Page 340 - Construction Waterproofing Handbook

7.8 CHAPTER SEVEN
For example, clear the penetrating water repellents discussed in Chap. 3, use the capillary
voids to grow crystalline particles that actually repel the water. Reducing the size of these
capillary voids reduces the available space for the crystalline growth and therefore the effec-
tiveness of the water repellency. While the admixture use itself may have increased the con-
crete’s ability to repel water, it has also reduced the repellent’s ability to function properly.
Therefore in this situation, rather than supplying “belt and suspenders” protection, the
admixture provides no additional protection for the additional costs of construction.
The same situation can also affect the cementitious coatings discussed in both Chaps. 2
and 3. Since coatings use the capillary voids for waterproofing reactions or bonding to the
substrate, the admixture can also detrimentally effect their performance. Therefore, any-
time admixtures are specified for use in the concrete portions of the envelope, including
precast units, their compatibility with the proposed waterproofing systems should be
reviewed with the manufacturer of the waterproofing materials.
Due to the number of different types of admixtures available, it would be appropriate to
complete a field test to verify compatibility before the actual installation is completed. Not
only can the admixture affect the waterproofing characteristics of the products, it also can
deter the bonding capability of the waterproofing system to the concrete.
Use of fluid-applied membranes, cementitious systems, penetrating sealers, and even
sealants over concrete supplemented with admixtures should be tested, and manufacturers
consulted, to ensure compatibility.