On 16 June, 14:31, rpgs rock dvds wrote:
Big puddle of white stuff on patio snip from O.P.

Update - spotted workman next door, told him about problem, he came
round with bucket of light blue liquid (not sure what this solution
was) and he brushed liquid over patio slabs with an "outside brush".
After area dried out, most of discolouration has gone - prolly all go
if I give it another clean myself.