Cement-rich grout as bonding agent

[ajk1]

I want to specify a cement-rich grout as a bonding agent, but would like to be more specific than just saying to use a cement-rich grout (although I have seen such a specification, it sees to me to be too nebulous). If I want a w/cm = 0.40 for the grout, how can I specify that by volume, to make it easy for any contractor? If a Canadian bag of Portland cement weighs 40 kg, then the amount of water to be added would be 16 kg per 40 kg bag of cement, which would correspond to 16 litres of water. Is there a standard pail size so I could say how much cement to put in the pail, and is there a difference between an American pail and a Canadian pail? Or should I just specify 16 litres of water per 40 kg bag of cement?

A supplementary question is, does "bulking" ahve to be taken into account when specifying the volumetric proportions?

 

[dhengr]

Ajk1:
Why not just specify it as 2.5kg of Type x cement per liter of clean water? Then if you doubt that he can weigh the cement and measure the water, wouldn’t you wonder if you want him working on the job too?

 

[Ron]

Agree with dhengr. You can also specify it as a neat cement paste.

 

[Leftwow]

what is your basis behind cement rich grout?

 

[ajk1]

My experience over the last 50 + years, is that repair contractors do not weigh materials on site, and they will think you are being pedantic if you ask the to do so. Perhaps you have more sophisticated repair contractors in your area. In the old days, and I am almost old enough to have been there, the Codes gave mix proportions by volume, perhaps because much of it was mixed on site and measuring by volume is easier than be weight.

What does a neat cement paste mean? How much water goes into a neat cement paste? If you specify it that way, the contractor will put in more water than is desirable for the paste to form a good bonding agent. He will put in lots of water because then he can spread the paste more easily. That is not what I want. Been there, done that, and have learned lesson.

Ok, I know you won't agree with what I just wrote, but anyway, I am looking for the answer to the question that I posed. Thanks for your thoughts though. They are much appreciated and what I would expect to be done in a better world, so from that point of view you are 100% right. Thanks for taking the time to respond.

 

[Ron]

"Paste" in and of itself, is the definition. Paste is a viscous liquid. Toothpaste, paste that the kids eat in school.....similar. If it has that consistency and is worked into the surface with a stiff brush, it will work. It has been used for about a hundred years as a bonding agent. Beats the hell out of synthetic bonding agents.

 

[SlideRuleEra]

I am almost old enough to have been there, the Codes gave mix proportions by volume, perhaps because much of it was mixed on site and measuring by volume is easier than be weight.

I'm not that old either... but my father was. A bag of portland cement in the US weighs 94 pounds. That is not an arbitrary number but the long assumed weight of exactly one cubic foot of loose portland cement. The 94 pound bag size is a direct carry over from the days when concrete was mixed by volume.

Do a little math, and I get the following proportions give a w/cm = 0.40:

3 parts water (by volume) to 5 parts loose portland cement (by volume).

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[MotorCity]

I would specify the required compressive strength, w/c, and that the contractor follow the manufacturer's requirements for batching, curing, etc. if it in a pre-mixed bag. I agree that simply specifying "cement rich" grout is meaningless. You need to define what you want such as cement content, w/c, etc. I have not heard of, nor would I suggest reference to water being added by the pail. Again, how big is a pail? If you want 16 liters of water with 40 kg of cement, than that is what you should specify. Use real measurements, not arbitrary, loose words that could be subject to misinterpretation.

 

[ajk1]

Thank you all for the comments. Much appreciated.