Failure mechanism of geopolymer cemented RAP concrete
To study the microscopic damage and mechanism of geopolymer cement RAP concrete,S-F geopolymer is prepared by selecting slag,fly ash and auxiliars.Reclaimed asphalt pavement(RAP)is used as aggregate.S-F Geopolymer cemented RAP concrete is prepared from S-F Geopolymer cemented RAP.The mechanical properties and damaged microstructure of S-F Geopolymer cemented RAP concrete are studied by mechanical property test and SEM-EDS.Our results show the reduction of slag content leads to the change of compressive strength of S-F Geopolymer 3 d,7 d,14 d and 28 d,which increases first and then decreases.The high content of fly ash and RAP is unfavorable to S-F Geopolymer compressive strength.Alkali concentration exerts a marked influence on the increase of compressive strength of S-F Geopolymer in the later period,but has no significant effect in the earlier period.The modulus change greatly impacts the compressive strength of S-F Geopolymer.S-F Geopolymer contains C-S-H gels,N-A-S-H gels and C-A-S-H gels in the process of strength formation.The distribution of Na,Ca,Al and Si elements is relatively uniform and there are many overlapping parts.The new aggregate and S-F Geopolymer materials have a good bond.The damage interface of S-F Geopolymer cemented RAP concrete mixed with RAP mainly includes three forms of damage in RAP aggregate,asphalt-asphalt bond and asphalt-aggregate bond.
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