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Mortar and Cement Details

Mortar makes up 7 to 15 percent of a wall's total area. Although that's a small percentage, the role it plays is not minor.

Everyone knows that it holds the unit masonry together so it forms a stable structure. But it also does a lot more. It protects masonry from water damage and weathering, so it lasts longer. It gives stone, brick or block work a clean, finished, uniform look.

 The key properties you need in it are workability, water retention, bond strength and durability. Since each of these depends on the others, you cant change just one. If, for example, you add more water to improve workability, you'll decrease it's strength. Changing one changes the others, often in ways you can't predict. Be careful when customizing a mortar mix.

Mortar Mix

QUIKRETE Mortar Mix is a blend of masonry cement and graded sand , designed to meet ASTM C 270 for Type N. Just add water.

Mortar Components

Mortar is made of four basic ingredients:

  1. Portland Cement
  2. Hydrated Lime
  3. Sand
  4. Water

We'll also take a good look at masonry cement. This is a manufactured, premixed, packaged combination of Portland cement, hydrated lime and optional admixtures. Masonry cement is so much easier to use that you don't often find anyone mixing mortar from scratch at a job site anymore although it is a cost effective way to do it.

Portland Cement

The binding agent is Portland cement. It was named after the Isle of Portland in the English Channel.

Type I Normal This is a general purpose cement. It's usually the only type you'll need. It comes in three varieties; regular, air-entrained and white. Regular Portland cement is gray in color and costs less than the white variety.

Type II Modified This type of Portland cement generates less heat than type I as it cures, and makes concrete that's moderately resistant to sulfate damage.

Type III High Early Strength Use this when you want concrete to set and cure as soon as possible. Here is an example. Let say you are on a job near Chicago. It's early October and the job's running behind schedule. Then a cold front rolls in. You can't stop work and wait out the weather. But you can mix concrete using type III Portland cement. This concrete will cure in just three days instead of seven needed to cure concrete made with type I cement.

Type IV Low Heat This generates even less heat than type II as it cures, but it's expensive. That's why it's only used on jobs such as dams that call for very large masses of concrete.

Type V Sulfate Resistant This Portland cement has a higher resistance to sulfate damage than Type II. Use it, instead of Type II, when job site conditions are more extreme. Usually you make mortar with type I, normal Portland cement. Once in a while you will use type III Portland cement to make it set up faster, in near freezing weather for example. The color is the one property that does not change how well it does its job.

Color

This property is the only one that has nothing to do with how well it does it's job. The color has absolutely no effect on a structure's safety or strength. But that doesn't mean you can afford to ignore it or treat it lightly. How something looks is always important to people. It's a big part of customer satisfaction although in this world of fast track construction quality does not always get you the job but is very important to me personally. Most people don't know or care about it's other properties, your work is judged mostly on how it looks. But to get it to look good for a long time you must have quality in your work beyond what the eye can see.

The mix calculations use densities set out by the ASTM. These are:

Minimum compressive mortar strengths, ASTM and its psi requirements

The ASTM assigns minimum required compressive strengths to the various mortar types. To meet the minimum psi requirements, a mix just has to be at or above the psi. It can be greatly above the psi. It only has to meet or beat the minimum psi.

Here are the ASTM minimums:

Type M: 2,500 psi
Type S: 1,800 psi
Type N: 750 psi
Type O: 350 psi
Type K: 75 psi

Portland cement

94 lbs/cuft

Hydrated lime

40 lbs/cuft

Sand

80 lbs/cuft

The purchased items are by these:

Portland cement

94 lb bags

Hydrated lime

50 lb bags

Sand

by the ton

Component amounts

Type N Mortar

This uses a 1 / 1 / 6 mix and results in a mortar with a 750 psi compressive strength. Type N is the normal, general purpose mortar mix and can be used in above grade work in both exterior and interior load-bearing installations.

To get 1 cuyd of N mortar, you need 27 cubic feet of the components in a 1 to 1 to 6 proportion.

Portland cement

3.375 cuft

Hydrated lime

3.375 cuft

Sand

20.25 cuft

Total

27 cuft

Based on the ASTM densities, this gives you 317.25 lbs of Portland cement, 135 lbs of hydrated lime and 1,620 lbs of sand.

To put together a single cubic yard of type N mortar, you need to buy and mix together:

3.375 bags of Portland cement (94 lb bags)

2.7 bags of hydrated lime (50 lb bags)

0.81 tons of sand

Type M Mortar

This uses a 3 / 1 / 12 mix and results in a mortar with a 2,500 psi compressive strength. Type M is used for below grade load-bearing masonry work and for chimneys and brick manholes.

To get 1 cuyd of M mortar, you need 27 cubic feet of the components in a 3 to 1 to 12 proportion.

