• Proceedings of the Korea Concrete Institute Conference
• /
• 2009.05a
• /
• pp.565-566
• /
• 2009

Supplementary cementing materials (SCM), such as silica fume, slag, and low-calcium fly ash, have been widely used as mineral admixtures in high strength and high performance concrete. Due to the chemical and physical effect of SCM on hydration, compared with Portland cement, hydration process of cement incorporating SCM is much more complex. This paper presents a numerical hydration model which is based on multi-component concept and can simulate hydration of cement incorporating SCM. The proposed model starts with mixture proportion of concrete and considers both chemical and physical effect of SCM on hydration. Using this proposed model, this paper predicts the following properties of hydrating cement-SCM blends as a function of hydration time: reaction ratio of SCM, calcium hydroxide content, heat evolution, porosity, chemically bound water and the development of the compressive strength of concrete. The prediction results agree well with experiment results.

• Computers and Concrete
• /
• v.11 no.1
• /
• pp.39-49
• /
• 2013

The use of ground fly ash in concrete can increase the risk of slump loss due to the drastic surface change of the particles after the grinding treatment and the accelerated reaction compared to the untreated ash. This study is aimed at the early age hydration and time-dependent rheology changes of cement paste containing ground fly ash. An original fly ash is ground into different fineness and the hydration of cement paste containing the ground fly ash is monitored with the ultrasound propagation method. The zeta potentials of the solid particles are measured and the changes of rheological parameters of the cement pastes with time are analyzed with a rheometer. A particle packing model is used to probe packing of the solid particles. The results show that the early age hydration of the paste is strongly promoted by replacing Portland cement with fly ash up to 30 percent (by mass), causing increase of the yield stress of the paste. The viscosity of a paste containing ground fly ash is lower than that containing the untreated ash, which is explained by the denser packing of the solid particles.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.04a
• /
• pp.33-39
• /
• 1999

This study was conducted to confirm the effect of bypass dust on the hydration and mechanical properties of the cement pastes and mortar obtained from ordinary Portland cement (OPC), OPC-slag and OPC-fly ash system. The rate of heat evolution is accelerated with the content of By-pass Dust(BD). total heat evolution increased because alkali-chlorides activated the hydration of blended cement. Compressive strength and bound water content show maximum value at 5wt% By-pass Dust(BD) on each curing time in ordinary Portland cement and slag blended cement. Ca(OH)2 content of Ordinary Portland Cement increased as the content of BD and curing time. In blended cement, the formation of Ca(OH)2 is active at early hydration stage. By pozzolanic reaction, the content of Ca(OH)2 is decreased as curing time goes by. According to the BD content stable chlorides complex of Friedel's salt (C3A·CaCl2·10H2O) is created. Due to the hydration activation effect of chlorides and alkali we observed Type II C-S-H, which developed into densest microstructure.

• Journal of Korea Technical Association of The Pulp and Paper Industry
• /
• v.40 no.2
• /
• pp.65-72
• /
• 2008

This work evaluated the extractability of tobacco stem biomass for the papermaking type Reconstituted Tobacco Sheet(RTS). The effects of the soaking conditions on the hydration of stem biomass and the effects of the hydrated state on the mechanical extraction were investigated. In order to simulate the mechanical expression process of a papermaking type RTS mill, for example, the screw press process, the novel mechanical pressing analyzer was developed for this study. The hydration of stem biomass by soaking process was greatly affected by the soaking time and the soaking temperature. The longer soaking time and the higher soaking temperature resulted in the higher hydrated stem biomass. Since the higher hydrated stem had more combined water in the inner structure and resulted in the more flexible structure, the higher hydrated stem leaded to the more compressed filter cake and the higher water contents in the filter cake after the mechanical pressing. The pilot pulping experiments showed the difference in hydration and extractability between burley and bright tobacco stem. The bulkier structure of the burley stem resulted in the faster hydration by pilot pulping and leaded to the larger reduction in water soluble components. And the hydration process showed the major influence on the separation efficiency of water soluble components.

• Proceedings of the Korean Institute of Building Construction Conference
• /
• 2003.05a
• /
• pp.67-71
• /
• 2003

This study is for the great quantity use of fly-ash. For the producing of high volume concrete from the use of fly-ash, the method of replacement between bonding agents and fine aggregate by fly-ash at the same time was used. It was used that the adiabatic temperature rise of concrete about the mass member which bad been produced by the method that was mentioned before, and the hydration heat of the core test pieces in concrete was measured. Also the core test pieces which were replaced with fly-ash was studied by the compressive streneth's comparison between standard care test pieces and core test pieces. In the case of mass test pieces, hydration heat and the tine to reach the highest temperature were decreased by an increase in replaced fly-ash's amounts of concrete. In addition, among the test pieces having the same amounts of concrete, the test pieces having more replaced amounts of fly-ash's fine aggregate showed higher hydration heat and the increased time to reach the highest temperature. Compressive strength was also increased by hydration heat's decrease according to fly-ash replacement. Replacement of fly-ash was more effective in high temperature environment.

