The Z'eer
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- Essex
This something that is REALLY annoying me, perhaps someone can help clear this up and advise where I've gone wrong.
Last October I laid a 15ft x 9ft slab via a delivery of on site mixed concrete.
This was my first experience of concreting and as such the mix was rather wet, not soupy but a high slump mix. I tamped and sawed with a piece of 2" x 4" and plenty of bleed water appeared, I used a bull float soon after to try and level the surface (further reading revealed this was a bad idea). It was over 18 hours before the surface began to dry out. Once fully cured the surface had a nasty dusty surface which through weathering disappeared and revealed exposed aggregate. I'm pretty sure from what I've read that this is was caused by too much bleed water and floating too early.
Next, I made a small path. 1 cement - 4 ballast. Due to it being late Autumn I used a rapid hardener. NO damp proof membrane underneath. This time I mixed the concrete myself in a wheel barrow, a drier mix was used. Less bleed water appeared and the curing process began far sooner. When ready I trowelled the area and edged it too. Months on NO exposed aggregate even via pressure washing. I followed the same method for producing some small steps, once again no issues.
Lastly, extended the original 15ft x 9ft base. Damp proof membrane used, drier mix but no rapid hardener. Curing began after a few hours, bleed water more or less gone, surface seemed ready for trowelling. Surface finished, but several days later seemed just slightly dusty. Pressure washed a few months on...exposed aggregate again!!
I've read plenty of info via the internet but I still can't find out the answer. I'd really like to establish what's causing this exposed aggregate. Any one have a remedy for this or can tell me where mistakes were made?
Thanks
Last October I laid a 15ft x 9ft slab via a delivery of on site mixed concrete.
This was my first experience of concreting and as such the mix was rather wet, not soupy but a high slump mix. I tamped and sawed with a piece of 2" x 4" and plenty of bleed water appeared, I used a bull float soon after to try and level the surface (further reading revealed this was a bad idea). It was over 18 hours before the surface began to dry out. Once fully cured the surface had a nasty dusty surface which through weathering disappeared and revealed exposed aggregate. I'm pretty sure from what I've read that this is was caused by too much bleed water and floating too early.
Next, I made a small path. 1 cement - 4 ballast. Due to it being late Autumn I used a rapid hardener. NO damp proof membrane underneath. This time I mixed the concrete myself in a wheel barrow, a drier mix was used. Less bleed water appeared and the curing process began far sooner. When ready I trowelled the area and edged it too. Months on NO exposed aggregate even via pressure washing. I followed the same method for producing some small steps, once again no issues.
Lastly, extended the original 15ft x 9ft base. Damp proof membrane used, drier mix but no rapid hardener. Curing began after a few hours, bleed water more or less gone, surface seemed ready for trowelling. Surface finished, but several days later seemed just slightly dusty. Pressure washed a few months on...exposed aggregate again!!

I've read plenty of info via the internet but I still can't find out the answer. I'd really like to establish what's causing this exposed aggregate. Any one have a remedy for this or can tell me where mistakes were made?
Thanks
