scholarly journals Influence of Fly Ash on Mechanical Properties and Hydration of Calcium Sulfoaluminate-Activated Supersulfated Cement

Materials ◽  
2020 ◽  
Vol 13 (11) ◽  
pp. 2514
Author(s):  
Zhengning Sun ◽  
Jian Zhou ◽  
Qiulin Qi ◽  
Hui Li ◽  
Na Zhang ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Flexural Strength ◽  
Heat Evolution ◽  
Hydration Products ◽  
X Ray Diffraction ◽  
Calcium Sulfoaluminate Cement ◽  
Calcium Sulfoaluminate ◽  
Granulated Blast Furnace Slag ◽  
Compressive And Flexural Strengths

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).

Utilization of CFB Fly Ash in Eco-Cement: Mechanical Properties and Microstructural Analysis

2010 ◽  
Vol 150-151 ◽  
pp. 885-889 ◽  
Author(s):  
Xiao Ming Liu ◽  
Yu Li ◽  
Ling Ling Zhang ◽  
Da Qing Cang
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Circulating Fluidized Bed ◽  
Microstructural Analysis ◽  
Hydration Products ◽  
X Ray Diffraction ◽  
Cement Pastes ◽  
X Ray ◽  
Xrd Techniques ◽  
Furnace Slag

The disposal of circulating fluidized bed (CFB) fly ash has been a serious environmental problem in the development of our society. In this work, the feasibility of recycling CFB fly ash as a blended material incorporating blast furnace slag (BFS), clinker and gypsum for the preparation of Eco-cement has been investigated. The mechanical properties of CFB fly ash based Eco-cements, including CFB fly ash–clinker system, CFB fly ash–ground BFS system, and CFB fly ash–ground BFS–clinker system, were evaluated in this paper. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) techniques were used to analyze the microstructural changes and the hydration products of the CFB fly ash based Eco-cement pastes. The results indicated that it is feasible to use CFB fly ash along with BFS and clinker to produce Eco-cement. The hydration products of CFB fly ash based Eco-cement are mostly ettringite and amorphous C-S-H gel, which are principally responsible for the strength and structure development of CFB fly ash based Eco-cement in the hydration process.

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

Materials ◽  
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.

scholarly journals Effect of Fine Aggregate Particle Characteristics on Mechanical Properties of Fly Ash-Based Geopolymer Mortar

Minerals ◽  
2021 ◽  
Vol 11 (8) ◽  
pp. 897
Author(s):  
Heng Li ◽  
Pengpeng Gao ◽  
Fang Xu ◽  
Tao Sun ◽  
Yu Zhou ◽  
...  
Keyword(s):  
Mechanical Properties ◽  
Fly Ash ◽  
Pass Rate ◽  
Fine Aggregate ◽  
X Ray Diffraction ◽  
River Sand ◽  
Fine Aggregates ◽  
Compressive And Flexural Strengths ◽  
Filling Coefficient ◽  
Fineness Modulus

This research aimed to investigate the effect of fine aggregate particles on mechanical properties of fly ash-based geopolymer mortar. In this work, seven kinds of river sand particles were designed based on different fine aggregate characteristics. The fineness modulus was adopted to quantitatively describe the gradation of sands. The fluidity, compressive, flexural, and tensile strengths of geopolymer mortar with different sand gradations were analyzed by laboratory tests. Furthermore, the composition and morphology of fly ash-based geopolymer mortar was analyzed by X-ray diffraction (XRD) and scanning electron microscopy (SEM). The reasonable gradation range and filling effect of sand were obtained. The results show that fluidity and compressive and flexural strengths of geopolymer mortar both improve with the increase of the fineness modulus, while specific surface area and voidage are opposite. The tensile strength of mortar largely lies on the interface properties between the geopolymer binder and fine aggregates. When the pass rate of the key sieving size 1.18 mm is 75–95%, the pass rate of the key sieving size 0.15 mm is 15–25%, the fineness modulus is 2.2–2.6 and the appropriate filling coefficient of geopolymer paste is around 1.0–1.15, the comprehensive performance of geopolymer mortar is the best. This research paper could provide a basis for the design of geopolymer mortar based on fly ash, and it is of great significance for its popularization and application.

scholarly journals Effect of Alkaline Salts on Calcium Sulfoaluminate Cement Hydration

Molecules ◽  
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.

scholarly journals Influence of Different Lithium Compounds on Hydration and Mechanical Properties of Calcium Sulfoaluminate Cement

Materials ◽  
2020 ◽  
Vol 13 (16) ◽  
pp. 3465
Author(s):  
Hongyang Deng ◽  
Xuanchun Wei ◽  
Shaoyan Liu ◽  
Shan Li ◽  
Xinhua Cai
Keyword(s):  
Mechanical Properties ◽  
Lithium Carbonate ◽  
X Ray Diffraction ◽  
Calcium Sulfoaluminate Cement ◽  
Early Hydration ◽  
Cement Pastes ◽  
Calcium Sulfoaluminate ◽  
Lithium Compounds ◽  
Different Content ◽  
Cement Mixtures

