1、Standard Method of Test for Estimating the Strength of Concrete in Transportation Construction by Maturity Tests AASHTO Designation: T 325-04 (2016) Release: Group 1 (April 2016) American Association of State Highway and Transportation Officials 444 North Capitol Street N.W., Suite 249 Washington, D
2、.C. 20001 TS-3b T 325-1 AASHTO Standard Method of Test for Estimating the Strength of Concrete in Transportation Construction by Maturity Tests AASHTO Designation: T 325-04 (2016) Release: Group 1 (April 2016) 1. SCOPE 1.1. This standard provides procedures for estimating concrete strength in roads,
3、 bridges, and other transportation structures through the use of a maturity index. 1.2. This standard requires determination of the strengthmaturity relationship of the approved concrete job mix in the laboratory and determination of the temperature history subsequent to placement in the field. 1.3.
4、 This standard may involve hazardous materials, operations, and equipment. It does not purport to address all of the safety concerns associated with its use. It is the responsibility of the user of this standard to consult and establish appropriate safety and health practices and determine the appli
5、cability of regulatory limitations prior to use. 2. REFERENCED DOCUMENTS 2.1. AASHTO Standards: R 9, Acceptance Sampling Plans for Highway Construction T 276, Measuring Early-Age Compression Strength and Projecting Later-Age Strength 2.2. ASTM Standards: C1074, Standard Practice for Estimating Concr
6、ete Strength by the Maturity Method D3665, Standard Practice for Random Sampling of Construction Materials E105, Standard Practice for Probability Sampling of Materials E122, Standard Practice for Calculating Sample Size to Estimate, With Specified Precision, the Average for a Characteristic of a Lo
7、t or Process E141, Standard Practice for Acceptance of Evidence Based on the Results of Probability Sampling 3. TERMINOLOGY 3.1. Definitions: 3.1.1. equivalent agethe number of days or hours at a specified temperature that would equal the maturity of a concrete at the actual age and temperature hist
8、ory that has been measured. 3.1.2. maturitythe extent of development of concrete properties that are dependent on cement hydration and pozzolanic reactions. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable la
9、w.TS-3b T 325-2 AASHTO 3.1.3. maturity functiona mathematical expression that converts the temperature history of concrete to an index, which indicates its maturity. 3.1.4. maturity indexan index, calculated by using a maturity function, which can be used as an indicator of strength development in c
10、oncrete. 3.1.5. strengthmaturity relationshipan empirical relationship between concrete strength and its maturity index, usually determined by comparing the strength of concrete cylinders, made from a specific concrete mix, to their maturity index at time of strength testing. 4. SIGNIFICANCE AND USE
11、 4.1. This standard can be used to estimate the strength of concrete placed in pavements and structures. These estimates provide guidance useful in making decisions concerning opening to traffic, form removal, post tensioning, termination of curing procedures, and initiation of strength tests on the
12、 in-place concrete, such as coring and pullout tests. 4.2. The most critical limitations of the procedures presented are (1) batching or placement errors that are not detected, (2) curing errors other than those that affect temperature that are not detected, and (3) the actual strength of the concre
13、te that is not measured. Note 1Concrete must be cured in a condition that supports cement hydration/pozzolanic reactions. 4.3. This standard provides technical personnel with a coordinated procedure for (1) developing a strengthmaturity relationship for the approved concrete job mix in the laborator
14、y, (2) determining the temperature history of the in-place concrete, (3) determining the maturity index of the in-place concrete, and (4) using the strengthmaturity relationship and the maturity index to estimate the strength of the in-place concrete. 5. APPARATUS 5.1. Laboratory Requirements: 5.1.1
15、. Personal safety equipment required by the laboratory or OSHA, or both, for work in the laboratory concrete mixing and testing areas. 5.1.2. Temperature sensors suitable for embedment in the center of cylindrical concrete test specimens and a device suitable for monitoring and recording the tempera
16、ture. 5.1.3. A computer terminal for input of laboratory test data or a supply of concrete test reports. 5.2. Field Requirements: 5.2.1. Personal safety equipment required by the laboratory/field organization or OSHA, or both, for work in the field concrete placement areas. 5.2.2. Temperature probes
17、/sensors suitable for embedment in the concrete placement. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 325-3 AASHTO 5.2.3. A device suitable for monitoring and recording the temperature of th
18、e concrete. The device may be a system with a computer remote from the job site that reads and logs the probes/sensors through a modem for necessary calculations; a system with a computer at the job site that automatically reads, logs, and makes the necessary calculations; or a system with a device
19、that automatically reads the probe/sensor signals, calculates the maturity index, and digitally displays the data on demand. Note 2Strategic Highway Research Program (SHRP) researchers identified eleven reusable maturity meters and three disposable maturity meters, all commercially available. Seven
20、used the Arrhenius maturity function, six used the Nurse-Saul maturity function, and one used either that was chosen. 6. HAZARDS 6.1. Observe the safety procedures required by the laboratory/field agency or OSHA, or both, for each laboratory and field operation, as applicable. 7. FIELD SAMPLING 7.1.
