Calcium Sulfoaluminate Cement Research Articles

Evaluating carbonation resistance and microstructural behaviors of calcium sulfoaluminate cement concrete incorporating fly ash and limestone powder

This study investigates the effects of accelerated carbonation on calcium sulfoaluminate (CSA) cement concrete, focusing on mixtures enhanced with 20 % fly ash (FA), 20 % remediated fly ash (RF), 15 % limestone powder (LP), and a combination of 20 % FA with 15 % LP (35 %). The study further evaluates the mechanical properties including compressive strength, splitting tensile strength, elastic modulus, along with drying shrinkage and bulk resistivity. To delve into the microstructural characteristics of moist curing versus carbonation exposure on the CSA cement system, X-ray diffraction (XRD) and thermogravimetric analysis (TGA) were employed, particularly analyzing phase assemblage changes. The results show that the addition of FA reduced the carbonation depth in concrete mixtures over time (105 days). However, LP and the combination of FA and LP presented mixed effects. The microstructural analysis highlighted ettringite as the predominant phase in samples moist cured for 3 days. In contrast, carbonation-cured samples were characterized by different calcium carbonate (CaCO3) polymorphs alongside aluminum hydroxide (Al(OH)3) and residual ye'elimite, with the formation of low-pH carbonic acid facilitating the conversion of ettringite into CaCO3. This study highlights the impact of different SCMs on the durability and microstructural characteristics of CSA cement concrete, underscoring the interplay between curing methods, effects of SCM, and carbonation processes.

Performance of high-strength green strain-hardening cementitious composites incorporating CSA/CAC cements and GGBS

Strain-hardening cementitious composites (SHCCs) possess crack control and durability properties. In the pursuit of reducing CO2 emissions and addressing potential issues of slow strength development for SHCCs with pozzolans, the objective of this study was to develop high-strength green SHCCs (HSG-SHCCs) that exhibit improved early strength, drying shrinkage, and environmental friendliness. A ternary binder system was proposed, comprising of ground granulated blast furnace slag (GGBS), ordinary Portland cement (OPC), and either calcium sulfoaluminate cement (CSA) or calcium aluminate cement (CAC). The fresh, mechanical, and durability properties of the proposed HSG-SHCCs were experimentally investigated. Additionally, the microstructures and chemical phases of the developed CSA/CAC-GGBS-OPC ternary binder system were analyzed using scanning electron microscopy (SEM) and X-ray diffraction (XRD). The results revealed that the developed HSG-SHCCs demonstrated 6-hour and 28-day strengths of up to 11 MPa and 110 MPa, respectively. The CSA/CAC-based ternary binder system also exhibited enhanced durability and improved drying shrinkage. However, the inclusion of CSA and CAC in HSG-SHCCs could lead to a reduction in tensile performance, specifically in strain capacity. The main hydration products of the CSA/CAC-GGBS-OPC ternary binder system were C-S-H, ettringite, gibbsite, and calcium hydrate. In addition to the fresh, mechanical, and durability properties, the environmental impact of the developed HSG-SHCCs was also assessed. The results indicated that a 30 % replacement of OPC with CSA cement in the HSG-SHCC mix notably improved the trade-off among CO2 emissions, compressive strength, and tensile cracking resistance.

Feasibility of Sprayable Engineered Cementitious Composites Using Natural Sand and Low Fiber Content: Effect of Hybrid Fiber System, Silica Fume, and Air-Entraining and Shrinkage-Reducing Admixtures