Portland cement

5.0625 cuft

Hydrated lime

1.6875 cuft

Sand

20.25 cuft

Total

27 cuft

Based on the ASTM densities, this gives you 475.875 lbs of Portland cement, 67.5 lbs of hydrated lime and 1,620 lbs of sand.

To put together a single cubic yard of type M mortar, you need to buy and mix:

5.0625 bags of Portland cement (94 lb bags)

1.35 bags of hydrated lime (50 lb bags)

0.81 tons of sand

Type S Mortar

This uses a 2 / 1 / 9 mix and results in a mortar with a 1,800 psi compressive strength. Type S is used for below grade work and in such areas as masonry foundation walls, brick manholes, retaining walls, sewers, brick walkways, brick pavement and brick patios.

To get 1 cuyd of S mortar, you need 27 cubic feet of the components in a 2 to 1 to 9 proportion.

Portland cement

4.5 cuft

Hydrated lime

2.25 cuft

Sand

20.25 cuft

Total

27 cuft

Based on the ASTM densities, this gives you 423 lbs of Portland cement, 90 lbs of hydrated lime and 1,620 lbs of sand.

To put together a single cubic yard of type S mortar, you need to buy and mix:

4.5 bags of Portland cement (94 lb bags)

1.8 bags of hydrated lime (50 lb bags)

0.81 tons of sand

Type O Mortar

This uses a 1 / 2 / 9 mix and results in a mortar with a 350 psi compressive strength. Type O is a lime rich mortar and is also referred to as "pointing" mortar. It is used in above grade, non-load bearing situations in both interior and exterior environments.

To get 1 cuyd of O mortar, you need 27 cubic feet of the components in a 1 to 2 to 9 proportion.

Portland cement

2.25 cuft

Hydrated lime

4.5 cuft

Sand

20.25 cuft

Total

27 cuft

Based on the ASTM densities, this gives you 211.5 lbs of Portland cement, 180 lbs of hydrated lime and 1,620 lbs of sand.

To put together a single cubic yard of type O mortar, you need to buy and mix together:

2.25 bags of Portland cement (94 lb bags)

3.6 bags of hydrated lime (50 lb bags)

0.81 tons of sand

Type K Mortar

This uses a 1 / 3 / 10 mix and results in a mortar with but a 75 psi compressive strength. Type K is useful only in historic preservation situations where load bearing strength is not of importance and the porous qualities of this mortar allows very little movement due to temperature and moisture fluctuations. This aids in prolonging the integrity of the old or even ancient bricks in historic structures.

To get 1 cuyd of K mortar, you need 27 cubic feet of the components in a 1 to 3 to 10 proportion.

Portland cement

1.93 cuft

Hydrated lime

5.79 cuft

Sand

19.29 cuft

Total

27 cuft

Based on the ASTM densities, this gives you 181.42 lbs of Portland cement, 231.6 lbs of hydrated lime and 1,543.2 lbs of sand.

To put together a single cubic yard of type K mortar, you need to buy:

1.93 bags of Portland cement

4.632 bags of hydrated lime

0.7716 tons of sand

Straight Lime Mortar

This uses a 0 / 1 / 3 mix and is used now only to recreate the construction and review the methods of times past or maybe for purely visual purposes. This mortar was made before Portland cement was available in many areas and so this is what was used. Sometimes you'll see straight lime mortar called "L" mortar (for lime) but this is not designating it as "type L" mortar as in the MSNOK types. There is no "type L" mortar.

To get 1 cuyd of lime mortar, you need 27 cubic feet of the components in a 0 to 1 to 3 proportion.

Portland cement

none

Hydrated lime

6.75 cuft

Sand

20.25 cuft

Total

27 cuft

Based on the ASTM densities, this gives you no Portland cement, 270 lbs of hydrated lime and 1,620 lbs of sand.

To put together a single cubic yard of lime mortar, you need to buy:

No bags of Portland cement

5.4 bags of hydrated lime (50 lb bags)

0.81 tons of sand

Glass Block Mortar

This uses a 1 / 1 / 4 mix and is used with as little water as possible. This is a mix designed specifically for glass block. Also, note that it uses waterproof Portland cement in place of "regular" Portland cement.

To get 1 cuyd of glass block mortar, you need 27 cubic feet of the components in a 1 to 1 to 4 proportion.

Waterproof Portland cement

4.5 cuft

Hydrated lime

4.5 cuft

Sand

18 cuft

Total

27 cuft

Based on the ASTM densities, this gives you 423 lbs of waterproof Portland cement, 180 lbs of hydrated lime and 1,440 lbs of sand.

To put together a single cubic yard of glass block mortar, you need to buy and mix:

4.5 bags of Portland cement (94 lb bags)

3.6 bags of hydrated lime (50 lb bags)

0.72 tons of sand


Mortar Net
is a proven way to control efflorescence on masonry walls.


Go to How to clean brick from mortar page



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Mortar Net
is a proven way to control efflorescence on masonry walls.