Can anyone help me with a recipe for white concrete suitable for a paved surface. I understand the use of white cement. Its mostly the importance of the aggregate that Im concerned about. Im having trouble finding a suitable white sand here in the Guildford area. How important is the sand colour (Ditto the stone colour.) I can use a shingle to get a lighter aggregate colouring if this is important.)
I have been advised that a normal builders merchant sharp sand will give me a suitable creamy colour. Is this correct or shall I continue to try to source a white or silver sand
Thanks
Sam
Recipe for white concrete - White concrete mix
-
London Stone Paving
- Posts: 2199
- Joined: Mon May 10, 2010 1:07 pm
- Location: Surrey
- Contact:
-
Brucieboy
- Posts: 162
- Joined: Sun Jul 17, 2011 1:21 am
- Location: Essex
Thanks Steve - just read your PM. Sam - to produce white concrete, you do as you say need to use as lighter sand as possible. The lightest is generally silver sand which, depending on the source, can vary from almost white to buff. Try Hanson at Reigate (not far from you) - I think they still produce special sands.
If you're using coarse aggregate as well, go for a light, uniform coloured materal such as limestone. It doesn't make a significant difference but it all helps.
Be aware that silica sands can be somewhat single sized (the majority of the particles are of one size) and therefore not particularly ideal for making concrete - the mix tends to bleed. Consequently it requires a highish cement content, say minimum 350 - 400 kg/m3, to minimise the passage of water bleeding to the surface. To reduce the amount of added water it's beneficial to use a water reducing admixture such as a mid-range superplasticiser. However, avoid using a lignosulphonate-blended one as they're usually brown in colour (wood resin based) and this can affect the whiteness of the concrete (albeit marginal). If you're laying a slab as opposed to making paving units, you should also use an air entraining agent to provide frost resistance - it will also help to reduce bleed.
To further whiten the concrete, you could try adding white pigment (titanium oxide) at say 5% by weight of cement or even white microsilica (silica fume) - however, this very much depends on your budget as they're not particularly cheap to buy.
Whatever you end up using, always batch materials accurately for consistency. Do a trial mix first and let the concrete harden for a few days to assess the final colour. Also note that a trowelled surface will generally be lighter than a moulded surface.
Hope this helps.
If you're using coarse aggregate as well, go for a light, uniform coloured materal such as limestone. It doesn't make a significant difference but it all helps.
Be aware that silica sands can be somewhat single sized (the majority of the particles are of one size) and therefore not particularly ideal for making concrete - the mix tends to bleed. Consequently it requires a highish cement content, say minimum 350 - 400 kg/m3, to minimise the passage of water bleeding to the surface. To reduce the amount of added water it's beneficial to use a water reducing admixture such as a mid-range superplasticiser. However, avoid using a lignosulphonate-blended one as they're usually brown in colour (wood resin based) and this can affect the whiteness of the concrete (albeit marginal). If you're laying a slab as opposed to making paving units, you should also use an air entraining agent to provide frost resistance - it will also help to reduce bleed.
To further whiten the concrete, you could try adding white pigment (titanium oxide) at say 5% by weight of cement or even white microsilica (silica fume) - however, this very much depends on your budget as they're not particularly cheap to buy.
Whatever you end up using, always batch materials accurately for consistency. Do a trial mix first and let the concrete harden for a few days to assess the final colour. Also note that a trowelled surface will generally be lighter than a moulded surface.
Hope this helps.
Retired DIY'er
-
London Stone Paving
- Posts: 2199
- Joined: Mon May 10, 2010 1:07 pm
- Location: Surrey
- Contact:
-
TheRockConcreting
- Posts: 169
- Joined: Wed Nov 28, 2012 4:26 pm
- Location: Cambridgeshire