Water reducers retarding action

Aluminium hydroxide is essentially non-toxic, but does require high addition levels to be effective. As a result, the physical properties of the compound usually suffer. Its fire retardancy action results from the endothermic reaction which releases water under fire conditions and produces a protective char . The endothermic reaction draws heat from the rubber/filler mass and thus reduces the thermal decomposition rate. The water release dilutes the available fuel supply, cooling the rubber surface and mass. 

The fact that the water-reducing effects of superplasticizers are similar to those of conventional water reducers used in similar concentrations suggests that the modes of action are similar, and that the essential difference is that the properties that limit the concentrations in which conventional water reducers can be used are weaker or absent in superplastizers. These properties comprise retardation, air entrainment and in some cases flash setting. 

In order to improve the flame retarding action of these Fyarestor additives, antimony trioxide can be enqployed as a flame retarding synergist in these applications which tolerate the use of a powdered additive. The use of this metal oxide will reduce the flame retarding cost. Also, the Fyarestor products can be emulsified for use in water-based systems. Typical Properties ... 

Several explanations have been offered to account for the retarding action of water reducers. They are based on the following theories ... 

The versatility of the thermal analysis techniques such as TG, DTG, DTA, DSC, and conduction calorimetry for evaluating the role of admixtures in concrete is demonstrated in Chs. 5 through 8. The actions of accelerators, retarding/water-reducing admixtures, superplasticizers and supplementary cementing, and other admixtures are described in Chs. 5,6,... 

The performance of aluminium hydroxide/magnesium hydroxide-filled systems can be enhanced by incorporation of zinc hydroxystannate in halogen-free rubbers giving reduced smoke and toxic gas emission, coupled with higher flame retardancy. This action will be complimentary to the water release and endothermic effects of aluminium hydroxide/magnesium hydroxide filler systems. 

To address emissions of flame-retardants, a Voluntary Emissions Control Action Program (VECAP ) was initiated by the Bromine Science and Environmental Forum (BSEF).112 The VECAP Pilot program was initiated in the U.K. textiles industries in 2004 to reduced emissions of deca-BDE in line with the Code of Good Practice. After 1 year of implementation, the U.K. Pilot Program achieved a 75% reduction in emissions to water.113 The second year, a total of 90% reduction in emissions was then realized. 

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