Masonry grout

[hello12345hello]

I have masonry wall and have vertical rebar at every 32" o.c. so i will grout those cells only where i have vertical rebar. but if i will add horizontal rebar at every 48" o.c. due to shear wall then do i have to use solid grouted wall or i should just add bond beam at 48" o.c. with rebar. so that i do not have make solid grouted wall?

 

[JedClampett]

First of all, get familiar with the cap shift key on your keyboard.
Secondly, you don't have to make the wall solidly grouted for a shear wall as long as the section works vs. the shear allowables. And the requirement for horizontal reinforcing is independent of whether the wall is solidly grouted or not.

 

[msquared48]

Technically, in most cases, you only have to grout those cells that have reinforcing, vertical or horizontal.

Mike McCann
MMC Engineering

 

[concretemasonry]

There are masonry units made for those common construction situations.

There are many regional solutions that have been developed for the details/reinforcement commonly encountered locally.

Just do not arbitrarily dump all available cores because this can be detrimental.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[hokie66]

I disagree with Dick, and most contractors where I am would prefer to fill all cores if there are horizontal bars. I have yet to be convinced that this is detrimental.

 

[charliealphabravo]

there is no need to fill the wall solid if you have gone through the design process in ACI530 or most prescriptive methods/codes/tables.

i would consider the regional practices since they may have a larger effect on the cost, especially as the wall height increases and when the number of pour stages increases. there is no need to double or triple the grout requirement arbitrarily.

...shift key sticking all of a sudden

 

[concretemasonry]

Excessive grouting changes the rigidity of the walls and the building (especially taller) will not react as assumed in the original design and assumption of loads on the elements.

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[hokie66]

So...do you agree that if greater rigidity is beneficial for a particular building, filling all cores is good?

 

[concretemasonry]

The actual building should reflect the decisions made by the design professional and arbitrary additional well-meaning gestures can be detrimental in the building and proper distribution of loads to the different elements.

A noted masonry guru, James Amrhein, always said "Do not count on what you cannot see and be aware of what is buried, no mater what the intent is". This was obvious when we conducted the damage survey after the Northridge, CA earthquake. - Some areas were arbitrarily over-grouted (around corners and openings and wherever grout was used) and the excess was dumped in and proper spec grout has the ability to perform well even if not vibrated and cared for. Due to the excessive grout those areas absorbed an excessive amount of energy and did not allow it to be absorbed by other portions of the building. The result was sudden failures, deflections and later load redistributions as evidenced by the hospital with several sections of differing building heights.

The projects surveyed were built near the end of the period of "dump it full" in masonry construction that changed the behavior of structures. Now we are graduating to eliminate the high strength grout and using f'm based on averages determined with excessive high strength grout, when the external critical fibers are normally the most highly stressed because of the habit of not matching grout strengths with the strength of the units specified. It is unfortunate because higher masonry unit strengths are very cheap to obtain and 4500 psi hollow prism strength can obtained with 8" 8500 psi hollow block and 2500psi mortar. Not all producers can make 8500 psi, but block strengths can be increased by 50% with just the addition of a little water in the zero slump mix.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[hokie66]

I was wondering how long it would take for you to invoke the late Mr Amrhein. To my mind, trying to select grouted areas in masonry in order to evenly distribute energy absorption is taking the principle too far, beyond the capability of designers to predict structure performance. Masonry is an inherently rigid material, and trying to make it more flexible/ductile is not going to work. Just because a fully grouted section of wall failed suddenly does not mean that the same wall would have not exhibited the same behaviour if partially grouted.

 

[msquared48]

I agree Hokie.

Same as saying that just because a fully inebriated man falls down suddenly does not mean that the same man would not exhbit the same behaviour if partially inebriated.

Just thought you'd like to know...

Mike McCann
MMC Engineering