Hot asphalts

Asphalt concrete is primarily used as a structural pavement surface constructed over a subgrade and a subbase. It is designed to support the traffic load and distribute the load over the roadbed. Asphalt concrete pavements can be constructed using hot mix or cold mix asphalt. Hot mix asphalt is a mixture of tine and coarse aggregate with asphalt cement binder that is mixed, placed, and compacted in a heated condition. Cold mix asphalt is a mixture of emulsified asphalt and aggregate, produced, placed, and compacted at ambient air temperature. Cold mix asphalt pavement usually requires an overlay of hot mix asphalt or surface treatment to resist traffic action. 

SAS mixtures using batch-type asphalt hot mix facilities. 

Construction Procedure. Paving with a sulfur—asphalt hot mix is exactly the same as with asphalt. Conventional dump trucks are used to haul the hot mix from the asphalt plant to the road. There the mix is spread with standard pavement equipment and compacted with conventional rollers. Measurements on the completed pavements verify that sulfur asphalt mixes have good workability and are virtually indistinguishable from conventional asphalt. 

Asphalt Asphalt Hot Sand Sulphur-Asphalt Hot Sarid Sulphur Asphalt Hot Sand Asphalt Asphalt Type 0 Sulphur Asphalt ... 

The remaining 10.8 wt % of sulfur performs as a mix filler. These large agglomerations of sulfur do not perform in the same way as conventional mineral fillers which are dispersed in asphalt hot-mix. The latter, at the concentrations typically used, generally improve the void filling capacity of the asphalt binder (or reduce the VMA) without effecting such dramatic changes to mix stability as does sulfur. 

The more common membrane is asphalt, hot applied. It is a different formulation than that used in road or roof construction and is designed for maximum corrosion resistance. It is impermeable to fluids. At elevated floors, all openings in floor and at edges must be curbed, with membrane extending to the top of... 

Asphalt Hot-Mix Emission Study, Research Report RR-75-1, The Asphalt Institute, College Park, Md., 1975. 

Solid or liquid sulfur could be readily mixed with aggregates and asphalt in a batch-type asphalt hot-mix plant. 

The patching mix may be processed in an asphalt hot-mix plant and transported to the various patching sites in a heated vessel. Alternatively, the patching mix may be produced by remelting previously made hardened mix in a mobile heated vessel equipped with an agitator. The latter process is particularly adaptable for use during the winter in areas where hot-mix plants are not normally operational. 

The minimum rolling time depends on the type of material. The minimum rolling time for asphalt concretes and porous asphalts is 20 min, whereas the minimum rolling time for stone mastic asphalt, hot rolled asphalt and mastic asphalt is 30 min. In the case of coated chippings, the minimum rolling time is 10 min. 

The asphalts (hot, warm, semi-warm mixed or cold mixed) used for the construction of asphalt base, binder course and surface layers together with their mechanical and other properties are described in detail in Chapters 5, 6 and 7. In addition, details on their production, laying, compaction and control of quality can be found in Chapters 8 and 9. 

When it is time to replace part of the asphalt layers, or to place an overlay, the use of modified bitumen in the new asphalt hot mix is recommended in most cases. The use of asphalt-reinforcing grids, or other reflection cracking-reducing technique, is also advised to be considered. For details, see Section 15.6. 

Hot-Applied Rubberized Asphalt. Hot-applied rubberized asphalts consist of proprietary blends of asphalt, mineral fillers, elastomers (natural, synthetic, or a blend of both), virgin or reclaimed oil, and a thermoplastic resin. It is applied hot in such a manner as to form an impermeable monolithic membrane over the surface to be waterproofed, which may be concrete, gypsum board or wood. Improved versions of this type of system consist of two coats of rubberized asphalt with a polyester mat in between, ealled the fully reinforced or two-ply system. 

Dispersion at temperatures of 90—110°C is a common final step io European mills processiog wax-coated old cormgated containers. Dispersion temperatures less than 90°C are reported to reduce wax particle size to improve pulp drainage properties on paper machines while improving paper strength (45). Dispersion has been used to reduce hot-melt adhesive, plastic coating, and asphalt particle size. These low density particles can then be removed from the pulp by flotation (46). 

Built-Up Roofing. Built-up roofing (BUR) is a continuous-membrane covering manufactured on-site from alternate layers of bitumen, bitumen-saturated or coated felts, or asphalt-impregnated glass mats and surfacings. These membranes are generally appHed with hot bitumens or cold apphed bituminous adhesives (qv). 

