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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
 
#150 ·
You two Gentlemen please feel free to attend our next preparation meeting with the ACOE. At that day and time I'm sure you will be enlightened beyond belief. I guess government work isn't for everyone. The ACOE can and have it their way period. Sorry to step on toes that haven't performed work of this nature. As I've said previously we call the ACOE directives, blessings for a very good reason.
 
#151 ·
Would that be, say, the Corp of Engineers? Maybe Department of Defense, Army, Airforce? How about University of Texas, State of Texas, various city governments, etc.?

Because I have shut all of those guys bull**** down when my customers were called on field testing of mortar. It is not allowed, although you are welcome to agree to it, there IS NO METHOD OF TESTING IT, period.
 
#153 · (Edited)
It would be interesting to see the comments on the specifications for mortar and masonry units since they are intertwined in the end.

I would be glad to show those to the ASTM committees (C12 & C15) that write the pertinent specifications and let them decipher what ACOE is and the association credentials and activities are.

I could also present the information to the joint ACI/TMS/NCMA/BIA committee that controls the ACI Doument (ACI 530) plus the ASTM standards committee for testing and standards that covers the design and construction of masonry for the U.S. and about 20 other counties by adoption.
 
#155 ·
I'm in total agreement with both of you"ll. We are at Ft. Bragg and the Savannah District over sees operations.
I will follow up with your advice at initial for next job thank you very much, any and all help greatly appreciated. I will contact our PM to arm him with this information for submittal process of our contracts. I'll update immediately. Gonna poke around through old paper work and see if I can reference their directives.
 
#157 ·
There are 2 methods. The first is a proportion specification, where you simply use ASTM 270 Chart 2 to determine the ratios of sand/lime/cement to achieve the desired strength. This is the best and most common method, and it works just fine, even though a field collected mortar sample may or may not pass a lab compressive test, it doesn't have to.

The second is the properties specification where you take the materials to be used in the field to the lab and test them in accordance with several different ASTM standards including the mixing, curing, and testing of the materials. This is done prior to the start of construction.

Those are the only two methods to specify mortar strength, and it is an either/or choice, although many specs reference both. Either way, there is NO specification or method for collecting field mixed mortar and then testing it in the lab. No method or specification= no such thing as "failing" a test. What test? what method? what specification?
 
#158 ·
There are cubical samples collected daily. They are placed in plastic/ fiberglass looking trays with dividers in them. Then a plastic bag is placed over the jig to avoid contamination I guess or something to do with curing process as we are required to cover all work. Then the sample is left in a restricted/ designated area overnight and collected the following day. Off to the lab it goes. Then the process is repeated each day.
I could care less what they do with it where it goes or what the results are. The GC is the agency requesting and footing the bill for the testing agencies service. They also the GC collects and retains the test results.
On another job breaks were nearly 500lbs. off. No work was torn down I'm assuming because of the stipulations with testing you've explained thoroughly. Just know it is what it is I give mortar away all day long to different trades for different reasons so why should I even care that they're wasting our tax dollars doing testing that has no legitimacy.
 
#159 ·
Taking mortar samples is OK, so long as they understand that they have no standing in relationship to your contract. When they "fail" you for a collected field sample, then there is an issue, one that they will lose every single time, usually with a couple phone calls or at worst a jobsite meeting.
 
#160 ·
There is no accepted standard for field samples. Even if a sample is taken there is no basis, since it is just information of the mortar after it was mixed and not the wall.

Actually, the field strength of mortar is meaningless.

For masonry wall strengths, mortar has little effect on the compressive strength of a wall. The governing method to verify the wall strength is a 2 block high, hollow face shell bedded prism that is tested at 7 or 28 days to determine the masonry strength (f'm) that is the only number that should be in a correct specification and is referenced in all major codes and standards. In the mortar specification (ASTM C270), in the appendix, it states that weakest mortar possible to carry the structural loads should be used because the weaker mortar possesses other properties, such as workability that are important. 2000 psi mortar can be used to get a 4500 psi masonry strength, since the unit strengths control the wall strength.
 
#163 · (Edited)
What about ASTM E 447 tscar, two unit mortar test?

Unfortunately a 14" CMU test weighs over 150 lbs one of five required.... and if grouted needs a 400 ton capacity lab press.

Currently involved in a grout testing scam by national engineering lab that has been over-billing customers by ignoring the IBC prohibitions on these redundant and superfluous testing regimes.

Returning to original issue of post, masonry sand that is graded nearly perfectly, and with the greatest possible % of large grains can be mixed at ratios exceeding 3 to one and still yield mortars that are "rich"/plastic, won't shrink crack, and meet any strength tests, As with any other cemented aggregate the larger the particles allowed less % of filler paste needed.

