Impact of Extremely Hot Weather and Mixing Method on Changes in Properties of Ready Mixed Concrete during Delivery

Abstract

Riyadh is located in central Saudi Arabia. Its extremely hot, dry environment was used to investigate concrete compressive strength, slump, and temperature changes during ready mixed concrete (RMC) delivery. Representing three plants employing a truck-mixing method and three plants employing a central-mixing method in their operations, testing was performed using a total of 80 delivery trucks. Differences in RMC property changes that were not significant were indicated by study results during delivery in both Riyadh's extremely hot, dry summertime environmental conditions and the midwestern United States' much milder summer conditions. The study showed that during summertime delivery, concrete slump lost 37% of its initial value and concrete temperature increased by an average of 1.1 degrees Celsius (2.0 degrees Fahrenheit). There was a slightly higher compressive strength at the site than at the plant. Long travel times did not significantly affect compressive strength. Effective control of adverse hot weather effects on concrete production and delivery, even under the region's extremely hot prevailing weather conditions, was shown possible by controlling concrete temperature, avoiding delivery during noon hours, and using water-reducing and retarding admixtures, per ACI 305R recommendations. In this study, there was no observation of the anticipated increased slump loss rate problem associated with hot weather use of water-reducing and retarding admixtures.