On-site measurement of heat of hydration of delivered mass concrete

In this study, measurements of the heat of hydration of mass concrete delivered on-site were proposed. A one-meter concrete cube, cast adjacent to the real structure, was developed as an on-site semi-adiabatic calorimeter. A table was established for the required insulation of the cube in different ambient temperatures. To simplify the measurement process and cost, a method was developed to obtain the concrete adiabatic temperature rise (ATR) by simply using the measured temperature at the center of the cube. The finite element method (FEM) was used to calculate the required insulation for various ambient conditions between -10 to 30 degrees C so that the ATR could be accurately estimated using only the measured center temperature. The predicted ATR and the actual ATR showed less than 1% error. The proposed heat of hydration measurement was tested during four on-site field castings at three different districts in West Virginia. Two of the field batches contained 50% Grade 100 ground granulated blast furnace slag replacements. The fourth field batch had 30% Class F fly ash replacement. The material collected from each field test was also used to perform laboratory adiabatic and isothermal heat of hydration measurements. The ATR calculated from the on-site cube data compared well with the results from both adiabatic and isothermal calorimetry tests. The heat of hydration parameters were successfully obtained based on the ATR calculated from each on-site casting. Results show that the proposed on-site heat measurement can be a simple and accurate approach to measure the heat of hydration of a delivered concrete batch. (C) 2020 Elsevier Ltd. All rights reserved.

Automated summary

This study proposed a method for measuring the heat of hydration of mass concrete delivered on-site, using a one-meter concrete cube as a semi-adiabatic calorimeter. The method includes developing a table for insulation requirements in different ambient temperatures, as well as a simplified way to calculate the adiabatic temperature rise. Results showed that the proposed on-site heat measurement is a simple and accurate approach for measuring the heat of hydration of delivered concrete batches.