Lime To Whiten Concrete

[RATTER15]

I have been looking at various youtube vids about lime being used to whiten concrete. Does anybody have any experience of using lime this way. Is hydraulic lime better that hydrated lime etc, what mix ratio etc?

The youtube clips does not cover this in any detail., I imagine this is another one for "The Builder"

[The Builder]

Lime is added to sand & cement mixes for added plasticity in mortars and rendering. It's still used by "old school" tradesmen. Modern additives mostly make this unnecessary, although you'll never convince them ;o)

Lime was used in concrete until burning lime in lime kilns resulted in the production of today's OPC (ordinary portland cement.)

There's no advantage in adding lime to modern concrete mixes. Certainly not in terms of added strength.

There's a lot of confusion over limes.
Hydraulic (or NHL natural hydraulic lime) sets under water. In short, it'll be harder and able to live happily outdoors.
Non-hydraulic needs air to set and harden. Tends to be softer and thus better for interiors.

This is where it gets silly .... Hydrated can be either Hydraulic or Non-hydraulic. Simply put, water is added in the production process to make it more stable and predictable. Modern "Blue Circle" is a hydraulic lime, but it is also hydrated. If you used lime in your projects, this is what you would use.

However .............. after all that...... you really don't need it. No lime will ever be as "white" as "Snowcrete" alone. The type of sand is much more of a colour factor.

[RATTER15]

Thanks for that, what sand would you recommend, anything particular, it doesn't have to be white, just as near as poss.

[The Builder]

Ratts, you didn't think any more about that sand I mentioned in Cornwall?

[RATTER15]

Hi, Yes I did enquire, the sand was cheap enough but the delivery was out of the question, so I have given up on the silver sand for the time being.
These white stones are for a different job though.

[The Builder]

Ok. I would say the best thing is just to see what your local builders' merchants have. It'll depend on the quarries you have in your area.

You remember when you ere in Northam? When I was in that area, we used beach sand know locally as "Grade A". It used to be dredged from the Taw estuary. I don't know if anything like that is available here you are now, but the light beige colour used to go well with white cement. Nowhere near as white as silver sand, but acceptable.

The main thing for you is to use a sand with as little "fines" as possible. The powderiness of very fine sand can result in crazing and cracking. I would say a "coarse" sand is best for you.

[The Builder]

Sorry about the typos, but I think you should get the picture.

[RATTER15]

Many thanks, I will try a course sand and see how that goes.