huangyhg

waterproof mortar
i have a job with load-bearing concrete masonry shear walls. the architect wants me to include a note in my drawings saying "masonry to be dry-block with waterproof mortar".
dry-block is an admixture in the cmu that gives it a level of water repellency. i don't know what waterproof mortar is.
does anyone know what waterproof mortar is? and it seems to me that dry-block and waterproof mortar will have some bond issues, therefore reducing or eliminating my shear capacity. wouldn't water repellent cmu not bond properly with the mortar?
contact w.r. grace for test results on the effects of dry-block on shear strength.
if you are determining the masonry strength (f'm) by prism tests, make sure the prisims are made using dry-block in both the mortar and the block. using the conservative tables (unit strength and mortar type) to determine f'm, the conservative nature of the tables should be adequate if block made with dry-block were tested to determine the unit cmu compressive strength.
i assume this is an exterior wall since dry-block is required. if so, is it a single wythe wall or double wythe wall? both should be properly detailed with the apprpriate weeps and flashing otherwise the dry-block is an unnecessary cost for questionable results.
i hope your architect realizes that all shapes of block in the walls must be made using dry-block. this includes full units, corners, half length, bond beams and lintels. it makes little sense to require it on just a portion of the wall. in my 20 years in the block industry, i refused to supply water proofing block without making special runs of all block shapes for the project and charging the appropriate premium cost for the production, materials and liability.
with the loose dosage rates for different types of mortar, some contractors may can be expected to submit alternates because of the implied liability if the is any leakage from any cause.

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