Hematite Concrete

[slickdeals]

Folks,
Has anyone spec'd or used Hematite Concrete before? It is a request from the client to use in a radioactive environment. He wants to specify hematite concrete for walls surrounding a room for radioactive material storage in a health care facility.

I have looked on the internet but not found reliable sources for proportions (mix design), strength, workability etc.

Thanks

 

[ACtrafficengr]

What makes you think it would be different than other aggregates?

As an aside, the pier failure of the Crown Point Bridge in NY and VT was in part due to iron ore used as aggregate. It was due to oxidation of the iron expanding the aggregate and cracking the piers. In an indoor environment, that shouldn't be a problem.



"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust

 

[Ron]

Agree with ACTrafficengr...in the mix design, absolute volumes are used, so the only difference will be a higher unit weight of the concrete.

 

[concretemasonry]

Ron's comments on the absolute volumes of the different aggregates is critical when compared tot he volume of cementitious materials.

I was involved in the manufacturing and supply of high density concrete masonry units for use in shielding and protection in nuclear power plants. Masonry was used because it was very reliable, verifiable in advance and usable in the safe completion of the interior of the facilities.

These were dry-tamp or zero slump units made using controlled vibration and extremely accurate gradation and moisture control. As I remember, Hemaltite and similar materials have relatively cubic structure even after crushing. Since particle shape and gradation are far more critical for concrete units it was in our interest to use 100% hematite for both of the two aggregates (3/8" maximum and clean-up to to 1/4" sand) for testing, ordering and production planning. Keep in mind that the finer particles usually have a lower S.G., which can complicate projections, so 100% hematite is more predictable.

Masonry specs are based on performance and never on proportions, except for mortar. The solid masonry walls (variable thickness up to 48" thick with 6" solid units) were laid in a bonding arrangement to eliminate any possible radiation paths through the joints.

As you can imagine, the advance work for verification, testing and production can easily increase the cost by 2x to 5x not including the time required.

Any time you get into a request from a client, it is political. If you get into pure performance and justification of performance, there is a host of problems, cost and added time.

Dick

Engineer and international traveler interested in construction techniques, problems and proper design.

 

[Ron]

Dick,
Excellent points. One thing to consider when using hematite in the lower coarse aggregate/upper fine aggregate gradation range is that you might need to make a correction for specific surface because of the higher specific gravity.

When compared to conventional aggregates, a higher specific gravity will make the calculations seem like larger particles are present, when in fact smaller particles are present and thus will have more surface to cover by the paste....in short, the paste volume will have to increase.

 

[B16A2]

For radioactive encapsulation I would suggest looking into Alkali Activated Slag Cement, Geopolymeric Cement, or maybe a super sulfated cement. These provide excellent resistance to aggressive environments.

 

[Ron]

A storage room for radioactive medical supplies would not be an aggressive environment. Concrete is innocuous to such doses of radioactivity.

 

[ACtrafficengr]

So, in short, is it correct to say if you use a weight-based mix design, you need to adjust for density, but a volume-based mix should be the same?

"...students of traffic are beginning to realize the false economy of mechanically controlled traffic, and hand work by trained officers will again prevail." - Wm. Phelps Eno, ca. 1928

"I'm searching for the questions, so my answers will make sense." - Stephen Brust