How to make a good mortar?

Class of mortar to be used in a given construction project should always be determined in technical specifications. Recommendations for general construction advise against using higher class mortars than that given in the specifications. This specific recommendation results not only from economical, but also from technological reasoning. Higher compressive strength of mortar (when higher compressive strength class is actually used instead of the class specified in the design documentation) usually compromises some other mortar properties, such as bond to mortar units or mortar plasticity, which in turn affect the durability of the construction unit. This rule is reflected by the values presented in the table below, which shows approximate mortar classes depending on construction unit.

The choice of suitable cement with the right parameters is of major importance in mortar and concrete production processes. Inappropriate choice of cement might result in reducing the technical parameters of a construction unit and its poor performance, or it might even lead to a building disaster. Too-strong mortar or cement negatively affects the economical aspect of a construction process by generating unnecessary cost.



Lime mortars
Freshly-made cement mortar has poor workability while hardened cement mortar is rigid and prone to cracking. Lime based mortars, however, do not present such disadvantages. Lime increases bending strength in mortars. Performance of lime based mortars used in wall construction, where an excellent adhesion and bond to construction units play a very important role, proves to be even greater thanks to the positive influence of the lime itself on the properties of the mortar used.

Cement mortars
Cement mortars also fall into the category of general purpose mortars. They are used in places where wall construction is likely to be continuously exposed to water penetration. Such disadvantageous properties of cement mortars as poor workability, low water retention and others can be modified by the use of various admixtures. Since the reaction of a mortar to admixtures is rather complex, admixture application should be under constant laboratory control. Thus, in situations when the construction design documentation recommends using cement mortars, it is advisable to use ready mixed cement mortars instead of free use of admixtures.

Masonry cement mortars

Mortars made with Cement Normal 32.5

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