concrete confusion
concrete confusion
(OP)
BS 5328 'concrete' replaced with BS EN 206-1 and BS 8500
In new code slump is reported to the nearest 10mm - in BS 5328 it was 5mm.
More confusing is in BS EN 206-1 the the slump is defined by class; as S2,S3,S4 and consistence is workability in BS 5328.
What about S1 class?.
How we specify the slump to redy mix supplier?
Please comments on this subject....... I will be obliged
In new code slump is reported to the nearest 10mm - in BS 5328 it was 5mm.
More confusing is in BS EN 206-1 the the slump is defined by class; as S2,S3,S4 and consistence is workability in BS 5328.
What about S1 class?.
How we specify the slump to redy mix supplier?
Please comments on this subject....... I will be obliged





RE: concrete confusion
Anything I can do to help, please let me know
RE: concrete confusion
RE: concrete confusion
The specified classes for slump include an S1, and go up to S5. The way the new system works is that is reccomends the use of slump classes, as opposed to the previous method of target slump - please note reccomends.
When it comes to what each slump must meet when measured, it depends on who you are, if you are the producer doing confirmity testing, you have a tighter range than for the user doing identity testing on site. The idea behind this new method, is a reflection of moving from British Standards to European Standards, and it is reflected in ALL the NEW BS EN, not just concrete, but soils, aggregates, kids toys, condoms etc....
Below is a summary of each class, target slump, conformity range and Identity range:
Class/target/conformty range/identity range
S1/20mm/0-60mm/0-70mm
S2/70mm/40-110mm/30-120mm
S3/120mm/90-170mm/80-180mm
S4/180mm/150-230mm/140-240mm
S5/>210mm/>210mm/>200mm
The're the numbers but you also need to be aware of the principle behind the change, and this is the crux of it all.
The leading people behind the production of ready mix concrete lay a significant proportion of blame for concrete failure at the door of consultants. They feel that what has become common practice to specify a minimum water:cement ratio, and target slumps of 50mm has resulted in a high proportion of concrete being delivered to site which is too stiff to place and which has then resulted in the site adding water to increase workability, thus having a detrimental effect on the water:cement ratio. If you have seen concrete placed in the UK you will have noted that it had become common practice to add water on site before placement -THIS IS BAD YOU MUST NOT DO IT!!!!
So, under the new system when you specify what you want, you tell the ready mix supplier the information you know and can control, this should include:
Design life of structure - guidance in BS EN 206/BS 8500
Exposure conditions - guidance in BS EN 206/BS8500
Target Strength - Structural design requirements
Maximum aggregate size (reference to reinforcement being used)
Concrete consistence class - Slump or flow in UK, sufficiently high to prevent the need to add additional water.
Any other relevant info to do with specific part of structure, allowable/required use of admixtures etc..
Things to do with cement type and blend, water cement ratio required use of admixtures etc.. will be under the control of the ready mix supplier, they know hao to make concrete and they should be able to guarantee that the concrete will meet the site requirements. They have to use high levels of confirmity testing to control this, and the site can/may use identitiy testing to check what has been delivered is what the supplier said he was going to deliver. This IS different to the old system, and is quite difficult to summarise here.
There is lots of info out there if you know who to ask, please do, you don't want to get bitten. The new system could mean that if concrete fails, it is always the designers fault if he doesn't understand the system!
RE: concrete confusion
RE: concrete confusion
This is probably over simplified and very cynical, but it is a real problem, and a worry, and no one is really sure how it will pan out. We have already introduced the new standards for Concrete, aggreagtes and earthworks materials started from June this year, asphalt is to follow shortly - boy am I glad I changed jobs!
RE: concrete confusion
RE: concrete confusion
RE: concrete confusion
regards
saleemangilath@hotmail.com