Deterioration of corrugated steel culverts (CSCs) is a significant problem for the Virginia Department of Transportation and other U.S. transportation agencies. Spray-on lining using shotcrete engineered cementitious composites (ECCs) is a promising structural repair strategy for deteriorated CSCs. This study evaluates the feasibility of practical sprayable ECCs using natural silica sand and low fiber content, while forgoing the use of commonly utilized calcium sulfoaluminate cement to allow for delivery of the materials via ready-mixed concrete trucks. Aspects of the compositional space evaluated include the effect of a hybrid polyvinyl alcohol/polyethylene fiber system, silica fume (SF), shrinkage reducing admixture (SRA), and air-entraining admixture (AEA) on the properties of the composites. Experimental results suggested that the development of the proposed materials is feasible, because flow characteristics associated with shotcrete ECCs and ECC-like tensile ductility were achieved in the fresh and hardened state, respectively. Notwithstanding, further mixture optimization may be required for satisfactory field performance, which should be assessed through field testing. Generally, the use of the hybrid fiber system tended to improve the strength and ductility of the composites, especially when coupled with the use of SF. Furthermore, SF was effective at mitigating the strength loss associated with the incorporation of AEA and SRA, and meaningfully improved surface resistivity. SF also tended to reduce the mixture’s flow, whereas the contrary occurred with the use of SRA and AEA. SRA contributed to the reduction in drying shrinkage at early ages. However, the effect of SRA in reducing shrinkage was negligible at later ages.

Study on the composite compatibility and interfacial properties of excess sulfate phosphogypsum cementing system to OPC and C[formula omitted]A

Releasable sulfate contained in the Excess Sulfate Phosphogypsum Cementing System (ESPCS) potentially degrades interfaces when contacted with conventional cements, raising compatibility concerns. This work evaluated fresh connection, adhesion, and aggregate embedment of ESPCS to ordinary Portland cement (OPC) and Calcium sulfoaluminate cement (CS¯A), with mechanical and interfacial properties studied. Results indicate the discrepancy in hydration properties gives Excess-sulfate Phosphogypsum Slag Cement (EPSC) uncoordinated expansion to OPC, followed by cracks (95 μm) generation. Meanwhile, expansive ettringite forms in the interface due to bleeding sulfate-rich water concentration, thus leaving a porous contact zone (1240 μm, 11.29%) and resultant flexural strength reduction of OPC-EPSC mortar (by >36 %). Conversely, EPSC and CS¯A are close in phase assemblages, resulting in compact interface and higher bond strength. Incorporating the Phosphogypsum-based Cold Bonded Aggregates (PCBAs) into OPC induces the interfacial ettringite formation-sulfate attack by internal curing water, yielding the worst composite performance, i.e., the lowest 360 d compressive strength (38.8 MPa) of concrete OPCC, lower than EPSCC (48.6 MPa) and CS¯AC (50.3 MPa). ESPCS is more compatible to CS¯A than OPC which is advised against exposing directly with ESPCS. This work helps specify composite feasibility and conditions of ESPCS with typical cement composites.

Effects of EVA and SAE Emulsions on Hydration and Drying Shrinkage of Calcium Sulfoaluminate Cement Pastes

Effects of EVA and SAE Emulsions on Hydration and Drying Shrinkage of Calcium Sulfoaluminate Cement Pastes

Improving the performance of iron-rich calcium sulfoaluminate cement from municipal solid waste incineration fly ash through diverse pretreatment approaches

The utilization of municipal solid waste incineration fly ash (MSWI-FA) is environmentally significant. In this study, MSWI-FA was pretreated using organic acid solution and CO2 microbubble carbonation washing. The pretreated MSWI-FAs were then used to produce Iron-rich calcium sulfoaluminate (IR-CSA) cement at different substitution rates (CFA) for various raw materials. The evolution of iron phase distribution, mineral composition, and hydration of IR-CSA cement were investigated, alongside heavy metal migration. The results showed that the MSWI-FA-based IR-CSA clinker had suitable mineralogical phases. However, gehlenite in MSWI-FA reduced CaO availability in the clinker formation reaction, hindering the involvement of Fe2O3 in the ye'elimite formation reaction. The calcination temperature was increased to facilitate clinker and iron phase formation in the case of high CFA levels. CO2 microbubble carbonation washing pretreatment of MSWI-FA, with which the IR-CSA clinker achieved suitable pH values and alkali content, facilitated the early growth and chained evolution of ettringite, resulting in a denser microstructure and lower cumulative hydration heat. Consequently, the compressive strength of MSWI-FA-based IR-CSA cement increased, with a maximum gain of 43.65MPa. Chromium content in the residual form increased, and heavy metal leaching was well below standard limits. This approach provides a new perspective for the purification treatment of MSWI-FA and its high-value, large-scale recycling in low-carbon cement.