The USSR developed many different ways to test Concrete with out expensive test equipment to enforce QC.

A half unit grouted full with a 3/8" x 6" deep anchor bolt as pull test sample, cost about 5.00$ per test, could be tested on site with simple pump jack rig.....Nah too simple for an engineer, no profit margin for a lab, an no reason for a new standard every 3 years for ASTM standards gold diggers.
 
#165 ·
The Russian testing is really a comedy of errors. The problem is the "bigger is better" concept, compared to U.S. and European specs and concepts.

In the CIS/USSR, for a precast building made using plant produced reinforced concrete modules, the module has 8" thick walls and measured approximately 10' x 12' x 20'. They tested it by placing it on two points about 16' apart and then applied a vertical load at the center to break it like a beam.

For block prism testing, I saw a 8"(20cm) unit test where they made a "prism" that measured about 32"(80cm) x 32"(80cm) x 64"(160cm).

The concept of testing a solid grouted 2 block prism of 14" block that weighs 140# gives a meaningless result. In the civilized world, prisms are tested hollow/ungrouted with mortared joints, since the codes are based on the ungrouted strength of the masonry units. The strength of the masonry units controls the strength of the prism (filled or not) because the failure mode is in diagonal shear and not direct compression.

There are truck loads of testing results that have been analyzed and conducted for about 50 years to determine the relationship of the wall strength with the unit strength, since the strength of mortar is not a factor in compressive strength. - It all depends on way the design codes are developed with accurate testing methods.

ASTM is not a for-profit organization. Membership is for individuals. The committes that write the specs/standards are individuals with one vote per person and is a balanced membership between designers, contractors, users, academic and interested/public parties. Anyone can join and participate in committee activities, but voting memberships take experience and time. I was an engineer for about 5 years before I joined. A few years later, I tried to get more involved and got on some committees. After about 10 or 15 years of waiting, I got a voting membership opened up and I got to vote. Membership is cheap ($75/year and you get a free copy of one standard of your choice every year to keep current), they do not make money selling standards.
 
#166 · (Edited)
CM the Grouted Unit was only for the grout test, a single unit grouted at the same time as the wall panel... the mortar test would of course have just the shells spread for intermediate coursing, or the shells and webs for the first two or last two courses.

I didn't make my self clear, the USSR reference was to circa WWII concrete NDT...I don't know anything RE soviet masonry tests.(there is a vanishing academic field...)

"they do not make $ selling standards..." The boy scouts are not for profit" too, and everyone at the National level is "comfortable".:whistling
IMO, ASTM standards have gone the way of USA college textbooks, as soon as the market is saturated with the current edition, change a chapter or two, a few new diagrams, 250.00$ for this years standard...burn the now useless legacy codes.

For the climate in my area, the mortar strength is more of freeze thaw resistance guide then wall strength correlation, above a certain minimum strength the mortar lasts through far more freeze/thaw cycles.

Single wythe masonry of course, multi wythe brick was/is its own world.

Heavy C's attachments show a test jig? I thought was supposed to be made out the same material as the Units laid in the mortar, fired clay for brick, and super special CMU form just for the mortar cube former for concrete units...
the mold in the pictures appears to be plastic? and of course the above jigs can't be reused due to the pores filling with cement and minerals wicked from the mortar every use.... lowering the porosity of the jig..
Just as the C1019? requires NEW block for every test, Unless one was using used block in the wall assemblies.
 
#167 ·
Fourthgeneration -

Where are you and what standards are in effect?

Take a look at ACI 530 (Design and Specifications for Masonry Structures). It is the bible for masony in the U.S. and many foreign countries. It is published by ACI since they have the systems and means to distribute document. The document is written jointly by the MJSC (Masonry Joint Standards Committee), TMS (The Masonry Society) that has member that are contractors, engineers unions, material suppliers, state and national associations and educators, the NCMA (National Concrete Masonry Association that is comprised for material manufacturers and sellers), the BIA (brick manufacturers and distributers), masonry contractors and few others. These groups also are respondible for the the ASTM standards for specification of material standards, test and sampling methods and reporting. It is a very valuable that addresses masonry design and construction in a good format with some tables, drawings.

I am not aware of any place where a one block with grouted cores is acceptible unless it is in a location with unique standards or spec writers with strange ideas. The commonly used site sampling and preparation of site is a 4"x4"x8" cube that is form when 4 block are laid to make a 4"x4" square to be filled with grout after some absorptive paper lines the cavity. This allows the block to absorb the excess moisture as it sets and cures and is truely indicative of the properties of the grout in place and the block are not adhered to the sample that can be removed after the block are removed. - A core of a single block is irregular, impossible to measure and cannot be removed, so the block will affect the test. As you know, the cores of the block are not square and the widthe of the core varies since the block have tapered cores and the top may have a flaired face shell and webs for the convenience of contractors. - There is a similar test for grout in brick construction, where the brick are stacked in a similar pattern.

