Concrete Maturity Method

Learn how the Concrete Maturity Method estimates in-place concrete strength through age and temperature correlations, offering real-time data for construction decisions.

Richard Howland, Director of Infrastructure Operations

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INTRODUCTION

The concrete maturity method is the development of an age/temperature relationship to concrete strength. Heat is generated in concrete during its curing period after placement by a chemical reaction (hydration) that takes place when water and cement powder come into contact with a concrete mixture. Other contributors to heat are ambient temperature, the temperature of the materials incorporated at the time of batching, water/cement ratio, the fineness or the size of the cement particles increasing or decreasing available surface area for cement to water contact, and the use of admixtures. These variables can increase or retard the hydration process affecting temperature and strength.

MATURITY METHOD

Maturity is used as a non-destructive means to estimate in-place concrete strength gains used for quality control and construction production purposes. The estimated strength gains are correlated by the use of laboratory fabricated strength test specimens kept in a controlled environment and tested by traditional methods i.e., compressive, or flexural strength. Strict laboratory controls are necessary to establish a maturity index that is a reliable and repeatable predictor of strength. The correlation of maturity to strength, once developed, is concrete mix design-specific and is not interchangeable nor a reliable method to determine the strength of other mixes. Maturity testing is performed in accordance with ASTM C1074.

The concept of concrete strength in relationship to maturity "maturity rule” was pioneered by Saul in 1951 and was followed up by other studies and contributors in this field soon thereafter. Currently, this idea is being considered by several DOT’s across the county including Caltrans as an alternative or augmented means of acceptance. Proponents of this method of determining strength suggest maturity has superior qualities to traditional testing of strength specimens for time-saving and practical purposes. Whereas concrete test specimens are minute in volume or mass in relation to the structural element they represent. Test specimens are susceptible to mishandling or environmental impact. Maturity readings are available immediately for timely decision-making during construction, such as the stripping of forms, opening of concrete paving to traffic or construction equipment, or if a load can be applied.

Monitoring takes place in the in-situ concrete, that is exposed to actual environmental and physical conditions. There are limitations to maturity. Maturity cannot take into account physical characteristic variables that may be encountered in the concrete mix during production. Such as reduced strength due to a poor bond between aggregates and cement paste in the concrete. This impeded bond is due to the potential for objectionable coatings on the aggregates which can reduce concrete strength. Testing used to determine the presence of aggregate coatings are cleanness value and sand equivalent testing. The industry has determined maximum allowances for the degree of coating that can be present before becoming detrimental to the concrete integrity.

There are many providers of maturity monitoring equipment on the market that provide training and technical support with their products. The best system must be considered by the purchaser since there are many price points and equipment options like wireless Bluetooth, remote data acquisition, duration of readings, frequency of readings, and so forth. Maturity is monitored by the use of embedded sensors in the subject concrete that are ultimately abandoned after use. Special attention to the location of the embedded sensors is critical to acquiring useful representative data. Information logging is captured by a recording device that displays and/or retains the data for analysis and interpretations in relationship to the laboratory developed maturity index.

CONCLUSION

Maturity does not appear to be a replacement for current conventional means of determining in-situ concrete strengths but possibly complements current methods offering another aspect for consideration in engineering during production, an additional measure of the concrete integrity, greater safety during construction, and the service life of the final product.

REFERENCES

American Standard Test Methods ASTM C1074-17

National Institute of Standards and Technology (NIST)Publication Maturity Method: From Theory to Application by N.J.Carino and H.S.Lew

Command Center TM

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