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Mortar mixing ratio

267K views 170 replies 36 participants last post by  Tscarborough 
#1 ·
Ok dumb question time. As some of you may know Im still new to the brick laying trade. So far I have only done some small projects and heve been using the premixed morter. I now have a project that would be better using some sand and cement and mixing my own morter.
What I need to know is what is the best mix ratio. I have looked around the internet and found a few charts that only confuse me. So I figure that I had better consult the all knowing wise masters on this one.
Thanks in advance
Smitty
 
#97 · (Edited)
I agree about the 6" block. Many contractors lay it cheaper than a 4" because it is more stable (not tippy) and not that heavy. In many countries, it is the preferred size for high rise load-bearing masonry because of the cost advantage.
 
#100 ·
mortar

I have not read all these posts. They are all interesting.From the data i read the ability of a lime / cement mortar to have the ability to self heal (autogenous healing) may be a myth the producers would like us to believe . I have read that the intrduction of even a small amount of OPC "binds up" the lime and leaves no "Free" lime to perform that task
 
#101 ·
Ok dumb question time
The only pre-mix that was good for laying and structurally true I ever used is glass block mix by Pittsburgh Corning.
Best is to know psi of material, inside/outside average permanent temps. Use smoothest sand available in your area.
Ratios of cement, sand & plasticizers per use.
Experiment, yourself though, my own hit 6800 psi with stone that hit 17,000 and pleased the inspector.
3 parts smooth sand, 1 part cement, 16oz. of secret sauce.
Just experiment at home. Take notes. Study and apply.
To this day I can not understand why Trump Tower in New York has the greatest psi for concrete and cost so much for it... speced @ 10,000psi
 
#102 ·
From what I've read and experience on elevator shafts, light weight block have a better fire rating due to the expanded clay mixed with the aggregates to save weight. Also 5/8 drywall glued to the block definitely adds to the fire rating. And to tie it back to the original thread, we've always used shovels to measure out sand, but we have a pretty experienced crew so its pretty consistent.
Also we have two main suppliers of sand around here, one is pretty fine, really sticky, and tools really nice, and another that is a lot more course seems more workable and I would imagine a little stronger although 17 sand to a bag of masonry is as much as you can add without making it too sandy.
 
#106 · (Edited)
Around here our light weight block are called haydite and they carry a full two hour fire rating, the heavy weights are 90 minutes.

The sand all the pits around here are screening is very fine, in my opinion its too fine and gives up a fair amount of strength. Really sticky, thats why the block guys like it, but it isn't worth the time of day for laying brick.

24 well rounded shovels of wet sand per 70 lb bag of type N masonry cement. Read the bag, get your shovel out and do the math. A guy can vary a little either way, but a 70 lb bag has about 8 shovels of cement in it.
 
#105 ·
When I was in block business we did not produce the sand but sold it as a convenience to the contractor because we had contacts with all the concrete dispatchers and they could give good directions to the site since they already were dealing with some very vague contractor directions (as an extreme, go to where the red car was parked, turn left and go up the hill and honk the horn and someone will lead your in) for jobs about 30 miles away.

We handled 2 different mason sands (one clean and fine and one coarser and a little dirty) and every contractor had a preference for his crew, so we had to just order the sand for the job from the right sand supplier.

Every good masonry contractor has a handle on what is needed for the crews (price not important, but service and advance delivery in the winter is) to get the job done right. the specs for masonry sand are loose, just as the dual specs for ASTM Mortar Specifications are because of the allowable variances of materials. - It is more of an art.

TS - Not rocket science, but I did crawl up and around F1 rocket engines to get information. I did work for a rocket engine manufacturer and saw my first rocket test at Edwards AFB for the F1 (Appollo) acceptance stands. Everything on the mountainside test stand (18,000# of fuel and a similar amount of oxidizer) blew up and I had to go to a debriefing hearing the day after and they asked me what I saw that was out of the ordinary. What could I say when it was the first one I saw at that facility, but I witnessed many more good tests in that god-forsaken place. In those days, it was not rocket science. - Before the man on the moon.
 
#110 ·
I've had an inflammed rotater cuff in my strong shoulder since May2011.. It's still inhibiting. I can't bench or anything anymore, I'll still throw a bucket or bump it up staging. Even throwing a football stinks.. But yeah that's me, I used to think people complained to much about injuries you can't see. I was always asked: 'Are you gonna be a ^#%$%#@$ all your life'- reminiscing
 
#111 ·
You might want to research prolotherapy. It might help.

