Maturity Method

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06/18/2024 Added

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Maturity Method

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[00:00:00.252](upbeat music)
[00:00:09.510]The maturity method concept has been around
[00:00:11.910]since the 1950s, but it has been more recently
[00:00:15.090]that Nebraska fully implemented its use.
[00:00:18.150]The Nebraska Department of Roads has used this method
[00:00:21.180]for acceptance testing since 2001.
[00:00:24.450]The maturity method is a simple technique
[00:00:26.940]for predicting concrete strength
[00:00:29.040]in place of conventional cylinders
[00:00:31.050]based on the measurement of time and temperature history.
[00:00:35.160]Prior to construction, a relationship is established
[00:00:38.280]between mixed strength and time temperature history
[00:00:41.250]to estimate reliable realtime in situ strength.
[00:00:46.050]This maturity method monitoring training video
[00:00:48.750]will cover the basic principles, terminology,
[00:00:51.630]and field applications of the maturity method
[00:00:54.660]and the equipment and techniques
[00:00:56.580]needed to perform the maturity testing.
[00:01:00.060]The training follows ASTM C1074 standard practice
[00:01:05.070]for estimating concrete strength
[00:01:07.050]by the maturity method.
[00:01:09.420]Keep in mind that this training does not address all issues
[00:01:12.780]that may develop during construction.
[00:01:17.820]The contractor may request the use
[00:01:19.830]of the maturity method on a project basis.
[00:01:23.130]The request shall be made in writing to the materials
[00:01:25.890]and research engineer or certified consultant.
[00:01:29.340]Materials and research division
[00:01:30.810]will establish the relationship between mixed strength
[00:01:33.780]and time temperature history
[00:01:35.310]to estimate real time in situ strength.
[00:01:38.310]This relationship is represented by generating a curve,
[00:01:41.790]which is then submitted to the project engineer
[00:01:44.460]and field inspectors.
[00:01:46.950]The inspectors will use
[00:01:48.540]the minimum target time temperature factor
[00:01:50.940]developed for the maturity curve
[00:01:52.740]for structure form removal, opening,
[00:01:55.410]and/or acceptance design compressive strength.
[00:01:59.460]The target time temperature factor value shown
[00:02:02.310]represents an estimated opening concrete strength
[00:02:05.490]of 3,000 PSI for this concrete mix design.
[00:02:09.930]This will be of significant use
[00:02:11.880]to the project field inspector during the monitoring
[00:02:14.850]of the daily concrete placement.
[00:02:18.930]The maturity method can be conducted
[00:02:20.970]using minimum equipment.
[00:02:23.550]Some of the required tools and equipment
[00:02:25.650]needed to perform the maturity monitoring are shown.
[00:02:29.490]A digital thermometer, maturity meter,
[00:02:34.020]type T thermocouple wire with type T mini connectors,
[00:02:37.980]and tools such as tape, a screwdriver, wire snips,
[00:02:42.240]paint, ribbons, a stake, and hammer.
[00:02:49.260]The preparation of the thermocouple wire
[00:02:51.660]is extremely important
[00:02:52.980]for successfully acquiring temperature data.
[00:02:56.490]This is a correctly prepared mini connector end wire.
[00:02:59.970]The wires are attached to the correct screws,
[00:03:02.520]nickel to nickel and copper to copper.
[00:03:06.120]When the wires are connected to the incorrect screws,
[00:03:09.030]it will cause an inaccurate temperature reading.
[00:03:12.240]This shows an incorrect wire assembly
[00:03:14.280]due to the wires being too long, causing the wires to touch.
[00:03:17.910]This will also give an inaccurate temperature reading.
[00:03:22.200]The temperature sensing wire end
[00:03:24.030]requires proper preparation.
[00:03:26.250]Strip off approximately one inch of the wire insulation.
[00:03:30.270]Next, twist the copper and nickel wires together
[00:03:33.420]to form a closed circuit.
[00:03:35.580]The last step is to snip the wire off
[00:03:37.590]so there is approximately half an inch of wire exposed.
[00:03:41.460]The most common failure occurs at this point.
[00:03:44.430]One of the wires may break during the twisting of the wire.
[00:03:48.600]A prepared thermocouple wire length will depend
[00:03:51.330]on the application.
[00:03:53.010]A thermocouple wire may be prepared longer
[00:03:55.380]than would normally be needed for a one-time use
[00:03:58.230]to allow for multiple uses of the wire.
[00:04:03.240]Two maturity installation applications
[00:04:05.790]will be presented in this training.
[00:04:08.400]One application will cover pavement repairs
[00:04:11.130]and miscellaneous placements,
[00:04:13.590]and the second application will cover
[00:04:15.390]mainline paving operations and structures.
[00:04:24.780]The first step is to determine where the thermocouple wires
[00:04:28.140]and connectors will be placed.
