Crack prevention

As already pointed out, poured concrete is a good retarder for radon gas and soil gas. The major problems will be cracks, joints, and penetrations. The focus of this subsection will be on crack prevention and sealing joints and penetrations. A good deal of this material applies to both poured concrete and masonry walls. 

Exudation in Cast Explosives in Presence of Crack-Preventing Additives. See under "Anticracking Additives to Cast Explosives" in Vol 1, pp A461-R to A462-R... 

Crack-preventing additives to cast expls see Anti-cracking additives to cast expls 1 A461-A462... 

Fruit with cracks around the stems shoulders may be green or yellow. Cause Uneven irrigation. Cracks start at the stem and extend out, or are semi-circular splits on the shoulders of the fruit. Rots may invade fruit through cracks. Prevent problems by keeping soil evenly moist throughout the season and by planting crack-resistant cultivars such as Early Girl , Jet Star , and fioma . 

Use Substitute for camauba and beeswax, shoe and furniture polishes, phonograph records, roofing paints, rendering paints waterproof, adhesive pastes, electric insulating compositions, paper-sizing compositions, carbon papers, wire coating, sun-crack preventive in rubber products. 

Biostabiliser Incorporated into plastics Anti-fungi, algae and bacteria Prevent discoloration Stop cracking Prevent pitting Prevent brittleness Improve product life span Maintain aesthetic appeal Mediiun to long life... 

Stress corrosion cracking is a form of localized corrosion, where the simultaneous presence of tensile stresses and a specific corrosive environment prodnces metal cracks [157, 168]. Stress corrosion cracking generally occnrs only in alloys (e.g., Cn-Zn, Cu-Al, Cu-Si, austenitic stainless steels, titaninm alloys, and zirconinm alloys) and only when the alloy is exposed to a specific environment (e.g., brass in ammonia or a titaninm alloy in chloride solutions). Removal of either the stress on the metal (which must have a surface tensile component) or the corrosive environment will prevent crack initiation or cause the arrest of cracks that have already propagated. Stress corrosion cracking often occurs where the protective passive film breaks down. The continual plastic deformation of the metal at the tip of the crack prevents repassivation of the metal surface and allows for continued localized metal corrosion. 

Figure 14.24. (a) Deflection of a crack prevents total film detachment, (b) Peeling at a plastic hinge, fc) Stopping of peel crack as the hinge deflects. 

Alloy type Environment Type of cracking Preventive or remedial measures... 

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