An　investigation　was　carried　out　on　the　behavior　of　concrete　under　both　sulfate　attack　and　mechanical　stress.　The　specimens　of　concrete　with/without　fly　ash　were　subjected　to　flexural　load　with　a　level　of　0.2　and　0.4　of　their　initial　strength　and　also　immersed　into　a　10%　sodium　sulfate　solution　or　water　respectively.　The　bending　strength　of　the　concrete　was　tested　at　certain　time　intervals.　The　results　indicate　that　fly　ash　could　effectively　relieve　the　deterioration　of　the　concrete　in　corrosive　environment;　flexural　load　could　accelerate　the　corrosion　damage　and　that　the　development　of　concrete　strength　is　related　to　the　internal　structure,　hydration　product　and　the　interface　between　coarse　aggregate　and　cement　paste.