# Forum Home Renovation Concreting  My Experience doing Exposed Aggregate Concrete

## zacnelson

I have recently completed doing exposed aggregate pathways at 5 locations around my house; I have attached photos showing some of my work.  I have yet to do my driveway; I want to leave that for a long time because over the next year or so I will have plenty of trucks coming to deliver things and I want to minimise the chance of my driveway cracking.  I would be interested to know if anybody has any tips for people who wish to undertake exposed aggregate concreting; I will add a few here. 
1) It is hard to get the rounded edging to work correctly.  I discovered that the best approach is to use the edger immediately after the initial floating, while the concrete is still very fresh.  Then later at the trowelling stage you can go over it with the edger again to get a neater finish.  If you try and just do the edging at the trowelling stage, it all falls apart and it is a nightmare.   
2) It is very important to have the edges very tightly compacted and strong, because when you blast the surface with the high pressure spray the edges can be destroyed otherwise. 
3) I used BASF Expose as a surface retardant.  It said on the container that you should wait around 12 hours before removing the top layer of cement with the high pressure spray.  This proved to be too long a wait.  
4) I recommend trowelling a little too early (ie whilst the surface is still a little too fresh and watery, maybe an hour too early).  When trowelling, give it a vigorous rub with a steel float to give the stippled surface look, mainly in order to further depress the aggregate and embed it below the fines.  Then give it a smooth stainless-steel trowelled finish.   
5) Wait only a couple of hours after trowelling before you blast it with the water.  This way you should be able to spray it from a slightly further distance away, which will eliminate the possibility of creating localised pits, less demage to the edges, and less stone removal.  I did all my work using a cheap Karcher bottom-of-the-range pressure washer and it did the job fine. 
6) Remove the formwork BEFORE you coat the surface with the sealer, otherwise the sealer will make the formwork stick to the edges of the concrete and you could possibly break a little of the concrete away.

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## wrexter

Wow great results, if you can write a procedure up that would be brilliant as i want to undertake this soon. 
I know it wont be easy and it would be good to know all the facts before i get into it. 
Cheers.

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## Godzilla73

G'day, 
Looks good mate.  :2thumbsup:

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## Concretecure

Hi zac looks like a pro job!! I have done quite a few exposed jobs for customers over the years and the tips you have posted are spot on. here are some more which may be of assistance.
1 Acid etch or acid wash the area with 5% -10% solution.Pour it on and brush with rigid brush allow to sit for five mins before pressure washing off. This will take off the fine layer of milky residual cement and bring out the colours of the aggregate.Do this before you seal the job.
2 To minimise cracking  practise the "6 P's rule" (proper prearation prevents piss pore performance) Ground preparation is important to be uniform over the whole area as concrete tends to find its weakest point and cracks at that point. The way i achieve this is scrape ground to desired levels. Apply 20-50mm crushed rock base, screed the rock as you would the concrete dead flat, then apply heavy compaction, pour the concrete in driveway area a little thicker than normal and last but not least 30 mm deep saw cuts at pressure point and min distances.2mts min 3mts max apart. Pattern saw cuts can be expensive but can look really good and minimise visible cracking.Eg 800mm  square or diagonal tile pattern 
Other than that i think you have it down to a tee. Keep up the good work!

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## Godzilla73

G'day Zac, 
Hope you're still on here, any chance you could tell me what make/model pressure washer you used and how many psi it was punching out. I'm planning on doing some exposed agg soon and a few of the retarder manufacturers recommend 3000 psi +, my Karcher is good for only 2200 ish so i may need to hire one. 
Any info would be great, thanks.

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