• Journal of the Korean Ceramic Society
• /
• v.17 no.4
• /
• pp.208-212
• /
• 1980

In order to clarify the mechanism of the hydration of supersulphated slag cement, the experiments of suspension hydration were performed in the mixtures of slag+CaSO4+water or NaOH solutions with a liquid/solid ratio of 10. The liquid and solid phase of the suspension was chemically analysed and discussed. In the slag-$CaSO_4$--NaOH system, $Al_2O_3$ was dissolved under high pH condition, and the ettringite was formed by a reaction of $CaSO_4$ and $Al_2O_3$ released in the solution. As hydration progressed, ettringite coated the surface of unhydrated slag grains and inhibited the hydration reaction of slag. $CaSO_4$ was not only an activator for slag hydration, but a reactant in the hydration.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2001.11a
• /
• pp.409-414
• /
• 2001

The hydration of cement paste occurs when the cement is mixed with water. During the hydration, hydration heat causes the thermal stress depending on the size 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 investigate 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.

• 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.14 no.3
• /
• pp.247-262
• /
• 2014

Partial replacement of Portland cement by slag can reduce the energy consumption and $CO_2$ emission therefore is beneficial to circular economy and sustainable development. Compressive strength is the most important engineering property of concrete. This paper presents a numerical procedure to predict the development of compressive strength of slag blended concrete. This numerical procedure starts with a kinetic hydration model for cement-slag blends by considering the production of calcium hydroxide in cement hydration and its consumption in slag reactions. Reaction degrees of cement slag are obtained as accompanied results from the hydration model. Gel-space ratio of hardening slag blended concrete is determined using reaction degrees of cement and slag, mixing proportions of concrete, and volume stoichiometries of cement hydration and slag reaction. Furthermore, the development of compressive strength is evaluated through Powers' gel-space ratio theory considering the contributions of cement hydration and slag reaction. The proposed model is verified through experimental data on concrete with different water-to-binder ratios and slag substitution ratios.

• Computers and Concrete
• /
• v.7 no.1
• /
• pp.17-38
• /
• 2010

This research aimed to investigate the influence of high-volume mineral admixtures (MAs), i.e., fly ash and slag, on the hydration characteristics and microstructures of cement pastes. Degree of cement hydration was quantified by the loss-on-ignition technique and degree of pozzolanic reaction was determined by a selective dissolution method. The influence of MAs on the pore structure of paste was measured by mercury intrusion porosimetry. The results showed that the hydration properties of the blended pastes were a function of water to binder ratio, cement replacement level by MAs, and curing age. Pastes containing fly ash exhibited strongly reduced early strength, especially for mix with 45% fly ash. Moreover, at a similar cement replacement level, slag incorporated cement paste showed higher degrees of cement hydration and pozzolanic reaction than that of fly ash incorporated cement paste. Thus, the present study demonstrates that high substitution rates of slag for cement result in better effects on the short- and long-term hydration properties of cement pastes.

• Computers and Concrete
• /
• v.13 no.3
• /
• pp.309-323
• /
• 2014

Based on the compositions and structures of cement-based materials, the geometrical models of the tortuosity of transport paths in hardened cement pastes, mortar and concrete, which are associated with the capillary porosity, cement hydration degree, mixture particle shape, aggregate volume fraction and water-cement ratio, are established by using a geometric approach. Numerical simulations are carried out to investigate the effects of material parameters such as water-cement ratio, volume fraction of the mixtures, shape and size of aggregates and cement hydration degree, on the tortuosity of transport paths in hardened cement pastes, mortar and concrete. Results indicate that the transport tortuosity in cement-based materials decreases with the increasing of water-cement ratio, and increases with the cement hydration degree, the volume fraction of cement and aggregate, the shape factor and diameter of aggregates, and the material parameters related to cement pastes, such as the water-cement ratio, cement hydration degree and cement volume fraction, are the primary factors that influence the transport tortuosity of cement-based materials.