• Journal of the Korea Institute of Building Construction
• /
• v.16 no.2
• /
• pp.185-192
• /
• 2016

The semi-adiabatic calorimetry technique is a robust and easy technique that can be used to measure the temperature rise of concrete. This method is often used for investigating the maturity of concrete, as well as to predict maximum temperature rise of mass concrete using various heat loss compensating models. Semi-adiabatic calorimetry can also be used for predicting setting time of concrete. However, it has seldom been used to investigate the hydration characteristics of various cement paste samples. In this research, semi-adiabatic calorimetry and X-ray diffraction methods were used to investigate the hydration characteristics of 3 different ASTM type I Portland cements. First derivative of temperature rise (dT/dt) curve was used to isolate individual peaks. Based on the results of the experiments, a combination of dT/dt curve with XRD could be used to successfully identify hydration at a specific time period, showing its potential to be used as an alternative tool for hydration studies of cement-based materials.

• Journal of the Korea Institute of Building Construction
• /
• v.2 no.2
• /
• pp.145-150
• /
• 2002

The hydration of cement paste occurs when the cement is miked with water. During the hydration, hydration heat causes the thermal stress depending on the site of concrete and the cement content. Especially in the high-strength concrete, we must give care to the concrete due to its large cement content. In this study conduction calorimeter and concrete insulation hydration heat meter were used to investigation the hydration heat characteristics of cement and concrete. To reduce hydration heat of high-strength concrete, several types of replacement of fly-ash and blast-furnace slag powder were used in this experiment. As a result of this study, it was found that hydration heat of high-strength concrete was reduced by replacement of fly-ash and blast-furnace slag powder. In case of high-strength concrete using blast-furnace slag powder, the max-heat arrival time was delayed but an effect of heat reduction was lower than a case of high-strength concrete using fly-ash, because it was considered that the heat-dependence property of blast-furnace slag powder was higher than that of fly-ash.

• Journal of the Korea Institute of Building Construction
• /
• v.12 no.5
• /
• pp.460-467
• /
• 2012

When recycled aggregate with old mortar and particles is used in concrete mixing, such aggregates can affect hydration reaction by promoting or inhibiting it. In this study, the possibility of hydration reaction on old mortar and particle was analyzed. Hydration reaction was carried out in old mortar that is finely crushed by an impact machine in the production of recycled aggregates, and it was found that this did have an impact on the strength development of concrete. Unlike in old cement, the hydration reaction did not progress in the particles, and it had high amounts of silica powder and calcium carbonate. In conclusion, the old mortar can have the influence of improving compressive strength, but the particles can delay the setting time of recycled aggregate concrete.

• Journal of the Korean Ceramic Society
• /
• v.18 no.4
• /
• pp.237-246
• /
• 1981

The effects of impurities, included in the by-produced phosphogypsum from the dihydrate process, on the hydration of portland cement were studied. Six gypsums were adopted in this study; four different raw phosphogypsums from domestic fertilizer plants, a reprocessed phosphogypsum and a reagent grade pure gypsum. Cements with differing $SO_3$ content, were synthesized by grinding two different commercial clinkers and the above six gypsums together. The effects of the impurities were investigated by measuring the setting time, the non-evaporable water coatent, X-ray phase analysis of cement pastes and the compressive strength of cement mortar specimens. It was found that the soluble $P_2O_5$ known as one of injurious impurities on the hydration of portland cement, included in the demestic raw phosghoypsum cxneedigply by far the specified amounts of the Korean Industrial Standards (L9005), and retarded the setting time severely, thus the strength development of cement was delayed at the earlier stage of hydration.

• Korean journal of food and cookery science
• /
• v.7 no.2
• /
• pp.25-40
• /
• 1991

Five-brown-rice-variety, Akibare, Odaebyeo, Taebaegbyeo, Nonglim Na 1 and Hankangchalbyeo, was prepared and examinated the hydration kinetics and the cooking qualities. Before the hydration the L/W ratio of raw Taebaegbyeo was the biggest value among the five brown rices. The water uptake was directly proportional to the square root of soaking time. During the hydration water uptake of high yielding brown rices was bigger than those of traditional brown rices among the nonglutenious varieties but waxy brown rices were not. Generally volume increase constant was directly proportional to the water uptake constant, which were different a little with brown rices was hydrated which was inversed proportional to the water uptake degree. According to the instrumental result using the rheometer of cooked brown rice with increased soaking times that was decreased the hardness and was increased the adhesiveness. The sensory evaluation test indicated that the hardness and the stickiness value of cooked brown rices were proper after 15-hour-soaking time and it was identical result to the instrumental result using the rheometer.