differant shades of concrete ??

Hi all, i have been trying to do a concrete pathway for my mother with that stuff you mix in with the concrete mix to colour it, trouble is i can't work any more than about 2 hours a day due to my health, so i have been doing a small section at a time when i am able to.
Its coming out ok its nearly finished, its a grey colour but i have got differant shades of grey in the differant sections, anyone got any good tips to make it the same colour all over.
appreciate any good advise, thanks

 

With concrete, a lot of factors can affect the color.
One factor is the amount of water added. If you are mixing by eye instead of with a measuring vessel, then it's no wonder they're different colors. More water usually produces a lighter colored and weaker mix.
Another factor is the concrete itself. Are you buying from only one source, and are all the lot numbers the same? The raw materials in concrete vary from producer to producer. One might get his portland cement from one source, while another gets it elsewhere. One may use one type of sand, the other uses another type. Even the same producer's concrete can vary over time. If they can get a better deal on cement from month to month, they may switch suppliers.
Another factor is the way the "stones" were finished and/or cured. If some were made in cool, cloudy, or damp weather and some were made in bright, hot sun, they will be a lot different color. If some were rained on shortly after finishing, they will be a different color because they were essentially "water cured" for a short period.
Making stepping stones a few at a time, you will never get them the same color. Possibly if you add a coloring agent to the mix and do them under laboratory conditions, i.e. controlled environment and exact formulations, but even then there's no guarantee.
Actually, it's probably better that they are different colors. It will make the walkway look much more natural. If you look at real stones, they're never the exact same color either. You'll have to take several stones of each color and relocate them in the path so they will mix in among the other colors. Since they are about the same 5 or 6 shapes throughout the job, they should fit in easily like a puzzle piece. Your problem is a blessing in disguise, and you don't have to worry about perfection in making them. Good luck.

Pecos

 

I may have misread your thread. Do you mean you're making a pathway of separate stones, like with the quikrete pathmaker molds, or are you pouring a slab of concrete in small sections? If the molds, then the above advice will work. If a slab, you will need to stain the concrete after it's all done (and cured) with a pigmented concrete stain. Unfortunately, these types of stains are not that durable outdoors and will have to be reapplied on an ongoing basis. Good luck.

Pecos

 

If you are using pre-proportioned bags of concrete mix (Quikrete, Sakrete, etc.) and they all come from the same retailer, you probable have more consistancy of the materials than you get from a ready mix plant. The reason is that they usually do not switch brands of cement to frequently AND the aggregates are usually dry or within 1% of being dry when they are batched and weighed. In a ready mix plant, it is possible for the sand to vary from 1% to 8% and the batch weights are adjusted based on an average or estimated amount. After that, a variable amount of water is added to get the desired slump.

With unpigmented concrete, the keys to color consistance are the amount of water in the mix and the finishing.

When you add pigments, you are compounding the water and finishing factors in addition to making sure the mixing is consistant. Since the pigments are so strong, a small error in the weight will result in a big difference in color. The maximum pigment amount permitted is 10% of the cement, with average dosages in the range of 1% to 4% for the colors that are usually desired.

Synthetic iron oxides are the universally preferred pigments because of the color range possible (reds, yellows, browns, blacks, etc), purity and tinting strength. Natural oxides not used as commonly because the the limited colors, tinting strength and impurities. Carbon black is not a tinting pigment and is not acceptable for a durable color.

Pigments must be weighed and not added by volume. Because the pigments are so fine, they can take on moisture (not absorbed) over time, resulting in a different tinting strength due to the bulking. Handling will also affect the volume the same you it does to flour in a cake.

Dick

 

Thanks very much the both of you for your very detailed answers, i didn't expect such informative answers, you guys must be pro's at concreting.
I have been buying the sand and stones [ in bags ] and cement at the same place every time.
I was measuring the colour stuff exactly in every batch as i did with the amount of concrete i made, but never thought about the water factor.

Once finished [i don't really know what you mean by mixing in the coloured stones] and i don't really want to be reapplying it all the time with a stain, but doesn't look like i have any other options.
One thought i had, was after i completely finish is to use that Bondcrete stuff then mix enough to go all over the job with a tinted topping of mortar and broom that on all over the concrete, would that be a possibility ?
many thanks

 

I may have misunderstood your post.

I assumed you were trying to make colored concrete. Apparently you are using a product called "Bondcrete" for some other purpose.

Perhaps someone with better knowledge of treating concrete could add some information/

Dick

 

Dick, I think he used integral coloring to pour a slab sidewalk, a small section at a time. I originally thought he used the quikrete walkmaker molds to make individual "paver" stones that fit together like flagstone, but I was mistaken. The different sections of the walk are different colors. Now he wants to know if he can mix up a slurry with a bonding agent and apply it over the whole slab to make the color match everywhere. Is this correct?
If it is, there are overlay materials available to do what you want. You may be able to color them with the stuff you've been using, but it would depend on the product. That would be a question for the manufacturer to answer.
In general, a good overlay will work if applied correctly on a correctly prepped slab. Some climates are better than others for them. I personally don't care for overlays in a freeze/thaw climate, but a lot of folks make a living doing them. I've seen so many peel off during the winter that I shy away from them.
The short answer to your question is yes, it can be done. If not done correctly, however, it will most likely fail. Good luck.

Pecos

 

Listen to Pecos.

He knows more about his than I do. He has good hands-on experience with cast in place concrete and overlays.

Dick

 

Pecos was correct in thinking that i was asking if a bonding agent like [ " Boncrete " is used for baging up brickwork etc] and asking if i could make a slurry to go all over the job , once i had finished laying the concrete.

I am in Australia, we get cold winters but no ice or snowy conditions were i am, so if the freezing cold can effect the slurry and lifts it , we don't get those freezing cold conditions like the USA gets around xmas time, so it MAY be an option after all.

I have been Googling for answers to this problem before i found this forum, i seen that you can put a seal on the concrete and apparently i seen somewere that you can tint it to what ever colour is desired, i have no idea of costs though, and also you can buy a concrete paint but i don'y know how good this stuff is, i don't want to be painting it every couple of years or so but if it lasted about 10 years i would be interested in that option too.
thanks for all your help everyone, its very much appreciated.

 

If you're not in a freeze/thaw climate, almost anything you do will last better than it would here.
If you tint a sealer, you will have to make it opaque if you want it to all look the same. If you just tint it 'til it's translucent, the darker areas will still show up darker.
If you go with an overlay/slurry, try to make sure that you very carefully measure all of your ingredients, and try to do the job all at once. Before you apply it, make certain that the slab is very clean, and has enough profile to allow the stuff to stick. Most people do this by acid washing the slab first. Use about a 10:1 water to muriatic acid solution, apply it with an acid brush, and scrub it a bit. Use an ammonia/water solution to neutralize the acidic residue, then thoroughly rinse the surface with clean water. Apply your overlay. In your climate I think it would last a good while. Good luck.

Pecos

 

You guys are overthinking it. If he poured them at different times, they are probably just at different stages of hydration. Wait 6 months and I bet they are fine.

 

Thanks for sharing your knowledge Pecos, you have been very helpfull.

 

Thanks for your interest Tscarsborough, the batches were made up approx 2 days apart, over a total peroid of 10 days.
I will give it a few weeks just to see what happens, but i will probably do the slurry thing if it looks to bad.
thanks

 

Hi every one , i just want to ask ,if grout can be used instead of pigment , and how to add this , when making a new floor , that s going to be stamp with texture mats , hope to get a answer , tnx