Corrosion inhibitor for cement compositions

The invention relates to an anti-corrosion agent for use with reinforced cementitious compositions. An anti-corrosion agent for use with a cementitious composition which is to be reinforced, comprising one or more species selected from a group consisting of alkyldiamines represented by the general formula RHN-(CH)n-NH(in which R is an alkyl having Catoms, and n is an integer of 1-5) and alkylamines represented by the general formula R-NH(in which R is an alkyl having Catoms). The agents give good anti-corrosion performance which does not decline with time and exposure to the elements to the same extent as is the case with conventional anti-corrosion agents.