozzolanic reaction. Furthermore, the temperature distribution and temperature history in hardening blended concrete are evaluated based on the degree of hydration of the cement and the mineral admixtures. The proposed model is verified through experimental data on concrete with different water-to-cement ratios and mineral admixture substitution ratios.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2009년도 춘계 학술대회 제21권1호
• /
• pp.351-352
• /
• 2009

본 연구는 광물성 혼화재를 혼입한 혼합 콘크리트의 역학적 특성을 평가하기 위하여 광물성 혼화재의 종류 및 치환율 그리고 양생온도 및 조건에 따른 공기량, 슬럼프, 공기구조, 정적강도를 측정하였다.

• 한국콘크리트학회:학술대회논문집
• /
• 한국콘크리트학회 2003년도 가을 학술발표회 논문집
• /
• pp.505-508
• /
• 2003

The rheological properties of cement paste system mixed with mineral admixture for the purpose of increasing the strength and improving durability and rheology of concrete were investigated. The results were as follows: The rheological properties of one-ingredient paste system were improved with increasing the dosage of superplasticizer. For two-ingredients paste system, increasing the replacement rate of BFS(blast furnace slag) and FA(fly ash), the yield value and plastic viscosity were decreased compared with non-replacement. In the OPC(ordinary portland cement)-SF(silica fume) system, increasing the replacement rate of SF, the plastic viscosity and yield value increased linearly. In three-ingredients paste system, both OPC-BFS-SF and OPC-FA-SF system, the rheological properties were improved compared with the only replacement of SF. Both two- and three- ingredients paste system, the rheological properties using BFS were improved more than FA.