International Concrete Abstracts Portal

A methodology has been developed for designing precast, fiber reinforced polymer concrete (FPC) vaults to be used in underground applications. The approach used in the design was to consider the vault as a series of plates: cover, walls, and foundation slab. Each plate was subjected to loads resulting from soil pressure, live loading, and dead weight and was analyzed using classical plate theory. This approach was verified by testing two quarter-scale models of a typical vault. Upon completion of the laboratory evaluation, two vaults were designed for use as underground, natural gas regulator stations. The vaults were manufactured and subsequently placed into service by Brooklyn Union Gas Company, and the Consolidated Edison Company of New York.

Given the breakthrough technology creating nonshrinking unsaturated polyester resin, this paper examines what this new technology might do if utilized in polymer concrete. The paper defines the criteria for success for polymer concrete in cast metal applications and, utilizing these criteria, compares the performance of the newly developed, low-shrink, polyester-based systems with an accepted standard epoxy. Criteria examined include (1) stiffness-to-weight ratio equal to cast iron, (2) low coefficient of thermal expansion, (3) temperature insensitive mechanical properties, (4) adhesion to insert materials, (5) low shrinkage, (6) good composite flow and consolidation characteristics, and (7) comparable cost to machined cast metals. The data tends to show that for most applications, these new low-shrink, polyester-based polymer concretes may, in fact, be a new polymer-based alternative for cast metals. Given the lower costs of these low-shrink polymer concrete systems, an exciting new opportunity may be defined. Observations on initial field trials are also noted.

A major problem confronting transportation departments is the surface deterioration of portland cement concrete (PCC) pavements and bridge decks. Some of these defects include cracking, spalling, polishing, and surface erosion. Each of these defects contributes to further deterioration within the concrete structure by allowing an infiltration of moisture, oxygen, deicing salts, chlorides, and other contaminants. Upon contact with the reinforcing steel, rusting occurs, causing internal tensile stresses that result in further surface spalling, hollow plane delamination and cracking. One effective technique used since the middle 1950s is to retard this corrosion process by preventing the penetration of chlorides and moisture into the concrete with in impermeable epoxy polymer concrete (EPC) overlay. These overlays also provide wear-resistant surfaces and extend the service life of the pavement or deck. Documented experience indicates that EPC overlays are cost effective, reduce overall annual maintenance costs, and provide a safe driving surface. This paper presents two project tracking studies. The first is a comparison of a new PCC slab placement to a thin EPC overlayment on an existing PCC pavement installed 15 years ago; the pavements are side-by-side. The documentation compares traffic volumes and surface deteriorations, such as wearability, spalling, polishing, and cracks. The second study involves a thin EPC overlay placed on a badly deteriorated PCC bridge deck 10 years ago to improve skid properties and provide an overall safer driving surface.

Epoxy asphalt concrete is a polymer concrete with a 25-year history of application as a bridge deck surfacing. Since 1967, over 100 million pounds (50,000 tons) have been installed on 22 bridge decks totaling 6.5 million square feet. Most installations have exhibited excellent performance. The epoxy asphalt binder is a two-phase, thermoset chemical system in which the continuous phase is an acid cured epoxy and the discontinuous phase is a mixture of asphalts. The aggregates and gradation are similar to those used in asphalt concrete. The epoxy asphalt binder components are premixed before being combined with the heated aggregate in a conventional asphalt batch plant and applied through conventional asphalt paving equipment. Epoxy asphalt concrete has found use as a pavement for new orthotropic steel bridge decks and as an overlay for existing concrete bridge decks. Epoxy asphalt has also been applied as a chip-seal. On one project, the epoxy asphalt concrete was shop applied to steel plates that were later installed as a bridge deck. Several installations have not performed as expected. Successful installations require close temperature control of aggregates and careful attention to early compaction. This paper also provides a history of the commercial use of epoxy asphalt in the United States and Canada.

An analytical procedure was developed by which thermally-induced stresses in polymer concrete overlays can be quantified. The distribution and the magnitude of thermally-induced stresses can be determined using the proposed procedure. The main variables which influence the thermal stress development are found to be the thickness ratio and the modular ratio of the polymer concrete to the portland cement concrete, the difference in the coefficients of thermal expansion, and the temperature change. The relationships between the variables and the thermal stresses are determined and presented. Analyses reveal that thermally-induced interface stresses decrease as the elastic modulus and the thickness of the overlay decrease for the thin polymer concrete overlays. The analyses assumed isothermal conditions.