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Mortar Mixing in Masonry Work

 

Mortar Mixing in Masonry Work

 

In construction industry, mixing of mortar ingredients plays a very important role. Improper mixing may lead to the development of cracks and reduction in strength.

What is Mortar?

It is the binding material of various building materials like bricks, stones and concrete blocks etc.

Mixture of cement and sand along with the water is called wet mortar mix.

 Mixture of cement and sand along without water is called Dry mortar mix.

Common problems in construction while mortar mixing and their effects.

  • ·      Without measurement box.

          The mortar ingredients to be added with proper measurements. Often it seen that the mortars are mixed with random thumb rule without standard measuring box which leads to the variation in mortar ratio and hence it adversely affects the strength.

 ·        Without non absorbent sheet.

            Non absorbent sheet should be laid underneath the place where mortar is mixed. Without such arrangement the mortar may loose water content which is present in it, and hence the strength of mortar may be affected.

 ·        Preparation of large amount mortar at a time.

            It will affect the strength as part of mortar passes the initial setting time of cement before using in the construction.

 

   How to minimize the quality issues in mortar mixing?

Mortar mixing should be carried out on a  non-absorbent sheet  or on a water tight platform in order to prevent the loss of water from the mortar to the ground. The mixed mortar should be used within the initial setting time of cement. Generally, only as much quantity of cement mortar as would be sufficient for 30 minutes, work shall be mixed at a time. But, often it is observed in construction sites that the labors mix the mortar in large amount and use the prepared mortar after the completion of initial setting time of cement. This can affect the workability of mortar and cracks may develop in the masonry work.  In order to overcome this type of quality lapse, dry mixing should be done. Figure 1, shows the dry mix mortar kept separately. Nowadays, dry mixed mortar bags are also available in the market.

Also, the mortar that has stiffened because of evaporation of water from the mortar may be re-tempered by adding water as frequently as needed to restore the requirements of consistency. But this re-tempering shall be permitted only within 60 minutes from the time of addition of cement.

       

 

                    Figure 1                                                Figure 2

 

 

 

 

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