1156 posts
New products Question 1
What is the difference between type 1 cement and type 3 cement? Our ready- mixers are trying to come up with a mix that we can strike with a straight edge and make it look nice but get up to 3500 psi in 4 hours Right now we are using a stone mix with 8 1/3 sack and 7.5 per cent NCA.
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1156 posts
Re: New products
Essentially Type 3 is a finer ground version of Type 1 cement and would normally be made from the same clinker source as Type 1. For Type 3 cement there are minimum strength specifications in the ASTM standard C150 for 1 day strength (none are set for Type 1) and at 3 days the strength minimum specified is twice that set for Type 1 cement. The concrete strength requirement of 3500 psi at 4 hours is quite demanding and would need careful control of the concrete mix with accelerating additives/high range water reducers which do not retard the mix.
1156 posts
New products Question 2
I understand that the cement manufacturing industry is considering the use of copperas (ferrous sulphate) in the manufacture of cement to reduce chromium 6 allergy problems for the end user. My company produces the only trouble free copperas saturator on the market. Our saturator accepts crystal copperas generates a stream of aqueous ferrous sulphate solution for dosing mainly to sewage to remove phosphates or to control odour and septicity in sewers and sewage works. I am interested to understand the mechanisms underlieing the use of copperas for cement production.
1156 posts
Re: New products
You are right that cement companies are considering the addition of ferrous sulphate to their cement in order to meet the stricter limits on hexavalent chromium that are being introduced. The application involves adding solid ferrous sulphate to the cement either at the milling or packing stage and relying on this to reduce any hexavalent chromium present in the cement. The industry knows that this solution has its limitations, not least being that the activity of the solid ferrous sulphate will deterioratr with time and this will confer a "shelf-life" to cement treated in this way to meet the directive.