Damp Proof and Sealing Additive
Performance of Damp Proof and Sealing Additive in Concrete
Hardened Portland cement has pores and scattered capillaries of different sizes depending on the water-cement ratio and the amount of cement hydration.
The pores are mostly between 0.05 micron to 1 micron in diameter and water moves in them due to the capillary property or application of pressure. Damp proof and sealing additives are used when the concrete structure is exposed to salt, moisture, salted water or hydrostatic pressure of water. Another function of permeability reducing additives is preventing problems derived from the movement of water inside the concrete, such as damage caused by the thawing and freezing cycles, corrosion, carbonatation, and efflorescence.
The sealing additives are used depending on the operating conditions of the concrete structure. Damp proofers such as NSG-Z90 are used when the concrete structure is not under the static water pressure, and in other cases, the additives like NSG-N50 are applied that consist of neutral filler as well as very fine solid particles that react chemically with the materials obtained from cement hydration.
NSG-N50 makes concrete resistant against the water infiltration arisen from hydrostatic pressure even up to several meters. In addition, the increased contact angle as a consequence of applying NSG-Z90 makes the needed pressure for water infiltration on the surface become positive, and as a result, the water movement in the capillaries will be insignificant. Although this amount is negligible compared to the additive-free concrete (the concrete without NSG-N50), the use of NSG-Z90 as the final protective coating on the concrete surface reduces the concrete permeability to zero.
