Development of Time Domain Reflectometry Instrument for QA/QC of Fresh and Early Stage Concrete

摘要

The project developed a new instrument based on Time Domain Reflectometry (TDR) for measuring properties of fresh and early age concrete as an alternative to traditional quality control methods that rely heavily on the slump value and compressive strength and do not always produce durable concrete. Work in the first stage focused on the design and development of a prototype sensor system for use on fresh and early age concrete. An experimental program systematically evaluated the sensor systems ability to measure the performance properties of concrete. The program tested several representative concrete specimens used in highway pavement, bridge, and industrial and residential structures. TDR signals were collected on concrete specimens subjected to different curing conditions, including early freezing, and the results were correlated with data obtained by standard test methods. The results indicated that the TDR sensor system could reliably measure or estimate concrete properties, such as free water content, density, air void content, initial and final setting times, and mechanical strength. New test results also showed promise of advancing this technology to estimate the thermal properties of concrete, such as the thermal conductivity and heat capacity.