Waste paper sludge ash used as replacement for cement in concrete production

Abstract

The use of waste is rapidly becoming a newly emerging supra-disciplinary field in most parts of the world where the use of industrial wastes like fly ash, granulated steel slag, silica fume, waste fibers etc., in construction has become very popular since the last half of the 20th century. However, lack of standards and the existing concept of trying to match or possibly exceed the strength of a control mix made with 100% Portland cement is hampering the increased use of waste materials in construction. Waste paper mill sludge is a major economic and environmental problem for the paper and board industry. Enormous quantities of waste paper sludge are generated all around the world. The material is a by-product of the de-inking and re-pulping of paper during the production of new papers, boards and recycled papers. The main recycling and disposal processes for the waste paper sludge are either as agricultural fertilizer where the sludge is dried and spread directly over agricultural land for its lime content, incineration at the paper mills as a source of heat for the mill’s boilers, or simply transported and dumped onto public or private landfills. This study looked at the chemical, physical, and mineralogical characterization of the waste paper sludge ash (WPSA), from a South African source. The influence of the waste paper sludge ash on concrete incorporating 5%, 10%, 20%, 30% and 50% of the waste sludge were investigated with a constant water to binder ratio of 0.5. The results of the investigation conclude that WPSA is a viable cement extender and has potential for use in the construction industry.