Environmental reduction factor

The American Concrete Institute guidehnes (ACI-440.2R-02 2002) suggest that the design ultimate strength, be determined by modifying the reported strength,/ , by an environmental reduction factor, Ce ... 

Exposure condition Fibre and resin type Environmental reduction factor, Ce... 

Exposure condition Fiber type Environmental reduction factor Cg... 

Oxidation-reduction (redox) reactions, along with hydrolysis and acid-base reactions, account for the vast majority of chemical reactions that occur in aquatic environmental systems. Factors that affect redox kinetics include environmental redox conditions, ionic strength, pH-value, temperature, speciation, and sorption (Tratnyek and Macalady, 2000). Sediment and particulate matter in water bodies may influence greatly the efficacy of abiotic transformations by altering the truly dissolved (i.e., non-sorbed) fraction of the compounds — the only fraction available for reactions (Weber and Wolfe, 1987). Among the possible abiotic transformation pathways, hydrolysis has received the most attention, though only some compound classes are potentially hydrolyzable (e.g., alkyl halides, amides, amines, carbamates, esters, epoxides, and nitriles [Harris, 1990 Peijnenburg, 1991]). Current efforts to incorporate reaction kinetics and pathways for reductive transformations into environmental exposure models are due to the fact that many of them result in reaction products that may be of more concern than the parent compounds (Tratnyek et al., 2003). 

A measure of the damages affecting the bonded joints is the loss of strength of the aged test pieces in contrast to the nonaged test pieces, which may be indicated in the form of reduction factors (Section 10.2.2). Only property testing of bonded joints under these complex stresses composed of mechanical and environmental influences enables an extensive statement on the behavior in practical application. 

CATEGORIZATION OF NAMED REDUCTION REACTIONS (WITH RESPECT TO SUBSTRATE OF INTEREST) BY MINIMUM ATOM ECONOMY, MAXIMUM ENVIRONMENTAL IMPACT FACTOR, MAXIMUM MOLECULAR WEIGHT FRACTION OF SACRIFICIAL REAGENTS, HYPSICITY INDEX... 

Young et al. (2000) developed environmental impact factors calculated using the Waste Reduction (WAR) algorithm. These factors encompass (1) physical potential impacts (acidification of soil, greenhouse enhancement, ozone depletion, and photochemical oxidant depletion), (2) human toxicity effects (air, water, and soil), and (3) eco-toxicity effects (aquatic and terrestrial). The important parameters are as follows ... 

To account for the material evolutions, guidelines dedicated to the external or internal reinforcements of concrete structures using FRP composites usually introduce substantial durability parameters (reduction factors on FRP tensile properties and on shear characteristics of FRP/concrete bonded interfaces, creep stress levels and fatigue limits) see, for instance, ACI 440.2R-08 (2008) and ACI 440.1R-06 (2006). However, further research is still needed to refine the design codes and better calibrate the durability reduction factors taking into account synergistic effects between various environmental factors. 

For plastics parts prone to creep and environmental influences, increased safety factors in addition to materials-dependent reduction factors need to be applied. 

Strength reduction factors, environmental effects, and the effects of aging on short-term properties could also be revisited. The subsequent subsections briefly describe the current activities in this regard in ASME and JSME. 

Product standards may stipulate performance characteristics, dimensions, quaUty factors, methods of measurement, and tolerances and safety, health, and environmental protection specifications. These are introduced principally to provide for interchangeabiUty and reduction of variety. The latter procedure is referred to as rationalization of the product offering, ie, designation of sizes, ratings, etc, for the attribute range covered and the steps within the range. The designated steps may foUow a modular format or a preferred number sequence. 

Environmental Factors. The control, recovery, and disposal of mercury-bearing waste products are as important to the mercurials industry as the manufacturing process. The difficulties involved in removing mercury from waste-product streams and the problems of recovery or disposal have resulted in a substantial reduction in the number of manufacturers of mercury compounds as well as in the variety of mercury compounds being manufactured. Moreover, the manufacturing process used for a mercury compound may not necessarily be the most efficient or economical. Rather, the choice may depend on the nature of the by-products, the toxic hazard of the process, and the ease of recovery of the mercury from the waste-product stream. 

Since SCC is often dependent on environmental factors other than stress and exposure to a specific corrodent, appropriate alteration of these other factors may be effective. For example, a reduction in metal temperature, a change in pH, or a reduction in the levels of oxygen or oxidizing ions may reduce or eliminate SCC. 

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