Corrosion Resistance of Magnesium Ammonium Phosphate Cement-Based Coatings Modified by Calcium Sulfoaluminate Cement on Carbon Steel in a Saline Medium

Corrosion Resistance of Magnesium Ammonium Phosphate Cement-Based Coatings Modified by Calcium Sulfoaluminate Cement on Carbon Steel in a Saline Medium

Chinese raw vermiculite: A potential additive for improving the thermal properties of calcium sulfoaluminate cement-blended mortars for applications in hot regions

Reducing the thermal conductivity (TC) of a cementitious building material can help to slow the rate at which it heats and cools. The present project aims to develop a new construction material with low TC for use in hot regions. The construction material is produced by blending Chinese raw vermiculite (CRV) with calcium sulfoaluminate (CSA) cement in mortar. CSA mortar specimens were cast and tested for a variety of properties, including dry density (σ), void content, ultrasonic pulse velocity (UPV), thermogravimetric variations, microstructure, TC, thermal diffusivity, and specific heat capacity. CSA mortars mixed with CRV had improved workability and σ. However, compared to plain CSA mortar, the compressive strength of the CSA mortars incorporating 60 % and 100 % CRV was reduced by 10 % and 24 %, respectively. This reduction in strength is still acceptable for non-structural applications, and the decrease in strength remains close to that of CSA mortars without CRV. The TC of CSA mortar with 0 % fine aggregate replacement was 1.99 ± 0.17 W/mK, which is 95.07 % higher than when 100 % CRV was used as the fine aggregate replacement. The addition of CRV slows CSA mortar heating by 20 %. The findings confirms CRV's potential as an eco-friendly, energy-efficient construction material.

In situ concrete sewer performance: comparison of Portland cement, calcium sulfoaluminate cement, and calcium aluminate cement

In situ concrete sewer performance: comparison of Portland cement, calcium sulfoaluminate cement, and calcium aluminate cement

Enhancing geomechanical characteristics of calcium sulfoaluminate (CSA) cement-treated soil under low confining pressures

This study examines the efficacy of employing calcium sulfoaluminate (CSA) cement, an environmentally friendly binder, for enhancing the geomechanical characteristics of sand, particularly under low confining pressure conditions. A series of triaxial consolidated drained tests were performed on sand samples treated with varying content (5, 7, and 10%) of CSA cement and 10% ordinary Portland cement (OPC) under various low confining pressures (50, 100, 200, and 400 kPa). The test findings demonstrated the importance of cement content and confining pressure on the mode of failure, stress–strain and volumetric behavior, failure characteristics, and shear strength parameters of the treated quartz sand. After a curing period of 14 days, samples treated with 10% CSA cement exhibited a remarkable 212% increase in peak deviator stress and an 89% reduction in axial strain at failure, indicating higher initial stiffness compared to untreated samples under a 400 kPa confining pressure. Furthermore, the samples treated with 10% CSA exhibited higher peak deviator stress, initial stiffness, and strength development compared to those treated with 10% OPC. The scanning electron microscopy analysis provides insights into particle breakage and bond degradation processes, which increase with confining pressure in CSA-treated samples. Also, the mode of failure analysis reveals a transition from ductile to slightly brittle behavior with increasing cement content. Notably, the geomechanical properties of the treated material emphasized the significant impact of CSA cement on soil improvement. Thus offering a sustainable alternative for soil improvement in construction projects.

