Leaching and solidification behavior of Cu2+, Cr3+ and Cd2+ in the hydration products of calcium sulfoaluminate cement

This paper aimed to report the effects of fly ash (FA) on the mechanical properties and hydration of calcium sulfoaluminate-activated supersulfated cement (CSA-SSC). The CSA-SSC comprises of 80% granulated blast furnace slag (GBFS), 15% anhydrite, and 5% high-belite calcium sulfoaluminate cement (HB-CSA) clinker. The hydration products of CSA-SSC with or without FA were investigated by X-ray diffraction and thermogravimetric analysis. The experimental results indicated that the addition of FA by 10% to 30% resulted in a decrease in the rate of heat evolution and total heat evolution of CSA-SSC. As the content of FA was increased in the CSA-SSC system, the compressive and flexural strengths of the CSA-SSC with FA after 1 day of hydration were decreased. After 7 days of hydration, the compressive and flexural strength of CSA-SSC mixed with 10 wt.% and 20 wt.% of FA rapidly increased and exceeded that of ordinary Portland cement (OPC), especially the flexural strength. Moreover, the compressive strength of CSA-SSC mixed with 30 wt.% of FA after 90 days of hydration was close to that of OPC, and flexural strength of CSA-SSC mixed with 30 wt.% of FA after 7 days of hydration was close to that of OPC. The hydration products of the CSA-SSC and CSA-SSC mixed with FA were mainly ettringite and calcium silicate hydrate (C-S-H).

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Properties of calcium sulfoaluminate cement-based grouting materials with LiAl-layered double hydroxides slurries

Advanced Composites Letters ◽

10.1177/2633366x20926522 ◽

2020 ◽

Vol 29 ◽

pp. 2633366X2092652 ◽

Cited By ~ 1

Author(s):

Haiyan Li ◽

Xianping Wang ◽

Xuemao Guan ◽

Dinghua Zou

Keyword(s):

Compressive Strength ◽

Specific Surface ◽

Surface Area ◽

Specific Surface Area ◽

Layered Double Hydroxides ◽

Setting Time ◽

Hydration Products ◽

Calcium Sulfoaluminate Cement ◽

Calcium Sulfoaluminate ◽

Double Hydroxides

In this study, LiAl-layered double hydroxides Lithium aluminum hydrotalcite (LiAl-LDH) with different specific surface area were prepared by the separate nucleation and aging steps (SNAS) method and then were employed to prepare calcium sulfoaluminate cement-based grouting material (CBGM) paste. The influence of LiAl-LDH slurries on fresh and hardened properties of the CBGM paste was investigated in terms of fluidity, stability, setting time, and compressive strength. Additionally, the hydration process and hydration products of the CBGM paste were characterized by hydration heat, X-ray diffraction, differential thermal analysis–thermogravimetry, and Fourier transform infrared analyses. The acquired results illustrated that LiAl-LDH with larger specific surface area led to a faster hydration rate at early age, a lower fluidity, a shorter setting time, and a higher stability. Furthermore, due to the crystal nucleation effect, the addition of LiAl-LDH slurries did not cause a new phase to form but changed the morphology and increased the amount of hydration products, yielding higher compressive strength.

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Influence of Cementitious System Composition on the Retarding Effects of Borax and Zinc Oxide

Materials ◽

10.3390/ma12152340 ◽

2019 ◽

Vol 12 (15) ◽

pp. 2340

Author(s):

Feraidon F. Ataie

Keyword(s):

Zinc Oxide ◽

Portland Cement ◽

Heat Of Hydration ◽

Hydration Products ◽

Calcium Sulfoaluminate Cement ◽

Calcium Sulfoaluminate ◽

System Composition ◽

Cementitious System ◽

Cementitious Systems ◽

Aluminate Cement

This research investigated the retarding impact of zinc oxide (ZnO) and borax (Na2[B4O5(OH)4]·8H2O) on hydration of Portland cement, calcium aluminate cement (CAC), and calcium sulfoaluminate cement (CSA). Heat of hydration of cement paste samples with and without ZnO and borax was used to measure the influence of ZnO and borax on the set time of these cementitious systems. It was found that both ZnO and borax can retard the set time of Portland cement systems; however, ZnO was shown to be a stronger set time retarder than borax for these systems. ZnO did not show any retarding impact on CAC and CSA systems while addition of borax in these systems prolonged the set time. It was concluded that ZnO does not poison the nucleation and/or growth of CSA and CAC hydration products. We suggest that borax retards the cement set time by suppressing the dissolution of cement phases.

