Florida Department of Transportation Requires Use of Maturity in Road and Bridge Projects
As outlined in the Standard Specifications for Road and Bridge Construction for opening to traffic, the Florida Department of Transportation (FDOT) requires the submittal of a strength-maturity relationship curve as determined by FM 3-C1074 during design mix verification. The state specifications also allow the contractor to use maturity in lieu of compressive strength cylinder testing every 24 hours before detensioning, and allows precast manufacturers to use maturity for determining form removal and handling strengths.
FDOT first required the use of maturity in its July 2016 specifications. Previously, maturity was allowed as an alternate to a protection set of concrete cylinders.
FDOT’s growing acceptance of the maturity method is due in part to a University of Florida study of maturity published in April 2014. The study, sponsored by FDOT, investigated the effectiveness and reliability of the maturity method to determine early-age strength of concrete in slab replacement applications.
The study began by examining the effectiveness of four different maturity monitoring devices; COMMAND Center, intelliRock, COMA meter, and Humboldt. After thoroughly testing the devices under various curing temperatures, researchers found COMMAND Center to be “the most effective system” because of its “accuracy, resolution, response time, and convenience of use.” The researchers then moved forward with the study using only COMMAND Center.
Researchers ran a set of lab experiments “to evaluate the possible effects of different placement and curing environments on the predicted strength of concrete from the maturity method and to determine the most appropriate procedure to be used to obtain accurate predicted strength of concrete.” They evaluated the Nurse-Saul and Arrhenius maturity functions, and concluded Arrhenius was most consistent under various curing conditions.
In the third and final section of the study, researchers conducted field studies to evaluate the effectiveness and reliability of the maturity method for predicting early-age concrete for slab replacement applications. The results indicated that “the maturity-strength prediction showed great accuracy” when the same concrete preparation time was applied to the concrete batches.
The study concluded that “the maturity method using the Arrhenius maturity function was found to be quite reliable and convenient for use in predicting the early-age compressive strength of concrete in slab replacement applications.” Because of the reliability and convenience, researchers recommended using maturity “to estimate the early-age compressive strength of concrete in slab replacement applications.”
FDOT’s January 2018 Standard Specifications for Road and Bridge Construction are currently available and will be implemented on all projects open for bidding from January 1 to June 30, 2018.
The Colorado Department of Transportation added a maturity meter requirement to its 2017 Road and Bridge Construction Specifications that took affect on October 1. The specs require for acceptance the use of the maturity method to determine concrete strength for removal of forms and falsework, loading of piers and abutments, opening of bridge decks and concrete pavement to traffic, and backfilling structures.
Several other states also include maturity in their specifications for various applications, including Texas, Alabama, Colorado, Idaho, Iowa, Kansas, Minnesota, Missouri, Montana, New Mexico, North Carolina, North Dakota, Ohio, Oklahoma, Oregon, Pennsylvania, Utah, Virginia, Washington, West Virginia, and Wisconsin.
What is Maturity?
Concrete maturity is a relationship between concrete temperature, time, and strength gain. It is a nondestructive test method that allows teams to evaluate concrete strength in real-time at their job site. There are many benefits to knowing real-time concrete strength gain including increased safety, expedited construction schedules, and improved construction methods. Knowing in-place concrete strength gain offers assurance that concrete has met adequate strengths for continued construction in cold weather, thus improving overall job safety. Maturity offers the potential to prove concrete has achieved adequate strength sooner than anticipated by traditional acceptance testing alone (i.e., cylinder or beam breaks). This can lead to stressing tendons, removing formwork, and applying loads sooner, and as a result, expediting construction schedules. Measuring real-time strength gain of in-place concrete can be an indicator of mix consistency and lead to a better-quality product, thereby improving construction methods.
See the benefits of maturity in construction projects: