Concrete Sensors FAQs

What is maturity and why should I monitor the maturity (gain of compressive strength) of my jobsite concrete?

Hilti Concrete Sensors helps enable contractors to monitor the strength of jobsite concrete in real-time.  When concrete ingredients are mixed with water, the mixture begins to set and gain compressive strength, also known as “curing”. The compressive strength is typically measured in either pounds per square inch (PSI) or megapascals (MPa). The warmer the ambient conditions, the faster it will gain strength.  The cooler the ambient conditions, the slower it will gain strength.  The term “maturity” refers to strength gained over a period of time. The industry standard cure time to reach the minimum design strength is 28 days.  For cast-in-place concrete on a jobsite, it can be beneficial to monitor the strength, not only to help ensure proper curing, but also to schedule work as efficiently as possible.  For any strength data reported in the Hilti Concrete Sensors software, it’s the discretion of the customer and appropriate project stakeholders to make decisions for the project based on this information.

Why should I monitor the temperature of my jobsite concrete?

Hilti Concrete Sensors enables contractors to monitor the temperature of jobsite concrete in real-time.  Monitoring internal concrete curing temperature (and temperature differentials between multiple points within the concrete) can help ensure proper curing and achievement of the minimum design strength. It also helps ensure compliance with building code, specifications, industry standards and thermal control plans. Thermal control plans are guidelines for contractors to execute proper curing and are typically written by an engineer.  One example of an industry standard contractors must comply with, is ACI 306R (Cold Weather), requiring them to manage the curing process in such a way that the internal concrete curing temperature stays within certain thresholds.  Another example is ACI 207.1 / ACI 116 (Mass Concrete) which requires contractors to manage the curing process for extra thick (typically 3+ feet) concrete in such a way to prevent the temperature differential from center to surface from exceeding a specified threshold and to prevent the center temperature from exceeding a specified threshold. Management of the mass concrete curing process might include a specialized mix design, cooling the interior of the concrete or warming the exterior of the concrete. Hilti Concrete Sensors record and store a temperature datapoint every 15 minutes which is used for the temperature reports/alerts and for calculating the strength data as referenced above.

What is Relative Humidity and why should I monitor it in my in-place concrete?

Hilti Concrete Sensors enables contractors to monitor the Relative Humidity (RH%) of jobsite concrete in real-time.  RH% is a critical measurement for ensuring proper adhesion of finishes to the surface of concrete (i.e. flooring, roofing, paints, coatings). Contractors can benefit from monitoring RH% during the drying process (which typically takes several months) in order to more efficiently schedule the respective subcontractor’s independent test and application of finishes, but also to retain supplemental data in case of the need for conflict resolution if an application fails.  

The concrete drying process:  

  • The rate at which concrete loses moisture is affected by many variables, including but not limited to temperature, ambient humidity, exposure to elements, air flow, slab thickness, mix design, and one versus two-sided evaporation
  • The RH% of freshly poured concrete is 100%
  • For concrete that remains exposed to the elements, the RH% will remain at 100% indefinitely
  • When concrete is permanently protected from the elements and in climate-controlled conditions, it may take 10+ months for the sensors to report a drop from 100%

Besides monitoring maturity (gain of concrete strength) Hilti’s Concrete Sensors HCS TH1 record RH% and temperature sample pairs (1 RH% plus 1 Temp reading) every 6 hours: 4 sample pairs per day.

Why is “concrete calibration” needed for maturity (gain of concrete strength) monitoring?

Concrete gains strength at various rates depending on the mix design and curing temperatures. 

For temperatures: the hotter the curing conditions, the faster strength will be gained; the colder the curing conditions, the slower strength will be gained.

The key to accurate monitoring of jobsite concrete and estimating its strength is testing the mix design and leveraging the maturity methods in ASTM C1074 to create the most accurate maturity curve.  Due to the wide range of field temperatures and mix design variations, simply guessing the mix design curing temperature sensitivity without testing is not accurate for most field situations. 

The concrete calibration (maturity testing) for your specific concrete mix will be done in the Hilti in-house test lab and is the basis for the maturity (gain of strength monitoring) with Hilti Concrete Sensors.

What is the “concrete calibration” (maturity testing) process?

Hilti works directly with the customer and the project’s concrete supplier to coordinate shipment of a pallet of materials/admixtures to the Hilti in-house lab that is based on the mix design(s) approved by the Engineer of Record.  Once the pallet is received by Hilti’s lab team and your mix design(s) testing begins, it takes about 30 days to add the mix to the in-app library and then maturity monitoring of your jobsite concrete can begin.  

The Ultimate Lab Testing service consists of approximately (20) 4”x8” cylinders cured in a room-temp water bath and approximately (100) 2” mortar cubes cured in water baths of four different temperatures.  Ultimate Lab Testing follows ASTM C1074 Equivalent Age function, but rather than testing at the required minimum of three temperatures, Hilti decided on four in order to provide increased accuracy.

The Premium Lab Testing service consists of approximately (20) 4”x8” cylinders cured in a room-temp water bath and approximately (25) 2” mortar cubes cured in in a room-temp water bath.  Premium Lab Testing follows ASTM C1074 Nurse-Saul function, which only requires testing at one temperature but isn’t as accurate as following the Equivalent Age function, especially when curing temperatures of the in-place concrete vary over a wider range

What types of concrete mix designs can I monitor?

