Title: Utilizing Calcined Clay to Enable Aluminum Reinforced Concrete
Author(s): Harald Justnes
Publication: Symposium Paper
Appears on pages(s): 7.1-7.8
Keywords: aluminum, calcined clay, environment, reinforcement, supplementary cementitious materials
Regular concrete cannot be reinforced with aluminum metal due to high pH that will dissolve the protective oxide layer and evolve hydrogen gas. However, it has been demonstrated that replacement of 50% portland cement with calcined clay can prohibit hydrogen gas evolution in the early stage and will deplete all calcium hydroxide formed by cement hydration in the long run securing that gas evolution will not happen in the future either.
The advantages of such a "reduced pH" aluminum metal reinforced concrete is in many ways environmentally friendly as the reinforcement does not need to be protected by a dense concrete cover. The concrete can be made by higher w/c to achieve the required compressive strength and not over-shoot it for low permeability reasons. After all, most of the concrete made is below 35 MPa characteristic compressive strength. Hence, such high porosity concrete with only required strength according to its use will pick up CO2 from atmosphere faster and further lower the carbon footprint and secure a stable system. With appropriate Al alloying, even seawater can be used as mixing water, and with such high SCM dosage alkali reactive aggregate can be used, further adding to ecological benefits.