Mortar and Grout 6

[EIT2]

What is the difference between mortar and grout?
Where is each used? How is each used?
What compressive strengths can we expect?
What common misunderstandings or misuses shall we avoid?

What else should we know?

Thank you!

 

[pba]

Controversial and definitely non-dictionary answer:

Mortar is cement/lime/sand in varying proportions used in building masonry walls.

Grout is cementitious mixture of various properties used for many different purposes

 

[ERV]

EIT2,

to answer all your questions would require a lengthy post.
The basic difference between grouts and mortar could be defined by the workability (or plasticity) of the materials. The two are often used interchangeably, however, mortar usually has plastizers (such as clay or lime) added for workability to use for in masonry joints. Mortars also include stucco and plasters. Grout (commercial) usually has no plastizers added to achieve higher compressive strength and would be used to fill cells in hollow masonry units and many other uses where high compressive strength is needed.
Compressive strengths in mortar, dependent on mix can be as low as 375 psi and as high as 2500 psi, grouts (commercial, such as non-shrink) can be much higher.

An excellent site for more info:

http://www.ncma.org/

 

[BigH]

Now, I always thought grout was cementatious material plus water; mortar was grout with fine aggregate (sand) and concrete was mortar with coarse aggregate (gravel).???

 

[Zambo]

Seems that none of us knows the difference. I thought I did but now not so sure.

The lime used in masonary mortar is only to replace some of the cement so that the strength of the mortar is less than the masonary units but the mortar is still workable, therefore if there is cracking it will be at a joint not the masonary. So I am sure lime is not the defining factor.

I believe grouts can be cementitious material and water only with admixtures as required to stop shrinkage etc. But I thing that fine aggregate can be added and if flowable (pumpable) would still be grout.

Mortar I would expect to be trowelable and be a mixture of cementitious materials (lime replacement possibly), fine aggregate and admixtures (or additives) if required.

In summary I think there is a fine line between the two and the main difference being the workability, a secondary difference would be the fine aggregate. Mortar definetely containing fine aggregate and grout containing none or a lower amount.

Zambo

 

[npthao121]

The most important different between mortar & grout is shrinkage characteristic. The grout is non-shrinkage material while the mortar is shrinkage one. Moreover, the compressive strength of the grout is much higher than the mortar.

The grout is normally used when:

- Fill the anchor box of the machine foundation. The abchor box is bigger than the anchor bolt size, after erection of the machine is completed & anchor bolt is placed correctly, then grout mat'l will be poured to fill the box.
- Fill the gap between the surface of conc pedestal & the base plate of steel structure. We could not match the perfect level as design spec during the concrete pouring. We always finish the pedestal apprx 50 mm lower than the design level. During the erection of steel structure ... the level (elevation) will be adjusted to the design value. After that to finish everything, grout mat't will be put to fill the gap.

It is never acceptable to use the mortar instead of grout in 2 cases above. Adding some aggregate to grout mat'l is also unacceptable.

I have 1 bad experience with this wrong using of the mat'l. It costs a lot to repair & compensate to the owner.

However it depends to the type of grout & the spec of manufacturer.

SIKA company (Swiss) has some clear specs for their grout mat'l (component, usage, instruction ...). You can find these info in its website (try some search by Google).

Regards,

 

[MikeE55]

EIT2, I think the answer you are looking for is as follows:

Mortar is the material used to lay block or brick. You specify the strength of it by type, for example, type "S" mortar has a comp. strength of 1900 psi, which gives you a f'm of 1500 psi. (see Table 1, p. S-10 of ACI 530) Grout has a slump of 8" to 11", and is used to fill the cells of blocks at reinforcing. Grout must have a minimum comp. strength of 2000 psi. The most common misuse of mortar is to fill cells at reinforcing. Building Code Req. for Masonry, 1.12.1.2, says that reinforcing bars shall be embedded in grout. Although mortar has a similar strength, the slump is not high enough to give you reliable results as block fill. But trying to enforce that in my part of the country is a job for a full-time masonry inspector.

 

[UcfSE]

I spent 8 years while in high school and college in the field working with masonry and laying block, so let me see if I can help with this at all.

Mortar is a cementitious product, different from portland cement, that is mixed with water and sand. It's compressive strength as MikeE55 stated is specified by its letter designation. It is not grout. Grout is basically concrete with small aggregate, typically 3/8" maximum, and also contains some sand, and of course portland cement. That is one of the big differences between grout and mortar, besides compressive strength. The portland cement is much stronger, but also much less workable than the lime cement which is used for mortar.

The only time that I know of when mortar, not grout, is used to grout filled cells is when using some types of reinforced brick. For example, here in Orlando many fences are built using 6" or 8" Norweigian brick which have hollow cells and receive reinforcing. In this case the cells are grouted with mortar.