Abstract: A hardener composition useful for producing shaped cement articles while utilizing wastes such as waste incineration ash or papermaking sludge incineration ash and broken concrete; and a process for producing shaped cement articles by using this hardener composition.The process comprises kneading a hardener composition comprising 4.0 to 13.0 wt. % of sodium carbonate, 5.0 to 10.6 wt. % of potassium carbonate, 5.2 to 11.2 wt. % of sodium chloride, 1.1 to 4.1 wt. % of ammonium chloride, 0.1 to 1.5 wt. % of cobalt chloride, 0.4 to 8.6 wt. % of superplasticizer for concrete formation consisting maily of a polyalkylallyl-sulfonate salt, and 51.0 to 84.2 wt. % of water together with the wastes and cement and shaping and curing. The substances inducing secondary pollution which are contained in the wastes are prevented from dissolving away or exuding from the cement articles.