The paper industry in Korea has continued to grow at a high pace. The annual amount of paper sludge generated during the wastewater treatment process in the paper manufacturing process is about 1.6 million tons. In addition, paper sludge is recycled as paper ash after incineration, but most of it is landfilled. Therefore, this study aimed to use calcium based paper ash as cement admixture generated in the production process of neutral paper-making process to have various uses of paper ash. In order to use paper ash as a cement admixture, pre-treatments such as pre-hydration and hydration control are required. As a result, the characteristics of paper ash and the formation of ettringite were found to be good when 12% of hydration water and 10% of anhydrous gypsum were mixed. Also, it was shown that when pre-treated paper ash with a less than 10% of OPC was used as a cement admixture, good compressive strength and workability could be obtained. Especially, cement mixed with pretreated paper ash showed excellent shrinkage resistance performance compared to OPC.

Keywords: Paper ash, Cement admixture, Prehydration, Hydrate control, Waste recycling