[00:04:30.120]It is recommended that you place your wires
[00:04:32.280]at the beginning of the day's placement.
[00:04:34.650]It is suggested to set up as far away from traffic
[00:04:37.650]and construction equipment as possible.
[00:04:40.320]It is also recommended to install two thermocouple wires
[00:04:43.770]to monitor the concrete placement.
[00:04:45.900]Both wires may be installed at the same location
[00:04:48.660]at the beginning of the day's placement.
[00:04:51.150]Another option is to place one wire at the beginning
[00:04:54.090]and one at the end of the day's placement.
[00:04:56.970]Two thermocouple wires are always recommended
[00:04:59.550]in case of wire malfunction.
[00:05:02.940]The most common installation method is
[00:05:05.040]by attaching thermocouple wires by tying or taping them
[00:05:08.550]to an existing tie bar or dowel bar in the removal area.
[00:05:13.170]Run the wires onto the adjacent slab of the removal area.
[00:05:17.490]Test the wires for conductivity
[00:05:19.320]by taking a temperature reading with a monitoring device.
[00:05:23.520]Once the wires have been tested, it is recommended
[00:05:26.310]to take measures to protect the wires
[00:05:28.440]and connectors from being disturbed.
[00:05:31.560]This may be accomplished in several ways, not limited
[00:05:34.560]to the examples shown here.
[00:05:37.410]You can mark your locations with paint.
[00:05:41.400]You can attach ribbons to the wires.
[00:05:45.210]You may use a cone to protect your wires,
[00:05:49.920]or you may also place your wires in a cylinder mold.
[00:05:55.800]To install thermocouple where steel bars do not exist,
[00:05:59.280]you should place a stake
[00:06:00.840]or rod at a minimum of one foot from the edge
[00:06:03.600]of the existing slab
[00:06:05.070]and at approximately mid depth
[00:06:06.990]for the concrete slab placement.
[00:06:10.650]Next, attach thermocouple wires by taping them
[00:06:13.860]to the stake or rod.
[00:06:16.050]Protect the wires when possible
[00:06:18.000]by burying them in the subgrade
[00:06:20.100]and run the remaining wire onto the adjacent slab.
[00:06:25.020]Test your wire connectors for conductivity
[00:06:27.720]and take the necessary steps
[00:06:29.190]to protect the wire from being disturbed,
[00:06:31.170]as shown previously.
[00:06:38.070]Another application where the maturity method is utilized is
[00:06:41.610]for mainline slip form paving operations.
[00:06:45.330]Thermocouple wires can be used at any point
[00:06:47.910]along the pavement slab.
[00:06:50.520]A minimum of two wires shall be used
[00:06:52.800]in each day's placement.
[00:06:55.440]It has been found that concrete does not gain strength
[00:06:58.320]at the same rate.
[00:06:59.820]Therefore, it is recommended installing thermocouple wires
[00:07:02.970]at the beginning and at the end of the day's placement,
[00:07:07.170]and optionally installing one
[00:07:09.270]in the middle of the day's placement.
[00:07:11.880]After the location has been determined, mark the area.
[00:07:15.600]Next, by using a heavy gauge wire
[00:07:18.000]penetrate the side of the slab
[00:07:20.700]to a minimum of six inches at approximately mid depth.
[00:07:25.410]One method to install the wire into the slab is
[00:07:28.200]by placing the wire over the tip of the heavy gauge wire.
[00:07:31.980]Next, proceed to insert the thermocouple wire
[00:07:34.860]into the existing location.
[00:07:37.050]Then, utilizing fresh concrete,
[00:07:39.180]fill the void around the wire
[00:07:41.940]and proceed in checking the conductivity of the wire
[00:07:44.790]by taking a temperature reading with a monitoring device.
[00:07:48.360]Make sure to record the date and the time
[00:07:50.820]that the initial temperature was taken at each location.
[00:07:54.930]After the data is collected, it is recommended
[00:07:57.570]that measures be taken to protect the wires.
[00:08:02.280]The setup and monitoring procedures
[00:08:04.140]for structures are similar to those
[00:08:06.030]for slip form paving operations.
[00:08:09.450]It is recommended using a minimum of two thermocouple wires
[00:08:12.990]placed in the structure
[00:08:15.390]with a minimum concrete coverage of two and one half inches.
[00:08:19.890]The placement of the wires into the structure is
[00:08:22.680]at the discretion of the project engineer.
[00:08:26.250]Test the wires for conductivity
[00:08:28.170]by taking a temperature reading with a monitoring device.
[00:08:32.130]Once the wires are tested, it is recommended
[00:08:34.800]to take measures to protect the wires
[00:08:36.960]and connectors from being disturbed.
[00:08:46.350]The time temperature factor for concrete maturity method
[00:08:49.650]can be performed using two procedures,
[00:08:52.980]a concrete maturity meter
[00:08:55.380]or a digital thermometer.
[00:08:57.900]When using a concrete maturity meter,
[00:09:00.360]the time temperature factor value can be read
[00:09:03.150]from the meter in real time.
[00:09:05.820]The alternative method is taking the temperature readings
