An RFID tag (transponder) with a sensor and transmitter/receiver that is cast inside concrete structures. The signals from the tag(s) are transmitted to an external receiver/transmitter located outside the concrete. The signal from the external receiver/transmitter is then connected to the Internet via GPRS. The information is collected in a database where the concrete’s strength is calculated. This is done by using available theory on equivalent curing time and trend curves for a given quality of concrete. Information about the casting process is presented via a graphical interface. All data for ongoing and completed measurements is also readily accessible.