Reinforced hollow block masonry 1

[Bamsi786]

thread507-474133
İ need some guidance about reinforced hollow blovk masonry, we are in a bit of a situation, my last thread was really helpful the people who replied there were really helpful, ill mention their names and ids, im facing a problem where the grouting in the reinforced cells were not done properly, and now im not sure what to do, locals are suggesting just to open the shell at the top, and center and pour concrete with smaller crush. Please i need help ¢

 

[Bamsi786]

https://www.eng-tips.com/userinfo.cfm?member=Lomarandil

 

[Bamsi786]

https://www.eng-tips.com/userinfo.cfm?member=CivStruck

 

[Bamsi786]

İ used 8 inch blocks, not 6 inch, 8 by 8 by 16 hollow, with compressive strength of more than 2000 psi

 

[dik]

I've done several 18 storey buildings with 8" CMU walls nearly 40 years back, and not had a problem. What is the slump of your grout? You can actually see the moisture line as you fill the wall. Do your CMU units have 2 cores? or sometimes (not lately) have seen them with 3.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[rapt]

Years ago we filled some walls using the grout used in PT ducts when they were found to have missed being filled during construction. Pump in from the bottom with bleed holes at the top.

 

[dik]

There were clean-outs at the bottom... the CoW plan checkers were concerned about voids... but none were found. They would behave similar to a window but filled in with CMUs... never a concern. With a good grout mix... it was nearly 'foolproof'. You could actually see the line of the grout on the wall as the moisture soaked into the CMU units... no idea of what the resulting concrete strength was after the water was 'sucked out of the grout'.

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[Bamsi786]

Dik,these are loadbearing reinforced hollow blocks, no frame structure, using for a basement plus 2 storey house

 

[Bamsi786]

My CMUs have 2 cores and are more than 2000 psi in strength, using them as loadbearing masonry

 

[Tomfh]

Identify voids, inject grout.

 

[dik]

And so were these... #4@4'o/c... shear wall construction... prior to it being codified...

Rather than think climate change and the corona virus as science, think of it as the wrath of God. Feel any better?

-Dik

 

[STrctPono]

im facing a problem where the grouting in the reinforced cells were not done properly, and now im not sure what to do

Can you explain a bit more what you mean that it wasn't done properly? You have voids? How do you know? If you can identify the locations then do as rapt said. Drill 2 holes.... One at the bottom of the void and one at the top. Inject grout from bottom hole until it reaches and comes out top hole. Plug both holes. It's hard to offer advice though without knowing much more.

 

[masonrygeek]

There are some non-destructive and destructive methods you can conduct on reinforced masonry walls to determine both the presence of voids and/or rebar. These include acoustic methods, thermography and use of pachometers. The Masonry Society (TMS) has various publications on these subjects:

http://www.masonrysociety.org.

Repairs will depend on what is missing and how extensive the problem is. Some of the methods listed above will work.

To avoid these problems in the first place you can qualify contractors to make sure they are familiar with masonry construction and especially reinforced masonry. Groups such as the International Masonry Institute have language you can put into specs that require a minimum level of competence:

https://www.imiweb.org/training/grout-certification/.

This may not happen on residential construction though.

 

[Bamsi786]

Strctpono, the masons fid the pouring at door lintel height, whereas it should have been done in 2 stages, 4' height and 8 ' height, therefore the concrete never went all the way down. When we started chiseling for electrical and plumbing pipes we found out that the cores are void only with steel inside. Yes i bought a metal detector to locate the rebars the walls, and how do i inject should i use a mobile concrete pump to inject it upwards? Because i was thinking to fill it from the bottom, plug that hole then fill from the top. But i think what you are saying makes more sense but i dont know quite sure how to execute this

 

[STrctPono]

A good old fashion framing hammer and a keen ear tuned to the sound of hollow tiles vs solid grouted tiles is also a cheap way to check where the voids occur. You may also have to probe around a lot with coring to find the upper limits of the voids. In the end, any core holes will get patched, however. I would think a mobile concrete pump would work. A colloidal mixer would probably also be sufficient if you are going to be hand batching on site.

This is generally what I was thinking (see attached)...

You want to ensure you don't trap air in the cells. Pumping from the bottom allows you to expel the entrapped air out the top right beneath the limits of where the previous pour went cold. There certainly are ways you could do it from the top down but you would probably have to cut yourself out a bigger size window and tremie the grout down.

 

[Bamsi786]

Strctpono yes, the hammer check also works best and thanks for the link, it cleared out my concept, i'll try doing this tomorrow and give you the feedback

 

[rapt]

You need a grout pump. Talk to a PT company that does bonded PT.

 

[STrctPono]

rapt, I'm certainly no pump expert but my understanding between "grout" pumps and "concrete" pumps is more of a conversation of semantics. Both, to my understanding, are positive displacement pumps and the real difference is between horse power, line size, and whether the pump uses ball valves or swing valves. In essence, you would not use a low HP pump with ball valves and a 2" line to pump a 3/4" concrete. PT companies use skid mounted colloidal mixers as it allows them to mix a non-shrink prebagged grout on site. This grout is specially formulated and is not getting delivered from a ready-mix-company (at least not in the bridge industry).

Here is a typical PT company setup on a recent job of ours. I'm pretty sure that is a chemgrout brand rig.

 

[Tomfh]

General question - what sort of mix do they use for PT grout? I’ve seen lots of bags of cement on site for the PT guys, but I’m not sure the exact mix they use.

I’m in Australia.

 

[STrctPono]

Tomfh,

I'm not sure if other PT contractors try to batch their own mix on site but given the high importance and large repercussions of failure, using a prebagged grout is standard in my industry. This is a common one that we spec on our jobs.

Link

Positive net expansion, very-low/no bleed, low permeability, high workability, internal corrosion inhibitor, high strength are all important qualities. All the manufacturers come up with their own proprietary blend of supplementary cementitious material additives and very fine (no bigger than 300 microns) aggregate.