Utilization of Coal Combustion Ashes for the Synthesis of Ordinary and Special Cements

Abstract

Raw mixes containing pulverized coal fly ash (with limestone and silica sand) or fluidized bed coal combustion ash (fly and bottom, with added limestone, anodization mud, and, when necessary, flue gas desulfurization gypsum), aimed at generating ordinary Portland or calcium sulfoaluminate clinkers, respectively, were heated in a laboratory electric oven at temperatures ranging from 1150 to 1500 C and submitted to X-ray diffraction analysis. The former had the same qualitative phase composition as that of a reference mixture, composed by limestone and clay; furthermore, they exhibited an excellent burnability on the basis of their residual free lime contents, measured after heating at 1350 , 1400 , 1450 , and 1500 C. The latter showed very good results in terms of conversion of reactants and selectivity degree toward the main mineralogical constituent, calcium sulfoaluminate (4CaO Á 3Al 2 O 3 Á SO 3 ), even if the behavior of a reference mixture consisting of limestone, bauxite, and natural gypsum was slightly better. The introduction of a fluidized bed coal combustion ash in the raw mix generating calcium sulfoaluminate clinker implies a saving of bauxite and natural gypsum, which can be fully replaced through the addition of anodization mud and flue gas desulfurization gypsum, respectively.

Influence of Calcium Sulfoaluminate (CSA) Cement Content on Expansion and Hydration Behavior of Various Ordinary Portland Cement‐CSA Blends

“…Coussy 59 showed that the local crystallization stress, p c , can be related to the macroscopic stress, r * , by r * % bS c p c (7) S c in the above relationship can be calculated based on volume fraction of ettringite and total porosity of cement paste. And, p c is the local crystallization stress derived from supersaturation as shown in Eq.…”

“…In addition to two models described above, the crystallization stress was also estimated using poromechanics in August 2015 Expansion of OPC-CSA Blends accordance with Eq. (7). The Biot coefficient was assumed as 0.6 for cement paste 63 and S c was calculated by dividing the volume fraction of ettringite with the sum of capillary porosity and the volume fraction of ettringite.…”

“…The porous nature of CSA clinker makes it easily grindable, thus improving energy saving. In addition, a wide range of industrial wastes and by‐products, whose reuse and disposal is often quite complicated, can be used in manufacturing CSA cements . Early‐age volume change in CSA cement has been exploited for making shrinkage‐compensating cement .…”

Calcium Sulfoaluminate, Geopolymeric, and Cementitious Mortars for Structural Applications

“…As an example, low-CO 2 cements can be produced by using non-carbonated CaO sources as a constituent of the Portland clinker-generating raw mix [16,17] or increasing the production of blended cements, obtained by mixing Portland clinker with…”

Cadmium adsorption by coal combustion ashes-based sorbents—Relationship between sorbent properties and adsorption capacity

“…In this framework, any proposal aimed at employing this industrial waste should be carefully considered [1][2][3]. One of the main fields of CCA reuse is the cement and concrete industry [4] but, when this option is not economically convenient, alternative applications have to be searched for. In this context, adsorption can represent an interesting option.…”