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Effect of Naphthalene-Based Superplasticizer and Polycarboxylic Acid Superplasticizer on the Properties of Sulfoaluminate Cement

Materials ◽

10.3390/ma14030662 ◽

2021 ◽

Vol 14 (3) ◽

pp. 662

Author(s):

Yonghua Wu ◽

Qiqi Li ◽

Guoxin Li ◽

Shiying Tang ◽

Mengdie Niu ◽

...

Keyword(s):

Compressive Strength ◽

Setting Time ◽

Hydration Products ◽

Polycarboxylic Acid ◽

X Ray Diffraction ◽

Calcium Sulfoaluminate Cement ◽

X Ray ◽

Initial Setting Time ◽

Calcium Sulfoaluminate ◽

Initial Setting

In order to study what the effect of superplasticizers on the setting time, fluidity and compressive strength of calcium sulfoaluminate cement (CSA) a naphthalene-based superplasticizer (BNS) and a polycarboxylic acid superplasticizer (PC) were selected to interact with CSA pastes and ye’elimite, respectively. X-ray diffraction (XRD), thermogravimetric (TG) analysis and scanning electron microscopy (SEM) analytical methods were used to investigate the class, amount and microstructure of the CSA pastes and ye’elimite pastes hydration products under the effect of the superplasticizers. The results showed that the addition of BNS can promote ettringite generation and thus improve the early compressive strength. As the addition of BNS increased from 0.8 wt% to 2.0 wt%, the initial setting time was prolonged 10 min, the final setting time was prolonged 7 min, the 5 min fluidity was improved from no fluidity to 220 mm. However, as the addition of PC increased from 0.08 wt% to 0.20 wt%, the setting time of the PC just changed within 3 min; the 5 min fluidity increased from 110 mm to 195 mm and no 15 min fluidity at all was observed. AS seen by SEM, it can be stated that generated ettringite under the addition of PC was layered and lacking bonding, and its morphology changed from rod-like to flake-like, leading to a decrease in early compressive strength.

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Effect of Alkaline Salts on Calcium Sulfoaluminate Cement Hydration

Molecules ◽

10.3390/molecules26071938 ◽

2021 ◽

Vol 26 (7) ◽

pp. 1938

Author(s):

Luís Urbano D. Tambara Júnior ◽

Janaíde C. Rocha ◽

Malik Cheriaf ◽

Pilar Padilla-Encinas ◽

Ana Fernández-Jiménez ◽

...

Keyword(s):

Cement Hydration ◽

Hydration Products ◽

Reaction Products ◽

X Ray Diffraction ◽

Calcium Sulfoaluminate Cement ◽

Hydration Kinetics ◽

Sodium Salts ◽

X Ray ◽

Calcium Sulfoaluminate ◽

Ettringite Formation

This work analyzes the effect of the presence of 5 wt.% of solid sodium salts (Na2SO4, Na2CO3, and Na2SiO3) on calcium sulfoaluminate cement (CSA) hydration, addresses hydration kinetics; 2-, 28-, and 90-d mechanical strength, and reaction product microstructure (with X-ray diffraction (XRD), and Fourier transform infrared spectroscopy, (FTIR). The findings show that the anions affect primarily the reactions involved. Ettringite and AH3, are the majority hydration products, while monosulfates are absent in all of the samples. All three salts hasten CSA hydration and raise the amount of ettringite formed. Na2SO4 induces cracking in the ≥28-d pastes due to post-hardening gypsum and ettringite formation from the excess SO42– present. Anhydrite dissolves more rapidly in the presence of Na2CO3, prompting carbonation. Na2SiO3 raises compressive strength and exhibits strätlingite as one of its reaction products.

