Have you ever tried patching a hole in the wall and no matter what you or your hired tradesman did, you could never get the repair mortar to finish flush with the surface or to dry without unsightly crack lines? While this may be a common problem many people face, it is also important to understand that the issue may lie with using the wrong material.
Hence, knowing the differences between non-shrink grout and patch repair mortar will help you make the right choice and save you time, effort, and expense. Read on to find out more.
“Non-shrink” grouts are commonly used for a range of concrete repair applications including patching of honeycombs, tie-bolt holes, accidental damage, break-outs, and pack-filling of gaps and voids. Non-shrink grouts are selected because they are seen as good quality, high-strength mortars.
Patch repair mortars, also known as dry pack repairs, are usually small-scale, surface repairs performed without formwork construction. They are mixed to a sticky consistency to hold up well on vertical or overhead surfaces and yet creamy enough to be trowel-finished. Most importantly, they are resistant to drying shrinkage; the surface will not crater inwards or crack on drying. For increased cohesiveness in vertical and overhead applications, and for added crack resistance, fibres are sometimes included in the product formulation.
But, which is the right material for the work methods employed in the above repairs?
This question can be answered by looking at two special properties of “non-shrink grouts, and why they are important for their intended applications:
A) Shrinkage-compensation
“Non-shrink” grouts got their name due to containing additives that cause volume expansion either during the plastic stage and/or the hardening stage to counter the shrinkage that occurs when water is lost during drying; the intended result is no nett shrinkage.
This property is important for precision grouting and formwork repairs where the mixed mortar is poured or pumped into a constrained space and left to cure. The surface area of the fresh mortar exposed to air is small compared to its volume and, therefore, moisture loss during curing is well-controlled. This allows the grout to harden and gain strength without loss of volume, thereby maintaining full bearing contact with the substrate.
B) High flowability
Non-shrink grouts are formulated for mixing into a fluid consistency; this enables placement by pouring or pumping in precision grouting and formwork repair applications. It must be able to flow easily past congested spaces to fill voids completely without air entrapment. This is an important property as there is often no access to use tools to move or compact the material.
On the contrary, patch repair mortars can be used without formwork construction.
In conclusion, it is clear from the above comparison that the work method i.e. how the material is applied and the environment in which it is applied are important criteria for mortar selection and the success of the application. Additives for shrinkage-compensation and mortar fluidity add costs to the formulation of precision grouts but serve no purpose in patch repair materials. In fact, if mixed to the recommended water/powder ratios, it would be impossible to use precision grouts for patch repair applications.
Remember: choosing the right materials for the job saves you hours of anguish and gives you better results at lower costs.
At Mapei, a building material supplier in Singapore, we provide a wide range of construction materials for repairs and strengthening concrete for different application needs.
Get in touch with us today for any questions relating to your construction site.
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