Need fix window sill

[vw754]

Had an extension and the builder put new windows in and sills, the outside one got a chuck missing from it, i told builder not bother replacing it as ot would of meant, windows would have to be removed and didn't want the headache.
I have tried to fill it using some ready mixed mortar, but it fell out, what can i use that will hold? Can't seem to post pics.... Says security error try again, ive tried a few times.

 

[foxhole]

Chuck missing?

 

[StephenOak]

Chuck missing?

Chunk missing maybe.

 

[foxhole]

Chunk missing maybe.

Chunk of what though? Brick? Block? Render?

 

[vw754]

Sorry guys, chunk.... Basically a bit of the new sill broken off

 

[foxhole]

Sorry guys, chunk.... Basically a bit of the new sill broken off

What type of sill? Wood , plastic , concrete.?

 

[vw754]

What type of sill? Wood , plastic , concrete.?

Concrete

 

[foxhole]

Did you prime the surface before filling, resin type filler better for larger repairs , difficult to judge without pics. Did you select upload file from menu below the posting box? For pics .

 

[vw754]

Just tried filling it.
And yes i tried from menu below