International Concrete Abstracts Portal

Describes the use of expanded shale lightweight concrete for both older bridge widenings and new bridge construction on the California State Highway System in the past 30 years. Examples of major projects illustrate the durability and reliability of a properly designed and constructed lightweight aggregate bridge. Cost comparisons of lightweight aggregate structures bid in competition with structural steel and normal weight concrete alternative structures highlight the economic viability of this material. The outstanding performance of these lightweight bridges under heavy traffic and the close competition in bidding suggests that lightweight aggregate is a material that should be considered in future bridge designs, especially in earthquake country, where dead load is such an important factor in seismic design. The known consistent creep, shrinkage, and modulus properties of lightweight aggregate remove any doubts about performance, as certain structures have demonstrated. Industry advances in controlling moisture content have reduced considerably the handling and finishing problems of earlier years.

Project consists of a 15-story office tower and a 4-level parking structure. The advantages of lightweight concrete over other structural materials for this particular project, and the process followed for its selections, as well as different types of structural systems, are evaluated. The length of spans in both structures was a determining factor in the selection of the floor system. Lightweight concrete, 4000 psi, was chosen for the floors, and 6000-psi normal weight concrete was selected for the columns. As a first step of the design process, economic comparisons were made between concrete and structural steel. After determining that concrete was more economical, alternate floor systems were studied for constructability, function, economy, and availability of materials. Lightweight concrete was preferable for all floor systems, even though a premium cost of nearly 10 dollars per yd 3 is common for this geographic location.

This compilation of 12 papers addresses the performance of structural lightweight concrete, with topics ranging from fundamental laboratory studies to case histories of concrete performance. Note: The individual papers are also available as .pdf downloads.. Please click on the following link to view the papers available, or call 248.848.3800 to order. SP136

Presents information regarding highly confined, high-strength lightweight aggregate (LWA) concrete specimens, tested as part of a proprietary research program for which Phase I results have recently been released. The program specifically investigated the ultimate and post-ultimate behavior of members designed to resist high-intensity bending/punching shear loads, such as those imparted by massive ice features against offshore oil/gas platforms. Two special steel confining systems were utilized to confine the high-strength (compressive strengths nominally between 8000 and 9000 psi) LWA concrete; these were T-headed stirrup bars for use in reinforced concrete, and overlapping button-headed studs for use in plate-steel/concrete/plate-steel sandwich composites. These two confining systems both allowed the LWA concrete to exhibit extreme ductility prior to failure. Flexural, deflection, and ductility factors of over 40, and axial compressive strains of over 8 percent, were achieved, while maintaining essentially 100 percent of the ultimate capacity of the test specimens The tests were performed on 1- to 3.5-scale specimens, using a 4 million-lb capacity testing machine. Three approximately 16 x 16 x 42-in. prisms--two of reinforced concrete and one of sandwich composite concrete--were tested in axial compression. Also, four continuous beam specimens (one reinforced concrete and three sandwich composite concrete) were tested in bending/punching shear. These beam specimens were approximately 153 in. long, 36 in. wide, and had effective depths of approximately 13 in. Nonlinear finite element analyses of the beam specimens were also performed as part of the study.

This experimental investigation was aimed at gathering information on flexural properties, including ductility, of high-strength lightweight concrete members (concrete with a dry unit weight of approximately 120 lb/ft 3 and with compressive strength approaching 9 ksi at 56 days) under reversed cyclic loading. Two sets of six specimens each were manufactured using lightweight aggregate concrete having compressive strengths of 5 ksi at 28 days and 9 ksi at 56 days. The test variables were concrete strength, amount of longitudinal reinforcement, and spacing of ties. The test results, including hysteretic load-deflection curves, for specimens representing columns under zero axial load are reported.