According to Associated General Contractors of America, 70% of construction firms report difficulty finding qualified tradespeople, with concrete workers topping the list. Lack of skilled labor and construction inefficiency are adding extra hurdles, time, and expense to many projects just when owners increasingly demand fast-track completion to minimize disruption and economic impact. Even the slightest delay can significantly impact your bottom line.
To maintain profitability, many contractors are embracing high-tech materials and methods to improve productivity. One such solution is a ready-mix concrete that develops high mechanical resistance quickly after pouring, enabling contractors to rotate forms, load structural elements, and open pavements to traffic three to five times faster than standard concrete.
The mix delivers the same strength ordinary mixes gain at 28 days in 48, 24, 15, 6, or 4 hours. The product’s fluid consistency allows for transportation and usage for two hours without affecting handling, making it easy to use in all types of vertical and horizontal applications.
Formwork for walls, columns, and other vertical jobs can be removed after 4 hours instead of 12 hours to 20 hours, increasing productivity by doubling daily formwork operations. Horizontal work such as floor slabs, sidewalks, parking lots, and roads can reopen to traffic within 24 hours instead of the seven days typically required by other high-early-strength mixes.
Customized Fast-Track Concrete
Combining two hours of workability with rapid-early-strength gain is a significant technological achievement. Developed by LafargeHolcim US, Rapidforce is made possible by a blend of accelerating and slump-retaining admixtures. Designed in optimum proportions based on local raw material characterization, every customized mix is rigorously tested in LafargeHolcim’s quality-control laboratories to achieve targeted performance properties specific to application type.
These advanced early-strength mixes are providing significant return on investment in a wide variety of projects across the country where speed of construction is critical.
New Orleans’ Canal Street
When a portion of Canal Street in New Orleans collapsed in 2016, a massive sinkhole opened above a long-abandoned expressway tunnel. Although the tunnel had remained structurally sound, the temporary timber end walls left in place had deteriorated after decades of water intrusion.
One of the busiest thoroughfares used by tourists, Canal Street is home to many retail stores, hotels, restaurants, and entertainment venues. The mayor quickly declared a state of emergency.
The city set the repair schedule at 90 days and offered financial incentives for early completion. To accelerate repairs, general contractor Hard Rock Construction of Harvey, Louisiana, needed concrete that would achieve rapid strength gain and flow easily through a 2-inch line running hundreds of feet into the sinkhole. LafargeHolcim supplied 5,000 cubic yards of a custom-designed Rapidforce mix that eased placement and achieved 4,000 psi within 24 hours. The road was repaired with a mix designed to achieve 3,000 psi within 24 hours.
Repairs involved building a new support wall from within the sinkhole and resurfacing the damaged pavement. Crews poured a 4-foot-high footing and then built masonry walls on top, filling every block with the Rapidforce mix. Using the masonry walls as permanent forms, they sealed the tunnel by installing a 26-inch-thick cast-in-place reinforced Rapidforce wall.
Repairs were completed in 39 days—months earlier than expected—for $3.5 million on a job initially budgeted at $5 million. “Rapidforce made a tremendous contribution,” says Hard Rock Construction Project Manager Chris McLellan.
“With our economy struggling, the last thing we needed was to make it more complicated to get into and out of our businesses,” says a local business owner. “My employees and other shop owners are grateful the problem was resolved quickly and efficiently.”
Minnesota Gas Station
TruSeal America, an asphalt, concrete, and seal-coating contractor in Inver Grove Heights, Minnesota, needed to repave two lanes at Holiday Gas Station’s busy location in Savage, Minnesota. Normally, the company would use a standard high-early-strength mix that cures in seven days and phased construction to minimize construction impacts.
Instead, to speed things up, Truseal America used a Rapidforce mix designed to deliver 28-day strength in 4 hours to 48 hours while maintaining the design slump throughout the process.
