STRUCTURAL LIGHTWEIGHT CONCRETE
Structural lightweight concrete made with rotary kiln produced structural lightweight aggregate solves weight and durability problems in buildings and exposed structures. Structural lightweight concrete achieves strengths comparable to normal weight concrete, while being 20% to 30% lower in density.
Structural lightweight concrete offers design flexibility and substantial cost savings by providing reduced dead load, reduced seismic loading, longer spans, better fire ratings, thinner sections, decreased story height, smaller size structural members, less reinforcing steel, and lower foundations costs. Structural lightweight concrete precast elements have reduced trucking and placement costs. The excellent durability performance of structural lightweight concrete made with expanded shale, clay or slate (ESCS) structural lightweight aggregate is a result of the ceramic nature of the aggregate, and its exceptional bond to and elastic compatibility with the cementitious matrix.
Structural lightweight aggregate's cellular structure provides internal curing through water entrainment which is especially beneficial for high-performance concrete, (HPC). Internal curing improves the aggregate/paste contact zone which mitigates micro cracking.
Compared with ordinary concrete, lightweight concrete using ESCS lightweight aggregate has better thermal properties, higher fire ratings, reduced autogenous shrinkage, improved contact zone between aggregate and cement matrix, less micro-cracking as a result of better elastic compatibility, and better shock and sound absorption, high-performance lightweight aggregate concrete also has less cracking and improved skid resistance and is readily placed by pumping.
USES OF STRUCTURAL LIGHTWEIGHT CONCRETE
Floors in steel frame buildings (lightweight concrete on fire-rated steel deck assemblies)
Concrete frame buildings & parking structures (all types, including post-tensioned floor systems)
Bridge decks, piers & AASHTO girders
Specified density concrete (concrete between 120 pcf and 135 pcf)
Lightweight precast & prestressed concrete elements (beams, double-tees, tilt-up walls, raised access floor panel planks, hog slats, utility vaults, pipes, ornamentals, etc.)
Marine structures, floating docks, ships, & offshore oil platforms
SELECTED CASE STUDIES
PUMPING LIGHTWEIGHT CONCRETE 54 STORIES HIGH IN CHICAGO
When constructing high-rise buildings, every floor has to be strong enough to support the loads imposed on each level, and also provide the fire resistance required by the building code.
Recently, Ozinga Chicago was called on to supply lightweight concrete for a 54-story project on Lake Street in Chicago. The project is a steel frame building with a lightweight concrete slab on metal deck floor system, with a specified concrete compressive strength of 4,000 psi at 28 days and a maximum equilibrium density of 115 pounds per cubic foot.
Because of its lower heat conductance, lightweight concrete provides the required fire resistance with about 1/3 less thickness than required for normal weight concrete. Combined with a 1/5 reduction in density, the system reduced floor dead loads by about 45 percent.
PRECAST DOUBLE-TEES MADE WITH LIGHTWEIGHT AGGREGATE BIG PART OF ATLANTA’S SUNTRUST BALLPARK
Cranes tower above Cobb County Georgia’s Cumberland District. Down below, SunTrust Park, the new home of the Atlanta Braves, is taking shape. The ballpark and mixed-use development is the first of its kind: a place where fans can shop, eat and even live long after the game ends.
Lightweight aggregate from Arcosa Lightweight is used in the concrete mix poured into forms at the Hiram yard. The resulting product easily meets the project’s strict fire-rating requirements. “On a few of the parking decks at SunTrust park they have a fire rating requirement based on the building type classification. We use lightweight concrete. There are other benefits but in this case, it was due to the fire rating; you can achieve over 2-hours,” says San Martin.
Back at the project, trucks bring double-tees to the job site for placement. Transporting each of these pieces safely across busy Atlanta requires careful coordination and is a major expense for any project, especially one this large.