[00:09:08.730]using a digital thermometer.
[00:09:10.740]These temperature readings shall be taken in degrees Celsius
[00:09:14.340]and are used in calculating
[00:09:16.140]the time temperature factor value.
[00:09:20.160]The Nurse-Saul equation is used by NDOR
[00:09:23.250]for calculating the time temperature factor value by hand.
[00:09:27.960]The time temperature factor at age,
[00:09:30.090]which the calculation is performed,
[00:09:33.060]the average temperature using the initial temperature
[00:09:35.970]and the elapsed time temperature reading,
[00:09:39.270]the datum temperature, negative 10 degrees Celsius.
[00:09:42.600]This is the temperature at which concrete
[00:09:44.700]is no longer gaining strength,
[00:09:47.730]the time interval, which is represented in hours.
[00:09:52.950]This is an example problem
[00:09:54.540]calculating the time temperature factor value
[00:09:57.000]using the Nurse-Saul equation.
[00:09:59.550]inspectors take an initial temperature reading
[00:10:02.010]of 19.7 degrees Celsius.
[00:10:04.770]The temperature reading should be rounded
[00:10:06.570]to the nearest hole number 20 degrees Celsius.
[00:10:10.590]The initial temperature reading shall be taken
[00:10:12.690]within 10 minutes after the concrete has been placed.
[00:10:16.440]In this example, another temperature reading
[00:10:18.720]is taken three hours later at 50 degrees Celsius.
[00:10:23.370]Next, the average temperature is calculated
[00:10:25.920]using the initial temperature and the temperature reading
[00:10:28.530]taken at three hours.
[00:10:30.420]The average temperature calculated is 35 degrees Celsius
[00:10:34.710]and the delta T, the time interval, will be three hours.
[00:10:39.300]Following the Nurse-Saul equation,
[00:10:41.190]you must subtract the datum temperature
[00:10:43.440]from the average temperature of 35 degrees Celsius.
[00:10:46.680]The datum temperature used in this region of the country
[00:10:49.530]is negative 10 degrees Celsius.
[00:10:51.780]Always remember, subtracting a negative number
[00:10:54.660]is the same as adding a positive number.
[00:10:58.110]The result is 45 degrees Celsius,
[00:11:02.310]which is then multiplied by the time interval of three hours
[00:11:06.750]to give a time temperature factor value
[00:11:09.090]of 135 celsius per hour.
[00:11:12.780]This time, temperature factor value calculated must meet
[00:11:16.140]or exceed the target time temperature factor value
[00:11:19.020]from the maturity curve, which was generated
[00:11:21.450]for this specific mix design.
[00:11:24.900]An Excel spreadsheet may be used
[00:11:26.730]to calculate the time temperature factor value.
[00:11:30.120]This spreadsheet is used primarily for paving
[00:11:32.970]and structure applications,
[00:11:34.410]but may also be used for pavement repairs.
[00:11:38.460]Enter the data into the highlighted data field.
[00:11:41.610]The spreadsheet will calculate the time temperature factor
[00:11:44.580]at age and the sum time temperature factor
[00:11:48.210]for each individual date of data entry,
[00:11:51.000]providing the most current time temperature value
[00:11:54.090]for the last date of data entry.
[00:11:57.450]Contact the PCC laboratory
[00:11:59.790]for questions about testing procedures.
[00:12:02.594](upbeat music)
[00:12:09.000]Data acquired for determining the opening
[00:12:11.490]and acceptance of concrete placements
[00:12:13.620]shall be recorded into Site Manager.
[00:12:17.100]The Department of Roads requires
[00:12:19.080]that field personnel will be responsible
[00:12:21.360]for maintaining electronic documentation
[00:12:23.700]in the Site Manager application.
[00:12:26.490]There are two templates for entering the acquired data
[00:12:29.220]in Site Manager.
[00:12:30.450]Choose the correct template for the concrete application.
[00:12:34.500]This template in Site Manager
[00:12:36.270]represents the main line pavement
[00:12:38.100]structure maturity report.
[00:12:40.230]The intended use is to determine when to open a section
[00:12:43.530]of pavement or form removal or loading of a structure.
[00:12:47.460]Currently, NDOR does not use the maturity method
[00:12:50.610]for acceptance of concrete
[00:12:52.320]or mainline pavement and structures.
[00:12:56.040]This template represents
[00:12:57.360]the Pavement Repair Maturity Summary Report
[00:13:00.360]and is used for the determination of opening
[00:13:03.180]and acceptance of concrete pavement repairs.
[00:13:06.360]The Nebraska Department of Roads uses the maturity method
[00:13:09.630]as an option to test cylinders for the acceptance
[00:13:12.450]of concrete pavement repairs.
[00:13:16.620]This concludes the Maturity Method
[00:13:18.480]Field Monitoring Training.
[00:13:20.400]There will now be a short quiz covering
[00:13:22.470]what you have learned.
[00:13:24.039](upbeat music continues)

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Maturity Method

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