• Journal of the Korean Recycled Construction Resources Institute
• /
• v.9 no.1
• /
• pp.92-99
• /
• 2021

CaO-based by-products composed of CaO, SO3, Al2O3, etc. are generally used as raw materials for CaO compounds. When applied to the recovered water of ready-mixed concrete, the hydration reaction of the powder material is accelerated and concrete performance can be improved. In this study, activated sludge was prepared to apply to the recovered water of ready-mixed concrete by mixing CaO-based hot-rolled slag(C12A7) in the recycling water of ready-m ixed concrete. Cem ent paste setting time and mortar compressive strength performance tests confirmed the effect on the hydration reaction. Therefore, the possibility of concrete application using activated sludge was confirmed.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.9 no.4
• /
• pp.413-418
• /
• 2021

In this study, as a basic study to use recycled limestone powder as a secondary product mixture for concrete, it was found that the compressive and flexural strengths were equal to or slightly improved compared to Plain up to 10% and 20% of the RLP mixing ratio, but the strength was rather decreased at 30% mixing. As a result of the heat of hydration experiment, as the RLP mixing rate increased, the heat of hydration decreased, and the elapsed time of the maximum heat was also delayed. As a result of the drying shrinkage test, as the fine powder RLP filled the internal pores of the cement mortar, the drying shrinkage decreased as the mixing rate increased. The compressive strength, water absorption rate, and compressive strength after freezing and thawing of the concrete block mixed with RLP 20% all satisfied the group standard criteria of the Korea Concrete Industry Cooperative Federation, confirming the possibility of use as a mixed material.

• Advances in concrete construction
• /
• v.12 no.6
• /
• pp.479-490
• /
• 2021

Present research is mainly focused on, microstructural and durability analysis of Graphene Oxide (GO) in Wollastonite (WO) induced cement mortar with silica fume. The study was conducted by evaluating the mechanical properties (compressive and flexural strength), durability properties (water absorption, sorptivity and sulphate resistance) and microstructural analysis by SEM. Cement mortar mix prepared by replacing 10% ordinary portland cement with SF was considered as the control mix. Wollastonite replacement level varied from 0 to 20% by weight of cement. The optimum replacement of wollastonite was found to be 15% and this was followed by four sets of mortar specimens with varying substitution levels of cementitious material with GO at dosage rates of 0.1%, 0.2%, 0.3% and 0.4% by weight. The results indicated that the addition of up to 15%WO and 0.3% GO improves the hydration process and increase the compressive strength and flexural strength of the mortar due to the pore volume reduction, thereby strengthening the mortar mix. The resistance to water penetration and sulphate attack of mortar mixes were generally improved with the dosage of GO in presence of 15% Wollastonite and 10% silica fume content in the mortar mix. Furthermore, FE-SEM test results showed that the WO influences the lattice framework of the cement hydration products increasing the bonding between silica fume particles and cement. The optimum mix containing 0.3% GO with 15% WO replacement exhibited extensive C-S-H formation along with a uniform densified structure indicating that calcium meta-silicate has filled the pores.

• Journal of the Korean Recycled Construction Resources Institute
• /
• v.11 no.2
• /
• pp.145-152
• /
• 2023

In this study, microscopic observation was made on the surface of cement paste immersed in an aquatic environment for 100 days at electrochemical treatment to mitigate the leaching of alkali ions. To quantitatively rank the hydration products, unhydrated grains and porosity in the interfacial region, the backscattered electron(BSE) images were obtained by scanninng electron microscopy. As a result, it was found that the porosity on the surface was significantly reduced by the electrochemical treatment, while unhydrated grains were more or less increased presumably limited hydration reaction under electric charge. At electrochemical treatment, Ca²⁺ ions present in C-S-H gel could be precipitated with OH^- to form Ca(OH)₂ then to lower C-S-H gel and simultaneously to enhance Ca(OH)₂. Substantially, the risk of alkali leaching could be lowered by the limited ionized matrix under electrochemical treatment.

• Journal of the Korean Crystal Growth and Crystal Technology
• /
• v.33 no.6
• /
• pp.244-249
• /
• 2023

In this study, various experimental parameters were investigated for high-purity C₃A synthesis. As a results of experiment, it was verified that the calcined temperature was the most important parameter for the synthesis of high-purity C₃A. In addition, more synthesis time was needed when large amount of C₃A synthesis to achieve high-purity. Meanwhile, the C₃A blended with CaCO₃ showed different reaction products compared to normal cement because C15 and C30 had monocarbocaluminate as a reaction product at early stage of hydration. Furthermore, the production amount and formation rate of monocarboaluminate formation was different varying with the CaCO₃ a mounts.

