Synthesis of low-temperature calcium sulfoaluminate-belite cements from industrial wastes and their hydration: Comparative studies between lignite fly ash and bottom ash

Research on the Preparation and Properties of High Belite Sulphoaluminate Cement (HBSAC) Based on Various Industrial Solid Wastes

“…It can be seen that the C content in the clinker is not as high as possible, a lower or higher C content in the clinker may have a negative impact on the compressive strength. The reasons are as follows: when the C content is lower, the AFt phase formed in the early hydration stage is partly converted to the AFm (ettringite, C 3 A·CaSO 4 ·12H 2 O) phase in the later hydration stage [37,38,39], as shown in Figure 10, which results in a decrease in the compressive strength; when the C content is higher, the rate of the AFt phase formation in the early hydration stage is too fast, and the crystal structure continues to grow in the later hydration stage, which causes expansion and microcrack damage [26], and also results in a decrease in the compressive strength. According to the results of this experiment, 15% is the optimal C content in this kind of cement clinker; under this content, the lowest compressive strengths are 42.1 MPa, 46.3 MPa, and the highest are 52.8 MPa, 64.3 MPa at 3 days and 28 days, respectively.…”

Compressive Strength of Marginal Lateritic Soil Stabilized

“…The optimum L contents increased as the BA content increased for all Na2SiO3:NaOH ratios; i.e., the L values of MLS-BA geopolymer samples of 70:30, 50:50 and 30:70 were about 10, 11 and 14%. This increase in L was due to BA, which has high surface particles [11] Fig. 5-7 indicate the 7-day UCS of MLS-BA geopolymer samples at various MLS/BA ratios of 70/30, 50/50 and 30/70, Na2SiO3:NaOH ratios of 0:100, 10:90, 30:70, 50:50, 70:30 and 80:20 and L of 0.8OLC, 1.0OLC and 1.2OLC.…”

Effect of Residual CaSO4 in Clinker on Properties of High Belite Sulfoaluminate Cement Based on Solid Wastes

“…The compressive strength of both GF-HBSAC-10% and GF-HBSAC-20% cement shows a tendency of retrogression, and the relationship between the compressive strength of three cements is GF-HBSAC-15% > GF-HBSAC-20% > GF-HBSAC-10%. The reason is that the strength growth is mainly due to the hydration of C 4 A 3 S to form AFt within 7 days, and the increase of CaSO 4 content can accelerate the hydration rate of C 4 A 3 S. During 7 days to 28 days, the decrease in strength of GF-HBSAC-10% cement may be attributed to the formation of AFm [5,16,39], while the decrease in strength of GF-HBSAC-20% cement may be due to the micro-cracks, which are caused by the pressure of AFt crystals formed rapidly in the early stage continuous growth, and the pressure of gel filling cement paste pore in the later stage [35,40,41].…”

“…The raw materials for production are usually limestone, clay, bauxite, and gypsum [1,2]. However, with the long-term and large-scale exploitation of natural resources, the above-mentioned raw materials are becoming more and more scarce, and all kinds of industrial solid wastes are beginning to be used as alternative raw materials, including calcium solid waste materials such as marble sludge waste [3], steel slag [4,5], lithium slag [6] and municipal solid incineration wastes [7], sulfur solid waste materials such as phosphogypsum [8,9] and desulfurization gypsum [10,11], and aluminum-silicon solid waste materials such as fly ash (FA) [11][12][13][14][15][16], coal gangue [17], red mud [10,18], aluminum anodizing sludge [19], and tailings [20]. C 4 A 3 S is an indispensable component in the hydration of HBSAC, and the main chemical reactions in the hydration process are shown in Equations (1) and (2).…”