Evaluation of Lightweight High Performance Concrete in Bulb-T Beams and Decks in Two Bridges on Route 33 in Virginia

摘要

Lightweight high performance concrete (LWHPC) is expected to provide high strength and high durability along with reduced weight. The purpose of this research was to evaluate and compare the prestressed LWHPC bulb-T beams and decks in two bridge structures. The bridges are on Route 33 near the confluence of the Mattaponi and Pamunkey Rivers into the York River at West Point, Virginia. Each bridge has both normal weight and lightweight bulb-T beams. The decks on the lightweight beams are also lightweight. Two distinctly different high-strength lightweight concrete mix designs and curing procedures (steam cured versus moist cured) were used for the beams of the two bridges. The results indicate that LWHPC with satisfactory strength and permeability can be achieved for beams and decks. These concretes are expected to be durable and cost-effective. The initial cost of LWHPC is higher than for conventional high performance concrete. However, the reduced dead load of LWHPC would result in longer spans, reduced number of piers or smaller piers, reduced substructure requirements, and easier transportation and erection of elements, leading to substantial savings, as was evidenced in this study. The study recommends that the use of LWHPC should continue for beams and decks and possibly for accelerated construction with precast units in substructures or superstructures, especially for rehabilitation projects. Elements cast off site would be prepared under more controlled conditions and reduced traffic interruptions. In addition, handling and delivery would be easier than for conventional concrete because of the reduced weight. If the improved quality through use of LWHPC resulted in a 10% increase in service life, large savings would occur. In Fiscal Years 2003 through 2008, the Virginia Department of Transportation spent an average of $10.68 million per year on prestressed concrete beams. Thus VDOT could save close to $1 million each year through the improvements expected with LWHPC.