Highway sealant

POLYETHYLENE FOAM BACKER ROD FOR PAVEMENT AND HIGHWAY JOINT SEALANT BACKUP... 

Two types of PE foam backer rod, available from Applied Extrusion Technologies, are briefly described. Type HBR XL is for concrete pavements and type HBR is for highway use. The use of a backer rod in the joint, below the surface, limits the depth of sealant placed on top of it, helps prevent excessive sealant use and prolongs sealant service life. APPLIED EXTRUSION TECHNOLOGIES INC. 

Sealants have been used for difficult building joints with high movement, as well as for highways, where joint failure is a major problem and a tougher... 

Tolerances are also not well understood. A fuel cell stack with over 400 cells operating in this environment contains sealant, which is literally miles long. Seals will start to fail after the fuel cell is bumped and jostled on the highway and while temperature shifts between hot and cold, and the cell is turned off and on. With zero tolerance for safety failures, hydrogen leaks cannot occur with these vehicles. Additionally, every cell has to be identical or the system cannot be managed. Unfortunately, that kind of tolerance control is not yet available. 

OTHER COMMENTS used in the manufacture of mortars for building blocks, bricks, stone and pre-cast items also used as a moisture sealant for exterior of concrete blocks used in concrete on highway paving, domestic and commercial building construction, and in pre-cast concrete articles useful in light-weight concrete, terrazzo, stucco, asbestos cement products, interior surfaces, and exterior surfaces. 

In addition to their use on highways and roofs, both hot poured and room temperature hardening bituminous compositions have been used as caulking materials and sealants in building construction. The classical agphalt/ashestos sealants contained volatile solvents and their resistance to solvents was increased by the incorporation of coal tar. These sealants have also been modified by the addition of elastomers, such as powdered rubber, and fillers, such as sawdust.12... 

For many applications these sealants are too high in modulus. For places sealed with silicone sealants that see tremendous movement (>25% expansion and contraction), like expansion joints in highways or buildings, the toughness of the above sealant results in undue stress on the bond line at high elongation. In these applications, either the sealant will fail adhesively or the sealant will pull the concrete surface (or similar surface) apart. 

Information About Silicone Sealants - Dow Coming 888 Highway Joint Sealant. Bulletin 61-408-78 (1978). 

Airfield Highway Joint Sealant - Resists fuel spillage resists softening in heat withstands jet blast during "rotation". 

For highway sealants (119), the desired properties are adhesion (without primer), weatherability (adequate retention of properties for more than 10 years), resilience, temperature stability, hardness range for hot or cold (firm enough to resist incompressibles, puncture and tear resistant), good uncured consistency, solvent resistance, repairability, and abrasion resistance. Silicones, especially those of low-modulus, offer nearly all the properties desired as a good highway sealant. 

In the past five years, the People s Republic of China (PRC) has been striving to make progress under the Four Modernizations movement (1). There has been a frenzied pace, of construction in public buildings, public dwellings, and highways. Consequently, there has been a constant demand for materials such as adhesives and sealants for construction. 

The elastomeric sealants should be based on polysulfide or urethane rubbers (preferably a two-component formulation in traffic grade) and comply with Federal Specification TT-S-00227E. The epoxy sealers may be epoxy-polysulfides (complying with Corps of Engineers Specification MMM B-350A) or epoxy-polyamides (complying with Specification M-200-65 of the American Association of State Highway and Transportation Officials). The epoxy compounds are described in Table 5.65. 

Urethane sealants have good elongation and recovery, excellent abrasion resistance and tear strength their resistance to indentation make them the preferred compounds for floor joint compounds, highway and airfield joint materials, and preformed gasket seals in clay and concrete pipe. Low temperature performance (to below —40°C) is superior to that of the... 

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