• Proceedings of the Korean Geotechical Society Conference
• /
• 2002.03a
• /
• pp.321-328
• /
• 2002

Various geosynthetics used as liners or the Protection layers are installed in the solid waste landfill. The interface shear strength between geosynthetics installed at the slope of the landfill is a very important variable for the safe design of bottom and cover systems in the solid waste landfill. The interface shear strengths between (1) Geomembrane(GM)/Geotexile(GT) and (2) Geomembrane(GM)/Geosynthetic Clay Liner(GCL) were estimated by a large direct shear test in this study and were evaluated by the Mohr-Coulomb failure criterion. Especially, this research is focused on the effect of water which exists between geosynthetics because interfaces become easily wet or hydrated by rain, leachate and groundwater beneath liners. The strength reduction at large displacement and the effects of the magnitude of normal stresses and GCL hydration methods also investigated. The test results showed that the interface shear strength and shear behavior varied depending upon the magnitude of normal stresses, water at the interface, and hydration methods. Summary of secant friction angles, which could be used as reference values at a site where similar geosynthetics are installed, together with normal stress and hydration condition are presented.

• Journal of the Korean Society of Food Science and Nutrition
• /
• v.24 no.2
• /
• pp.286-292
• /
• 1995

Proximate composition, dimension, water uptake and volume increase rates of three cultivars of Korean kidney beans, Pink(PKB), Red(RKB) and White(WKB) were compared. Significant differences in the proximate composition and calorie were not observed among samples. Hull removed samples showed the lowest ash content and the highest calorie. The rates of water uptake increased as the soaking temperature increased from 10~4$0^{\circ}C$. The moisture gain of the kidney beans during soaking showed a similar pattern to volume increase. Water uptake and volume increase rates were in the decreasing order of PKB, RKB and WKB. Moisture and volume gains held a linear relation with the square root of soaking time regardless soaking temperatures. The activation energies of water uptake and volume increase were 3033~3087 and 3077~ 3161 kcal/mole, respectively. The log time to reach a fixed moisture content showed a linear relation with soaking temperature regardless soaking temperatures. The z-values calculated from weight and volume changes decreased in proportions to the increase of hydration. The z-values of weight and volume to reach 50% hydration were 50.5~56.6$^{\circ}C$ and 48.4~61.2$^{\circ}C$, respectively.

• Journal of the Korean Ceramic Society
• /
• v.43 no.3 s.286
• /
• pp.156-161
• /
• 2006

Impedance spectroscopy was applied to the initial hydration of calcium phosphate bone cements in order to investigate the electrical/dielectric properties. Hydration or equivalently setting was monitored as a function of the amount of water and initial powder characteristics. Higher amounts of water produced more open microstructures, leading to higher conductivity and enhanced dielectric constant. The effects of the initial characteristics in the powder were investigated using bone cement powder prepared with and without granulation. Granulated powder exhibited a significant change in resistance and produced a higher dielectric constant than those of conventional powder. Through a simplified modeling, the effects of thickness in reaction products and pore sizes were estimated by the frequency-dependent impedance measurements. Furthermore, impedance spectroscopy was proven to be a highly reliable tool for evaluating the continuous change in pore structure occurring in calcium phosphate bone cements.

• Applied Biological Chemistry
• /
• v.31 no.1
• /
• pp.46-51
• /
• 1988

The effects of temperature on the water uptake rate of soybeans soaked in tap water and 0.5% $NaHCO_3$ solution were studied. The higher the soaking temperature, the faster the hydration rate, and among the three soybean varieties (Tanyob, Kwanggyo and Saeal), Tanyob(the smallest variety) showed faster rate than ocher varieties when soaking in tap water and 0.5% $NaHCO_3$ solution. Activation energy due to weight increase was calculated using Arrhenius equation. z-Values calculated from weight changes to reach different degrees of hydration during soaking showed the tendency to decrease with the increase of hydration degree when soaking in tap water and 0.5% $NaHCO_3$ solution.