Development of Jobsite Cylinder Curing Practices for the Alabama Concrete Industry
Type of DegreeMaster's Thesis
Civil and Environmental Engineering
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In concrete construction projects, quality assurance test cylinders are made to evaluate the quality of the concrete delivered to a jobsite. In order to accurately evaluate these cylinders, they must be cured according to specific requirements. The Alabama Department of Transportation outlines these specifications in ALDOT 501.02 section (d) “Sampling and Inspection”. Nine jobsite visits were conducted to review and evaluate the current practices used by jobsite technicians and contractors to sample and cure concrete test cylinders as well as assess the effects of non-standard curing on the 28-day compressive strength when exposed to summertime placement conditions. To accomplish this, at each jobsite visit, samples of the provided concrete were collected, cylinders made, and cured in two different initial curing environments. The 28-day compressive strength results of these cylinders were then compared along with the temperature data within each jobsite visit. The results clearly indicate that a significant decrease in 28-day compressive strength occurs when cylinders are cured in conditions different than those required by ALDOT 501 (2022) and AASHTO T 23 (2018). The maximum decrease in 28-day compressive strength was 22%. Additionally, it was found that cylinder curing boxes supplied with continuous power and a water circulation pump were capable of maintaining the specified water temperature range of 60 to 80°F for the entire initial curing duration. Therefore, it is recommended that continuous power be provided for the cylinder curing box along with fuel if a generator is used for the power source. Lastly, the results show that it is only necessary to record the minimum and maximum temperatures of the water in the cylinder curing box and not the temperature of the concrete specimens. Recommended changes to ALDOT 501 to improve the jobsite curing practices are provided in this thesis.