BACKGROUND: Use of high-strength prestressed concrete girders and high-performance bridge decks has become accepted practice by many state highway agencies because of their technical and economic benefits. These girders and decks are generally manufactured with concrete made with natural normalweight aggregates. Use of manufactured lightweight coarse aggregates, such as expanded shale, slate, and clay to produce lightweight concrete offers the benefit of reducing the weight of the superstructure, leading to reductions in the size of girders, substructure, and foundations. These size and weight reductions facilitate shipping, handling, and construction or replacement of bridge elements, and result in economic benefits.
Recent advances in high-performance/high-strength lightweight concrete have had limited application in bridge construction because of the lack of design and construction guidelines and concerns about material properties and their impact on performance. Research is needed to address the factors that significantly influence the design, constructibility, and performance of high-strength prestressed concrete bridge girders and high-performance bridge decks and recommend changes to the AASHTO LRFD bridge specifications. These modified specifications will provide highway agencies with the information necessary for considering lightweight concrete mixtures that are expected to yield economic benefits.
OBJECTIVES: The objectives of this research are to (1) develop guide specifications for the use of lightweight concrete in high-strength prestressed concrete girders and in high-performance bridge decks and (2) recommend changes to the AASHTO LRFD Bridge Design and Construction Specifications relevant to high-strength lightweight concrete girders and high-performance lightweight concrete decks. It will deal with mixtures made with normalweight fine aggregates and manufactured lightweight shale, clay, or slate coarse aggregates to produce concrete with equilibrium density, as determined according to ASTM C 567, of not more than 125 pcf.
Status: The project is complete; the report has been published as NCHRP Report 733 available at
https://onlinepubs.trb.org/onlinepubs/nchrp/nchrp_rpt_733.pdf
