huangyhg

mortar used in lieu of grout for precast concrete lintel
i have been asked to comment on a concern with the construction of a lintel. the lintels are 2 courses high. the bottom course is a precast concrete,4000 psi, u-block unit with 1 #5 bar and the top course is a masonry unit, f'm =1500 psi, with 1-#5 bar. type s mortar was used in lieu of 3000 psi grout for the reinforcing embedment. is there a way to calculate something like this or should i refer them to the precast concrete manufacturer's consulting engineer? thanks for any help.
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if the precast works by itself unfilled then you know you're ok no matter what. the easiet thing to do is tear it out and make them do it right. are you the eor or did they hire you to check it? i would ask for tests of the the mortar to confirm its strength. with that, you may be able to check the lintel as a masonry beam with the masonry code. i can't imagine why on earth a mason would fill a precast with mortar. they should know better.
thank you for your reply, ucfse. you are right they should know better. i was hired by the masonry contractor to comment and provide calculations showing the strength of the as-built assembly.
if a testing program will be developed for the mortar, compressive strength determination alone will not suffice since there are other forces in play. bond strength is very important. compared to the bond between grout and reinforcing steel, i am pretty sure the bond between reinforcement and mortar is very low.
the precast lintel must be strong enough to carry the load above the opening by itself. there is no point in testing the mortar. there is no design method or allowance in any code i am aware of that allows for designing a bond beam using mortar instead of grout.
regards.

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