IntroductionThe main objectives of this project were to establish a correlation between maturity development and degree of hydration of cement and to establish equivalent curing methods for concrete specimens that can accurately represent the curing conditions of concrete in pavement. To achieve these objectives, the following tasks were performed.1. The maturity development of cement in relation to cement hydration was evaluated. 2. The influences of different specimen curing conditions and specimen types on the flexural strength, compressive strength, and maturity development of pavement concrete were evaluated.
FindingsBased on the research results presented in this document, the following conclusions were drawn from the study. 1. There existed a good correlation between maturity development of cement paste and the degree of hydration of cement. This correlation was valid only if sufficient moisture was available for continuous hydration of the specimens. The maturitydegree of hydration correlation could also be extended to concrete since the maturity development in cement paste and concrete was found to be similar. 2. With respect to flexural strength of the specimens, curing specimens in the lime bath or in the sandpit produced specimens with equivalent flexural strengths. Air curing of specimens did not produce specimens with a strength equivalent to the strength of specimens cured in either the lime bath or sandpit. 3. The temperature-matched curing technique was able to produce specimens with strengths within 10 percent of the flexural strength required for opening the pavement to traffic. This result was repeated in the field based on maturity values. 4. With respect to compressive strength, the specimens cured in the sandpit and the specimens cured in air were the most similar. The strengths of the specimens cured in the lime bath were different than the strengths of the specimens cured in the other two curing conditions. 5. The ambient temperature in which the concrete was cured had a significant influence on the maturity development of the concrete. The sandpit-cured specimens most accurately matched the maturity development of the pavement in the field study (within 6 percent). The lime-bath, sandpit and air-cured specimens all matched the maturity of the pavement to within 14 percent. The temperature-match cured specimens matched the maturity development in the pavement to within 1 percent in laboratory studies. 6. It appears that there was no difference between the maturity development in beam specimens and cylinder specimens. Air curing of specimens has a greater effect on the maturity-strength relationship of beam specimens than on cylinder specimens. Also, the temperature match-cured specimens validated the maturity curve for the concrete.
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ImplementationCurrently INDOT specifies two different types of field curing: lime bath and sandpit curing. Lime bath curing is used for QC/QA pavement construction for specimens made to determine the 7 day flexural strength of the concrete. Sandpit curing...
The release of the Mechanistic–Empirical Design Guide for New and Rehabilitated Pavement Structures (M-E design guide) generated a new paradigm for designing and analyzing pavement structures. It is expected to replace the commonly used empirical design methodologies. The M-E design guide uses a comprehensive suite of input parameters deemed necessary to design pavements with high reliability and to predict pavement performance and distresses realistically. However, the considerable amount of input needed and the selection of the corresponding reliability level for each might present state highway agencies with complexities and challenges in its implementation. An overview is presented of ongoing investigative studies, sensitivity analyses, and preimplementation initiatives conducted by the Indiana Department of Transportation (INDOT) in an effort to accelerate the adoption of the new pavement design guide by efficiently using existing design parameters and determining those parameters that influence the predicted performance the most. Once the sensitive inputs are identified, the large amount of other required design input parameters can be significantly reduced to a manageable level for implementation purposes. A matrix of trial runs conducted with the M-E design guide software suggests that a higher design level input does not necessarily guarantee a higher accuracy in predicting pavement performance. The software runs also confirmed the need to use input values obtained from local rather than national calibration. Such findings are important for state highway agencies such as INDOT in drafting initiatives for implementing the M-E design guide.
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