Study On The Properties Of One-component CFBC Ash/Slag Geopolymer

Circulating fluidized bed combustion ash is the ash produced in the fluidized bed coalfired boiler.The output of CFBC ash is increasing year by year in China.However,the main disposal of CFBC ash is stacking and landfill.The treatment of CFBC ash is relatively single,which will cause devastating damage to the ecological environment for a long time.Therefore,it is urgent to find a suitable resource utilization method of CFBC ash.Geopolymer cementitious material has high mechanical properties,excellent thermal stability,good corrosion resistance and durability,and it is a kind of green cementing material which is expected to replace the traditional cement.Active amorphous silicon-aluminium contained by CFBC ash can be used to prepare geopolymer.At present,using CFBC ash to prepare geopolymer provides a new way for the resource utilization of CFBC ash.In this paper,CFBC ash and slag were used as raw materials,and gypsum,sodium metasilicate and sodium carbonate were used as chemical activators to prepare one-component geopolymer.The workability and mechanical properties of CFBC ash/slag geopolymer have been studied.The feasibility of the solid activators to activate the CFBC ash was explored,and the performance of CFBC ash geopolymer activated by soild activators was evaluated.On this basis,the effect of slag on the performance of one-component CFBC ash-slag geopolymer was studied.Then,the effects of lignosulfonate superplasticizer,naphthalene superplasticizer and polycarboxylate superplasticizer on the workability and strength of CFBC ash-slag geopolymer were evaluated,XRD,FT-IR and other microscopic methods were used to explore the mechanism of related phenomena.The main results were as follows:(1)The order of paste fluidity of CFBC ash geopolymer activated by three kinds of activators from small to large was: gypsum<sodium carbonate<sodium metasilicate.The paste fluidity of CFBC ash geopolymer was the largest when the sodium metasilicate contant was10%,which is 100 mm.The order of 28 d compressive strength of CFBC ash geopolymer activated by three kinds of activators was as follows: sodium carbonate<gypsum< sodium metasilicate.The highest 28 d compressive strength was 5 MPa,when the sodium metasilicate content was 10%;(2)With the increase of slag content,the paste fluidity of CFBC ash-slag geopolymer activated by three kinds of activators increased in varying degrees,and the compressive strength of CFBC ash-slag geopolymer activated by three kinds of activators increased a lot.The highest28 d compressive strength of geopolymer activated by sodium metasilicate was 37.1 MPa;(3)The addition of three kinds of superplasticizers can improve the initial fluidity of CFBC ash-slag geopolymer acticated by gypsum,and the addition of three kinds of superplasticizers can inhibit the geopolymerization reaction to a certain extent.The addition of three kinds of superplasticizers to the fluidity dispersion of CFBC ash-slag geopolymer paste activated by sodium metasilicate or sodium carbonate was poor,but it can inhibit the geopolymerization reaction to a certain extent;(4)With the increase of superplasticizer content,the strength of CFBC ash-slag geopolymer decreased gradually.However,the addition of superplasticizers did not change the mineral composition of CFBC ash-slag geopolymer.