The content optimization of supplementary cementitious materials in coral sand-seawater cement mortar: A focus on mechanical properties and transportation costs

This study examines how supplementary cementitious materials (SCMs) such as fly ash (FA), blast furnace slag (BFS), and metakaolin (MK) affect the mechanical properties and transportation costs of coral sand-seawater cement mortar (CSSC). The Dinger-Funk equation was used to obtain the most densely packed design and preparation of coral sand and cementitious materials. The mechanical properties of CSSC were assessed utilizing the RMT testing apparatus. A thorough examination of the mechanical properties and transportation costs of CSSC was undertaken using the principle of value engineering and the effectiveness coefficient approach. Research results show that BFS10 has outstanding mechanical qualities in the binary cementitious system. Within the ternary cementitious system, the mechanical qualities typically exceed those of the binary system, with FA15BFS15 demonstrating the highest performance. The best appropriate mix ratio is FA15BFS15, as determined by a thorough examination and cost-benefit analysis. This ratio offers temporal sensitivity and maximized transit capacity. The SVR model is highly proficient in forecasting the compressive strength of CSSC, showcasing accurate prediction and data interpretation abilities. The research findings provide practical evidence for optimizing the proportion of CSSC in calcium sulfoaluminate cement, considering transportation expenses and algorithm prediction needs.

Bond of textile-reinforced belite calcium sulfoaluminate cement mortar to concrete substrate

The fast aging of existing building stock requires effective and sustainable strengthening solutions. Textile-reinforced mortars (TRM) have already proved to be very effective as well as versatile retrofitting solutions for reinforced concrete and masonry structures. TRMs can enhance the load bearing capacity of reinforced concrete structures; however, current TRM systems are based on standard Portland cement-based binders, which largely contribute to global human-induced CO2 emissions. This work, for the first time, explores the use of belite calcium sulfoaluminate (BCSA) binder for carbon textile reinforcement through a cross-disciplinary study combining structural engineering and materials science. An experimental study was carried out on concrete block members with externally bonded strips of carbon textile-reinforced mortars, similar to a typical TRM retrofitting system for concrete beams. The textiles were embedded in an ordinary Portland cement-based (OPC) binder or in a BCSA-based binder to compare the bond behaviour to the concrete substrate. The tests revealed a superior bond between the BCSA mortar and the concrete, as well as outstanding adhesion to the textiles achieved using the BCSA binder, with performance levels largely surpassing those measured in their counterparts that used the OPC-based binder. Scanning Electron Microscopy, X-ray diffraction, and thermogravimetric analyses were used to understand this behaviour difference and it was concluded that the ettringite phase is responsible for the enhanced performance in the studied system. The results of this study suggest that BCSA binders have the potential to be a more effective and “greener” alternative to the standard binders based on Portland cement in TRM strengthening applications.

Impact of aluminate cements on the durability and mechanical performance of strain-hardening cementitious composites

Strain-hardening cementitious composites (SHCCs) are durable, ductile, fiber-reinforced cement-based materials. While fly ash (FA) is often used to partially replace Portland cement in SHCCs to enhance material performance, it can lead to long setting times and slow strength development. To address these limitations, this study investigates the use of aluminate cement as partial replacements for Portland cement in FA-based SHCCs. Furthermore, the study aims to fill a significant knowledge gap by thoroughly examining the influence of aluminate cement on the workability, durability, and strain-hardening behavior of SHCCs. Aluminate cements encompass both calcium sulfoaluminate (CSA) cement and calcium aluminate cement (CAC), distinguished by their composition rich in calcium aluminate phases. This study investigated the use of CSA and CAC cements as partial replacements for Portland cement in SHCCs. Both fresh and hardened properties of the CSA- and CAC-SHCCs were examined, while their microstructures and chemical phases were investigated using SEM and XRD analyses. Results showed that CSA and CAC cements reduced fluidity, setting time, and drying shrinkage but increased porosity and early strength development for SHCCs. CSA-SHCCs showed enhanced impermeability due to the refinement of interior pore space through the hydration products. While all modified SHCCs retained tensile strain hardening behavior, the tensile performance degraded due to the hydration effects of ye'elimite and calcium aluminates. The reduced tensile strain capacity was elucidated using the theory of steady-state crack opening.

