Synthesis of waste-based carbonation cement

Calcium silicate based cementitious materials are well known by its reactivity with carbon dioxide to produce high early strength through carbonation curing. Since the early strength gain is due to the reaction between calcium silicates and carbon dioxide, carbonation cement can be formulated with calcium silicates of any polymorph with reduced synthesizing temperature. Its early strength is expected from carbonation activation and late strength by hydration reaction. Such a cement can be made exclusively with industry wastes at low temperature. This paper is to examine the feasibility of synthesizing carbonation cement for carbonation process from two industry wastes: ladle slag fines for calcium and waste glass for silica. A synthesis process involving burning the mixture of ladle slag and waste glass was developed to produce low energy carbonation cement capable of gaining strength when activated by carbonation. The glass to slag ratio and clinkering temperature were determined based on carbonation and hydration strength of the binder. Performance was assessed by compressive strength tests, X-ray fluorescence analysis, X-ray diffraction analysis, and thermogravimetry analysis. The results suggested that supplementing the ladle slag with additions of waste glass had promoted the conversion of calcium to more value-added calcium silicate phases which could be activated by carbon dioxide to produce early strength. The carbonation cement so produced consumes no natural resources and has shown the potential for carbon sequestration.