Development of Thai lignite fly ash and metakaolin for pervious geopolymer concrete

The study was to use Thai lignite fly ash and metakaolin to produce geopolymer paste as binder material in pervious concrete. The proper ratio of fly ash to metakaolin were varied as 100:0, 70:30, and 50:50. Alkali solution to pozzolan (L/P) ratios viz., 0.5, 0.6 and 0.8 by weight were prepared. The mechanical and characterization of pervious geopolymer concrete (PGC) were carried out. The results presented that the particle of fly ash was sphere with smooth surface, while metakaolin was partly agglomerated and irregular shaped. The increase of fly ash in the ratio of fly ash to metakaolin affected the lower requirement of volume of alkali solution. The compressive strength and of pervious geopolymer concrete at 28 days were 3.7-5.4 MPa. The void ratio and water permeability were 28.5-30.7% and 1.9-2.1 cm/sec, respectively. Therefore, geopolymer paste from fly ash and metakaolin could be used for pervious concrete with satisfied properties according to standard of ACI 522R-10

Development of microwave-assisted sintering of Portland cement raw meal

Typically, using a rotary furnace as a heat generator, a temperature of approximately 1450 °C and a time of 60 min is needed to produce clinker requiring large amounts of energy. Recently, a method of sintering Portland cement by microwave furnace has been developed with the aim to reduce this high consumption of energy in the conventional cement production. In this work, cement raw meal was calcined by a microwave furnace operating at 2.45 GHz with 900 W at 1150 °C at several periods of time but was not completely successful in terms of clinker formation. Therefore, an electric furnace was used at 1300 °C and 1350 °C for 30 min to further heat the material. Chemical compositions of the formed clinker, characterized by XRD, presented C3S, C2S, C3A and C4AF as the main constituents confirming a clinker similar to those of clinker produced by rotary kiln or conventional technique. Loss on ignition and insoluble residue of the resultant clinker were analyzed by chemical analysis and the results were found to pass ASTM C-114. It was found that the raw meal sintering process using a microwave furnace followed by transfer to an electric furnace could reduce not only the temperature by at least 100 °C but also the processing time of the clinker. In addition, there is no grinding cost for clinker preparation in this process. This processing of clinker would decrease energy consumption and carbon dioxide emission to the atmosphere, a major cause of global warming