Abrasive water jet machining of fly ash and metakaolin based geo-polymers

Abstract

In the present study, the abrasive water jet machining (AWJM) of geopolymers prepared from fly ash, metakaolin and sand is discussed. The samples were prepared from sodium promoter, fly ash / metakaolin and sand. The process of activation was made using a 10M sodium hydroxide solution combined with a sodium silicate solution (the ratio of liquid glass - 1:2.5). To produce geopolymers, flakes of technical sodium hydroxide were used and an aqueous solution of sodium silicate (R-145) with a molar module of 2.5 and a density of around 1.45 g/cm3 the tap water. The alkaline solution was prepared by means of pouring the aqueous solution of sodium silicate over the solid sodium hydroxide. The solution was mixed and left until its temperature stablised and the concentrations equalised, which took around 2 hours. The fly ash, sand and alkaline solution were mixed for around 10 minutes using a low-speed mixing machine (in order to obtain a homogeneous paste). The paste was allowed to dry in the shade. The paper investigates the AWJM studies on the prepared geopolymer specimens with varyied input parameters such as standoff distance (1.2 and 3 mm), water pressure (120, 140 and 160 MPa) and feed rate (5, 10 and 15 mm/min). The output parameters such as kerf angle and material removal rate (MRR) were studied with the varying combination of input parameters. From the results, the optimal parameters for machining the geopolymer composites were interpreted.