All types of concrete mix designs can be tested (calibrated) per ASTM C1074, which is a precondition for the maturity (strength) monitoring of the concrete with Hilti Concrete Sensors.

What types of concrete elements can I monitor?

All types of structural and nonstructural concrete elements can be monitored using Hilti Concrete Sensors, including but not limited to slabs, walls, columns, beams, foundations, roads, etc.

What Return on Investment (ROI) can I expect?

Hilti Concrete Sensors provide accurate real time information about your jobsite concrete helping you make faster and better decisions and get your projects done ahead of schedule and under budget.  

What would it mean for you if you could save up to one day per pour on your projects? Hilti Concrete Sensors enable you to monitor the jobsite strength of your concrete in real-time, helping your jobs move faster:

  • Remove formwork sooner
  • Stress post-tensioned slabs earlier

Monitoring the temperature of your jobsite concrete with Hilti wireless concrete sensors and customized automatic alerts empower you to take early actions before a problem forms, protecting your concrete from damage. This helps you stay compliant with thermal control plans and potentially reduce heating costs in cold weather.

Please contact Hilti for a Concrete Sensor demo or consultation. 

Which sensor models do I need?

The Hilti Concrete Sensor sales program is designed to best meet the needs of your specific application (type of monitoring), and offers a variety of different models. Please contact Hilti for a Concrete Sensor demo or consultation.

How do I order Hilti Concrete Sensors?

Hilti Concrete Sensors can be conveniently ordered through our different sales channels. If you need assistance selecting the right sensor model or have other questions, please don’t hesitate to contact Hilti.

What is the lead time to receive sensors?

Standard versions of Hilti Concrete Sensors are in stock and readily available (shop online). Cabled versions for custom monitoring depths are available upon request with special order; please contact Hilti for lead time.

How do I install the sensors?

Hilti sensors should be attached to the reinforcement with the included zip-ties at a maximum depth of 6 inches below the concrete surface. Follow the instructions for use or watch the how-to-video. If you need additional support, please contact Hilti.

How deep can Hilti Concrete Sensors be installed?

Hilti Concrete Sensors consist of the sensor and a transmitter for the wireless transfer of the monitoring data. The standard Hilti Concrete Sensors HCS TH1, HCS T1 and HCS T2 with the sensor and transmitter integrated in one housing can be installed up to 6 inches below the concrete surface. The standard cabled versions HCS T1-Bx and HCS T2-Bx allow base module to be installed up to 6 inches but the sensor can be installed up to 15 feet deep. Cabled versions with custom installation depths up to 100 feet are available upon request with special order.

What data collection option is right for me (Bluetooth or Long Range), and why?

Long Range data collection with HCS T2 concrete sensors and HCS Gateway is fully automated and sensors can be accessed anytime 24/7 from virtually anywhere without having to be on the jobsite. This option is very efficient and ideal for projects that require continuous monitoring with real-time alerts, such as mass concrete or cold weather. The required HCS Gateway can be rented from Hilti for the monitoring period.

Bluetooth data collection is the lower cost option and requires at least 1 person onsite to connect to sensors.  This option is efficient and ideal for projects that don’t require continuous off-hours monitoring.

If you are unsure what is the better option for you, please contact Hilti for a demo or consultation.

What types of devices and operating systems does the Hilti Concrete Sensor software (mobile app) support?

The Hilti Concrete Sensor mobile app is available for free download for iPhones and Android phones.

Download iOS app

Download Android app

How do I get the software application?

Simply search “Hilti concrete sensors” in the Apple App Store for iOS and in Google Play for Android.

How do I review or share sensor data?

Data can be viewed directly on your mobile device with the Concrete Sensor mobile app.  It can also be exported as raw data or full in-color PDF graphs/reports.  You may invite others to join the project and review data from their own devices at no charge.  There is also an option to set up alerts (push notifications) per device for Strength (maturity), Maximum Temperature, Minimum Temperature, RH% and Temperature Differentials.

Why can't I connect to a sensor?

Bluetooth:  Ensure Bluetooth is turned on in your mobile device. Ensure there are no obstructions between your mobile device and the location of the sensor in the concrete (standing water/ice/snow, equipment, materials, formwork, etc.).  Try removing protective case from your mobile device.  Try moving slowly in small circles over the sensor location.

Long Range:  Ensure HCS Gateway is added to the project.  Ensure there is consistent power to the HCS Gateway.  Ensure gateway is showing a green checkmark in the mobile app.   

Why can't I invite collaborators?

For iOS the Hilti Concrete Sensor mobile app will try to connect to your email via the default email app – if you are using a different app for email, please copy the link that appears on screen and paste it into an email or text to the intended collaborator(s).

Why does my data look wrong?

Check whether the pour date/time of your pour in the mobile app is correct.  If not, go to ‘Edit Pour’ and adjust accordingly. If something still doesn’t look right, please contact Hilti for support.

Why am I missing data?

Check to ensure your mobile device has an internet connection (mobile network and/or WiFi) – it should sync automatically.  If something still seems to be missing, please contact Hilti for support.

Why isn't my HCS Gateway showing a green checkmark in the mobile app, indicating it's online?

Ensure the gateway is added to the project.  Ensure there is consistent power to the gateway. If there is still no green checkmark showing in the mobile app, please contact Hilti for support.

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