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Archive for January, 2007
Limestone Powder in Concrete 1
Posted by William (Ronnie) from Olmsted L&D, IL, US on January 23, 2007
I\\\’m working with a tremie concrete mix that has 252 lbs. of limestone powder in it. The mix also has Cement, GGBFS, Fly Ash \\\”F\\\” and silica fume. The specification I\\\’m working with has a max w/c of 0.38. My problem is I can not count the weight of the limestone powder in working the w/c and the limestome powder has a big demand for water. Do you know a publication where limestone powder can be counted as cementitious? I have 35 years with USACE, this is a first for me.
Ronnie:
You are working with a water repellent mix no doubt; utilizing the silica and the limestone for density and for placement flowability at a low w/c ratio.
I think that as far as the w/c ratio goes the limestone would count under a total cementitious value...what do the aci offer? concrete.org
Otherwise I might offer a pre-mix paste of limestone powder and water being added to the pre-mixer...offered to your specifier as an additive/admix product that can be dosed by its own unit weight?
Please let me know what you actually find--I'm not sure on this either...
Regards,
Robert
sailo design
Posted by satish from mumbai, OH, IN on January 18, 2007
1)Wate should be the exact angle of sailo?
2)Why the materialis sticking on the wall of the sailo?(material is Mortor i.e. cement and sand.)
Satish:
Go to concreteproducts.com and enter "silodesign" to get a paper I authored on this subject.
For sand and cement bulk storage the job is difficult if there is any moisture whatsoever in sand. Ideally a 70-degree slope should be used in a sand/cement combo bin. An air cannon or a wide opening utilizing a belt feeder discharge is best.
Regards,
Robert
hollow core slabs
Posted by aziz from abu dhabi, NV, AE on January 6, 2007
what is the mix design that i can use in hollow core slabs to achieve 50 Mpa at 28 days.
This question is best answered by a local materials engineer given experience with your local cement and aggregates. Your hollow-core machinery manufacturer can also assist if they are familiar with the locale.
Kind regards,
Robert
Basic Concept.
Posted by John from Chicago, IL, US on January 5, 2007
Near what material a concrete plant (to manufacture cement) should be set up, considering the importance of that material?
The three most important factors: limestone; water, and fuel.
Many more lessor factors follow from labor costs/availability to transportation. However, the very most important overall factor: a market. If you meant a concrete plant as opposed to a cement manufacturing plant, then the answer would be: aggregates & cement source. Marketplace and location to that market remain important for any supply/service business...
Regards,
Robert
High Strength Concrete
Posted by Bob from Carol Stream, IL, US on January 4, 2007
What types of aggregate would you use to manufacturer high stength concrete? Is there any relation to the specific gravity of the rock? What additives would you use to strenghten the bond?
Bob:
There is an HPC workshop coming up put on by the NRMCA. email: mbarringer@nrmca.org for details. It's in Dallas--which isn't too close I know, but may be worth checking into. Closer to Carol Stream, IL was the recent HPC Symposium held in Chicago, the full report is available by phoning 847-491-3858, or go to www.acbm.info
Keep in mind that HPC is like high-performance anything--so many ranges and such a broad description. Obviously, as I am always saying: to make high-performance concrete we need higher performing materials as well as high-performance mixing equipment. The stronger the aggregate, the stronger the concrete. The denser the mixture i.e. silica, slag, and cement ratio to fines and water--the higher performance raw materials base. this + the all important admixtures to affect workability and setup times...get you into the range of HPC mixtures.
Have a look at the HPC report, and don't forget to visit concrete.org and click on HPC and UHPC (Ultra...)
Regards,
Robert
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