Introducing a settimeter, a concrete setting time measuring device using surface hardness

Abstract

The research aims to introduce a new device for determining the setting time of concrete by measuring surface hardness and to prove its reliability. At the construction site, the setting time of the concrete is a critical point for concrete works, such as starting the surface finishing and starting the following works on the surface of the hardened concrete. The quality of finishing work for concrete surfaces is significantly related to setting time. Nevertheless, in an actual construction site, it is challenging to execute the current methods of evaluating the setting time of the placed concrete, such as the penetration resistance method of ASTM or other Non-destructive testing (NDT) methods. Therefore, in this research, based on the idea of measuring the hardness of materials, a settimeter (a combined word of setting time and meter), modified for concrete surface hardness measurement, was introduced, and evaluate the reliability under the various setting time conditions with retarding admixture and curing temperature. To evaluate the reliability of settimeter, the setting time of concrete mixtures was controlled with retarder and curing temperature. Compared with the current ASTM method of penetration resistance values, a settimeter showed similar timings of initial and final setting times with the penetration resistance test method. Finally, the experimental results obtained sufficient reliability with 0.82 of R<^>2 value between the settimeter and penetration resistance test values. Based on the research results, the suggested settimeter is expected to be a favorable method of determining the setting time of concrete on construction sites.