The Influence of Mayenite Employed as a Functional Component on Hydration Properties of Ordinary Portland Cement

Abstract

Influence of C12A7 (12CaO·7Al2O3) as a functional component on hydration properties of Ordinary Portland Cement is studied using isothermal microcalorimetric technique, X-ray diffraction analysis, and thermodynamic calculation. Meanwhile, hydrate assemblages are simulated by hydrothermal software. C2AH8 (2CaO·Al2O3·8H2O) is generated as a transition phase during the hydration of pure C12A7, while formation of CAH10 (CaO·Al2O3·10H2O) is uncertain. Heat-releasing behavior of Ordinary Portland Cement (OPC) could be noticeably affected by C12A7, especially for the duration of interaction at boundary stage reduces with C12A7 replacement. Correspondingly, all hydration kinetic parameters first increase and then diminish with C12A7 replacement. Simulation results manifest in the main hydration products of OPC being ettringite, C-S-H (Calcium-Silicate-Hydrate) gel, portlandite and brucite. Increasing C12A7 replacement accelerates the consumption rates of gypsum and calcite that are typically included in OPC, and thus the ettringite content is changed and carbonate phases will be produced. Therefore, the microstructure properties of hydrated products of OPC are affected and the compressive strength is influenced. These predications are in good agreement with experimental findings. C12A7 can be used as a functional component to adjust the consumption rate of suphates in OPC, and also components of carbonate phases can be modified in hydrate assemblage.

Blended Cement Mixed with Basic Oxygen Steelmaking Slag (BOF) as an Alternative Green Building Material

“…In particular, the parameters of the dilation angle, eccentricity, , K , and viscosity are determined following the study [ 64 ]. Figure 8 c,d present the experimentally measured compressive and tensile behaviors of the OPC, respectively, which are comparable with the results presented in the existing study [ 65 ]. The compressive and tensile relations are used to define the OPC in the FE models.…”

“…the experimentally measured compressive and tensile behaviors of the OPC, respectively, which are comparable with the results presented in the existing study [65]. The compressive and tensile relations are used to define the OPC in the FE models.…”

Assessment of a Municipal Solid Waste Incinerator Bottom Ash as a Candidate Pozzolanic Material: Comparison of Test Methods

“…Conversely, at a low substitution rate, i.e., at 10%w, the initial setting time increases by about 40%, with few reductions as regards the final setting (−10%). The results obtained here can be justified according to the mineralogic composition of the raw MSWI BA, which displays some relevant XRD peaks corresponding to mayenite, a mineral that hydrates very quickly and is responsible for rapid-strength gain in some calciumaluminate cements [47,55,56]. Mayenite is a crystalline phase that has been detected in other bottom ashes too, e.g., in references [38,57], and in ladle furnace slags [58,59].…”

“…Particularly, mayenite (C12A7) is widely used in calcium aluminate cements as a minor phase, and even in geopolymers to improve setting and early-age strength. It is well recognized that this mineral could lead to an improvement in the hydraulic reactivity of cements, especially at young ages [47,48]. However, recent studies demonstrated that rapid hydration of C12A7 may cause flocculation in the system, leading to the formation of regions with local defects within their mineralogic structure and, thus, to possible weakening of the paste matrix in cement-based materials [49].…”

Analytical chemistry in technical approaches: immobilization of biosorbent waste containing heavy metals in cemented materials

“…The quartz content remained relatively high with the addition of residue and plays a key role in the formation of the CSH gel that reacts with cementitious materials that influence compressive strength [43,44]. Schwertmannite and mayenite, which appeared in modified mortar samples, could be by-products of cement hydration, as well as the output from cement and residues [63][64][65][66]. Heavy metals were undetectable during XRD analysis because their concentrations were too low.…”