Reclaimed aggregate material

Reclaimed concrete material (RCM) is sometimes referred to as recycled concrete pavement (RCP), or crushed concrete [ 159-162]. It consists of high-quality, well-graded aggregates, bonded by a hardened cementitious paste. The aggregates comprise approximately 60-75% of the total volume of concrete. RCM is generated through the demolition of Portland cement concrete elements of roads, runways, and structures during road reconstruction, utility excavations, or demolition operations. 

Bottom ash has been used as an aggregate material in flowable fill mixes Ponded ash also has the potential for being reclaimed and used in flowable fill Since most flowable fill mixes involve the development of comparatively low compressive strength, no advance processing of bottom ash or ponded ash is needed... 

To produce a granular base or subbase aggregate, RAP must be crushed, screened, and blended with conventional granular aggregate, or sometimes-reclaimed concrete material... 

Travel plant mixing and blade mixing are used when the cold bituminous mixture is to be produced from virgin aggregate material. Rotary/reclaimer mixing is normally used when the cold bituminous mixture consists of reclaimed material. 

The particle size distribution of milled or crushed RAP may vary to some extent depending on the type of equipment used to produce the RAP, the type of aggregate in the pavement, and whether any imderlying base or sub-base aggregate has been mixed in with the reclaimed asphalt pavement material during the pavement removal. 

Foundry sand (FS) - In typical foundry processes, sand from collapsed molds or cores can be reclaimed and reused - Little information is available regarding the amount of FS that is used for purposes other than in-plant reclamation, but spent FS has been used as a fine aggregate substitute in construction applications and as kiln feed in the manufacture of Portland cement - Most of the spent FS from green sand operations is land filled, sometimes being used as a supplemental cover material at landfill sites 81-87... 

As can be seen in Table 3.24, the energy consumption for the construction of a concrete layer is higher than that of the asphalt layer with virgin materials. Similarly, when 20% reclaimed material is used, the energy consumed for an asphalt base layer is less than that for an asphalt base layer with virgin materials. The processes that use unheated aggregate and cold applied binders utilise the least amount of energy per tonne. 

Regarding the constituent materials used in the production of HRAs, such as binder, aggregates and the use of reclaimed asphalt and additives, all are referred to Section 5.4.1.1 and Sections 5.4.1.1.1 through 5.4.1.1.3 apply. 

The target composition should declare and document the materials, from which the mixture is composed, namely, the particle size distribution of the aggregate mix (grading), the bitumen content and whether reclaimed asphalt or other additives are used. 

The separation or screening unit includes a series of sieves that separate hot aggregates (inclusive of reclaimed asphalt if used and fed before screening) into fractions (usually between four and six) of specified size and reject the oversized aggregates. The fractions of aggregates are stored temporarily in hot bins. Each bin is equipped with an overflow tube of appropriate diameter to prevent the material from overflowing into other bins. 

Another technique is the development of a double-barrel dryer/mixer (see Figure 8.6). In this technique, the aggregate is dried and heated in an inner rotating drum, while mixing of the constituent materials of the asphalt (aggregates, bitumen, reclaimed asphalt, etc.) takes place in the outer shell (barrel). This provides more efficient drying and mixing at a lower... 

Part of the FPC system requirements specified by CEN EN 13108-21 (2008) is inspection and testing on incoming constituent materials and on finished bituminous mixture (delivered product). As constituent materials, the following are distinguished aggregates, filler, binders, additives and reclaimed asphalt. 

The constituent materials, such as aggregates, filler, binders, additives and reclaimed asphalt, should be inspected and tested on a regular basis. 

The material removed from the asphalt layers to be re-used, hence recycled, containing bitumen and aggregates, is called reclaimed asphalt (RA), under European Union terminology, or reclaimed asphalt pavement (RAP), under US terminology. 

As for the reclaimed concrete, after removing the steel, when properly crushed and screened, it can be used as aggregate replacement in hot mix production, as a granular base or sub-base or as an embankment or fill material. 

The reclaimed material from old concrete slabs (crushed and screened concrete particles) can be used as aggregate for (a) production of concrete, (b) stabilised or non-stabilised base and sub-base material, (c) construction of embankments or drainage filters, (d) construction of shoulders and (e) production of asphalts for base and binder courses. 

Stroup-Gardiner M. and T. Wattenberg-Komas. 2013. Recycled Materials and Byproducts in Highway Applications Volume 6 Reclaimed Asphalt Pavement, Recycled Concrete Aggregate, and Construction Demolition Waste. NCHRP Synthesis 435. Washington, DC TRB, National Academy of Science. 

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