First Bridge Structure with Lightweight High-Performance Concrete Beams and Deck in Virginia.

摘要

This study involved the construction and early performance of the first bridge in Virginia constructed with lightweight high-performance concrete (LWHPC) having a density of 120 lb/ft3 in the beams and deck. The design strength and permeability were 8,000 psi and 1500 coulombs, respectively, for the beams and 4,000 psi and 2500 coulombs, respectively for the deck. The concretes were tested for slump, density, air content, compressive strength, flexural strength, permeability, elastic modulus, freeze-thaw durability, and shrinkage. The effectiveness of using fibers to control cracking over one of the two piers in the continuous deck was also investigated. The results indicate that LWHPC can be produced such that the material is workable, strong, volumetrically stable, and resistant to cycles of freezing and thawing, thus leading to a long service life with minimal maintenance. After 4 years of exposure, there was limited cracking in areas both with and without fibers. LWHPC is recommended for use in beams and decks for reduced weight. The volumetric method for measuring air content is time-consuming and can cause adverse delays when a continuous deck is placed. Density measurements to control the air content of the LWHPC are recommended after a relationship is established. The enhanced durability of LWHPC is expected to lead to extended service life with minimal maintenance costs. The lower initial cost due to the lighter weight concrete elements and the increase in the service life of the bridge because of the enhanced durability should result in significant savings.