Suitability of alkali activated ggbs/fly ash concrete for chloride environments

This study investigates chloride ingress into alkali-activated slag/fly ash (AA-S/F) concretes with various ratios of slag to fly ash (80/20, 60/40,40/60 and 20/80). Alkaline activators were a mixture of sodium hydroxide and sodium silicate to obtain between 6-8% sodium hydroxide (NaOH) concentration by weight of cementitious material. The Si0₂/Na₂0 ratios (silica modulus, Ms) of mixtures were 0.45, 1.0 and 1.25. Tests applied included typical fresh and hardened properties, air content, slump, compressive strength, bulk resistivity and non-steady state chloride migration. The results show that while attractive engineering properties can be achieved, the chloride ingress in the AA-S/F concretes studied here with > 20% fly ash is moderate to high and this may make them unsuitable for use in reinforced concrete in chloride environments

Development of Autonomous UHF RFID Sensors Embedded in Concrete for the Monitoring of Infrastructures in Marine Environments

International audienceChloride ingress in reinforced concrete infrastructures is of crucial importance when considering structural health monitoring applications in marine environments. It indeed leads to the depassivation and corrosion of steel and hence to the degradation of the whole infrastructure. The present study reports the development of an embedded wireless autonomous sensor dedicated to the monitoring of corrosivity of concrete initiated by such ingress. The sensor is based on the ultra high frequency (UHF) radiofrequency identification (RFID) technology. The communication between a commercial RFID reader and a specific optimized embedded antenna in concrete is experimentally demonstrated. In the last part of the study, a resistive corrosion sensor connected to the RFID chip is proposed for the evaluation of chloride ingress