Existing Form of Arginine in “Environmentally Active Concrete” and the Elution Behavior in Water

The blocks containing amino acid, arginine, were developed as” Environmentally Active Concrete”. It has been reported that the block accelerated to form marine periphytic algae on the concrete block in the actual water area. This work aimed to investigate the behavior of amino acids in the concrete block in laboratory to ensure the control of the existing form of arginine in concrete and the life time of elution. Extraction experiments with water, acid and alkali revealed that about 80% of arginine in the concrete was able to elute into water. And there were adsorption equilibriums between arginine and concrete constituents (cement paste and aggregate) at mildly alkaline pH. A part of arginine has a positive charge at mildly alkaline pH. In addition, the concrete block containing arginine was put in the tank poured marine water by pump. Blocks were periodically salvaged. And time course of elution rates of arginine in the blocks was analyzed. pH of the surface of immersed block decreased till pH8.5. The elution of arginine was considered to be affected by not only diffusion but adsorption equilibrium at stable phase in analogy with Ca in the concrete.