Study of Eco-Friendly Belite-Calcium Sulfoaluminate Cements Obtained from Special Wastes

Abstract

Belite-calcium sulfoaluminate (BCSA) cements are special binders obtained from non-Portland clinkers; they have become increasingly more important due to their environmental impact during the manufacturing process compared to Portland cements, such as lower energy consumption and CO2 emissions. The aim of this paper was to assess the possible use of titanogypsum (T) and water potabilization sludge (W) to reduce the amount of natural raw materials (natural gypsum and clay, respectively) used in the production of BCSA cements. Three BCSA clinker generating raw mixes, containing T and/or W, and a reference mix based only on natural materials (limestone, clay, bauxite and natural gypsum) were heated in an electric furnace at temperatures ranging from 1200 to 1350 °C. Quantitative X-ray diffraction (XRD) analysis of the burnt products showed high conversion of reactants towards the main hydraulically active BCSA clinkers components of C2S and C4A3$, particularly at temperatures of 1300 and 1350 °C. Isothermal calorimetric measurements, differential thermal–thermogravimetric and XRD analyses as well as porosimetric measurements showed that all BCSA cements, from mixing the clinkers (at optimum temperatures) with commercial anhydrite, exhibited similar hydration behavior.

Effect of Fly Ash Belite Cement on Hydration Performance of Portland Cement

“…In order to maintain the solid-liquid equilibrium, there is a need to ensure that hydration of Portland cement is in the affirmative direction, and C-S-H hydration products are gradually increased. The reaction equation is shown in Formulas (1) and (2). Figure 5b shows the XRD spectrum of composite cement hardened paste at 28 d. Although C-S-H gel and Ettringite (Ca 6 Al 2 (OH) 12 (SO 4 ) 3 •26H 2 O, AFt, 2θ = 9.2 • ) are generated in large quantities, there are still un-hydrated silicate clinker minerals in the hardened paste, while mullite and quartz particles from fly ash (2θ = 25~28 • ) are abundant [22].…”

“…Fly ash belite cement (FABC), which is prepared from fly ash and lime by hydrothermal synthesis and low-temperature calcination (<900 • C), contains hydraulic minerals of calcium silicate (2CaO•SiO 2 ; β-C 2 S) and calcium aluminate (12CaO•7Al 2 O 3 ; C 12 A 7 ). Previous studies have described it as a new type of green low carbon cementitious material [2][3][4][5]. Its mineral components, β-C 2 S and C 12 A 7 , which are formed at low temperature, are in a metastable state, and possess hydration rates, setting times, strength and other properties that are significantly different from those of Portland cement [6,7].…”

Use of Potabilized Water Sludge in the Production of Low-Energy Blended Calcium Sulfoaluminate Cements

“…The cement manufacturing industry is one of the largest consumers of fuel and raw materials, and one of the main producers of CO2 emissions [1]. In 2019, worldwide production of Portland cement was estimated at 4.10 billion tonnes, producing 8% of global anthropogenic carbon dioxide emissions [2].…”

The Influence of Chemical Activators on the Hydration Behavior and Technical Properties of Calcium Sulfoaluminate Cements Blended with Ground Granulated Blast Furnace Slags

“…Cement production requires a great number of raw materials and a large amount of energy and represents one of the leading causes of climate change due to greenhouse gas emissions, particularly CO 2 . In 2019, the cement production all over the world was equal to around 4.10 billion tons and its contribution to the anthropogenic carbon dioxide emissions was estimated to be as high as 8% [1][2][3]. With a growing focus on energy efficiency and sustainable production [4], technological advancements in cement production have revealed methods to reduce CO 2 emissions in the following ways: (a) more efficient manufacturing processes; (b) targeted use of non-traditional fuels and raw materials (e.g., non-carbonated CaO sources instead of limestone); (c) carbon capture and storage technologies [5]; (d) increased utilization of blended Portland cements; (e) further use of special hydraulic binders (such as alkali-activated and magnesium-based cements as well as calcium sulfoaluminate (CSA), belite and belite-calcium sulfoaluminate (BCSA) binders) [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]).…”