Type S mortar is a medium-strength mortar with a compressive strength of around 1800 PSI. Type S mortar can be used to hard coat classic stucco systems on at-grade or below-grade external walls. It is available in dry powder form and can also be mixed with sand or gravel as a concrete replacement for piers, footings, and driveways.
Type Q mortar is a low-strength mortar with a compressive strength of around 1100 PSI. Type Q mortar can be used where durability is preferred over strength, such as for face joints in classic stucco systems on at-grade or below-grade external walls.
Type M mortar is a strong mortar used primarily for its water resistance. Type M mortar has a minimum compressive strength of 2100 PSI and is available in dry powder form. It can also be mixed with sand or gravel as a concrete replacement for piers, footings, and driveways.
Type W mortar is a wet mix mortar used for its water-resistant qualities. Type W mortar has a minimum compressive strength of 2500 PSI and is available in dry powder form.
Type S mortar is utilized in load-bearing structural applications as well as external applications at or below grade. Type M is a high-strength mortar that may be used for load-bearing or freeze-thaw applications. It can also be used in internal applications above grade.
Type S has a minimum strength of 20 minutes while Type M has a minimum strength of 30 minutes. The type designation indicates the minimum time required to reach maximum strength under specified conditions. For example, if a Type S mortar reaches maximum strength in 40 hours, it means that it will lose strength over time. Type M mortars do not typically lose strength over time.
The types of mortars are determined by testing them according to standards set by the American Society of Testing and Materials (ASTM). These tests measure the properties of fresh mortar and indicate how long it will take for it to become weak enough for water to penetrate it. Weakness is measured in terms of "minimum" strength. Mortar must attain this minimum strength within a specified period or else it is considered unsuitable for its intended use.
Type S mortars are designed for applications where full strength concrete needs to stay strong for a long time after it's poured. This allows the mortar to gain strength over time through a process called "creep".
It is also more resistant to freeze-thaw degradation. It has a copper wire reinforcement added during its production which gives it greater strength and durability than Type S.
Load-bearing structural applications include walls, floors, and roofs. External applications include fence posts and driveways. Freezer-thaw degradation is the deterioration of concrete caused by repeated freezing and thawing of water inside the concrete. This problem can be minimized by using an adequate type and amount of admixture. Admixtures are substances mixed with cement to improve its workability, durability, or other properties.
Type M has a silver rate of 2.0 percent by weight while Type S has a silver rate of 4.0 percent by weight. The difference between these two types of mortars is how much silver nitrate is added during their production process. Mortar that is produced without any silver nitrate will have a Type S label and vice versa.
Silver nitrate is a salt that when dissolved into water becomes silver ions. These ions bond to oxygen molecules present in the air when the mixture is stirred together to create a solid product.