• Proceedings of the Korea Concrete Institute Conference
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• 1996.10a
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• pp.154-165
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• 1996

As II-anhydrite reacts with C3A(aluminate), C4AF(ferrite) at initial hydration of cement and assists the hydrolysis of C3S(calcium silicate), the production rate of ettringite(3C3A.3CaSO4.32H2O) and C-S-H gel was acclerated. It was known that compressive strength of cement concrete improved due to the effect of II-anhydrite. For the checking these effects of II-anhydrite, the fluidity and compressive strength of cementmortar admixed with II-anhydrite and pozollanic fine powders were investigated. By means of SEM analysis, the surface structure of mortar with the condition of steam curing at curing days=28 was investigated. As a result of this experiment, it was examined that II-anhydrite had an increase on the fluidity of cementpaste and compressive strength of mortar.

• Journal of the Korean Ceramic Society
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• v.34 no.12
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• pp.1261-1267
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• 1997

Four kids of powder admixtures(A, B, C, D) based on anhydrite were manufactured by mixing at a fixed rate of II-anhydrite, fly ash and active silica as an industrial by-product. Fluidity properties of cement paste such as mini-slump, apparent viscosity with elapsed time, as well as setting time of cement pastes of these admixtures substituted up to 11wt% of cement were compared to those of cement paste(SS) substisuted by marketed high-strength powder admixture(S). Among these powder admixtures, the fluidity of cement pastes(PA, PC) substituted by A and C powder admixtures manufactured from II-anhydrite and fly ash had an excellent property than that of cement paste substituted by marketed powder admixture and also a good fluidity-retention effect with elapsed time by adding of superplasticizer. The setting time of cement paste substituted by powder admixtures based on anhydrite slightly retarded than that of cement paste substituted by marketed powder admixture.

• Proceedings of the Korea Concrete Institute Conference
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• 2004.05a
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• pp.228-231
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• 2004

The purpose of this study evaluates possibilities of waste phosphogypsum into concrete by steam curing admixture. The waste phosphogypsums were classified into 4 forms(Dihydrate, $\beta-Hemihydrate$, III-Anhydrite and II-Anhydrite) which were changed to in low temperature of calcination. Also, various admixtures were made of waste phosphogypsum(PG) and pozollanic fine powderers (Fly-ash, Blast Furnace Slag), and the basic properties of the cement mortars incorporating with these admixtures were examined and analyzed under a verity of experimental conditions. As a result, III-Anhydrite, these is similar to II-Anhydrite from compressive strength and are great in the effect of strength improvement. also, it was proved that specimens made on type III-Anhydrite of waste phosphogypsum and blast furnace slag increased on the compressive strength of cement mortar. Therefore, III-Anhydrite phosphogypsum calcined at lower temperature could be used as steam curing admixture for concrete 2th production.

• Proceedings of the Korea Concrete Institute Conference
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• 1997.04a
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• pp.136-145
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• 1997

The purpose of this study is to develope of alternative adimixture for manufacture of PHC pile(compressive strength above 800kg/$\textrm{cm}^2$). For the investigation, properties of alternative admixture admixed with II-anhydrite and pozollanic fine powders(e.q., Fly-ash, Silica-Fume), the fluidity and viscosity in the cement pastes, the fluidity and compressive strength in mortars at steam curing condition, were respectively examined. Also, properties of compressive strength of concretes with exiting admixture(specimen name SM) and alterantive admixture(specimen name AP) for PHC pile, at steam and standard curing condition, were compared each other. As a result of this experimental study, it was found that specimens admixed with II-anhydrite and pozollanic fine powders had an increase on the fluidity of cement paste and mortar, and compressive strength of mortar and concrete was as good as concrete with SM.

• Journal of the Korean Ceramic Society
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• v.37 no.8
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• pp.751-759
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• 2000

Effects of the dosage change, from 0 to 2.0 wt% based on cement weight, of naphthalenic (NSF) and polycarboxylic(NT-2) superplasticizers, on the fluidity of cement paste substituted by 10 wt% II-anhydrite and fly ash respectively as well as II-anhydrite and fly ash itself were investigated. Dispersion properties between particles in suspension were investigated by zeta potential test. Initial fluidity and slump loss in the paste system were observed through mini-slump and apparent viscosity changes with elapsed time. Zeta potential on the particle surface was a tendency to increase according to increasing of NSF dosage. Especially, zeta potential of fly ash has the highest value among all particles equivalent to NSF dosage. In the fluidity of cement paste substituted by inorganic particles, the specimen with substitution of 10 wt% II-anhydrite and fly ash for cement was more effective than cement itself to improve initial fluidity and retain stable fluidity of cement paste. In addition, effect of NT-2 and NSF to improve the fluidity of cement paste, addition of 1.0 wt% NT-2 was more effective than 1.5wt% NSF.

