The Brew Cabin

Posted: **Mon Dec 13, 2010 9:59 pm**

Having just looked at sean&ruby's rebar work I just decided I should research rebar best standards and looked at this page:

http://www.pavingexpert.com/reinfrc1.htm

As the site says, rebar work is a trade in itself and is currently beyond the scope of the site.

I regularly cast pillars and beams onsite folowing engineer's diagrams and these frequently only allow a couple (sometimes just one) of centimetre's coverage between the edge of the stirrup and the shuttering (ie, less than the 50mm specified for sheet mesh in a slab).

Now, a beam or pillar is not a slab and I am not an engineer but it has crossed my mind before as to whether this failure to encase the beam/pillar reinforcement in less than 50mm of concrete is a 'developing world' money-saving technique (I work in the 'developing world').

Is there a site or book that anyone knows of that is good for the layman (ie, not an engineer) to learn a bit more about casting and specifying reinforced concrete? I am also keen to learn more about best practice in overlapping bars...

I had a very good book 'For Pros by Pros - Concrete Work' but I do seem to remember it being more for slabs than beams and pillars. I think I have it in storage somewhere so will try and dig it out but would like some other suggestions...

Thanks

Posted: **Mon Dec 13, 2010 10:14 pm**

i have that one but its a bit american focussed on mainly basements or concrete drives

there will be books out there, but we just follow the engineered designs

like you say steel fixing is a trade in itself and alot of people have the attitude as long as there is steel in there it will be fine

check amazon out for some more detailed books, most likely american in origin i bet

Posted: **Mon Dec 13, 2010 10:26 pm**

It is a bit American - it took me quite a while to work out some of the terminology!

The other book I have is 'Concrete - Microstructure, Properties and Materials', written by two CEng Phds from Berkeley - I found it rather it heavy-going! I may dig it out and give it another go but ideally I want something in between these two titles (and ideally less American).

I have been watching a block of flats go up by Wandsworth Bridge on the south side and they seem to put more concrete encasement around their reinforced pillars (and they have some very fancy shuttering equipment that I am quite jealous of). They also seem to be able to do larger spans between their pillars so I wonder if these engineers in Angola are missing a trick or two.

Posted: **Tue Dec 14, 2010 7:12 am**

as a rule of thumb, a splice is usually 40 the circumference. It can be 32 x or even 50 x depending on what your using. For small jobs i'd go with 40 unless specified.

Posted: **Tue Dec 14, 2010 8:38 am**

I had a book 30-odd years ago when I first had to fix steel. I borrowed it off a lad at college, but for the life of me I can't recall the title.

There wasn't much to it - maybe 24 or 32 pages, A5-ish, with the basics about how to interpret site drawings, bar schedules, methods of tieing, etc. I have a feeling it was published by British Steel (now I really am showing my age!)

It must have been reasonably good at teaching me the basic principles, because we did quite a few steel fixing jobs up until the mid-90s when I got fed-up of having shredded hands all the time, and so started subbing-out the jobs to a Polish lad from Westhoughton who was much faster than me and worked out cheaper.

I've scanned my bookshelves but no sign of it. In fact, I can't recall seeing it for at least 20 years. It probably got lent to one of our trainees, never to be returned.

Posted: **Wed Dec 15, 2010 12:24 pm**

seanandruby wrote:as a rule of thumb, a splice is usually 40 the circumference. It can be 32 x or even 50 x depending on what your using. For small jobs i'd go with 40 unless specified.

Well that is interesting.

I was told by a Portuguese engineer in Angola to splice 16mm bar 600mm, 12mm bar 400mm and 10mm bar 300mm and these splices are way bigger than those done by 99% of contractors out there.

I regularly see splices done by other contractors that are as little as 50mm or 100mm with all the splices in the same part of a beam - I normally try and stagger my splices on beams but this can be a bit awkward on pillars. Amazingly, very few of the horrendously built structures by other contractors seem to fall down.

Are you sure you meant circumference and not diameter?

If you meant circumference then my splices are still way less than British best practice, but if you meant diameter I am more or less on par.

Posted: **Wed Dec 15, 2010 12:31 pm**

Tony McC wrote:I had a book 30-odd years ago when I first had to fix steel. I borrowed it off a lad at college, but for the life of me I can't recall the title.

That is a shame - I can't find anything that quite suits my requirements on Amazon. Amazon lists several titles that look promising but they are no longer available either.

The Brew Cabin

Rebar - best practice - Specifying rebar in structural concrete