الفهرس 
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Abstract
Twenty clay samples were collected from running clay quarries at El- Faiyum (9 samples), from Wadi El Rayan and Qasr El Sagha Formations that are of Middle and Late Eocene ages, respectively; Giza (6 samples) from Wadi El Rayan Formation of Middle Eocene age; Al-Alamine city (3 samples) and Mersa-Matrouh (2 samples) of Moghra and Marmarica Formations of Early and Middle Miocene ages; respectively.
The creation of thermochemical models to forecast the dependent variables governing the bloatability of lightweight aggregates (LWAs) is the goal of this work. Laser particle size analysis, XRD, XRF, IR, TGA-DTA, SEM- EDX, Laser imaging system, µ-CT, hot-stage microscope and Factsage (8.3) thermochemical modeling software were used for raw clays and LWAs characterization as well as phase composition prediction in the temperature range 900-1250°C. In addition, SPSS software was used for data analysis and modeling.
It was found that the LWAs bloating zone occurs at 1050-1250°C with a minimum bulk density (BD) of (0.74g/cm3) at 1250°C. During the LWAs pyroplastic state, the crystallization of anorthite from the silicate melt lowers its viscosity due mainly to the uptake of the melt alkalis into the anorthite lattice. However, the silicate melt is still viscous enough to trigger the reduction of hematite to guarantee the evolution of bloating gases. The simultaneous association of higher evolved gas with less melt
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content of higher viscosity promotes the LWAs bloatability, however, the higher gas associated with lower melt content of lower viscosity would loosen the LWAs their consistency and sphericity upon sudden cooling.
Based on the LWAs bulk density and lab experimental observations, the production window limits of successful LWAs are ≥40wt.% silicate melt of 103-107Pa.s viscosity that accompanied with (0.50-4.00wt.%) gas content. This production window has been verified by Liapor industrial kiln feed. The stepwise predicting regression models for the LWAs after cooling characteristics and during their pyroplastic state (melt content and viscosity, gas pressure as well as systems enthalpies) are all significant (<0.05). These models are statistically verified by the multi-collinearity testing which shows VIF values <10 indicating the absence of any multi- collinearity among the models’ explanatory variables.