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Strength Performance and Microstructure of Calcium Sulfoaluminate Cement-Stabilized Soft Soil

Sustainability ◽

10.3390/su13042295 ◽

2021 ◽

Vol 13 (4) ◽

pp. 2295

Author(s):

Hailong Liu ◽

Jiuye Zhao ◽

Yu Wang ◽

Nangai Yi ◽

Chunyi Cui

Keyword(s):

Soft Soil ◽

Hydration Product ◽

X Ray Diffraction ◽

Calcium Sulfoaluminate Cement ◽

Strength Performance ◽

X Ray ◽

Calcium Sulfoaluminate ◽

Stabilized Soil ◽

Calcium Silicates ◽

Hydrated Calcium

Calcium sulfoaluminate cement (CSA) was used to stabilize a type of marine soft soil in Dalian China. Unconfined compressive strength (UCS) of CSA-stabilized soil was tested and compared to ordinary Portland cement (OPC); meanwhile the influence of amounts of gypsum in CSA and cement contents in stabilized soils on the strength of stabilized soils were investigated. X-ray diffraction (XRD) tests were employed to detect generated hydration products, and scanning electron microscopy (SEM) was conducted to analyze microstructures of CSA-stabilized soils. The results showed that UCS of CSA-stabilized soils at 1, 3, and 28 d firstly increased and then decreased with contents of gypsum increasing from 0 to 40 wt.%, and CSA-stabilized soils exhibited the highest UCS when the content of gypsum equaled 25 wt.%. When the mixing amounts of OPC and CSA were the same, CSA-stabilized soils had a significantly higher early strength (1 and 3 d) than OPC. For CSA-stabilized soil with 0 wt.% gypsum, monosulfate (AFm) was detected as a major hydration product. As for CSA-stabilized soil with certain amounts of gypsum, the intensity of ettringite (Aft) was significantly higher than that in the sample hydrating without gypsum, but a tiny peak of AFm also could be detected in the sample with 15 wt.% gypsum at 28 d. Additionally, the intensity of AFt increased with the contents of gypsum increasing from 0 to 25 wt.%. When contents of gypsum increased from 25 to 40 wt.%, the intensity of AFt tended to decrease slightly, and residual gypsum could be detected in the sample with 40 wt.% gypsum at 28 d. In the microstructure of OPC-stabilized soils, hexagonal plate-shaped calcium hydroxide (CH) constituted skeleton structures, and clusters of hydrated calcium silicates (C-S-H) gel adhered to particles of soils. In the microstructure of CSA-stabilized soils, AFt constituted skeleton structures, and the crystalline sizes of ettringite increased with contents of gypsum increasing; meanwhile, clusters of the aluminum hydroxide (AH3) phase could be observed to adhere to particles of soils and strengthen the interaction.

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Effect of Flue Gas Desulfurization Gypsum on the Properties of Calcium Sulfoaluminate Cement Blended with Ground Granulated Blast Furnace Slag

Materials ◽

10.3390/ma14020382 ◽

2021 ◽

Vol 14 (2) ◽

pp. 382 ◽

Cited By ~ 1

Author(s):

Danying Gao ◽

Zhenqing Zhang ◽

Yang Meng ◽

Jiyu Tang ◽

Lin Yang

Keyword(s):

Blast Furnace ◽

Mechanical Strength ◽

Flue Gas ◽

Blast Furnace Slag ◽

Setting Time ◽

Flue Gas Desulfurization ◽

Calcium Sulfoaluminate Cement ◽

Calcium Sulfoaluminate ◽

Granulated Blast Furnace Slag ◽

Furnace Slag

This work aims to investigate the effect of additional flue gas desulfurization gypsum (FGDG) on the properties of calcium sulfoaluminate cement (CSAC) blended with ground granulated blast furnace slag (GGBFS). The hydration rate, setting time, mechanical strength, pore structure and hydration products of the CSAC-GGBFS mixture containing FGDG were investigated systematically. The results show that the addition of FGDG promotes the hydration of the CSAC-GGBFS mixture and improves its mechanical strength; however, the FGDG content should not exceed 6%.