Effect of chloride binding and sulfate ion attack on the chloride diffusion in calcium sulfoaluminate-based material under seawater environment

The diffusion of chloride ions in reinforced concrete under the seawater environment will affect the physical or mechanical properties and durability. Sulfate ions also influence the diffusion of chloride ions by generating expansion products through physical and chemical reactions. Further research on the effects of chloride binding and sulfate ion attack on chloride ion diffusion will deepen the understanding of concrete failure mechanism. In this paper, a quaternary blend based on calcium sulfoaluminate (CSA) cement was prepared and laboratory immersion tests were conducted in artificial seawater with varying salt concentrations. Initially, chloride ion concentration measurements and XRD tests were conducted at different corrosion ages and salt concentrations. Subsequently, the chloride binding properties of CSA-based materials was quantified through the analysis of chloride ion concentration and the phases of hydration products. Meanwhile, the corrosive effect of sulfate ions on chloride ion diffusion was determined corresponds to the content of expansive hydration products. Furthermore, numerical simulations were employed to evaluate the impact of sulfate ion corrosion, chloride binding, and their combined effects on chloride ion diffusion, and the results were compared with free chloride ion concentration (Cf). The results indicate that the total chloride ion concentration (Ct) exhibits a linear relationship with increasing salt concentrations of seawater in CSA-based materials. Meanwhile, the bound chloride ion concentration (Cb) follows a logarithmic growth pattern. The chloride binding rate experiences a linear decline with the increase of chloride ion concentration in the artificial seawater. Additionally, the relationship between Cf and Cb or Ct can be described using different isothermal adsorption models for the CSA-based materials. Among these models, the Langmuir model is suitable for characterizing the relationship between Cf and Cb, while the Freundlich model is suitable for describing the relationship between Cf and Ct. Furthermore, it is noteworthy that sulfate ion attack and chloride binding exert nearly equivalent effects on the diffusion of chloride ions in CSA-based materials at short corrosion age and low chloride ion concentration. However, the corrosive impact of sulfate ions gradually evolves into the dominant factor in the progression of corrosion over time and the increase in seawater salt concentration.

Effects of recycled scrap alumina on the physical and mechanical properties of calcium sulfo-aluminate cement products

Effects of recycled scrap alumina on the physical and mechanical properties of calcium sulfo-aluminate cement products

Investigation on the preparation of low carbon cement materials from industrial solid waste phosphogypsum: Clinker preparation, cement properties, and hydration mechanism

Low-carbon calcium sulfoaluminate (CSA) cement can be prepared with industrial by-product phosphogypsum (PG). This paper uses PG to replace natural gypsum in preparing PG-based CSA (PGCSA) cement as a raw material and mineral admixture, and the mechanical properties and hydration mechanism of PGCSA cement are explored. The results showed that the clinker with ye'elimite mineral content of 67.23% was fired at 1250 °C by mixing 19.52% PG into the raw materials. The participation of PG in hydration can accelerate the hardening of paste and improve the compressive strength of cement. The optimum dosage of PG as a mineral admixture was 20%, and the compressive strength reached 88.4 MPa at 28 days. Added PG promoted the early hydration of ye'elimite, and reaching 60% hydration within 1 day. The hydration mechanism was believed that a large amount of Ca2+ released by PG dissolution increased the ion concentration and promoted the hydration of ye'elimite. The PGCSA cement prepared in this study at 1250 °C had low carbon emission and PG utilization was higher than 40%. In addition, the pH and exothermic hydration of PGCSA cement were reduced about 2 and 100 J/g compared to that of CSA cement. This paper provides a feasible solution for PG resource utilization and carbon reduction.

Effects of Lithium Carbonate and Superplasticizer on Ultra-Early Strength of Alite-Ye'elimite-Belite-Ferrite Cement.

