Study On The Influence Of Additives On The Performance Of CFB Ash And Slag Dry-mixed Plastering Mortar

Circulating fluidized bed ash and slag（CFB ash and slag）is the main industrial by-product discharged after combustion of coal in a circulating fluidized bed boiler at a temperature of 850～900℃.Compared with ordinary fly ash and machine-made sand,CFB ash and slag has loose and porous surface,high content of Ca O and II-Ca SO₄,and certain self-hardening,pozzolanic activity and expansion characteristics.At present,due to the lack of reasonable utilization mode,the scale utilization rate of CFB ash and slag is low.This thesis selects CFB ash and slag from Guojin Power Plant in Changzhi City,Shanxi Province.Since Guojin Power Plant uses a variety of coal-fired types and currently improves the desulfurization method of circulating fluidized bed boilers,the SO₃ content of CFB ash and slag produced by the power plant fluctuates strongly,which increases the difficulty of CFB ash and slag utilization.In order to utilize CFB ash and slag in Guojin Power Plant,the effect of CFB ash and slag with different SO₃ content on the performance of dry-mixed plastering mortar was studied.In order to further improve the working,mechanical and durability performance of CFB ash and slag dry-mixed plastering mortar,from the perspective of admixture,the effects of polycarboxylate superplasticizer,air-entraining agent and retarders on the performance of CFB ash and slag dry-mixed plastering mortar are compared.The admixture suitable for CFB ash and slag dry-mixed plastering mortar and the corresponding optimal dosage are selected,and the special composite admixture suitable for CFB ash and slag dry-mixed plastering mortar is prepared,so as to improve the performance of CFB ash and slag dry-mixed plastering mortar to meet the requirements of engineering use.By adding the best dosage of the special composite admixture in CFB ash and slag dry mixed plastering mortar,the comprehensive performance of CFB ash and slag dry mixed plastering mortar with different strength grades and the finished dry mixed plastering mortar of a dry mixed mortar factory in Wuhan was compared and studied.The results show that the water retention rate,compressive strength,flexibility,adhesive tensile strength,and frost resistance of CFB ash and slag dry-mixed mortar are superior to those of finished dry-mixed mortar produced by a dry-mixed mortar factory in Wuhan.For example,the water retention rate of CFB ash and slag dry-mixed mortar with a strength grade of M10 is 5.10%higher than that of finished dry-mixed mortar,and the compressive strength of CFB ash and slag dry-mixed mortar after 28d is 50.70%higher,the compression ratio after 28d is 7.75%lower,and the tensile bond strength after 28d is14.29%higher,After 50 freeze-thaw cycles,the quality loss rate and strength loss rate of CFB ash and slag dry-mixed mortar test blocks were reduced by 5.42%and 18.90%respectively compared to the finished dry-mixed mortar test blocks.Compared with finished dry-mixed plastering mortar,CFB ash and slag dry-mixed plastering mortar has some shortcomings in terms of its 2h consistency loss and setting time.Its 2h consistency loss increased by 3.22%and setting time decreased by 19.05%,but both meet the performance requirements of the national standard Ready Mixed Mortar（GB/T 25181-2019）for plastering mortar.CFB ash and slag dry-mixed plastering mortar has a lower cost and can be widely used,save a lot of material costs.