Baker has used intelliRock's technology for years, but two recent projects really stand out.
First, Baker used intelliRock to complete the new CEMEX headquarters building on schedule, under budget, and with LEED points. Even while using lean mix designs with fly ash, Baker was able to stress PT beams in 18 hours and strip decks in 20 hours. And the lean mix design saved CEMEX approximately $130,000 in material costs. "The CEMEX headquarters project should serve as the poster-child for intelliRock because everything went exactly according to plan and we kept right on schedule." says Baker Senior Project Executive Aaron Smith. Case Study
Most recently, Baker completed the University of Texas, MD Anderson Cancer Center Mid-Campus Building 1 (MDACC) project. Located in Houston's Medical Center, the project consisted of three structures - 26 stories, 21 stories, and 5 stories. Not only was intelliRock used to monitor temperatures on what was the second largest mat pour placed in the united states, intelliRock technology was used to monitor deck strength in real-time greatly reducing the time that would be otherwise be necessary if using only traditional concrete cylinders to determine concrete strength. "Using the intelliRock system allowed the crew to gain half a day on almost every pour, which is significant when there are three pours per floor and 26 floors. Baker brought the project in three weeks ahead of our original schedule even after an additional floor was added to our scope," said Garret Benson, Baker Project Manager. Read more in Baker's newsletter (reprinted here with permission from Baker).
Baker has been ranked among ENR's top 3 specialty contractors for the past 20 years. Learn more about Baker on their website
Clayco, Inc. and concrete sub Concrete Strategies, Inc. recently completed a 2 story parking garage for online brokerage firm Scottrade in St. Louis, Missouri. Information from intelliRock concrete maturity sensors was used to time critical workflow activities such as post tensioning.
Left: Scottrade Building HQ and garage site in St. Louis, MO.
Right: Post tension cables which were stressed in two stages, 1600 PSI and 3000 PSI
Concrete Strategies VP, Barclay Gebel explains “For crack controlling reasons we stressed the PT cables in two stages. The first stage was when the concrete achieved 1600 psi and the second stage was 3000 psi. We use intelliRock to determine when to do the stressing.”
Project engineer Curt Costello continues, ”We were able to determine when different crews would come in to start stripping forms and preparing the PT cables for stressing. Once the strengths were met, we were able to stress the cables without losing much time. This was because we were able to anticipate concrete strengths based on information from intelliRock.”
The graph above is an example of the information available to Concrete Strategies in real-time at the jobsite. intelliRock sensors evaluated the concrete’s maturity every 60 seconds. The maturity reading could be correlated to a concrete strength using a calibration curve for the mix design. This gave Concrete Strategies up-to-the-minute concrete strength values.
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Clayco, Inc. is one of the nation's largest, privately owned real estate, architecture and engineering, design/build and construction firms. Read more about Clayco at www.claycorp.com.
Concrete Strategies is a leading edge, full service, design/build and general contracting firm specializing in all forms of concrete and structural steel construction. The firm operates nationally and has an unparalleled track record in architectural site cast concrete, structural concrete, flatwork and all types of self-perform construction related to commercial projects. For more information see their website at www.concretestrategies.com
"With the performance-based mass concrete in hand, and intelliRock loggers in the concrete, Walsh uses the new wireless data transmission system to overcome the data collection challenges."
"About the Author: Eric Hayes is an assistant project manager for Walsh Construction, currently on-site managing the construction of the twin Allegheny River Bridges. For more information about Walsh Construction, visit www.walshgroup.com."
Read the case study from Modern Contractor magazine here!
If you’re ever wondering what a maturity calibration curve (graph shows strength vs maturity in °C-Hrs) could tell you about the time needed to reach a target strength, there is a simple calculation can give you enough information to at least see what’s feasible.
Maturity, using the Nurse-Saul method, is given in units of °C-Hours. The calculation is simply “Time x Temperature” with the units of time being hours, and units of temperature in °C. Assuming the common datum temperature of 0 °C, the math gets that simple: Maturity = Time x Temperature. Just be sure you get the units right.
Let’s assume you need 4,000 PSI and your calibration curve says the maturity needed for 4,000 PSI is 3,500 °C-Hrs. How long is that? A convenient first approximation is to see how long 3,500 °C-Hrs is at a comfortable 23 °C (73 °F) temperature. Maturity/Temperature = time, 3500 °C-hrs/23 °C = 152 hours, which is a little over 6 days. If your goal is 4,000 PSI in 7 days and it’s warm outside, then you’re probably fine with that mix design. If you need the 4,000 PSI in 3 days, then what do you need to do to get there? You need higher temperatures! How high? Temp = Maturity/Time, Temp = 3,500 °C-Hrs/(3 days* 24hrs/day) = 49 °C (104 °F). Is it reasonable for the concrete to have an average curing temperature of at least 49 °C? Mass concrete in Florida during July – you’re just fine. A thin elevated deck during January in Chicago – you’ll either have to supply supplementary heat or use a “hotter” mix.
This simple calculation is especially insightful when considering leaner, lower cost mix designs. Take the example where you need to achieve 3,000 PSI in 2 days and your maturity data says you are achieving 5,000 PSI in 2 days using your expensive high-early mix. Would a standard lower-cost mix design still get you there? Grab the calibration curve for the leaner mix, see what maturity is necessary, divide maturity by 48 hours and see what average curing temperature you need (remember, that’s the temperature of the concrete, not the ambient temperature). Compare the calculated temperature to the temperatures profile you’re currently getting with the high-early mix. Considering that the leaner mix will run somewhat cooler, is it likely that the average 48 hour concrete temperature will be at or above what the maturity calculation said? This simple calculation can at least tell you yes, no or maybe. For a 60 second effort, that’s a lot of insight.
Over the years intelliRock has been used on jobsites with extremely harsh conditions for electrical instrumentation. For these applications we developed “armored” cables to protect the download wires from being damaged as the concrete was being placed. These tough cables, suitably dubbed “yellow wire loggers”, were so reliable we started using the tougher wire on all loggers with cable lengths over 4 ft. Today 4ft red-black cables are still available on loggers as a cost-effective solution on small concrete placements. However, on large placements we highly recommend that 8ft or longer cables be used to maximize durability and reliability even if the placement isn’t considered a “mass concrete” pour.
intelliRock loggers are currently available with the following cable lengths: 4ft, 8ft*, 15ft*, 30ft*, 50ft*, and 100ft* (* denotes loggers with tough “yellow wire” cables) . Cables longer than 100ft are available by special order.
Special loggers are available for users needing to monitor mass concrete temperatures over "years." These loggers were originally developed to monitor long-term temperatures on the Tom Sauk Reservoir rebuild where engineers wanted a way to conveniently monitor mass concrete temperatures as long as possible. The "MEGA" loggers are physically larger than standard intelliRock loggers because they contain larger batteries. Although only guaranteed for three years, the larger battery theoretically gives the loggers enough power to log for 5 to 10 years.
If you have a mass concrete monitoring project where you could employ MEGA loggers, give us a call and we can discuss needs and capabilities!