Currently using 1 pt cement to 2 pt sand and 1 pt stones.

A previously built ramp ( 6 months ) has lost the smooth finish exposing the stones. Don't know if it needed more cement or less.

Thanks for help.

Current mix sounds OK to me, but I suspect the previous one had less cement?

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Maybe too much water, the little pictures on the back of the cement sack show you the correct quantities. For a normal job: 4 / stones, 2 / sand, 1 / cement. And a half of what ever measure you are using for the water. It needs tamping down and maybe protecting from the sun.

Most people (especially in Thailand) add water until it is like soup, the cement can only deal with a limited amount of water, the rest just rests in limbo inside the concrete.

Do a 1/3 mix of cement/sand rendering on top of your spalling concrete, should be ok.

1-2-3 for most jobs cement sand stone

What? How long have you been supervising building sites? Waste of money for most jobs.

Current mix sounds OK to me, but I suspect the previous one had less cement?

.

No, same mix. Interestingly, I made the ramp in 2 parts ( it goes over a water pipe ) and one side is still smooth, the other has lost the smooth surface. Same ingredients both sides, same ratios, made a few days apart.

I always cover the new concrete with wet cloth for a day once it has set.

I didn't add too much water, as I did not use boxing on the sides, and it had to retain it's shape unsupported.

Thanks for all the replies.

1-2-3 for most jobs cement sand  stone

Yes, I always use this ratio too.

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New cement should be hosed down every day for at least a month good thai builders will wrap cling film around new cement posts to retain moisture and leave for a number of weeks it needs time to cure If I am right the hoover dam took over 40 years to reach its full strength you also need to ensure it is well tampered to ensure a smooth finish and that could be your problem. 1-2-3 is a good mix but should not be made to wet

Current mix sounds OK to me, but I suspect the previous one had less cement?

.

No, same mix. Interestingly, I made the ramp in 2 parts ( it goes over a water pipe ) and one side is still smooth, the other has lost the smooth surface. Same ingredients both sides, same ratios, made a few days apart.

I always cover the new concrete with wet cloth for a day once it has set.

I didn't add too much water, as I did not use boxing on the sides, and it had to retain it's shape unsupported.

Thanks for all the replies.

Another factor could be temperature. A significant delta in the ambient temps could explain the differant results. Concrete will continue to hydrate for 20+ years (read harden) but you will achieve 90+% in the first 4 weeks. As mentioned elsewhere here excessive evaporation will result in a poor cure, high winds and temps are your enimies in this regard. Keep a new pour moist for 4 weeks and you should have no problems.

Thanks for the info about keeping it wetted down for a month. That's something I never knew.

99% of the people would be so much better off if they just followed the recommended mixture nicely illustrated on every bag of cement for each type of application. But most don't read the bag and just make something up. Proper curing is critical because it impacts every single attribute of concrete. Those first few days are awfully important and will make or break a job. I like to start with a week with forms still on and keeping it covered with burlap bags kept continually wet. If you want to learn more than you would ever want to know about curing, see ACI 308 "Guide to Curing Concrete". It covers different strategies and timelines for getting your project cured optimally.

99% of the people would be so much better off if they just followed the recommended mixture nicely illustrated on every bag of cement for each type of application. But most don't read the bag and just make something up. Proper curing is critical because it impacts every single attribute of concrete. Those first few days are awfully important and will make or break a job. I like to start with a week with forms still on and keeping it covered with burlap bags kept continually wet. If you want to learn more than you would ever want to know about curing, see ACI 308 "Guide to Curing Concrete". It covers different strategies and timelines for getting your project cured optimally.

To add: even more important is to read if the cement is cement....There are premixed cements on the market the bags look similar. And I saw my people happily use the premix to mix concrete in the same ratio I told them to mix with real 100% cement.

What? How long have you been supervising building sites? Waste of money for most jobs.

Is that aimed at me?

What? How long have you been supervising building sites? Waste of money for most jobs.

Is that aimed at me?

I'm afraid so. 1:2:4 is the usual accepted mixture when doing it by hand.

What? How long have you been supervising building sites? Waste of money for most jobs.

Is that aimed at me?

I'm afraid so. 1:2:4 is the usual accepted mixture when doing it by hand.

http://www.aggregates4less.co.uk/how-much-ballast-do-i-need-to-mix-concrete/

High strength concrete 1-2-3 not for high strength 1-2-4 BUT as Thais like to add shed loads of water to it little point 1-2-6 for footings, dont fancy that myself though.

Edited September 23, 201312 yr by kannot