21、 Select the temperature sampling sites for installing probes/sensors by determining the quantity of concrete that is to be evaluated and dividing the concrete placement into lots that approximate the quantities indicated in Table 1. For the purposes of this standard, the quantity of pavement shall b
22、e estimated in square meters and the quantity of structural concrete shall be estimated in cubic meters. Table 1Minimum Number of Probes/Sensors Required to Be Placed in Each Concrete Lot Structure Component Quantity of Concrete in Lot Number of Probes/Sensors Slabs, beams, and abutment walls 100 m3
23、5 Columns 210 m31 Columns More than 10 m32 Pavement, pavement overlays 1000 m22 Pavement repairs Per repair or per 750 m2, whichever is smaller 2 7.2. Select temperature sampling alternates in the following manner: 7.2.1. When the maturity of all lots is to be determined, use a stratified random sel
24、ection procedure in determining where to place the temperature probes/sensors in each concrete lot to be evaluated, as indicated in Table 1. 7.2.2. When the maturity of only a fraction of the total lots is to be measured, determine the number of lots in accordance with Equation 1: 1 LL FT L= (1) whe
25、re: L1= lots to be randomly chosen, F = fraction of lots to be sampled for maturity testing, T = total number of lots, and LL= last lot placed. 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 325
26、-4 AASHTO 7.2.2.1. Round L1to the next higher whole number. Then randomly select the number of lots, L1, from the available lots, excluding the last lot placed, LL. Add LLto the list of randomly chosen lots scheduled for maturity testing. Finally, use a stratified random selection procedure to deter
27、mine where to place each of the temperature probes/sensors, as indicated in Table 1, in each concrete lot scheduled for evaluation. Note 3Example: If T = 10 and F = 1/8, then L1= 0.25. Rounding to the next higher whole number, L1= 1. Then, excluding the last lot placed, there are (10 LL) = 9 lots fr
28、om which L1is randomly selected. Assume that lot number 4 is the randomly selected lot and that lot number 10 is LL, the last lot placed. Then lots numbered 4 and 10 are scheduled for maturity testing. The purpose for excluding LLfrom the random selection of lots scheduled for testing and then speci
29、fically including LLin the list of lots scheduled for testing is to assure that the lot containing the last concrete placed is one of those evaluated in the maturity testing process. If all other factors are equal, LLwill be the weakest lot at the times likely to be of interest during the constructi
30、on process. A similar approach should be followed with regard to a lot(s) that will be exposed to significantly more adverse curing conditions than other lots under evaluation. Note 4ASTM D3665 contains a table of random numbers, including instructions for use. AASHTO R 9 and ASTM E105, E122, and E1
31、41 contain additional information concerning sampling practices. 8. PREPARATIONS 8.1. Laboratory OperationsPrior to the initiation of the laboratory concrete placement operation, check to ensure that an adequate supply of temperature sensors is available for the scheduled work, and prepare the concr
32、ete temperature monitoring and recording device for attachment to the temperature sensors immediately after they are embedded in the concrete cylinders. 8.2. Field OperationsPrior to the initiation of the field concrete placement operation (1) select which sampling alternate is to be used, (2) check
33、 to ensure that an adequate supply of temperature probes/sensors is available for the scheduled concrete placement, (3) determine the locations at which the temperature probes/sensors will be installed, and (4) prepare the concrete temperature monitoring and recording system for attachment to the te
34、mperature probes/sensors immediately after placement of the concrete lot. 9. STANDARDIZATION 9.1. Verify the calibration of systems used for monitoring the maturity of concrete on a periodic basis. Note 5System verification can be accomplished by placing the temperature probe/sensor in a controlled
35、temperature water bath and recording whether the indicated result agrees with the known temperature of the water bath. Use at least three different temperature points (e.g., 5C, 25C, and 45C). 10. PROCEDURE 10.1. Develop the strengthmaturity relationship for the approved concrete job mix in accordan
