Active Control of Concrete Curing Monitored by Acoustic Emission

The quality of concrete is strongly dependent on the curing process. Environmental changes in temperature and relative humidity can result in premature drying, which in turn can cause cracking on the surface of the material. Hence, monitoring the concrete curing is essential to prevent undesirable behavior. Techniques such as Acoustic Emission (AE) have proven very promising for monitoring the curing of cement-based materials due to their high sensitivity level. Shrinkage cracking can be mitigated using admixtures such as SuperAbsorbent Polymers (SAPs) which provide internal curing for several hours after casting by releasing entrained mixing water back into the concrete matrix. This action taking place in the microstructure, although beneficial, is difficult to monitor or control. However, recently it was shown that release of SAP water into the cementitious matrix is accompanied by high AE recordings enabling, therefore, the monitoring of the process. This paper discusses the possibility of controlling the internal curing of concrete based on real-time AE data in order to ensure the desired concrete performance. The results showed that by applying a curing agent on the concrete surface, at the moments dictated by the increase of AE, the SAP activity is postponed. This indicates that their action can be deactivated and reactivated multiple times during curing, resulting in prolonged internal curing and thus, better hydration. The mechanical properties are also investigated, showing an increase in the compressive strength for the actively controlled SAP specimens.