Polymeric Ma.teria.Is, The single-ply membranes are made from a wide variety of polymers. The following is a brief description of those polymers and their characteristics. There are three thermosetting-type elastomeric membranes as of this writing (1996) neoprene, CSPE, and EPDM. Neoprene is stiU used where oil resistance is needed. Eor instance. Hydrotech uses neoprene flashings, the base of which is hot-set in mbberized asphalt (see ElASTOL RS, SYNTHETIC-POLYCm.OROPRENE). 

Tanks are used to store hquids over a wide temperature range. Cryogerhc hquids, such as hquefied hydrocarbon gases, can be as low as —201 C(—330 F). Some hot hquids, such as asphalt (qv) tanks, can have a normal storage temperature as high as 260—316°C (500—600°F). However, most storage temperatures are either at or a htde above or below ambient temperatures. 

Tar sand, also variously called oil sand (in Canada) or bituminous sand, is the term commonly used to describe a sandstone reservoir that is impregnated with a heavy, viscous black extra heavy cmde oil, referred to as bitumen (or, incorrectly, as native asphalt). Tar sand is a mixture of sand, water, and bitumen, but many of the tar sand deposits in the United States lack the water layer that is beHeved to cover the Athabasca sand in Alberta, Canada, thereby faciHtating the hot-water recovery process from the latter deposit. The heavy asphaltic organic material has a high viscosity under reservoir conditions and caimot be retrieved through a weU by conventional production techniques. 

Waterproof. Waterproofing barrier systems may be either hot- or cold-appHed. The hot-appHed generaUy involve a bituminous material such as asphalt used in conjunction with a reinforcing fabric such as roofing felt, cotton, or glass cloth. Cold-appHed can be bituminous or elastomeric materials either in Hquid or sheet form, with or without fabric reinforcement. Liquid elastomeric treatments include neoprene, polyurethanes, and blends of these or epoxies with bituminous materials. Among the commonly used precured elastomeric sheet materials are neoprene, polyisobutylene, EPDM mbber, and plasticized PVC. Polyethylene and PVC films and nonwoven plastic or glass fabric coated with bituminous materials also find use (78). Because these... 

Preparation is accompHshed by simple blending of the diluent into the hot base asphalt. This is generally accompHshed in tanks equipped with coils for air agitation or with a mechanical stirrer or a vortex mixer. Line blending in a batch circulation system or in a continuous fashion (40) is used where the volume produced justifies the extra faciUties. A continuous, line-blending system is appHcable to the manufacture of cutback asphalts and asphalt cements (Fig. 8). 

If straight-mn asphalts are reduced to a hardness below 300 penetration (30 mm), they are termed asphalt cements. For hot-mix paving, either the AC-10 viscosity grade or the next harder AC-20 grade is commonly specified. 

Asphalt emulsions are dispersioas of asphalt ia water that are stabilized iato micelles with either an anionic or cationic surfactant. To manufacture an emulsion, hot asphalt is mixed with water and surfactant ia a coUoid mill that produces very small particles of asphalt oa the order of 3 p.m. These small particles of asphalt are preveated from agglomerating iato larger particles by a coatiag of water that is held ia place by the surfactant. If the asphalt particles agglomerate, they could settle out of the emulsion. The decision on whether a cationic or anionic surfactant is used depends on the appHcation. Cationic stabilized emulsions are broken, ie, have the asphalt settle out, by contact with metal or siHcate materials as weU as by evaporation of the water. Siace most rocks are siHcate-based materials, cationic emulsions are commonly used for subbase stabilization and other similar appHcations. In contrast, anionic emulsions only set or break by water evaporation thus an anionic emulsion would be used to make a cold patch compound. 

Typical apphcation of a BUR would be to mop or apply asphalt to a substrate to approximately 1.1 kg/m (23 lbs/100 ft ), or the thickness of a dime. A ply sheet would then be unroUed into the hot asphalt. Additional ply are then mopped in, with each layer offset so that the roof has three or four phes of felt over the entire roof. The amount of offset is calculated by the formula, offset = 34 in. (86.4 cm) /number of pHes. Manufacturers of pHes print laying lines on the felts at the correct locations to assist in laying up the roof with the correct offset. 

SBS membrane systems are generally installed in hot asphalt but can be installed using a torch like APP products or in some cold apphcation cement systems. Like APP systems, they are generally installed in multiple layers. The undedayment layers are generally standard BUR felts or basesheets. SBS membrane sheets can also be formulated to be self-adhering. These products are no longer used in membrane appHcations but are used as ice and water dam matedals on the eaves under shingle roofs in cold climates. 

Type IV asphalt is not common except in very hot climates. It has softening points between 96 and 107°C with penetration at 25°C between 12 and 25 mm /10. It is for roof slopes greater than 1 per 12, and is also called special steep asphalt. Type IV asphalt is used on flashings and in hot climates to keep the roofing system from sliding off the roof in hot weather. 

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