Concrete Products

JAN 2019

Concrete Products covers the issues that attract producers of ready mixed and manufactured concrete focusing on equipment and material technology, market development and management topics.

Issue link:

Contents of this Issue


Page 71 of 103

66 • January 2019 FEATURE BY DON MARSH Prospects for high performance concrete in the Los Angeles Basin have been tempered by the average quality of sand & gravel deposits in southern California, and limited demand for higher than conventional design strength mixes due to past preeminence of structural steel in mid- to high-rise construction. Raw-material logistics, market demands and enlightened engi- neering practices are turning the tide in HPC's favor: A new source of premium sand & gravel, critical to attainment of compressive strength and modulus of elasticity (MOE) thresholds exceeding 8,000 psi and 4,000 ksi, supports a strong case for reinforced concrete in vertical and horizontal conditions subject to high seismic and wind loads. Developers responding to a downtown and west Los Angeles residen- tial and commercial boom are pursuing tighter schedules on projects calling for leaner shear walls and columns or stiffened core walls with an eye to floor plates offering more usable square footage. And, engineers and agencies looking beyond compressive strength and MOE metrics are tapping the premium aggregates' potential to raise concrete performance for non-building work. Sand & gravel at the heart of the Los Angeles market's HPC embrace is sourced from the Orca Quarry, a 130 million-ton glacial deposit developed by Vancouver, B.C.-based Polaris Materials Corp. Inordinately clean and dense, with natural micro surface texturing characteristics primed for strong matrix bonding, the material yields engineering properties matching or exceeding those of mixes in the leading HPC markets of Chicago and New York. In conjunction with synergistic-admixture dosing, portland cement and supplemental cementitious materials optimization, temperature control simplifi- cation on mass pours, plus elevated-slab, column and shear wall schedule reductions, Orca aggregates competes against local fine and coarse stock on mix design and in-place concrete cost criteria. Polaris Materials' U.S. subsidiary Eagle Rock Aggregates Inc. began supplying southern California concrete producers with three Orca grades in 2015, permitting a four-acre Port of Long Beach terminal for 1 million tons annually. Approvals from leading structural engi- neers and key agencies confirm how Orca washed sand and ½-in. or 1-in. gravel have already changed the Los Angeles County concrete market and justified pursuit of a second permit, awarded in fall 2018, increasing terminal throughput up to 2 million tons annually. Against old methods and materials, Orca aggregate has rewritten the reinforced concrete value proposition around accelerated project schedules; simplified mix designs lighter on cement and admixture requirements; and, finished slabs or structures inviting character- izations like "smaller," "thinner," "stiffer," "optimal," "completed faster," "of lower embodied carbon," and "less prone to early and longer-term deflection." In under three years, structural engineers and agencies have acknowledged Orca aggregate concrete advantages and specified or approved the premium sand & gravel for more than 30 high profile building or public works jobs. Eagle Rock continues market development with the help of Los Angeles ready mixed pro- ducers and mobile batch plant-equipped contractors. Stiff Competition U.S. Concrete's Polaris Materials business unit delivers premium aggregate to southern California practitioners pressed for lofty strength, modulus of elasticity targets Along with the washed sand and ½-in. grade from Orca Quarry (left), the 1-in. gravel has density, shape and surface texture characteristics yielding high performance structural concrete with lower portland cement and admixture requirements than mixes bearing sand & gravel typical of the southern California market. Eagle Rock Aggregates promotes the material for its early and ultimate high strength develop- ment, low drying shrinkage, in-place concrete thermal control and modulus of elasticity qualities. MATERIAL, TERMINAL PHOTOS: Concrete Products PHOTO: Polaris Materials Corp.

Articles in this issue

Links on this page

Archives of this issue

view archives of Concrete Products - JAN 2019