Advice requested - stained fibreglass

[davidej]

Concrete can can react with GRP and cause massive failure, of which you will have little or no warning.

DONT MIX Concrete and GRP!

How does this happen?

 

[PaulJS]

Concrete in the bilges of a GRP boat? WALK AWAY FROM IT.

Concrete can can react with GRP and cause massive failure, of which you will have little or no warning.

A nice little 17 footer in our yard had had 50kg of concrete poured into her bilge to 'make her a bit more stable'. Some time later it was decided she didnt need it (!) and the owner started chipping it out again - to find the GRP on which it had lain had been attacked and had become like soggy cardboard. The glass mat had of course survived, but the resin binder had failed completely. I have no idea what grade of concrete had been used or why this had happened. But be warned - it can and does!

DONT MIX Concrete and GRP!

Damn!! I'd just about decided that the concrete was nothing to worry about, and as my other concerns only require a modest application of the green folding stuff, that I'd put in a bid for this particular boat.
Must admit though that I can't imagine why concrete would attack glassfibre in the way you describe, and everything appeared to be absolutely solid from the outside...
Anyone else know anything about this sort of reaction?

 

[CAPTAIN FANTASTIC]

The pH value of concrete can be very high, during the initial stages until complete curing which will last for 7 days. However, there is no way to my knowledge that the chemical compounds of the cement, or pH will attack grp and epoxies. We actually, use grp and cement/concrete composite structures as they are very compatible and create good structural integrity structures.

 

[PaulJS]

The pH value of concrete can be very high, during the initial stages until complete curing which will last for 7 days. However, there is no way to my knowledge that the chemical compounds of the cement, or pH will attack grp and epoxies. We actually, use grp and cement/concrete composite structures as they are very compatible and create good structural integrity structures.

That puts my mind at ease!!