The microstructure and products of long-term geopolymer synergistically synthesized from calcined ore-dressing tailing of bauxite and slag

【Author】

Wensheng Zhang;Jiayuan Ye;Di Shi;

【Abstract】

<正>The ore-dressing tailing of bauxite(hereinafter referred to as tailing),one new kind waste of Chinese aluminium industry due to the application of ore-dressing-Bayer process and ore-dressing-sintering process in China,is rich in aliuminosilicate minerals such as kaolinite and thus meets the requirements of starting materials for geopolymer preparation.Geopolymer,derived from various waste,is considered as the low-carbon and environmental cementitious materials.The inadequate long-term results,however, is severely harmful to its extensive application in practice,especially in construction.In this paper,the strength development of geopolymer mortars cured for 6 years is investigated.The geopolymerisition products and microstructure evolution are also studied using XRD,ESEM,TG-DSC and Mercury Intrusion Pore structure analysis (MIP).The results show that the strength of long-term mortars dose not reduce but steadily increases from 60.0MPa at 28 days to 75.0MPa at 6 years.The hardened samples become more compact with curing time because of the continuous geopolymerisition reaction,which leads the porosity to increase and the amount of large pores to reduce.The presence of visible clacite in XRD patterns of long-term specimen implies the occurrence of carbonation of gels with atmospheric CO_2.This carbonation is also confirmed by TG-DSC curves with an endothermic peak and weight loss of approximate 3%at 680℃.According to above observation,the geopolymer should be improved in the resistance to carbonation if it is used as binders in construction which is exposed to atmosphere or high CO_2 condition. Originality As far as authors known,the experiments related to long-term geopolymer are so insufficient that the application of geopolymer in engineering is limited.This paper not only provides the results about the changes in strength,microstructure and products in the range from month to year but also confirms the inherent disadvantage of carbonation of geopolymer.The 6 years is the longest experimental duration,and the relative results may help geopolymer to be used in practice.

【Keywords】

geopolymer;;ore-dressing tailing;;bauxite;;long-term performance;;strength;;microstructure;;porosity;;carbonation

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