Title: Service Life Design of Low-Carbon Concrete Containing Fly Ash and Slag under Marine Tidal Conditions
Author(s): Vute Sirivivatnanon, Caihong Xue, Radhe Khatri
Publication: Materials Journal
Appears on pages(s):
Keywords: aging factor; blended cement concrete; chloride diffusion coefficient; design service life; surface chloride concentration
The use of blended cements enables the production of concretes with low embodied carbon and improved resistance to chloride penetration compared to General Purpose (GP) cement concrete. This paper reports the chloride diffusion characteristics in terms of apparent diffusion coefficient (Da), surface chloride concentration (Cs), and corresponding aging factors (a & b) of these low carbon concrete (LCC) derived from up to 9-year long-term exposure of small reinforced concrete slabs in both laboratory-simulated and field marine tidal conditions. LCC with either 30% fly ash or 50% slag provides slightly to significantly lower 28-day compressive strength than GP cement concrete at the same water/binder ratio but significantly better resistance to chloride penetration. The long-term chloride profile necessary to determine the concrete cover where the chloride threshold is reached can be determined with the Da.t0, Cs.t0 and corresponding age factors a and b where t0 is the one-year time of exposure. The improved resistance to chloride penetration by use of fly ash and slag as cement replacement was largely due to their intrinsic influence on the microstructure of the concrete. The results highlight the difference in chloride penetration arises from the change in test methods thus the importance of calibration when data obtained from laboratory concrete were used as input for service life design.