RESOURCES RECYCLING AND ITS UTILIZATION OF CONCRETE AND GYPSUM BOARD WASTE

研究了以混凝土和石膏板废料为原料制备再生水泥和再生石膏，除CaO外，还需加入适量的Fe_2O_3和Al_2O_3，使其与普通水泥的化学组成相适应，28天后，再生水泥的抗压强度可提高到370kgf/cm~2，与普通水泥相当。由此可见，利用混凝土废料制备再生水泥是一种有效的回收钙资源的工艺。水泥细粉在人工海水中，在10kgf/cm2的二氧化碳压力下溶解60min，得到4.1g/dm3CaCO3。在含有过量CO_2的海水中溶解水泥微粉形成的氢氧化钙溶液中加入Ca(OH)_2，使溶解的钙离子在pH=7的条件下以碳酸钙的形式沉淀下来，并通过控制pH值控制在8以上，将沉淀后的残余液中的镁离子以水合镁的形式回收利用。研究了利用水板干湿法回收再生石膏半水合物制备硬化体的方法。二水石膏粉末被尽可能多地衬里分离出来。将石膏粉在200ﾟC下加热10min进行干燥处理，干燥处理后的再生半水石膏再老化60min。在12%H_2SO_4溶液中。干法再生半水石膏掺入煅烧石膏是一种有效的利用方法。例如，用等量的再生半水石膏和煅烧石膏制备的硬化体的强度几乎与独立煅烧的石膏相同。通过控制湿法处理后阿尔法型再生半水合物的携水能力和粒径为25%左右，硬化体的抗压强度可提高到110kgf/cm~2。

The reports were made to investigate preparations of reclaimed cement and reclaimed gypsum from concrete and gypsum board waste.It was needed to adjust closely to the chemical composition of normal cement by adding required amount of Fe_2O_3 and Al_2O_3 besides CaO.The compressive strength of the improved reclaimed cement was much increased to 370kgf/cm^2 after for 28 days which was almost the same to that of normal cement. A the above, it was apparent that the preparation of reclaimed cement from concrete waste was a useful process for recycling calcium resource.The cement fine powder in artificial sea water was dissolved 4.1g CaCO_3/dm^3 under CO_2 pressure of 10kgf/cm^2 for 60 min.. The dissolved calcium ion was deposited as calcium carbonate at pH 7 by adding Ca(OH)_2 in calcium hydrogencarbonate solution which formed by dissolving cement fine powder into sea water with an excess of CO_2. The magnesium ion in residual solution after depositing calcium carbonate was recovered as magnesium hydrate by controlling above pH 8.The present work was made to investigate preparation of hardened body from reclaimed gypsum hemihydrate obtained by dry or wet process of water board for resources recycling of waste gypsum board. The gypsum dihydrate powder which was separated as much as possible lining. The dry process was performed by heating the gypsum powder at 200ﾟC for 10min., reclaimed gypsum hemihydrate after dry process was aged the powder for 60 min. in 12% H_2SO_4 solution. The use of reclaimed gypsum hemihydrate after dry process was effective by mixing it in calcined gypsum. For example, the strength of hardened body prepared with equal quantities of reclaimed hemihydrate and calcined gypsum was almost the same that of independently calcined gypsum. By controlling water carrying capacity abdparticle size of the reclaimed hemihydrate containing alpha type of about 25% after wet process, the compressive strength of the hardened body was increased till 110kgf/cm^2.