This work investigated the influence of three different lithium compounds, lithium carbonate (Li2CO3), lithium sulfate (Li2SO4) and lithium chloride (LiCl), on the hydration and mechanical properties of calcium sulfoaluminate (CSA) cement mixtures. Five concentrations of Li+, 0, 0.05, 0.11, 0.16 and 0.22 mmol/g of cement, were chosen, and then the proportions (by mass) of three lithium compounds were determined. Compressive strengths at 8 h, 24 h and 28 days were tested. Meanwhile, an early hydration heat test, thermogravimetric (TG) analysis, X-ray diffraction (XRD) and scanning electron microscope (SEM) techniques were performed to study the influences of different lithium compounds on properties of CSA cement mixtures. The experimental results show that three lithium compounds can all accelerate the early hydration process of CSA cement. There is not a remarkable difference on the properties of CSA cement pastes with a different content of Li+. The anion of lithium compounds can also affect the properties of CSA cement pastes, the accelerating effects of LiCl and Li2SO4 are more significant than that of Li2CO3, but there is not a distinct difference between LiCl and Li2SO4.

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

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.

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

Materials ◽  
2021 ◽  
Vol 14 (2) ◽  
pp. 382 ◽  
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%.

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

Molecules ◽  
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.

scholarly journals Action Time-Effect and Mechanism of Low-Calcium Fly Ash in Cement-Based Composites

Crystals ◽  
2021 ◽  
Vol 11 (6) ◽  
pp. 681
Author(s):  
Na Yan ◽  
Qingqing Tang ◽  
Ying Zhang ◽  
Guowen Sun
Keyword(s):  
Fly Ash ◽  
Nitrogen Adsorption ◽  
Chemical Effect ◽  
Hydration Products ◽  
X Ray Diffraction ◽  
Degree Of Hydration ◽  
Surface Areas ◽  
Activity Effect ◽  
Low Calcium ◽  
Pore Size Distributions

This study was conducted in order to investigate when low-calcium fly ash plays a physical or chemical effect and what is the chemical effect proportion of low-calcium fly ash. Two types of low-calcium fly ash and quartz powder, with similar fineness as active and inert admixtures, were used as materials in this study. Under different water/binder ratios and hydration ages, the effects of the different types of admixtures and their dosages on the flexural and compressive strength of the composites were studied. X-ray diffraction (XRD), scanning electron microscopy (SEM) and nitrogen adsorption methods, in addition to an assessment of the degree of hydration of the fly ash, were employed to observe the hydration products at different ages, the microstructures of the hydration products, as well as their surface areas and pore size distributions. The results show that during the hydration period of 28 days, the low-calcium fly ash has a micro-aggregate filling physical effect. However, after 56 days, the hydration degree of fly ash begins to exceed 1%. This illustrates that the low-calcium fly ash has both the pozzolanic activity effect and micro-aggregate filling effect. In contrast, the low-calcium fly ash hydrated for 90 days is still dominated by the physical filling effect.

scholarly journals Assessment of the Rheological and Mechanical Properties of Geopolymer Concrete Comprising Fly Ash and Fluid Catalytic Cracking Residue as Aluminosilicate Precursor

2021 ◽  
Vol 11 (7) ◽  
pp. 3032
Author(s):  
Tuan Anh Le ◽  
Sinh Hoang Le ◽  
Thuy Ninh Nguyen ◽  
Khoa Tan Nguyen
Keyword(s):  
Mechanical Properties ◽  
Compressive Strength ◽  
Elastic Modulus ◽  
Fly Ash ◽  
Flexural Strength ◽  
Catalytic Cracking ◽  
Fluid Catalytic Cracking ◽  
High Alumina ◽  
Geopolymer Concrete ◽  
Sem Images

The use of fluid catalytic cracking (FCC) by-products as aluminosilicate precursors in geopolymer binders has attracted significant interest from researchers in recent years owing to their high alumina and silica contents. Introduced in this study is the use of geopolymer concrete comprising FCC residue combined with fly ash as the requisite source of aluminosilicate. Fly ash was replaced with various FCC residue contents ranging from 0–100% by mass of binder. Results from standard testing methods showed that geopolymer concrete rheological properties such as yield stress and plastic viscosity as well as mechanical properties including compressive strength, flexural strength, and elastic modulus were affected significantly by the FCC residue content. With alkali liquid to geopolymer solid ratios (AL:GS) of 0.4 and 0.5, a reduction in compressive and flexural strength was observed in the case of geopolymer concrete with increasing FCC residue content. On the contrary, geopolymer concrete with increasing FCC residue content exhibited improved strength with an AL:GS ratio of 0.65. Relationships enabling estimation of geopolymer elastic modulus based on compressive strength were investigated. Scanning electron microscope (SEM) images and X-ray diffraction (XRD) patterns revealed that the final product from the geopolymerization process consisting of FCC residue was similar to fly ash-based geopolymer concrete. These observations highlight the potential of FCC residue as an aluminosilicate source for geopolymer products.

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