Shrinkage, clay products

Clays or shales that may be utilized ia the manufacture of bricks, tiles, and other heavy clay products exist ia every state ia the United States. (See Building materials, survey). Some blending of materials is often necessary to control shrinkage of the product, and the economics of manufacture are governed by the demands of fuel, labor, transportation costs, and the market. 

Shrinkage of Structural Clay Products, Trans. British Ceram. Soc., (1960). 

Efremov GL (1960) Effect of the shape and distrihution of clay particles on shrinkage of products. J Glass Ceram 14, 6, 5/1 pp 201-205 doi 10.1007/BF00668286... 

Cancrinite crystals were used as aggregate in Portland type III cement mixtures to bind the crystals. Hard products were obtained only when the cancrinite was prepared from fired clays. It appears that any unreacted clay in the cement mixture will cause the cement to crumble when air dried. This may be due to shrinkage of the clay upon drying. 

The volume shrinkage characteristic of these clays subjects the structure of the product into which they enter to a severe strain, which, owing to the low tensile strength, may cause serious difiiculty due to cracking and checking, so that it may be... 

In the reaction of styrene hydrogenation in toluene, interlayer solvent displacement and clay shrinkage do not occur, as the product ethylbenzene is very similar in character to the solvent molecules. 

Microcellular crumbs can be used in considerable quantity along with china clay and whiting to reduce the product cost. Higher proportions of stearic acid (5-10 phr) are normally used in microcellular compounds in order to bring down the decomposition temperature of DNPT type blowing agents (see Appendix AlO). Post-cure oven stabilization of the microcellular sheets, typically at 100°C for 4 h, reduces the delayed shrinkage after cure to a minimum. 

Permeability also depends on the degree of vitrification. Mudrocks containing a high proportion of clay minerals produce less permeable products than clays with a high proportion of quartz, but the former types of clays may have a high drying shrinkage. 

Firing Shrinkage. The decrease in size that usually occurs when ceramic ware is fired it is usually expressed as a linear percentage contraction from the dry to the fired state. Firing shrinkage always occurs with shaped products containing plastic clay and often amounts to 5-6% (cf. after contraction). 

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