How to Prevent Efflorescence - Protecting your structures
To protect from efflorescence, we have to know how it comes. Generally, three cases must be occurred for forming efflorescence. They are-
- Water must present in the mortar bed
- Soluble salt must present. These salt can come from the manufacturing process of Portland cement
- Some type of transportation media like gravity force or any other thing that bring the salt to the surface
If one or more of these three occurs, salt with water comes in contact, and by the time water evaporates. Reacting with the carbon-di-oxide, the remaining salt then turn into white materials that we see.
So, in order to prevent efflorescence, we must prevent these three causes. Sometimes after eliminating these causes, again we see the efflorescence. Rising again these causes can create efflorescence again.
Some best options are here:
Site surface drainage, concrete not exceeding 4” slump, well-graded mix, well consolidated, welly cured-- these are some factors which can reduce the amount of bleed water and pores in which moisture moves, and thus reduce efflorescence significantly.
The next important step is replacing Portland cement with fly ash. Fly ash brings some benefits which help reducing efflorescence. It reduces free lime and salts. Moreover, it requires less water and denser paste that prevent moisture from moving inside to outside.
Curing is also an important factor here. We know moisture moves more slowly in denser concrete. If concrete is kept cured or moist for a longer period like a few days, more capillaries and pores fill partially or fully, hence, form a denser concrete and reduce efflorescence.
Besides all these measures, someone may consider the followings too-
- Using polymer fortified thin-set mortars.
- Using calcium aluminate cement-based grout
- If possible, slopping the area to evacuate water from the surface.
Besides exterior installation, the expert recommends ‘plaza and deck system’ as it prevents water from staying on the mortar. Use of an epoxy setting material (e.g. LATAPOXY® 300 Adhesive) may also help to reduce the efflorescence.
To prevent secondary efflorescence, admixtures containing aqueous-based calcium stearate dispersion (CSD) are often added. Normally, sand is first kept into the mixer, Oil-based primary anti-efflorescence admixture is then added with constant mixing that allows the oil to coat the sand which prevents further moist absorption.