transferredto either an open bed dump truck or 

### an agitator truck for transport to thejob site. 

### Shrink mixed concrete is concrete that is partially mixed at the central mix plant and then completely mixed in a truck mixer on the way to thejob site. Dry hatching, with concrete mixed and hauled to the construction site in dry form, is seldom, if ever, used.

1.3 Hot Mix ~s~hal?'~

Hot mix asphalt (HMA) paving materials are a mixture ofwell graded, high quality aggregate (which can include reclaimed asphaltpavement w]), and Liquid asphalt cement, which is heated and mixed in measured quantities 

### to produce 

### HMA. Aggregate and 

### RAP (ifused) constitute over 92percent by weight ofthe total mixture. Aside from the amount and grade of asphalt cement used, mix characteristics are determined by the relative amounts and types of aggregate and RAP used. A certain percentage offine aggregate (less 

### than 74 micrometers [pm] in physical diameter) is required for the production of good quality 

### HMA. Hot mix asphalt paving materials can be manufactured by: (1) batch mix plants, (2) continuousmix 

### (mix outside 

### drum) plants, 

### (3) parallel flow 

### drum mix plants, and (4) counterflow drum 

### mix plants. This order of listing generallyreflects the chronologicalorder of development and use 

### within the 

### HMA industry. An 

### HMA plant can be constructed as a permanentplant, a skid-mounted (easily relocated) plant, or aportable plant. All plants can have 

### RAP processing capabilities. Virtually all plants being manufactured today have RAP processing capability. A gendzedprocess diagram for hot mix asphalt is included in Appendix A oftIiis document

1.4 Vermiculite and Perlite ~rocessin~~~'

Vermiculite -

Vermiculite is the geologicalname givento a group ofhydrated laminar minerals that are aluminum-iron-magnesium silicates and that resemble 

### mica in appearance. The chemical formula for vermiculite is (Mg,Ca,K,Fe ) (Si,Al,Fe ) 

### 0(ON) 4H 

### 0. When subjected to heat, vermiculite

### has the unusual property of exfoliating, or expanding, due to the interlaminar generation of 

### steam. Uses ofunexpanded vermiculite include muds for oil-well drilling and fillers in fire-resistant wallboard. Vermiculite ore is minedusing open-pit methods. Beneficidon includes screening, flotation, drying inrotary or fluid bed dryers, and expansionby exposureto high heat. All mined vermiculite is dried and sized at the mine site prior to exfoliation. A generalized process diagramfor vermiculiteprocessing is included inAppendix A ofthis document.

Crude ore from open-pit mines is brought to the 

### mill by truck and is loaded onto outdoor stockpiles. 

### Primary processing consists of screeningthe raw material to remove the waste rock greater than 518 inch and 

### returningthe raw ore to stockpiles. Blending is accomplished as material isremoved from stockpiles and conveyed to the mill feed bin. The blended ore is fed to the dl, where it is separated into hctionsby wet screening and then concentratedby gravity. All concentrates are collected, dewatered, and dried in either a fluidizedbed or rotary dryer. Drying reduces the moisture content ofthe vermiculite concentratefkom approximately 15to 20 percent to approximately 2 to 6percent. At most facilities, the dryer products are transportedby bucket elevators to vibrating screens, where the material is classified. The dryer exhaust

Nh4MProc TSD 6-14-02 Created on 6/1812002 9:39:00 AM 3