Regarding ASTM standards, there many individual volumes on different related subject. There is one for mortar that also gives the standards of the components and the products themselves. The individual standards (ASTM C90 for concrete masonry units as an example) and others are revised when needed to keep current with others referenced in it. The volumes are reprinted very often and contain all the current standards whether they are changed or not for convenience. - I only really reference one volume for my purposes. Since, I am a member of ASTM ($75.00/year), I get a free volume of my choice annually (hard copy or on line in detail), so that is a great bargain and the $250 does not sound right. As a member, I can download any standard in the volume I choose and print it and use as I choose. Since I am a member, I can go to the site and reference any standard in any volume and buy it at a greatly reduced member price (not need to buy the entire volume of the set of about 30 volumes. - Take a look and you be surprised at what is available for $75 per year that is a business expense deduction.

Again, the "mortar" test you referred to does NOT test the strength of the mortar, but the strength of the mortar and block together. The compressive strength of mortar is not important in the strength of masonry since you can make a 2 block face shell bedded prism out of high strength block and 2000 psi mortar that tests almost 5000 psi, since the masonry unit strength governs. - This is all shown and explained in the ACI 530 I mentioned earlier.
 
#168 ·
I'm just curious if the testing is such a travesty. Why aren't any whistle blowers sounding off. Especially with the knowledge so apparently abundant. Seems redundant that no one is working on preserving OUR hard earned tax dollars on pointless unnecessary testing. Referencing Federal Governmental funded projects through out the USA? Must be a stich of validity somewhere.
 
#169 ·
Because, HeavyC, even done wrong, the samples seldom fail, and it is only an issue when they do.

The reality is that requiring the not-to-specification testing really means is that the one requiring them is getting a WORSE job than if it were done correctly.

This is because the masonry contractor will be sure not to fail, and the only real way to assure this is to make the mortar incorrectly, i.e. too strong for the actual design value required for the masonry assembly using the standards by which the assembly is engineered.

The real, actual reason for the not-to-specification testing, and why it so often occurs on government work is simply them covering their ass. Too bad it doesn't though when it gets down to it.
 
#170 · (Edited)
I'm in the center of flyover Country, between Two rivers....

Owned a copy for ~20 years, just about ready for latest version...
Yes the various committees does a good job in general, But many single issue lobbyists secure positions on the committees through patience and a little camouflage.

See rebar lap rules rewritten to 'encourage' the use of patented"tested" connectors.

Brick manufacturers packing committees to get former tiles declared brick by fiat,(previously ANY unit more the 25% cored was a tile.... )manufacturer saves a penny, I spend 3 cents filling the holes with much expensive mortar, raising walls costs and lowering masonry share of the Wall market.

See the "box" as a replacement for the block jig used in C 1019.

An unfilled unit/half unit the same age as the filled is used as the "control"/Tare block, subtract the unfilled break strength from the filled break= strength added by grouting divide by average # of square inches of cell area sections, = compressive strength of grout/PSI. much closer to actual wall samples. No this is just my idea of a workable repeatable cheap, easy, and positively reflects actual in wall grout strength.

Yes, I'm aware of the confined spaces effect, see concrete filled lolly tubes for a example that relates to "trapped" materials testing higher in compression than homogeneous material.... or a rubble filled castle wall.

For all the ten thousand year history of mortared masonry much of how it actually works remains a"undiscovered" country for Engineers.

Heavy C: I've tend to bid on over specified jobs because wiser heads don't want play the paper chase reindeer games.
My person experience is sadly most engineers are apprentice 'wizards' with little or no idea how the math formulas came about or when they aren't appropriate, Strictly "black box" button pushers.

I believe most standards are include on job documents to lend a mostly false air of academic and technical know how. They are spread through a epidemic of cutting and Pasting that isn't stopped because Subs DON"T CHARGE ENOUGH for having to plow through thousands of pages of wrongly invoked standards.

Most engineers are still trying to apply rules developed for Portland concrete construction to masonry grouts and mortars.

TScar: For me the biggest pain of over strength mortar and grout mixes is the double and triple costs of cleaning the walls and floors, followed distantly by a slight increase in visible cracks. More isn't always better...
I seen to many jobs that the foreman gun decked the tests and the workmanship on the head joints and flashing were non-existent, why bother testing see through walls that leak on day one?

Having worked with fat and thin mortars, I think any foreman would prefer lower strength higher lime content mortar vs uber strength Portland dominated mixes, or over sanded mixes that ruin masons' arms and lower production far beyond the few dollars saved. Forcing masons to crappy mortar to meet some lab rats ideal mortar is silly.
 
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