Economics densification

A characteristic of single sized sands is their comparatively high air void contents which usually exceed 30 percent. Since sulfur s role in SAS mixtures is to fill these air voids without the aid of mechanical densification, both economic and performance considerations would require analysis of the maximum permissible air void content the mixture may possess and still be relatively impermeable to water without sacrificing structural integrity. Figure 4 [15] shows the relationship between air voids content and permeability for both SAS and asphaltic concretes as determined... 

Based on the potential benefits for source densification an economic analysis was performed to quantify the dollar savings (2). A model of the collection process was developed that allowed comparison of the cost of conventional waste collection with proposed densified waste collection. 

The extremely variable and complex nature of the material makes it difficult to process. For successful economical source densification, the system must be designed to accommodate the material variations. 

The least densification and the most direct use of agricultural or wood residues makes the most sense from an energy and economic point of view. We recommend that residue producers or users look closely at their raw materials and design combustion processes around low density, low energy processes, which combine residues for their highest and best use. 

S-A-S materials should be prepared with a minimum of compaction or densification. This could result in a significant economic advantage of S-A-S over A/C during construction. 

The effect which the metals and compounds of metals have on the crystalhzation rate of the silica is not sufficiently pronounced to preclude their use under the conditions of the present invention. Desirable results were achieved by having the metal modifier present in a highly dispersed state so that upon densification of the powder the modifier is not concentrated into large crystals which would be objectionable. Furthermore, by reason of the highly dispersed condition of the metal modifier, the proportion of it which must be used is confined to a minimum, which is economically advantageous. 

The post-densification of SSiC by HIP is less complicated because no gastight encapsulation is necessary. Hence, not only is it possible to achieve more than 99% of the theoretical density, but the variation of density and strength can also be reduced. Pressureless sintering and HIP can now be performed within the same cycle, in a process termed sinter-HIP, and this offers clear economic benefits [273-275]. 

---