web cracking in prestressed hollowcore

[maddog67]

I work for a hollowcore company , who are suffering from a problem at present , where after detensioning , the webs of the slabs are suffering from lateral cracking / splitting .The hollowcore is produced by a slipforming process where the top and bottom of the unit is produced in seperate stages , and this is where the cracking occurs .
At first I thought it was a simple question of our concrete not being strong enough at release or the strands were over stressed , but these factors have now been ruled out .
If anyone has had any experience of such a problem , please
share your experience and hopefully some possible solutions .Please help cos I am at my wits end

 

[delavat]

Probably is worth to try few strands in upper part to compensate stresses.