INDUSTRIAL EFFORT ON LIMESTONE CALCINED CLAY CEMENT IN CHINA
Sui Tongbo Dr.-Ing., Prof., Director General of Sinoma Research Institute, Vice President of China Sinoma International Engineering Co. Ltd.
Bin, W. Research engineer, Sinoma International Engineering Co. Ltd., China
Alitinform №3 (56) 2019 г. 12-20 p.
This paper is a review of recent progress in China in developing a ternary low carbon binder system as limestone calcined clay cement (LC3) in which clinker can be replaced in a large volume without compromising the mechanical properties and durability of the resultant LC3 cement and concrete. An industrial waste from quartz-kaolinite clay refining process was identified and characterized as raw materials which well fits the basic requirement of LC3-50 solution, i.e., enabling equivalent 28-day compressive strength for resultant cement with a clinker factor of 50 % as compared with pure Portland cement. Thanks to the highly reactive metakaolin in the calcined clay obtained through heating the raw clay up to a higher temperature ranging from 750-800 °С as well as the synergy by limestone addition, which results in the excellent performance of LC3-50 cement. More importantly, large scale flash calcining system was designed and set up, by which the energy performance can further be enhanced in the process of the thermal activation of raw clay at high temperature. Industrial trial calcination of the raw clay with rotary kiln and flash calciner with a capacity of 600 t/d and thermal consumption of 600 kcal/kg were successfully carried out, and the reactivity of the resulting calcined products was proved to be excellent and in good agreement with the laboratory results when LC3-50 cement is formulated. Systematic evaluation of the performance of LC3 concrete is underway.
Calcined clay, Low carbon cement, Kaolinitic clay tailing, Thermal activation, Activity index, Flash calcining