Influence of the rheological properties of paste on the early-age tensile creep of high-volume fly ash concrete

It is one of important factors affecting on concrete tensile creep that the rheological properties of concrete paste. The microscopic mechanical properties and rheological characteristics of cementitious paste containing high volume fly ash (60wt%) were analyzed by nanoindentation. And the same time, the tensile creep law dependent on ages of high-volume fly ash concrete containing same cementitious paste was experimental studied. The predictive function expressions of the high volume fly ash concrete (HVFAC) tensile creep considering the rheological properties of paste were proposed. The nanoindentation results show that the fly ash promotes the paste's micro creep development of paste at the same test ages, and the micro creep of paste tends to converge quickly with the delay of test age which the cement is replaced with the same quality fly ash. The influence of fly ash and loading age on the development of HVFAC creep is consistent with the influence law of cementitious paste's micro creep without aggregate. Base on the correlation analysis on the parameters of the products of concrete elastic modulus at some age (0 d-28 d) and the final specific creep of Maxwell body and Kelvin spring body in the ZC model respectively (Et,28d/(EV+EH), Et,28d/χφ), the viscosity coefficient of concrete (φ) and relative compressive strength (fc(t0)/fc,28 d), the parameters of the microscopic creep modulus of paste (C), characteristic time (τ) and test ages, it shows that these parameters are in good agreement with the function y=axb. The tensile creep prediction expression of ZC model considering the rheological properties of cement paste can reflect the structure of the model unit cell. © 2024 Beijing University of Aeronautics and Astronautics (BUAA). All rights reserved.