Date: Tue, 02 Aug 2005 16:23:28 +0100 To: [EMAIL PROTECTED] From: Grimer <[EMAIL PROTECTED]> Subject: RE: Negative mass, etc.
At 06:57 am 02/08/2005 -0500, Fred wrote: > Very "Concrete" analogies, Frank. > > Portland cement manufacture is a "Basic" industry too. :-) > > Frederick Indeed it is - in more senses than one. And it is because of Portland Cement's "Basic" (as opposed to Acidic) properties that those rusty steel reinforcing bars that one sees lying around on building sites won't continue to rust when used for reinforcing concrete - as you are no doubt aware. 8-) Of course, if you economise on the cement content then over the years carbonation will reach down to the reinforcement which then begins to rust and spall off the concrete cover. When sprayed with phenolphthalein a section of such carbonated concrete will clearly show the depth that carbonation has reached by the intense pink colouration which reaches from the surface of the concrete to the steel. When aerated concrete manufacturers first started reinforcing their material and using it for structural members, they didn't realise the importance of the pacifying effect of alkaline OPC. Consequently their steel bars rusted to b******y in very short order with subsequent catastrophic collapse of the beams. Cheers, Frank