Funny story, I was working 7 days a week for a couple months 10 years ago. Well I set up just 3 heights and didn't level the pads so the screw jacks wernt on them flat. Of coarse I didn't have any inside cross braces on. Well I pissed off my helper and he tor ass down the staging. Yup opened up the frames and my planks fell. 12 feet straight down. Tore my AcL and McL. Not all the way but enough.

Anyways, 2 treatments of prolotherapy and the swelling and paint went away. Good as new now!
 
#126 ·
Che bello. Sono contento che tu abbia trovato queste fotografie della tua famiglia. Non li perdere che non ci sono molte famiglie che non sanno chi sono i loro nonni e che mestiere facevano

Might be crude translation but basically:

How nice.I am glad you showed these pictures of your family...There are a lot of people who forget/dont know their ancestors/grandparents and their roots/business..
 
#140 ·
The bilingual stuff reminds me of a funny story my Father in law yells. He worked for Hydro and once they were contracting out a sub station. One of the terms of the contract was that the contractor had to be bilingual (2 official languages in Canada, English and French). An Italian got the contract and during the review brought a friend with him who was interpreting. The Hydro official says in French "You do know that the contractor needs to be bilingual" and the interpreter answers "oh he speaks both Italian and Portugese fluently"
 
#145 ·
There has been a great deal of discussion on the methods of mixing mortar on here but I haven't seen the first post about why the ratio is what it is. If you have too much cement in your mix then you will end up with shrinkage cracks. Cement shrinks and if you don't have enough sand in your mix to spread out the particles of cement you will end up with to high a concentration of cement and risking shrinkage cracks in your wall or foundation. If your mix is testing two or three times the spec or the last test results that the manufacturer has documented (they give that out pretty handily if you ask for it) you are mixing too rich.

We've mixed with buckets for the last several years now and we were surprised how much farther we got on a bag of mortar when we put the proper ratio of sand in the mix. If you take your shovel count and throw it on a tarp and then get a cubic or half cubic foot box and put 3 cubic feet on a tarp next to the first pile you will see a difference. Most people will. Personally it spread better when we used that method. It cuts out so much guess work on how many shovels you have thrown in. Who wasn't mixing mortar at one point and someone comes up to you 5 shovels in and distracts you, then you lose count. If you have a set volume setting in front of your mixer you know how much you are putting in right off. So your only real variable is water content of the sand. It doesn't take much to gauge the water content of your sand. If your hand comes out wet if you stick it just inside the surface of the pile or bag then you may want to start out with a little less water than usual. If your pile is at the bottom of a hill collecting the property's water... that's your fault and you'll likely get some efflorescence to clean off later.

Someone mentioned in an earlier post about an employee getting injured hefting a bucket of sand. We use 2.5 gallon buckets. So you are using 8 per bag instead of 4. Using smaller buckets allows for a min or two more for mixing time anyway.
 
#146 ·
The mixing clock on mortar begins after all components are added. That gives a MAXIMUM of 5 min.
There is no need to lift buckets of sand if you think out side the BOX. That's all I can add on proper measurement of cubic feet. It took us several attempts through trial and also error to develop our method. Not about to let that trade secret out. May try to patent the design see where it goes? We under go scrupulous field drawn sample testing 3 times daily. Our breaks vary only in couple hundred pounds increments max.
On the 3 to 1 ratio, if you read the directions on the mortar bag. Some manufacturers are recommending 2 or 3 parts(cubic feet) of sand to each bag.
 
#148 ·
Tscar is absolutely correct. There is NO standard for field sampling and testing of mortar because of the variability of the materials from batch to batch. The applicable specification for mortar is ASTM 207, which is a laboratory method.

The moisture content of the sand varies by location of the sand taken, so a standard from the field is meaningless. There have be attempts to create a meaningful standard for over 75 years, but committees writing the specs (contractors, manufacturers and engineers) could not arrive at something worth controlling.

I knew of several mudmixers that were paid more than a mason because they were critical to real production than the masons. - This was for mid-rise loadbering construction where production and lack of excess mortar in the wall was always a problem when it comes to partial grouting. - The company was very critical about materials and wanted all block to oriented in a cube correctly (block top side up so the mortar beds made handing easier, especially for 8",10" and 12" 2 core block that were laid one-handed. When you lay 1 to 2,000,000 block a year, you get what you want at any price.
 
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