The　quantities　of　coal　ash　disposed　of　in　landfills　over　the　past　decades　add　up　to　billions　of　tons.　Weathering　in　landfill　would　impact　the　mineralogical,　chemical,　physical　and　toxicity　characteristics　of　coal　ash.　In　order　to　investigate　these　effects,　ashes　were　obtained　from　different　depths　of　landfills　representing　different　durations　of　disposal.　These　ashes　were　subjected　to　a　range　of　physical,　chemical,　and　toxicity　tests.　Aging　in　landfill　was　noted　to　produce　significant　changes　in　various　ash　properties.　The　trends　in　these　changes　with　increasing　disposal　duration　were　identified.　These　trends　were　explained　based　on　the　weathering　and　leaching　effects　experienced　by　the　coal　ash　in　landfills.　In　addition,　hydraulic　activity　and　reactivity　of　the　landfill　coal　ashes　were　determined　to　assess　their　potential　use　in　alternate　cement　production.