• Journal of the Korean Ceramic Society
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• v.34 no.8
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• pp.861-869
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• 1997

In order to investigate the reaction in the system of anhydrite II-blast furnace slag, the paste hydration which made up with a liquid/solid ratio of 0.45 for 1, 3, 7, 14, 28days by the addition of accelerators to 10~30wt.% slag with natural gypsum calcined for 1hour at 500/$700^{\circ}C$ was studied by combined water determination, XRD, DTA, DSC and SEM. As a result of this experiment, it was found that hydration rate was faster in the system calcined at 50$0^{\circ}C$. Therefore the anhydrite was converted to calcium sulfate dihydrate in the hydration for 1day but the slag was not almost reacted. For the gypsum calcined at $700^{\circ}C$, the hydraton rate in the system of K2SO4 addition was faster than others in the earier period, but the activated effect of the system of Al2(SO4)3 addition was regarded as the highest over 3days. As the amount of slag was increased, they dydration rate was delayed and ettringite was observed in the case of K2SO4 system. However both Al2(SO4)3 and AlK(SO4)2 systems showed calcium sulfate dhydrate only as hydrated products.

• Applied Chemistry for Engineering
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• v.9 no.3
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• pp.336-341
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• 1998

A comparative study on the effects of mean particle diameter and substitutional ratio of II-anhydrite on the fluidity of cement paste has been conducted. Three different mean particle diameters(4, 14 and $35{\mu}m$) and four different substitution ratios(3, 5, 10, 15wt%) have been tested while the dosage of two superplasticizers - naphtalenic(NSF) and polycarboxylic(NT-2) - has been varied from 0 to 2.0wt%. To investigate the effects of those parameters, the variation in fluidity and apparent viscosity of the cement paste has been observed as a function of the elapsed time. The initial fluidity of the cement paste is more affected by the increase in substitution ratio than by the mean particle size of the II-anhydrite. When the substitution ratio of the II-anhydrite is fixed at 10wt%, addition of 1.0wt% NT-2 improves the fluidity of paste cement more than that for NSF. This case has showed the best improvement of the fluidity in the range of parameters investigated. At the addition of 1.0wt% NT-2, apparent viscosity of the cement paste has been noticeably decreased as substitutional ratio of II-anhydrite increases. It was found that it would be more effective to substitute II-anhydrite at a certain ratio to improve the fluidity of the cement paste, in addition to adding NT-2.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.04a
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• pp.83-88
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• 1998

II-anhydrite, slag, and fly ash produced as industrial by-product were reutilized for the manufacture of high strength admixtures for cement and concrete. The effects of these admixtures on the compressive strength of cement mortar and concrete were examined with those of domestic admixture. At the condition mortar and concrete. Especially, adding of II-anhydrite was very effective for the increasing of compressive strength. Therefore it is possible that these admixture as a high strength admixture apply to cement and concrete.

• Cement Symposium
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• no.24
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• pp.67-74
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• 1996

• Journal of the Korea Concrete Institute
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• v.21 no.6
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• pp.729-735
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• 2009

In this study, it is experimentally verified a feasibility of the wasted phosphogypsum ($CaSO_4/H_2O$) that is a byproduct from the phosphoric acid process of manufacturing fertilizers can be applied as an admixture in slag cement. For the test, phosphogypsum is modified as dihydrate, hemihydrate, type III anhydrite, and type II anhydrite, and then chemical characteristics and mechanical properties of various slag cements containing above mentioned gypsum materials were analyzed. The test results show that the gypsum made at high temperature has better quality with decrease of water-soluble phosphoric acid ($S-P_2O_5$) which has an effect on the quality of cement. And type II anhydrite shows superior quality in terms of drying shrinkage and the compressive strength of cement paste with hemihydrate at 56 days is higher than other gypsum material.