Concept

What It Is?

Smart Sensors consists a rugged, waterproof, wireless sensor/logger for monitoring the temperature of concrete from fresh stage to hardened stage. It can be placed in the concrete formwork at the time of casting to monitor the temperature of concrete on site. The continuous measurements are recorded and can be downloaded at any time during the concrete setting and hardening stages.

The continuous monitoring of concrete temperature can be used as a QC/QA procedure as well as maturity-based strength estimation of concrete. The field monitoring of concrete temperature and strength using maturity meter can also help with optimizing the formwork removal time, application of load on the structure, stressing of post-tensioned cables, as well as opening traffic on concrete pavement.

Smart Sensors

How It Is Used?

  • Before constuction begins, a set of test specimens are cast to obtain Calibration Curve for the specific mix design
  • Maturity sensors are embedded in a separate specimen which measures maturity of concrete (°C-hours)
  • Specimens without sensors are used to find compressive strength at standard intervals of 1, 3, 7, 14 and 28 days using conventional cube test methodology
  • Maturity values (from sensors) are co-related with the compressive strength values and its graphical representation is as shown in the figure

Application

Smart Sensors monitors the temperature profile of fresh and hardened concrete.

  • Roadway Paving – Know exactly when to open to traffic
  • Bridges – Know when to strip forms, remove shoring and allow loads on the structure
  • Midrise Building – Know when to strip forms, remove shoring/reshoring and allow loads structure on the slabs, columns or shear walls
  • High-rise Building – Monitor the strength gain in columns when high strength concrete is used
  • Mass Pours – Use real time strength information to determine safe temperature gradients.
  • Precast Operations – Monitor element strengths to optimize processes and timing of shipments.
  • Moisture protection — Optimize curing operations
  • Post Tensioning – Optimize time-cycle of post-tensioning activities such as stressing
  • Form Stripping – Optimize the timing of form stripping operations

Features

  • Wireless technology
  • Ruggedized and waterproof design
  • Real-time on-site data of Temperature, Maturity & Strength
  • No waiting for 1, 3, 7, 14 or 28 day breaks
  • Continuous measurement and recording of temperature
  • Easy activation through tying the wires together
  • Extended temperature sensor for deep elements and mass concrete
  • Maturity calibration curve database
  • Long battery life
  • Dedicated software for tablet/smart phones
  • Easy data sharing and export in PDF and CSV file

Benefits

  • Real time data of poured concrete
  • Early-age strength estimation
  • Optimizing concrete mix designs
  • “Back-up” for faulty test samples

Comparison

Parameters Conventional Testing Smart Sensor
Frequency For 100m3 of concrete, minimum 30 cube specimen required (As Per IS 456). PTSI recommends two sensor for 100m3 of concrete.
Curing Continuous curing is required to maintain the temperature of the concrete element as well as w/c ratio. Temperature data are available at each 30 minute interval, which helps to provide adequate curing needed.
Securing Cube specimen should be accurate in size. Not required.
Preparing Concrete cube specimen should be prepared with controlled monitoring under supervision of engineer as per IS:516. Not required. Once installed it is ready to use.
Testing Concrete cube specimen are taken for testing on 3rd, 7th and 28th day to external labs. Gives real time data of temperature (°C), maturity (°C — Hours) and strength (MPa)
Timing Work is being delayed, due to waiting for the results of 3rd, 7th and 28th day. Work can be planned after getting real time concrete strength data collected in 24 hours.
Record Reports of tests conducted on 3rd, 7th and 28th day. Sensor gives data of all 30 days at every interval of 30 minutes.
Workmanship Skilled manpower is needed as per IS:516 to follow the method of measuring strength of concrete. Not Required.
Prediction No prediction until breakage of specimens Prediction of 28 days strength can be derived.
Costing Less Expensive & less information Little Expensive, but hassle free. Overall cost effective.
Construction flow Prediction becomes difficult due to limited number of readings obtained which makes it impossible to pre-plan the work-flow. Data can be extrapolated for strength prediction, which helps in pre-planning of work schedule.

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