A New Penetration Depth Method Using Proctor Compaction Test for Determining the Optimal Starting Time of Hardening Topping in Concrete Flooring

This article presents a development and validation of a method to determine the starting time for hardening concrete flooring mechanically floated using the Dry Shake Topping technique. Until now, an informal method based on shoeprint penetration depth of 3-4 mm into the hardening concrete floor has been used in practice, but it is prone to significant errors. The probe time method described in the literature also has multiple limitations and drawbacks. Currently, there is no scientifically verified method for accurately determining the setting time of concrete mix and its early compressive strength. This gap poses a research problem because incorrect early timing of topping floating leads to further defects in concrete flooring. Through various laboratory, pilot, and technical-scale tests, a new method was developed. According to this method, floating should begin when the penetration depth of the Proctor Compaction Test Apparatus in the concrete mix reaches 4-7 mm. This penetration depth corresponds to the point at which the hardening concrete mix achieves sufficient strength to support the floating equipment while remaining plastic enough to ensure a strong bond between the topping and concrete layers. The article presents correlations between the Proctor Compaction Test results and the early strength of young concrete. It also explains practical on-site application of the method, providing immediate results without the need for interpolation. This method can be applied to any concrete mix intended for use in concrete flooring.