36、ce with the StrengthMaturity Relationship section of ASTM C1074. Note 6Other standards that use strengthmaturity relationships include T 276. 10.2. Determine the temperature history of concrete after placement in the field as follows: 2016 by the American Association of State Highway and Transportat
37、ion Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 325-5 AASHTO 10.2.1. Insert the active end of the temperature probe/sensor in the fresh concrete at the predetermined location(s). If the probe/sensor is installed prior to placement of the concrete, tie the sens
38、or wire for reinforcement to prevent displacement during the placement of the concrete. Probes/sensors can be inserted through an open surface of the concrete or through very small holes in forms. 10.2.2. Generally, probes/sensors should be placed 50 to 100 mm from any surface of the concrete placem
39、ent. In a pavement overlay, place probes/sensors at mid-depth. 10.2.3. Protect the wires connecting the probes/sensors to meter locations from construction operations. In critical locations, use duplicate probes/sensors with separated wiring runs. Note 7SHRP research indicated that if a concrete sur
40、face is protected from a high rate of heat loss, the difference in maturity indexes between the center and surface of pavements, bridge decks, and structures 300 mm or less thick is negligible. 10.2.4. Make final maturity system connections with the probes/sensors immediately after concrete placemen
41、t and activate the system. 10.3. After placement of the concrete in the field, determine the maturity index at each probe/sensor location by reading the appropriate channel(s) of the maturity monitoring system. Note 8SHRP researchers recommend that all maturity meters used for highway pavement and s
42、tructures should use the Arrhenius function, because the Arrhenius function is better able to represent the effects of temperature on strength development than the Nurse-Saul function. Meters using the Nurse-Saul function will increasingly produce less accurate estimates of strength gain as the temp
43、erature deviates from the standard temperature used to establish the strengthmaturity relationship. 10.4. Estimate the in-place strength of concrete in the field using the strengthmaturity relationship and the maturity index. 10.4.1. Compare the maturity index determined in Section 10.3 to the stren
44、gthmaturity relationship determined in Section 10.1. The concrete strength value of the strengthmaturity relationship that corresponds to the measured maturity index from a particular probe/sensor location is the estimated concrete strength at that location. 10.4.2. Determine the estimated strength
45、of a concrete lot using Equation 2: ( )1estiniiLXSn=(2) where: SL(est)= estimated strength of the concrete lot, Xi= estimated strength of the concrete at a specific probe/sensor location, i = individual probe/sensor, and n = number of probes/sensors in the concrete lot. 11. REPORT 11.1. Report the f
46、ollowing laboratory information: 11.1.1. Identification of the laboratory and date of testing; 2016 by the American Association of State Highway and Transportation Officials.All rights reserved. Duplication is a violation of applicable law.TS-3b T 325-6 AASHTO 11.1.2. Identification of the concrete
47、job mix used for laboratory tests; 11.1.3. Strength of each test specimen and the average strength of test specimens at each test age; 11.1.4. Maturity index for each instrumented test specimen and the average maturity index for the instrumented specimens at each test age; 11.1.5. A graph of the ave
48、rage compressive strength versus the average value of the maturity index as described in the StrengthMaturity Relationship section of ASTM C1074; and 11.1.6. Any other information required by the laboratory organization. 11.2. Report the following field information: 11.2.1. Project and route number;
49、 and 11.2.2. A list for each concrete lot evaluated, identifying the concrete job mix used and showing the following: 11.2.2.1. Station numbers; 11.2.2.2. Offset; 11.2.2.3. Item number; 11.2.2.4. Quantity of concrete; 11.2.2.5. Number (how many) and location of each probe/sensor installed; 11.2.2.6. Maturity index determined for each probe/sensor location; 11.2.2.7. Estimated strength determined for each probe/sensor location; and 11.2.2.8. Estimated average strength for each concrete lot. 11.3. OptionalAny additional data require
