Investigation on Serviceability and Durability of Geopolymer Concrete Using Embedded Sensors

Abstract

With growing environmental demands for low carbon globally, Geopolymer concrete (GPC) has been developed as a green alternative to the Ordinary Portland cement (OPC) concrete over the last decades. It is estimated to result in a reduction of carbon dioxide (CO2) emissions up to 80% when replacing OPC concrete with GPC. However, there is limited research done in assessing the GPC performance of serviceability and durability. This thesis investigates the serviceability and durability of GPC using state-of-the-art embedded sensors and continuous monitoring systems. A long-term structural health monitoring system was installed in a GPC composite bridge. Vibrating Wire strain gauge were embedded in the bridge deck to collect strain and corresponding temperature data. This is a pioneering approach to assess the serviceability of the GPC bridge under in-service conditions. The results confirmed that the GPC slab performed well and was mainly affected by thermal loading. The thermal conductivity of GPC was measured and found to be smaller than the one of OPC concrete. The average temperature collected verified that the existing Australian Standard AS5100 specifications are suitable for GPC. Finite element model (FEM) was developed to verify the monitoring data. Simulation results indicated that cracking is more likely to form at the top of the bridge slab, which is consistent with the minor cracks observed by visual inspection. For the first time, high alkalinity resistance pH glass electrode has been used to successfully measure the pH value of GPC in both laboratory and field conditions. The results confirmed that the sensors are durable and successfully monitored the pH value of GPC for 12 months in the laboratory. The pH readings were found to be affected by the moisture, temperature and carbonation in concrete. A series of saturation tests were conducted on the GPC specimens to study the relationship between pH reading and moisture in concrete. A calibration model was then developed to correct the sensor readings affected by the moisture loss. The pH sensors have been applied to a real project in marine environment and successfully measured the pH value of GPC plank after 2 months of casting.