Alite-ye'elimite-belite-ferrite cement (AYBFC) integrates the advantages of calcium sulfoaluminate cement and Portland cement, but its ultra-early strength needs to be further improved when applied to rush repair and construction works. In this study, the ultra-early strength of AYBFC was improved using lithium carbonate (Li2CO3) and superplasticizer. The results showed that an appropriate amount of Li2CO3 could significantly improve the ultra-early strength of AYBFC, since it was capable of promoting the hydration reaction of AYBFC. After polycarboxylate superplasticizer was doped on this basis, the ultra-early compressive strength of AYBFC was further improved. This was because the superplasticizer could markedly enhance the matrix compactness despite its inhibitory effect on the hydration reaction of cement and the generation of hydration products.

Development of calcium sulfoaluminate cements from rich‐alumina bauxite and marble wastes: Physicochemical and microstructural characterization

AbstractThis work discusses the effect of rich alumina bauxite on the mineralogical composition of calcium sulfoaluminate (CSA) clinker cement on their performances. After preparation of different local raw materials (rich alumina bauxite and marble), they were mixed with 15 wt% of commercial gypsum and pressed at 2 MPa. The obtained pellets were thermally treated at 1200°C to produce clinker, which is use to synthesize the CSA cements. The raw materials as well as products were characterized by many analyses, such as FT‐IR, X‐ray fluorescence, X‐ray diffraction, differential scanning calorimetry (DSC)/thermogravimetry analysis (TGA), isothermal calorimetry (ICC), scanning electron microscope, and physico‐mechanical tests. ICC analysis of the powder of clinker cement showed that the reactions are strongly affected by gypsum content. XRD results revealed that clinker and cement present a strong intensity of ye'elimite as main mineral phase. Moreover, the hydrated cement exhibited ettringite and monosulfate as the new phases formed. The compressive strength of hydrated cement reached ∼21 and 28 MPa after 1 and 28 days of curing, respectively. From the aforementioned results, this local rich alumina bauxite can be used to produce high‐strength cement for self‐leveling materials, which allow their use in engineering and building applications.

Assessing the effect of test parameters on the determination of the rheological behavior of calcium sulfoaluminate cement pastes

Calcium sulfoaluminate cement (CSA) is renowned for its application in technologies that require rapid setting and high initial strengths, such as 3D concrete printing and repairs. However, their rheological behavior needs to be more adequately explored. This study assesses the impact of rotational rheometer test conditions on CSA pastes with different water-to-cement ratios. For the determination of static yield stress (τ0s), stress growth test with shear rates between 0.01 and 0.05 s−1 were employed. The results revealed that higher shear rates anticipated the occurrence of the material's peak destructuring and resulted in lower values of τ0s. In addition, the effects of geometry and testing routine on the flow curve were analyzed. The results showed that the use of vane geometry provides more consistent results of the measured dynamic yield stress, viscosity, and hysteresis area of CSA pastes than parallel plate geometry.

Passivation of Steel Reinforcement in Low Carbon Concrete

Both the high CO2 emissions associated with cement production and the increasing demand for concrete call for the use of binder types that can be produced in a more climate-friendly way than that of ordinary Portland cement. To ensure that these binders can also be used in reinforced concrete structures, their influence on the corrosion behavior of embedded steel reinforcement must be investigated. In the study presented here, the passivation behavior of steel in mortars made from various new types of binders is investigated. In addition to alkali-activated materials with high and low calcium contents, a calcium sulfoaluminate cement and a binder produced from calcium silicate hydrate (C-S-H) phases, synthesized in an autoclave, were investigated. While the steel clearly passivated in the alkali-activated slag and the C-S-H binder, the calcium sulfoaluminate cement showed the lowest open circuit potentials and polarization resistances, indicating a less effective level of passivation. The metakaolin geopolymer with a potassium-based activator showed an onset of passivation that was dependent on the environment of the specimens at an early age, whereas the alkali-activated fly ash with a sodium-based activator showed a delay in passivation that was not influenced by the environment of the specimens at an early age.