Nanoscratch on mechanical properties of interfacial transition zones (ITZs) in fly ash-based geopolymer composites

Interfacial transition zones (ITZs) of cementitious concrete are highly heterogeneous, which cause many challenges in accurately obtaining their properties. In this paper, regular aggregates were applied to prepare modelled geopolymer composites, in which ITZs exhibited neat boundaries. Nanoscratch technique with the ability to quickly scan a long distance was adopted to investigate mechanical properties of ITZ and geopolymer paste. To compare the properties of the ITZs and paste, abundant scratch data were analyzed in the form of histograms and Gaussian mixture models. The results showed that the ITZs in geopolymer with silica modulus of 1.5 presented similar properties with the paste, while the ITZs in geopolymer with silica modulus of 1.0 showed significantly higher scratch hardness but lower scratch friction coefficient than paste. Deconvolution analysis revealed that the abnormal hardness and friction coefficient of the paste in geopolymer with silica modulus of 1.0 could be caused by the defects related points. Compared with the traditional scratch scheme, the parallel scratch scheme based on modelled ITZ gave more stable results with a given number of test data, which can provide indepth information for comparative studies.

Automated summary

This paper investigates the mechanical properties of ITZ and geopolymer paste by using regular aggregates to prepare modelled geopolymer composites, revealing the differences between them under different silica modulus conditions. Nanoscratch technique is adopted for a quick scan of long distances, providing stable results with a given number of test data. Deconvolution analysis shows that abnormal properties of paste in geopolymer with a silica modulus of 1.0 could be related to defects.