Effect of phases on the creep properties of cement paste based on indentation test and homogenization scheme

•The homogenization results are improved by effective contact creep modulus of pore.•The HD and LD C-S-H should be treated separately in the homogenization calculation.•The UC is sole phase in the calculation with modulus obtained by nanoindentation. This article investigated the effect of the individual phases on the creep properties of cement paste. First of all, the contact creep modulus of the paste was obtained by the microindentation test, and the contact creep moduli of the individual phases in the paste were obtained by the nanoindentation test. Secondly, the volume fractions of individual phases were determined by micro test and statistical processing. Then, the contact creep modulus of the paste was calculated with the homogenization method of multiple scales and compared with the creep modulus of the paste measured by microindentation. Finally, the effect of pores, C-S-H, and unhydrated clinker (UC) on the creep modulus of the paste was quantitatively analyzed. The results showed that when the contact creep modulus of the pore was regarded as 0 GPa, the contact creep modulus of the paste was significantly underestimated. The effective contact creep modulus of the pore should be used for the homogenization calculation. The C-S-H gel with low density (LD) and C-S-H gel with high density (HD) had opposite effects on the modulus of creep of the paste so that those two gels needed to be treated separately during the homogenization process. The variation range of the contact creep modulus of UC was relatively large with slight effect on the homogenized contact creep modulus of the paste. Consequently, it can be treated as single-phase in the homogenization calculation.