New Approach to Calibrate the Mortar Flow Table

The flow table is a standardized test that is widely used to qualify a mortar for compressive strength and air content. The flow table is also the only standard test to quantify the workability of a mortar. Therefore, the calibration of this device is paramount, and it is done today by preparing a reference material consisting of a mixture of silica powder and oil. The two materials are mixed; tests are performed with the use of the reference flow table located in the Cement and Concrete Reference Laboratory. This flow table is identical to commercial versions currently used, and the values obtained with this flow table are considered the reference values for calibrating flow tables in the United States. This is an empirical procedure and relies heavily on one device that could break or generate results that can drift over time. This study reviewed the manufacturing process of the reference material, provided historical data, and proposed a more scientifically based approach to develop an improved reference material.