• International Journal of Concrete Structures and Materials
• /
• v.4 no.1
• /
• pp.37-43
• /
• 2010

Theoretical models based on modern interpretations of the morphology and interactions of cement hydration products are developed for prediction of the mechanical properties of hydrated cement paste (hcp). The models are based on the emerging nanostructural vision of calcium silicate hydrate (C-S-H) morphology, and account for the intermolecular interactions between nano-scale calcium C-S-H particles. The models also incorporate the effects of capillary porosity and microcracking within hydrated cement paste. The intrinsic modulus of elasticity and tensile strength of hydrated cement paste are determined based on intermolecular interactions between C-S-H nano-particles. Modeling of fracture toughness indicates that frictional pull-out of the micro-scale calcium hydroxide (CH) platelets makes major contributions to the fracture energy of hcp. A tensile strength model was developed for hcp based on the linear elastic fracture mechanics theories. The predicted theoretical models are in reasonable agreements with empirical models developed based on the experimental performance of hcp.

• The Korean Journal of Ceramics
• /
• v.3 no.2
• /
• pp.129-133
• /
• 1997

Fine powder of $\alpha$-tricalcium phosphate, tetracalcium phosphate and dicalcium phosphate were mixed together to prepare self-setting cements which form hydroxyapatite, one of the well-known biocompatible materials, as the end of products of hydration. Hardening behaviour of the cements was examined at the temperature range of 37~$70^{\circ}C$ and 150~$250^{\circ}C$ under the normal and hydrothermal condition respectively. The conversion of cements into hydroxyapatite was significantly improved ast elevated temperature and the paste was strengtheed by interlocking of hydroxyapatite crystals, indicating that the strength is determined by microtexture rather the amount of conversion of cements into hydroxyapatite.

• Proceedings of the Korea Concrete Institute Conference
• /
• 1999.04a
• /
• pp.64-69
• /
• 1999

Slags are by-products of the metallurgical industry. The most important slag from the standpoint of the quantity used as building material is iron blastfurnace slag. Slags are either crystalline stable solid used as aggregates or glassy material used as hydraulic binder. Slag cements are low heat of hydration cements. Slags react more slowly with than portland cement but they can be activated chemically. Activatiors can be either alkaline activators such as soda, lime, sodium carbonate, sodium silicate or sulphate activators such as calcium sulphate or phosphogypsum. So, in this study slaked lime was used as an activator that the compressive strength of this modified cement(M1 type) is high range in early age. And initial setting time of M1 type cement was shorter than conventional cements.

• Korean Journal of Pharmacognosy
• /
• v.51 no.1
• /
• pp.49-54
• /
• 2020

The aim of this study was to investigate the epidermal moisturizing effects of artocarpin on normal human epidermal keratinocytes (NHEKs). To investigate the effects of artocarpin on NHEKs, cell viability and the expression of mRNAs related to skin hydration were measured. In addition, hyaluronic acid (HA)-ELISA assay was performed. Here, the effects of artocarpin on AQP3, HAS2, KRT1, and KRT10 mRNA expression, and on HA production, following UVA treatment were reported. The Quantitative real-time PCR results demonstrate that artocarpin increased AQP3, HAS2, KRT1, and KRT10 mRNA levels. The HA-ELISA assay revealed that artocarpin also increased HA production in NHEKs. Through these experiments, the epidermal moisturizing effects of artocarpin have been elucidated, providing evidence that artocarpin may be a potent cosmetic ingredient in skin anti-aging and moisturizing products. Based on these results, I anticipate that further research on the mechanisms of action of artocarpin may allow the development of not only cosmetics, but also medicines and healthcare foods.

• Proceedings of the Korea Concrete Institute Conference
• /
• 2003.05a
• /
• pp.1077-1080
• /
• 2003

High reactivity metakaolin (HRM) is a manufactured pozzolan produced by thermal processing of purified kaolinitic clay. Field performance and laboratory research of concrete containing HRM have demonstrated its value for bridge decks, bridge deck overlays, high-strength concrete and masonry products. This paper discusses laboratory evaluations to assess the physical properties of antiwashout underwater concrete (AWC) containing HRM, such as pH value, suspended solids, slump flow, and compressive strength. There were not much variations of pH value with the changing HRM contents, but suspended solid test showed that the amount of suspended solids of AWC with 10 and 20% of HRM were reduced in comparison with plain. Due to the fast hydration and reaction property of HRM, slump flow was decreased with increasing HRM contents. According to the results of compressive strength test, AWC with 10 and 20% of HRM showed higher strength characteristic than plain at all curing ages.