Abstract: A concrete protective agent including an alkali metal-containing silicate and an alkaline electrolyzed water. A concrete protective agent including an alkali metal-containing silicate and silicon dioxide. Examples of the alkali metal-containing silicate include sodium silicate, potassium silicate and lithium silicate. By supplying the concrete protective agent to a concrete structure, the repair of the concrete structure can be performed. A concrete repairing agent having a significant repairing effect as compared with conventional concrete repairing agents.

Abstract: A modifying agent of an alkaline electrolyzed water. A substance being supplied to a concrete structure in order to produce calcium silicate for repairing concrete and including an alkali metal silicate is defined as a concrete protective agent. The modifying agent is supplied to the concrete structure in advance of the supply of the concrete protective agent. The alkali metal silicate and the calcium ion included in the concrete protective agent contribute to the production of the calcium silicate. A method for repairing a concrete structure includes supplying the concrete protective agent to the concrete structure and supplying a modifying agent for a concrete structure including an alkaline electrolyzed water to the concrete structure, the step supplying a modifying agent being performed before the step of supplying the concrete protective agent to promote production of the calcium silicate in step of supplying the concrete protective agent.