For a busy retail establishment, reopening to traffic even a day sooner than expected is a significant economic benefit.
“Rapidforce helped us complete a two-week project in 24 hours, saving significant labor costs,” says TruSeal America Owner Steve Tjornhom. “And our customer was happy to see their lanes were open for business in only one day.”
Buffalo Parking Garage
To help alleviate a critical parking shortage at Buffalo Niagara Medical Campus (BNMC) in New York, the City of Buffalo announced plans for accelerated construction of a new garage. The structure had to be built before a new medical school and children’s hospital opened, bringing thousands of students, employees, and patients.
Located in the heart of the emerging medical campus, the eight-level parking garage has more than 1,900 spaces and consists of long-span, cast-in-place, post-tensioned beams and deck slabs to provide column-free drive aisles. The project required a mix that would gain an early strength of 3,000 psi at 48 hours, for releasing the post-tensioning tendons, and a final specified design strength of 5,000 psi at 28 days.
To meet the deadline and achieve rapid strength gain, LafargeHolcim developed and supplied more than 18,000 cubic yards of a customized mix for all structural elements. Designed with a blended cement containing silica fume and slag to achieve high strength and low permeability, the concrete allowed for easier placement and consistently achieved the specified early-strength gain within two days.
Rapidforce delivered the specified 28-day strength of 5,000 psi in seven days, which allowed heavy equipment to be put on the concrete and work to continue up to higher levels ahead of schedule. The mix’s ability to achieve and maintain a high slump also resulted in nice, smooth finishes on the columns with minimal vibration, a huge benefit in terms of time and labor cost savings.
Construction finished weeks ahead of the new facilities’ scheduled opening.
Maryland Distribution Center
Traffic never stops moving through the U.S. Postal Service (USPS) Network Distribution Center in Capitol Heights, Maryland. When it was time to rebuild the severely deteriorated pavement in front of loading docks, it was imperative to complete the new pads as quickly as possible.
Chilar Construction of Beltsville, Maryland, considered a high-early-strength mix that would require three days to cure and gain proper strength, but USPS facility managers demanded an even quicker turnaround to minimize service disruptions: 24 hours.
The mix needed to achieve a specified strength of 5,000 psi. The old concrete was removed and replaced with 10-inch-thick pavement. Five to six docks were done at a time so fleets could continue delivering mail during construction.
Aggregate Industries supplied more than 1,500 cubic yards of a Rapidforce mix that delivered a 5,000-psi compressive strength in 24 hours. The project was completed a month ahead of schedule in 24 days.
“Like clockwork, we were removing traffic cones from the new pavement every 24 hours to allow the trucks to back up into the docks,” says Chilar Construction President Juan Calderon. “USPS was very happy about getting the work done so quickly, and it benefitted us with less labor time on the jobsite.”
Boston High-Rise
One Dalton Street tower is a notable addition to Boston’s skyline. Soon to be New England’s tallest residential skyscraper, the 60-story architectural landmark consumed 70,000 cubic yards of concrete.
Each floor was a 11,500-square-foot slab. The schedule required placing two floors each week. Specified strength gain was 24 hours.
“We needed an advanced high-early-strength concrete that would allow us to remove the formwork in a short amount of time and high-strength, self-consolidating mixes that would flow easily through and consolidate around congested reinforcement in the core walls and the uniquely tapered perimeter columns,” says Mike Curtis, president of G&C Concrete Construction in Haverhill, Massachusetts.
Like the eight-story parking garage in New York, Aggregate Industries supplied a Rapidforce mix that contained silica fume and fly ash. For the heavily reinforced columns and walls, G&C Concrete relied on high-strength Agileflow self-consolidating mixes to speed up pouring and meet the challenging performance criteria.
“The Rapidforce hit its high-early-strength consistently so we could strip out the forms early,” Curtis says. “The Agileflow eliminated the need for vibration in the heavy-rebar applications, and the column finishes were nice and smooth.”
