The SikaMix AE line of products are specifically formulated to help reduce efflorescence but at the same time improve the water repellency of concrete mixes. Efflorescence can be an issue that plagues any concrete producer and water repellency may be specified on masonry and concrete buildings to enhance its life. Read on for more information about water replellency and tips on efflorescence reduction.
SikaMix AE products can dramatically reduce primary and secondary efflorescence on concrete products. These products can also reduce concrete absorption making concrete “water repellent”.
According to ACI efflorescence is a deposit of salts, usually white, formed on a surface, the substance having emerged in solution from within either concrete or masonry and subsequently been precipitated by reaction, such as carbonation, or evaporation. In order for efflorescence to occur, three conditions must exist:
- There must be soluble salts available.
- There must be a source of water that is in contact with the salts, forming a salt solution.
- There must be a pathway for the salt solution to migrate to the surface and evaporate.
Chemical Reaction for Efflorescence
In an effort to reduce efflorescence you must address and limit one or more of the items above.
1. Utilize SikaMix Products (chemical admixtures)
- Plasticizers increase the density of the concrete thereby reducing efflorescence.
- At constant density, plasticizers improve strength. This correlates to a more impermeable system, thus reducing efflorescence
2) Efflorescence Control
- Pore-blocking component enhances surface tension so that water cannot wet-out the pore surfaces and efflorescence is blocked.
- Polymer component forms a protective coating in both the pore structure and on the pigment particles, thereby enhancing color vibrancy.
2.Optimize the mix design
1) Optimize cement content
- Too little leads to low density
- Too much leads to increased efflorescence
2) Optimize water content
- Enough for desired properties, but higher water contents correlate to increased tendency to effloresce.
3)Use well-graded aggregate to minimize porosity.
4)Use of low-alkali cements and de-ionized water may minimize efflorescence.
5)Use slag and/or fly ash
3.Provide a good curing environment for the concrete
1)Cure in warm moist environment (i.e. vapor) to insure concrete has high(er) strength/density before it is subject to weathering
- Allows the use of higher percent replacement of slag and/or fly ash
2)Exhaust in an effort to remove residual moisture from product surface, (an important step if fully wrapping)
4.Concrete should be protected against extraneous water for as long as possible, (condensation during spring & fall are often a problem).
5.Good air circulation and sufficient carbon dioxide will promote early carbonation and minimize both primary and secondary efflorescence.
6.Good mechanical compaction is essential to prevent efflorescence.
Water repellents can play an important role in extending the life of a concrete building.
- Reduced water absorption
- Improved freeze thaw durability
- Reduced deposition of de-icing salts within concrete
- Reduced spalling
2. Protects the overall investment
- Reduced risk of mold infestation
- Reduces risk of corrosion
To the left we see that the simple addition of SikaMix products to both the mortar and block has a significant impact on the ability to resist the penetration of water. These panels were tested according to ASTM E 514 and proved the performance of SikaMix products.
Water repellents work by reducing the surface tension of water and decreasing capillary action.When utilized it is typical to see an“umbrella effect” , such that water beads on the surface of the concrete. It is possible to see this same effect with the post application of a sealer, however, the huge advantage to utilizing an integral water repellent is that it is always there and never requires reapplication.
Beading & Reduced Capillary Effect