To study the influences of confinements and coarse aggregate types on compressive properties of ultra-high strength concrete (UHSC)

UHSC specimens with different types of coarse aggregates (basalt

quartz

marble) and the same mix proportion as well as their matrix mortar specimens were investigated by conventional triaxial test under six confinements (0

5

0

0

0

0 MPa). Test results show that the coarse aggregate type had a significant impact on the peak stress and elastic modulus of UHSC. The deformations of UHSC specimens with coarse aggregates decreased significantly under the same axial stress compared with the matrix mortar specimens. The axial strain at the peak point of UHSC increased linearly with the confinement and the failure modes could be classified into three types under different confinements: splitting failure at 0 confinement

shear failure at 5-40 MPa confinements

and squeeze flow failure at 70 MPa confinement. The growth rate of the peak stress gradually slowed down with the increase of confinement. The strength growth rate of UHSC with coarse aggregate was higher than its matrix mortar specimen under low confinements

while their rates tended to be the same at 40-70 MPa confinements. Different aggregates had different resistance to crack propagation

and the proportion of cracks passing through marbles was much larger than quartzs. Comparison of the fitting results by using Mohr-Coulomb criterion and Ansari criterion shows that Ansari criterion was more accurate than Mohr-Coulomb criterion in reflecting the change trend of concrete strength with confinement.