When it comes to testing concrete during placement, the most commonly used method for evaluating strength is the break test. Break tests require concrete sample cylinders to be subjected to high amounts of pressure in order to assess the material’s compressive strength. Although this test method is widely accepted, results found in the laboratory are often not representative of the in-situ element. Curing conditions, the size of the cylinders compared to the onsite concrete element, and transportation to the laboratory of field-cured specimens are all factors which can skew the setting, hardening and strength performance of the cylindrical concrete samples in comparison to the actual structural elements made from the same concrete material.
Technological advancements in the area of online concrete monitoring have made it possible to obtain in-place strength data faster, without performing break tests. In particular, SmartRock®, the most widely used wire-free concrete sensor in the world, helps construction companies build structures faster, more safely, and more efficiently. These user-friendly sensors are easily installed in the formwork (on the rebar) before pouring to continuously monitor the in-situ temperature and maturity of concrete, according to the ASTM C1074, Standard Practice for Estimating Concrete Strength by the Maturity Method.
This concrete maturity formula represents the progression of curing and hardening by measuring temperature, time, and correlating that to strength gain. Once installed, the embedded sensor is connected to any smartphone device via Bluetooth where data results are downloaded and analyzed automatically onsite using the free SmartRock® app (available for both Android/iOS mobile devices).The ability to fully embed these maturity meters within the formwork and obtain compressive strength testing results on the jobsite in real-time eliminates the need to transport samples to a laboratory and thus reduces the margin for error.
The Benefits of SmartRock® Wireless Sensors
By providing real-time data regarding your in-situ concrete, contractors and engineers obtain accurate predictive data on the temperature and strength of their concrete elements (including slabs, beams and foundations) which is updated every 15 minutes. With Giatec 360, an online concrete testing and reporting dashboard, and a SmartRock® mobile app add-on, users can manage data access levels to this information based on project role and generate PDF/CSV reports for distribution. This allows team members to eliminate guesswork and make timely and informed decisions regarding when to proceed to the next steps in a project, such as formwork removal or post-tensioning. In this way, workers have confidence in the quality of their structures and will not act prematurely by moving onto the next steps of a project before optimal results have been obtained, which could result in concrete cracking and reduce the overall strength of the structure.
Eliminating the use of break tests and switching to wire-free concrete strength testing onsite saves significant time on a project schedule. With break tests, as data is gathered through the casting and analysis of cylinders, it takes time to extract the specimen, send the samples to the lab, and retrieve results, often leading to half-a-day to a day of delay. With embedded wireless sensors, all of the information is gathered and logged onto a smart device in real-time, without interruption. Therefore, when a pour has reached 75% of its target compressive strength, team members are notified immediately. This reduces, and even eliminates, the need for break tests entirely, which Gilchrist Construction in Alexandria, LA found during the construction of a major bridge project. By avoiding the wait for early break test results, Project Manager Frank Maury estimated that the SmartRock® sensors saved his team 3 to 4 months on the entirety of the project.
SmartRock® sensors also save significant project costs. In a typical 40-storey high-rise concrete structure, 200 maturity meters are needed for real-time strength monitoring. Each wireless sensor helps save approximately 60 minutes spent on installation and data analysis. If the data from each sensor is collected on three separate occasions by a technician, with an hourly cost of $50, the total labor cost savings would be around $23,300. In addition, costs are significantly reduced due to the use of the maturity method which does not require any break tests. This alone accounts for $30K to $50K in savings, not including the potential for unexpected delays which often results in additional expenses from upwards of $15,000 per day, even more significant cost saving in financing associated with the early project completion.
These benefits are evident in the thousands of projects worldwide that use SmartRock® wireless sensors onsite. In Ottawa, Claridge Homes, with Bellai Brothers Construction Ltd., has utilized Tomlinson Group, as a Giatec SmartRock® Plus partner, to implement these devices in the construction of the Claridge Icon building.
The construction of this building marks the official debut of one of Canada’s most preeminent architectural firms in Ottawa: Hariri Pontarini. The building, located on Preston street, will be a 45-storey tower with parking, retail commercial space, and 320 condos. Workers are currently pouring the 27th floor and expect to have the project finished by April 2020, making it the tallest building in Ottawa. SmartRock® sensors have been installed on every floor during the construction of the Icon building. These embedded devices are being used onsite to confirm strength measurements of in-situ concrete obtained with the use of CIPPOC (cast-in-place-punch-out cylncore). This allows workers to ensure that the information collected is reliable. Join the 6,000 construction managers and site superinterdents every month who are getting access to accurate real-time maturity and temperature data by contacting Giatec at www.giatec.ca or +1 (877) 497-6278.
Note: This article was originally published in the OCA’s Construction Comment Magazine. Check out their latest issue: