To explore the influence of pore diameter and constraint degree on cracking time and crushing effect in static crushing process

static crushing tests of 13 plain concrete specimens were carried out. The ratio of concrete area in inscribed circle of test specimen to crushing agent area was defined as constraint ratio

which was used to express the constraint degree of concrete to crushing agent. Volume expansion rate of crushing agent was utilized to indicate the crushing effect of specimens. Results show that: 3 or 4 cracks appeared after the broken of the concrete blocks under a single hole

and 3 cracks were the commonest

when the cracks became stable

the distribution forms were in the shapes of “Y”

“T”

and “cross”; The time-history curve of the volume expansion rate of crushing agent after cracking was in the form of quadratic parabola

which developed rapidly in early stage

slowly in later stage

and gradually became stable; Both pore diameter and constraint degree had obvious effects on volume expansion rate of crushing agent

the larger the pore diameter was

the larger the volume expansion rate of crushing agent became

and the better the crushing effect was

as constraint ratio increased

volume expansion rate of crushing agent decreased

and crushing effect was weakened; When constraint ratio was small

pore diameter had major effects on cracking time

where the larger the pore diameter was

the shorter the cracking time became

when constraint ratio was large

constraint ratio had major effects on cracking time

where the larger the constraint ratio was

the longer the cracking time became.