Engius developed the intelliRock Maturity logger in 2002. It won the 2003 World of Concrete award for innovation and has seen rapid growth and adoption on many major US projects in a short time. The reason? It is a simple and extremely cost effective device. Scancem Materials, known for their introduction of leading edge concrete technology has been appointed as the exclusive distributor.
The concrete maturity method is a proven strength estimation technique (ASTM C 1074) that accounts for the effects of time and temperature on the strength development of in-place concrete. This method gives a continuous estimate of concrete strength during the curing period and can be used to:
The strength-maturity relationship is generated in the laboratory by first preparing cylindrical specimens made from the same mix-design that will be used in the field. Two specimens are instrumented, e.g. by intelliRock maturity loggers (figure 1), to record the time-temperature history and calculate the maturity while sets of 3 cylinders are typically crushed for strength at 1,2,4,7 and 14days (figure 2). Finally, a graph of maturity versus strength is generated (this can be done using the spreadsheet that comes with the intelliRock maturity reader).
The time-temperature history of the concrete insitu is now recorded and integrated over time. Using intelliRock maturity loggers this is extremely simple as the temperature gauge, temperature/time logger and the maturity integration are all undertaken in a 35mm long x 30mm diameter cell that is embedded in the concrete. A wire is taken to the surface where the maturity reader can be plugged in at any time to download or simply read off the maturity and hence strength (figure 3).
Maturity monitoring gives insitu strength but that strength can be used to determine if the structure is "cooked" from a load or durability perspective. The key difference is that for load the strength of the bulk concrete is required and for durability the strength of the cover zone is required.