By Alicia Hearns, for Giatec Scientific Inc.
A lack of productivity on site is one of the most frustrating issues facing the construction industry today. Think about the hours you spend in a single day with no choice but to sit around and wait. Historically, this issue has been largely neglected in the industry, with “up to 66 percent of the day on a construction site dedicated to anything but actual building work,” according to construction research conducted by Aarhus University in Denmark. An inefficient jobsite means that your project deadlines won’t be met, which directly affects your bottom line as more funding is required to pay for additional labor.
Don’t let concrete cylinder break tests delay your project schedule
The strength of in-place concrete is most commonly measured by sending field-cured cylinders to a lab where they undergo a break test in a compression machine. This practice has remained largely unchanged since the early 19th century. The problem with lab tests is that they frequently don’t return strength results in a timely fashion. As a result, despite your best efforts to guide a project to success, when lab results are late, everything in your schedule becomes a mess. This makes delays inevitable.
We’re sure this has happened to you before. You’re onsite, waiting to hear from the lab. The last concrete placement was done three days ago, and you’re certain the slab has reached 75 percent of target compressive strength. However, this information needs to be confirmed before stripping forms or tensioning the slab. The team has gotten as much work done as they can to move the jobsite along but without those test results, the project is at a standstill and minimal work is getting done. This lack of productivity on site can’t be helped, and you have no idea when you’re going to hear from the lab. You’re just hoping the team won’t have to work overtime to make sure the project is finished by the deadline that was promised.
This type of delay is not new. Though you may try to rearrange your schedule to predict when labs will get back to you, this is difficult to determine. More often than not, productivity is completely thrown out the window. Therefore, rather than staying ahead of schedule, you have to find a way to make up for lost time. And because everyone uses labs to test the strength of concrete, what other option is there?
Using wireless maturity sensors to shorten your project schedule
Dexter Construction, the largest civil contractor in Atlantic Canada, turned to wireless maturity sensors to test concrete strength onsite and reduce their reliance on third-party labs. During the construction of a large wharf, extreme temperature fluctuations meant that the team had to finish the project before the quality of their structure could be affected. They used 80 sensors in total, embedding three devices per 10-foot wall. This helped them accurately track concrete curing as the project progressed.
Cylinder break tests were used solely on day 28 to confirm 90 percent-plus strength results for acceptance purposes. This eliminated the extra costs of having a consultant visit the jobsite to test cylinder specimens on day-three or day-seven.
“Typically, we have three field-cured cylinders and now, we only have one—every second or third pour,” says Sheldon Roach, Dexter Construction quality control general manager.
As a result, the team was able to save two days per placement.
Wireless maturity sensors allow you to monitor the strength of your concrete directly onsite, according to the maturity method, as per ASTM C1074. This method is the most commonly used approach to reduce or eliminate the number of break tests needed to measure the strength of your in-place concrete and still obtain accurate data. The sensors are fully embedded in the concrete (secured on the rebar) before placement. Using a wireless connection, temperature and strength data is sent to your mobile device via an app and updated in real time every 15 minutes. This means your time isn’t wasted onsite waiting for data from an outsourced lab.
With wireless maturity sensors, such as SmartRock, you’re notified immediately when your in-place concrete has reached 75 percent compressive strength, whether it’s in 12 hours, two and a half days, or even five days. Workers can then take action right away. Ditching early and unnecessary break tests in order to get to the next steps in the construction process faster is the ultimate goal. With this method, not only will you meet your project deadlines, you will also save days in your schedule that would normally be spent waiting on lab results.
Editor’s Note: This article was contributed by Giatec Scientific Inc.