• Proceedings of the Korean Institute of Building Construction Conference
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• 2023.05a
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• pp.53-54
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• 2023

In recent decades, climate change has become an issue of global importance. The calcium sulfoaluminate (CSA) cement emits lower CO₂ than the Portland cements while manufacturing. However, ettringite, which is a main hydration product of CSA cement, starts dehydrating at a temperature above 100℃, hence it may limit the CSA cement for high temperature application. Recently, an early carbonation curing of cement-based material has been extensively studied in terms of carbon neutralization. The carbonation curing of CSA cement has a potential to transform the AFt and AFm phases into calcium carbonate, and the transformation of unstable hydrates to stable hydrates can increase the resistance to elevated temperature. This review study summarizes and discusses the carbonation curing effect of CSA cement and the thermal stability of CSA cement exposed to elevated temperatures.

• Cement Symposium
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• no.32
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• pp.107-115
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• 2005

• Journal of the Korean Recycled Construction Resources Institute
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• v.11 no.3
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• pp.202-209
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• 2023

In this study, microstructures and mechanical properties of repair materials using calcium sulfoaluminate (CSA) and/or amorphous calcium aluminate (ACA) cements were experimentally investigated. By XRD ansysis, the hydrates formed in repair materials were identified. In addition, the microstructures of repair materials were visually examined through SEM observation. Setting time of mortars made with repair materials were measured. The strength development and ultrasonic velocity of the mortars were also evaluated at the predetermined ages. As a result, it seems that ACA showed a benefit effect with respect to mechanical properties of mortars.

• Geomechanics and Engineering
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• v.33 no.1
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• pp.41-51
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• 2023

Cementitious materials such as Ordinary Portland Cement (OPC), fly ash, lime, and bitumen have been employed for soil improvement over the years. However, due to the environmental concerns associated with the use of OPC, substituting OPC with calcium sulfoaluminate (CSA) cement offers good potential for ground improvement because it is more eco-friendly. Although earlier research has investigated the stabilizing effects of CSA cement-treated sand, no attempt has been made to examine soil behavior under high confining pressure. As a result, this study aimed to investigate the shear strength and mechanical behavior of CSA cement-treated sand using a consolidated drained (CD) triaxial test with high confining pressure. The microstructure of the examined sand samples was investigated using scanning electron microscopy. This study used sand with CSA cement contents of 3%, 5%, and 7% and confining pressures of 0.5, 1.0, and 1.5 MPa. It revealed that the confining pressures and CSA cement content significantly affected the stress-strain and volumetric change behavior of CSA cement-treated sand at high confining pressures.

• Resources Recycling
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• v.32 no.6
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• pp.10-17
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• 2023

Calcium silicate cement (CSC) is an environmentally sustainable, low-carbon cement and has garnered significant attention in recent studies. However, the pre-curing step required to activate the carbon dioxide reaction and to handle the sample. This study aimed to examine the viability of extending the application of CSC without pre-curing by enhancing initial strength by mixing calcium sulfoaluminate (CSA) fast-hardening cement into CSC. The investigation assessed changes in compression strength and Q-XRD mineral characteristics concerning variations in the mixing ratio of CSC and CSA fast-hardening cement within a carbon dioxide atmosphere. The compressive strength results indicated that the 3-day and 7-day strengths were 14.18 MPa and 22.98 MPa, respectively, under the 50% CSC condition, meeting the type 1 cement KS standard. Mineral characteristics analysis revealed an increase in calcite mineral, a byproduct of the carbon dioxide reaction, contributing to strength enhancement. Even after seven days, substantial quantities of unreacted rankinitene and pseudowollastonite were observed, as well as dicalcium silicate and yeelimite, which are hydrated minerals. This observation was confirmed the possibility of strength improvement after 7 days.

• Proceedings of the Korea Concrete Institute Conference
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• 1998.10b
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• pp.888-893
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• 1998

Calcium sulfoaluminate, $C_4$A$_3$$\bar{S}$, was prepared for reutilizing industrial by-products, such as II-CaSO$_4$, Al(OH), CaF$_2$ and cement sludge wastes. Mixed powder was fired at 1,15$0^{\circ}C$. $C_4$A$_3$$\bar{S}$ clinkers fired at 1,15$0^{\circ}C$ were analyzed by SEM and XRD. Also were added in cement paste and mortar and characterized as setting time, flow values and compressive strength. $C_4$A$_3$$\bar{S}$ could be found in the X-ray diffraction pattern. The setting time of cement pastes added clinkers fired at 1,15$0^{\circ}C$ was shorter than that of ordinary portland cement. Also the compressive strengths of the cement mortar added clinkers was higher than those of ordinary portland cement.

• Proceedings of the Korean Ceranic Society Conference
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• 2000.04a
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• pp.25.1-25.1
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• 2000

• International Journal of Concrete Structures and Materials
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• v.11 no.1
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• pp.59-68
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• 2017

Mercury intrusion and nitrogen sorption porosimetry were employed to investigate the pore structure of calcium sulfoaluminate ($C{\bar{S}}A$) and portland cement pastes with cement-to-water ratio (w/c) of 0.40, 0.50, and 0.60. A unimodal distribution of pore size was drawn for $C{\bar{S}}A$ cement pastes, whereas a bimodal distribution was established for the portland cement pastes through analysis of mercury intrusion porosimetry. For the experimental results generated by nitrogen sorption porosimetry, the $C{\bar{S}}A$ cement pastes have a smaller and coarser pore volume than cement paste samples under the same w/c condition. The relative dynamic modulus and percentage weight loss were used for investigation of the concrete durability in freeze-thaw condition. When coarse aggregate with good freeze-thaw durability was mixed, air entrained portland cement concrete has the same durability in terms of relative dynamic modulus as $C{\bar{S}}A$ cement concrete in a freeze-thaw environment. The $C{\bar{S}}A$ cement concrete with poor performance of durability in a freeze-thaw environment demonstrates the improved durability by 300 % over portland cement concrete. The $C{\bar{S}}A$ concrete with good performance aggregate also exhibits less surface scaling in a freeze-thaw environment, losing 11 % less mass after 297 cycles.

• Proceedings of the Korean Ceranic Society Conference
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• 2000.10a
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• pp.60.1-60
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• 2000

• Proceedings of the Korean Institute of Resources Recycling Conference
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• 2005.10a
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• pp.330-334
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• 2005

본 연구에서는 유해 중금속을 다량 함유하고 있는 산업폐기물의 고화 처리에 사용되는 칼슘설포알루미네이트(4CaO $3Al_2O_3\;SO_4$ 이후부터 CSA로 기입)의 제조를 위해 철강부산물인 압연 슬러지를 활용하여 그 특성에 대해 조사하였다. 본 연구에서는 철강 부산물인 압연슬러지 외에 석회석 미분물, 인산부산 석고를 혼합하여 칼슘알루미네이트 상을 합성하였다. 합성 결과 소성온도 $1250^{\circ}C$에서부터 CSA가 합성되었고, 이와 함께 칼슘실리케이트$(2CaO\;SiO_2)$와 칼슘알루미노페라이트($4CaO\;Al_2O_3\;Fe_2O_3$)도 함께 합성되었다. CSA 합성에 미치는 중금속 영향을 관찰한 결과 원료의 중금속이 CSA 합성 온도를 낮추는 효과가 있는 것으로 나타났다. CSA를 이용한 철강산업 폐기물의 중금속 고용 처리 연구에서도 본 실험에서 합성된 CSA가 폐기물의 중금속 고화 처리에 효과가 있는 것으로 나타났다.