Plastic-concrete

Penicillin, gasoline, synthetic rubber, paper, plastic, concrete. 

Addition of a new section on miscellaneous admixtures including shotcrete admixtures, corrosion inhibitors, and admixtures for recycling wash water and plastic concrete. 

Dampproofing admixtures are formulated to affect the properties of the hardened concrete, and not those of concrete in its plastic state. In the case of materials based solely on calcium and aluminum stearates, stearic acid in solid or emulsion form, bitumens and hydrocarbon resins, there will be no effect on the properties of the plastic concrete with regard to air content, workability, mix design parameters, etc. When water-reducing admixtures or accelerators are included in the formulation, the effect on the concrete will be a function of the particular type of material used (see relevant section). The wax emulsions do appear to have an effect on the properties of the plastic concrete because of the lubrication effect of the very small... 

Accelerating admixtures based on calcium chloride, formate, nitrate, and thiocyanate have no significant effect on the workability, air content, mix stability, or water-cement ratio of concretes into which they are incorporated. The only properties of plastic concrete which are affected are the heat evolution and setting time. 

Every year millions of cubic meters of ready-mixed concrete are returned for disposal in dump sites. There are now increasing environmental concerns and restrictions regulating the disposal of returned plastic concrete. In the last decade, environmental protection agencies in Europe and North America have classified both returned plastic concrete and truck wash water as hazardous waste. Consequently, the conventional methods of disposal in slurry tanks and landfill sites have become redundant, and disposal of plastic concrete is now a major problem for the ready-mixed concrete industry [102]. 

Similarly, in plastic concrete, the presence of dissolved calcium, sodium, potassium and sulfate ions lowers slightly the freezing point of pore water, which begins to crystallize as ice at a concrete temperature of about -2° C (28°F) [110]. The addition of the proper combination of salts such as those contained in antifreeze admixtures can further reduce the temperature at which ice formation begins. 

The effects of water-reducing admixtures on the properties of plastic concrete... 

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