Uniaxial compression tests on cementitious grout specimens and ordinary concrete specimens with same strength at different ages (1 d≤t≤28 d) were carried out to investigate the compressive constitutive behavior of early-age cementitious grout. The effects of age on the characteristic parameters of stress-strain curves of cementitious grout specimens and concrete specimens under uniaxial compression were analyzed. The characteristic parameters of cementitious grout specimens were compared with those of concrete specimens. Results show that with the increase in specimen age

the peak stress

peak strain

ultimate strain

elastic modulus

peak secant modulus

strain ductility coefficient

and energy dissipation coefficient of the specimens gradually increased. The peak stress

peak strain

ultimate strain

strain ductility coefficient

and energy dissipation coefficient of cementitious grout specimens were greater than those of concrete specimens

while the elastic modulus and peak secant modulus were smaller. Considering the characteristics of cementitious grout

a modified segment-based compressive stress-strain model was proposed based on the existing compressive stress-strain models

and a statistical damage constitutive model was derived according to the statistical damage theory. The calculated results of the proposed models were in good agreement with the experimental results

which indicates that the proposed models can accurately describe the deformation characteristics of early-age cementitious grout under compression.