Alite abundance

Alite abundant, belite scarce, free lime abundant (evenly distributed) (a) Lime saturation too high (b) Sintering temperature too low (Hofmanner, 1973)... 

Alite size decreasing, alite abundance increasing Increasing burning temperature from 1500°C to 1700°C (Suzukawa, Kono, and Fukunaga, 1964)... 

Alite reacts with water to form calcium silicate hydrate and calcium hydroxide, which is also known as portlan-dite. The hardened paste has high strength when the reaction is completed, and because alite is the most abundant compound in cement, it also makes the dominant contribution to the mechanical properties of the final product. The hydration reaction proceeds at an appreciable rate a few hours after the addition of water and lasts up to about 20 days. The reaction of alite with water is accelerated by aluminate and gypsum. 

When examining a polished section or thin section, the viewer must constantly think in three dimensions, not merely in terms of the nearly two-dimensional view seen in the microscope. Dendritic periclase, therefore, should be considered as a three-dimensional, branching, treelike or skeletal crystal, typically growing within a liquid matrix, the surface of the section revealing only part of the tree. Alite, the most abundant phase in portland cement clinker, tends to form a somewhat discontinuous, open, three-dimensional framework of linked and stacked crys-... 

Note If MgO in clinker is higher than 1.8%, birefringence of alite in the table should be increased by 0.001. If MgO is less than 1.2%, birefringence is decreased by 0.001. Belite crystals with abundant dotlike impurities indicate slow cooling. Ono s numerical designations of 4, 3, 2, and 1 were placed in the table by the present writer. 

Bruggemann (1988), using the linear traverse technique for phase abundance, demonstrated that small, lattice defective, alite crystals produced in kilns with steep temperature profiles and short residence times improve grindability and cement quality. Ono s method, utilizing only a few crystals in a powder mount, was said to give doubtful results. ... 

Increase in silicate abundance, decrease in liquid, higher temperature required for oombination of feed ingredients, deorease in alite size Relatively higher silica ratio (Long, 1982b)... 

Photograph 7-11 Extremely heterogeneous clinker containing large concentrations of loosely packed yellow-amber belite and alite with a wide range of crystal sizes and, like the belite, a nonuniform distribution. Free lime is abundant (dark, round crystals). Sandy, silica-rich raw feed with coarse quartz. Gas-fired dry-process kiln, 3000 tons/day. (S A6631)... 

Increase in abundance of alite and belite Increase in TiO content in clinker (Knofel, 1977)... 

Zones in alite broaden toward nearby belite nests Calcium and silica abundant in nest area (Ono, Kawamura, and Soda, 1968)... 

Serrated alite High AljOj/FeO, especially when alkalies are abundant (Brown. 1948)... 

Relatively large belite inclusions in elite, large belite crystals (45 pm) Abundance of coarse quartz in feed belite and alite became much smaller upon use of finely ground friable silica (Dorn, 1980)... 

Photograph 7-26 Experimental laboratory burn with raw mix containing quartz (44-75 pm) as a silica source. Average alite crystal size = 44 pm. 1000°C for 30 min, 1425°C for 10 min. Very rapid temperature change. Note abundant free lime inclusions in alite. Clinker courtesy of Joe Garcia, Capitol Cement, San Antonio, Texas. (S A6646)... 

Photograph 7-27 Ragged belite crystals and belite coating on alite, one of which is twinned. Note abundant dotlike impurities in alite. Coarsely crystalline matrix with gray aluminate and relatively bright ferrite. Slowly cooled clinker. (S A6647)... 

Photograph 7-82 Free lime in clinker thin section. Crystals exhibit prominent cubic cleavage characteristic of free lime. An abundance of free-lime nests (some showing original limestone particle outline), anhedral alite, and extremely nonuniform distribution of silicates suggests poorly mixed coarse feed. Dry-process kiln, coal fired. (S A6700)... 

A relatively "hard-to-burn" feed from the western U.S., with a very impure dolomitic limestone, has 6.7% >125 pm and an acetic-acid insoluble residue of 9.5% >45 pm, the latter comprised of quartz, feldspar, medium to finely crystalline igneous and metamorphic rock fragments, and an abundance of ferro-magnesian minerals (mainly amphiboles and pyroxenes). = 1.6% and = 4.5%. Belite nests (many with tightly packed crystals), solitary belite, and periclase are abundant in this fine- to medium-crystalline clinker. Nevertheless, a high-compressive strength mortar (44.8 to 48.3 MPa) is made, mainly because of the small alite size and the well-scattered solitary belite. 

Efch reactivity variations (specify etch and length of time). Crystal morphology crystal surface characteristics (depth of alteration) internal structure tendency for coarse cannibalism (masses greater than 5 times the average alite crystal size) inclusions. Size and abundance variations within and between clinkers. 

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