Sources: CP staff; VCNA Prairie Material, Bridgeview, Ill.
A rapidly emerging, roller compacted concrete pavement finishing method nets surface durability and uniformity to give contractors or owners pause on incurring the added material and labor expenses of asphalt wear courses commonly specified over RCC bases.
After vibratory and static drum rollers compact the extremely dry RCC mixes—placed in single or multiple layers or lifts typically 6 inches or less—crews power trowel a silica-rich hardening and densifying agent into a slab’s critical upper layer, then sweep with a broom or smooth float, and spray with curing compound.
“This could be a game changer. We can now offer a monolithic roller compacted concrete slab with a finish much more typical of traffic-ready asphalt or conventional, broom-finished concrete,” says Prairie Material Marketing/Product Specialist Theron Tobolski, who has most recently overseen placement of 1,000 yd. of RCC mixes at Maryhill Cemetery in Niles, Ill. The new finishing process is a savings for the owner, he adds, when factoring costs associated with a wear course’s 2 in. of asphalt plus crew and equipment mobilization.
During a late-June to early-July window, Prairie Material and Hickory Hills, Ill. contractor J&R 1st in Asphalt Inc. demonstrated various RCC pavement options to replace old driveway, parking lot and service area asphalt at 246-acre Maryhill—one of the Archdiocese of Chicago’s 46 Catholic Cemeteries properties. An initial placement involved 4,000 sq. ft. of inconspicuous pavement at the rear of the facility’s maintenance shop. It consisted of conventional, two-layer RCC with rougher surface prone to superficial crazing, but density characteristics assuring long service life in the face of vehicle loads and Upper Midwest freeze-thaw cycles.
Catholic Cemeteries officials approved a demonstration the Prairie and J&R team proposed for the second placement: A more prominent shop area with power-troweled, broom-finished pavement, its top ¼-in. hardened and densified with the RCC Surface Pro nano-silica agent (Cemex, Andale RM pave way for smooth, monolithic RCC slabs). The quality of finish compelled a decision to maintain the new specification for two subsequent pavement sections under the Prairie and J&R contract—totaling 54,000 sq. ft.
Catholic Cemeteries staff will monitor troweled-RCC performance at Maryhill with an eye toward broader use throughout northern Illinois properties, which encompass 100-plus miles of lighter duty roads, most of asphalt construction. Most immediately, the organization has enlisted Prairie and J&R to deliver broom-finished RCC for a section of road at Resurrection Cemetery in Justice, Ill.