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Properties of Calcium Sulfoaluminate Cement Mortar Modified by Hydroxyethyl Methyl Celluloses with Different Degrees of Substitution

Molecules ◽

10.3390/molecules26082136 ◽

2021 ◽

Vol 26 (8) ◽

pp. 2136

Author(s):

Shaokang Zhang ◽

Ru Wang ◽

Linglin Xu ◽

Andreas Hecker ◽

Horst-Michael Ludwig ◽

...

Keyword(s):

Compressive Strength ◽

Flexural Strength ◽

Bond Strength ◽

Cement Mortar ◽

Retention Rate ◽

Methyl Cellulose ◽

Tensile Bond Strength ◽

Calcium Sulfoaluminate Cement ◽

Calcium Sulfoaluminate ◽

Cement Mortars

This paper studies the influence of hydroxyethyl methyl cellulose (HEMC) on the properties of calcium sulfoaluminate (CSA) cement mortar. In order to explore the applicability of different HEMCs in CSA cement mortars, HEMCs with higher and lower molar substitution (MS)/degree of substitution (DS) and polyacrylamide (PAAm) modification were used. At the same time, two kinds of CSA cements with different contents of ye’elimite were selected. Properties of cement mortar in fresh and hardened states were investigated, including the fluidity, consistency and water-retention rate of fresh mortar and the compressive strength, flexural strength, tensile bond strength and dry shrinkage rate of hardened mortar. The porosity and pore size distribution were also analyzed by mercury intrusion porosimetry (MIP). Results show that HEMCs improve the fresh state properties and tensile bond strength of both types of CSA cement mortars. However, the compressive strength of CSA cement mortars is greatly decreased by the addition of HEMCs, and the flexural strength is decreased slightly. The MIP measurement shows that HEMCs increase the amount of micron-level pores and the porosity. The HEMCs with different MS/DS have different effects on the improvement of tensile bond strength in different CSA cement mortars. PAAm modification can improve the tensile bond strength of HEMC-modified CSA cement mortar.

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Printability and Setting Time of CSA Cement with Na2SiO3 and Gypsum for Binder Jetting 3D Printing

Materials ◽

10.3390/ma14112811 ◽

2021 ◽

Vol 14 (11) ◽

pp. 2811

Author(s):

Okpin Na ◽

Kangmin Kim ◽

Hyunjoo Lee ◽

Hyunseung Lee

Keyword(s):

3D Printing ◽

Sodium Silicate ◽

Setting Time ◽

Sodium Silicate Solution ◽

Preliminary Test ◽

Silicate Solution ◽

Calcium Sulfoaluminate Cement ◽

Calcium Sulfoaluminate ◽

Parametric Studies ◽

Binder Jetting

The purpose of this study is to optimize the composition of CSA (calcium sulfoaluminate) cement with sodium silicate (Na2SiO3) and gypsum for binder jetting 3D printing. The preliminary test was carried out with an applicator to decide the proper thickness of one layer before using the 3D printer. A liquid binder was then selected to maintain the shape of the particles. Based on the results, the optimal mixture of dry materials and a liquid activator was derived through various parametric studies. For dry materials, the optimum composition of CSA cement, gypsum, and sand was suggested, and the liquid activator made with sodium silicate solution and VMA (viscosity modified agent) were selected. The setting time with gypsum and sodium silicate was controlled within 30 s. In case of the delayed setting time and the rapid setting mixture, the jetting line was printed thicker or thinner and the accuracy of the printout was degraded. In order to adjust the viscosity of the liquid activator, 10% of the VMA was used in 35% of sodium silicate solution and the viscosity of 200–400 cP was suitable to be sprayed from the nozzle. With this optimal mixture, a prototype of atypical decorative wall was printed, and the compressive strength was measured at about 7 MPa.

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