The Theodore Roosevelt Bridge in Washington, D.C. is being repaired with rapid-set latex modified concrete overlay. Photos: CTS Cement Manufacturing Corp.
Rapid-set cement is being used for the overlay of the 79-year-old Lewis and Clark Bridge over the Columbia River between Washington and Oregon.
Rapid-hardening cement has been used widely for bridge deck overlays with excellent results. For example, it enabled a contractor a few years ago to speed through refurbishing of much of the surface of the Lewis and Clark Bridge, which dates from 1929 and connects the communities of Rainier, Ore., and Longview, Wash. Although some sections of the deck had to be completely replaced, requiring partial closures for 18 months, the Washington State DOT (WSDOT) was keen on keeping bridge closures to a minimum. By using 450 cubic yards of rapid-hardening cement concrete (LMC-VE) for a 1575-foot length of overlay during one weekend, WSDOT saved at least nine days of closure as compared with traditional slower -setting concrete.
A few years ago, rapid-hardening cement was also used for resurfacing the main interstate bridge connecting Interstates 70, 64, and 55 across the Mississippi River in downtown St. Louis and passing near the Cardinals' baseball stadium. The Missouri DOT was concerned that the surface repairs not disrupt major league baseball. The fast set time of the cement enabled start and completion of the entire resurfacing job between Friday evening and noon Sunday, a time frame in which there were no home games. The contractor was successful in hitting an inside-the-time-frame home run.
Since 1998 rapid-hardening cement has been used in several states around the country in approximately 100 bridge deck overlays. It has also been used in buildings, tunnels, bridges, chemical plants and on highways and at airports when time is critical. While concrete generally is specified essentially as a commodity product, selecting a specific product mix with an eye to its features and benefits can increase the serviceability and longevity of the project.
— Rubin is a concrete consultant and was one of the developers of shrinkage-compensating cement (Type K) and concrete. He is a consultant to CTS Cement Manufacturing Corp.Extend concrete's service life … for less
The specially blended cement required for rapid-hardening cement concrete (LMC-VE) costs four times as much as Type I/II cements used in conventional latex-modified portland cement concrete (LMC) overlays. Type III cement (LMC-HE) carries a cost 20% higher than Type I/II cements used in the conventional LMC overlays. The higher cement prices increase the cubic yard cost of the concrete by approximately $90/cubic yard and $7/cubic yard respectively. But these added costs are more than compensated by the substantial savings in traffic-control costs. The costs for traffic control for LMC-VE overlays and for epoxy overlays are the same. For example, DOTs spending $5 million annually on deck rehabilitation can save as much as $1.25 million each year by using LMC-VE overlays. LMC-VE and LMC-HE overlays can run approximately 25% less than conventional LMC overlays
The advantages of rapid-hardening cement are three-fold:
- Completed overlays can open to traffic in three hours. An overlay installed overnight causes less inconvenience to the public even the very next morning. It has been found that the initial higher material cost is more than offset by the reduction in traffic control costs incurred for more extended closure.
- Rapid-hardening cement shrinks less and is more resistant to harsh chemical environments than portland cement (e.g., sulfates and reactive aggregates).
- Additives are available that allow for extended mixing and transport times, which can be convenient for high-volume applications or other applications where time of application is a consideration (a longer lead time is desirable).