huangyhg

28 days compressive strength of concrete in russian concrete
hi.
now i'm comparing russian concrete design code with american standard for my project, and i found some problems.
is there anyone who knows about russian concrete strength?
i want to know the 28 days compressive strength (cylinder, not cubic) of b25 and b35. in snip 2.03.01-84, there are design axial strength values of b25 and b35 for group 1 and 2. but i guess that it's not the same value of 28 day compressive strength.
thanks for your help in advance.

i would think the b25 and b35 grades are 25 mpa and 35 mpa respectively, and imagine they would be evaluated at 28 days, but i have no actual knowledge of russian standards.
thanks.
you are right. yesterday i found a sentence in snip 2.03.01-84.
"classes of concrete for compressive strength and axial tensile strength correspond to the value of guaranteed strength of concrete in mpa with reliability of 0.95"
so in case of b35, compressive strength of cubic (not cylindrical) specimen is 35mpa. but now i don't know the size of cubic specimen and the period (28 days or not). so i still cannot estimate the compressive strength (cylindrical test, 28 day) of russian concrete.
messara -
you can never be sure until you have all the information on the sampling, sample preparation, curing and testing procedures if you are concerned with russia. there are still many unusual testing and sampling methods in effect.
before my first of many trips, i was told - "if it does not make sense, it must be true". i have many russian friends, but is very applicable if you have an american background.
a couple of extreme examples that i saw in a lab -
1. in the u.s., a cmu block prism test is a measure of the strength of the combined block and mortar and the sample measures two blocks and mortar high for a total height of 400 mm and 200 mm wide nominal dimensions. in russia, the lab was testing a prism (made from 200 x 200 x 400 units) of block that measured measured about .5m x .5m x 1m high. there were also prisms that measured about 1m x 1m x 2m (40" x 40" x 80").
2. in the same lab facility they were testing a precast housing unit (2+ rooms) that had 8" thick walls and was 8' high, 12' wide and about 30' to 40' long. - they were testing it in flexure on rollers with a concentrated load applied at the center.
i assumed this was a research lab at a technical university, but it was to verify compliance with specifications for a project under construction. i still do not understand it, but that is what was considered the standard - granted this was about 10 years ago, but i received some e-mail photos about 2 years ago with similar testing and sample configurations.
the bottom line is that you do not make assumptions based on what you expect since there can be many substantial differences that you would not normally consider. we argue about concrete cylinder dimesions (diamter and height) and the effect on reliability, but never consider the possiblity of a difference in the shape or the relationship between the aggregate size to sample size. - keep an open mind. russians can be very thorough and precise, but pride in procedures and language differences compounded by the cyrillic aplphabet compound the challenge of getting agreement unless all details are considered.
great points. something i've noticed is that russia (and its then eastern european allies) seem to have developed their engineering 'art' separately from that norm in the west - you see this in geotechnical engineering where, while they get the same basic answers, their methods of analysis and how they get there diverge considerably from the uk/norway/usa/canada/swedish development. you can see this in the early winterkorn and fang (now fang) foundation engineering handbook. the chapters written by the easterners seemed to attack things from a different approach.
bigh -
a good observation.
because of the lack of communication and isolation imposed for decades, a different perspective has developed. this is reflected in the standards (prior to those changed after about 2000. fortunately, the mountains of available research conducted for years are still available if you can extract them.
russian trained engineers are very detailed, diligent and technically competent. i meet with and engineer that was a reputed expert on masonry mortar. when i asked a question, he said he was really not qualified because my question had to do with a masonry cement based mortar (which is available in russia). he was an expert in portland cement and lime mortars!
they also do not go according to our life-safety based concept of codes and like to think everything should stand no matter what kind of disaster or conditions exist.
the differences are fascinating and are a real eye-opener to make you think. i had a group of 15 engineers touring design offices and construction sites for 10 days. the questions were very educational for me.
dick
messara,
i think it is this formula that you need:
rb = (0,77– 0,001r)r
where
rb - cylinder strength,
r - cubic strength.

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