About the research
The objective of this research project is to identify, develop, and evaluate a simple, economical, and reliable calorimetry device and test method for monitoring heat evolution of pavement concrete. The project contains three phases: phase I—identifying user needs for calorimeter tests, phase II—identifying potential calorimeter devices and developing test procedures, and phase III—verifying the test procedures and the potential applications of calorimetry in field. In this report, the work done in phases I and II is briefly summarized and the study of phase III is presented.
The phase III study includes three parts: (1) field calorimetry tests, (2) lab tests for the field materials, and (3) implementation of calorimetry into pavement performance prediction. The field tests were conducted at three selected sites: US 71 (Atlantic, Iowa), Highway 95 (Alma Center, Wisconsin), and US 63 bypass (Ottumwa, Iowa). A simple isothermal calorimetry and two semi-adiabatic calorimetry (AdiaCal and IQ drum) tests were conducted at these sites. The general concrete, such as slump, air content, unit weight, placement temperature, ASTM C403 set time, and pavement properties, such as subbase temperature and sawing time were also measured. In the lab tests of the field materials, nine robust mixes for each field site, with different variations in water reducer and/or fly ash dosages were developed. AdiaCal and isothermal calorimeter tests were performed for each of the robust mixes. IQ drum and ASTM C403 set time tests were conducted for selected mixes. To implement the calorimetry test results into concrete performance prediction, the HIgh PERformance PAVing (HIPERPAV) computer program was modified, the calculated hydration curve parameters from selected calorimetry tests were used as inputs for the modified HIPERPAV program, and the temperature developments of in-situ pavements were then predicted. The phase III test results confirmed the major findings drawn in the phase II study. The results indicate that both the AdiaCal and semi-adiabactic calorimetry tests can provide valuable information on concrete performance. AdiaCal calorimetry is particularly good for field concrete set time prediction, and it is sensitive to the sample temperature. Isothermal calorimetry can provide users more detailed information on cement hydration and provide more consistent test results. The thermal set times obtained from both the AdiaCal and isothermal calorimetry tests are closely related to those measured from the ASTM C403 tests. Using the calorimetry test curve as inputs for the HIPERPAV computer program, in-situ concrete pavement temperatures can be predicted adequately.