Frosty Posted July 14, 2016 Share Posted July 14, 2016 Alan: If the mix is splattering you when ramming or vibrating it's too wet. In soil's lab or (competent) construction terminology it's called "free moisture." Reducing air entrainment in "wet mixes" like concrete or castable refractories the water does two things first it causes a chemical reaction in the cement component Calcium aluminate in the case of refractories, thank you Sky guy. or portland cement making concrete. What water does when compacting gravel or similar is act as a lubricant. Vibrating or crushing the air out of an aggregate, base course or asphalt macadam is all compacting is you're driving the particles together and the gradation needs to have particles sized to fill the voids between larger particles all the way down to the microscopic. The correct amount of moisture causes the particles to slide off each other without taking up space itself. When you're doing a vibratory or "Proctor" compaction test you gradually increase the moisture content in a series of test samples till you drive free moisture from the test sample. The sample before is USUALLY the most dense and becomes the target density for design and the construction crews. The test is to determine the optimum moisture content to achieve the maximum dry density. A Proctor is old school impact compaction test where a 5.5lb. (Yeah, I had to look it up) weight is dropped 12" 25 times, another lift is added to the sample and the drops are repeated. till the test cylinder is filled, they it's struck level. The sample is removed and weighed, then dried @ 230f. to determine the moisture content. Anyway, all that just says free moisture around the mold when compacting means the mix is too wet to achieve max density. The soil's lab quit using the Modified Proctor test about the time I changed jobs so I don't have personal experience with the vibratory compaction test other than talking to the guys. They loved the test, nobody had to drop the proctor hammer anymore and max density was achieved dry. Okay, all that long windedness is maybe just my memory talking through my fingers but I actually have experience with the subject. Vibrating the mix causes the particles to bounce off each other and seeing as nature HATES a vacuum any particle will fall into any void it fits. moisture lubes it so particles slide off each other. The bad thing is too much water. Water hates a vacuum as much as anything else and not being particles or compressible it doesn't bounce so mean old Mr. Gravity makes it find the lowest point. When it fills a void it can't be forced out by particles if it can't flow down hill. This results in a less dense final compaction. In a concrete product, be it side walks and bridges or castable refractories too wet prevents the "Cement" component from completely coating the aggregate and cementing it together so the final product is less strong than it should be. John: Following the directions isn't a lack of imagination it's good sense. Just because the final product isn't the "best" it COULD be doesn't mean it isn't more than good enough. Good Enough is just that good enough or "competent" in soil's lab lingo. Whatever the material, tool equipment, etc. it will do the job with an adequate safety margin. We don't need maximum density refractories, not at all. I vibrate mine because it's the best way I know to fill a mold completely and make a uniform density in the mix. Uniform is more important than maximum think of it like preventing cold shuts. Changes in physical properties concentrate energy and forces being conducted through a material and that's where a failure initiation point is most likely. And, that's enough for Frosty's more than anybody wants to read about stuff Thursday morning chatter. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Alan Evans Posted July 15, 2016 Share Posted July 15, 2016 An interesting read Frosty. I will log it away for future ref. I am laying blocks tomorrow and Monday Tuesday so will be on labouring duty mixing the muck for the bricky. Re. the Green's castable...I am a goody goody and always read and follow the instructions. Maybe splattering was not the best description. Particle displacement due to the violence of the hammer blows, might have been better. That is not to say it was not too wet none the less. I am still using the floor of the first furnace I cast about 25 years ago and the first punching furnace which I thought would be replaced on a monthly basis was broken up (still working) after fifteen years or so when we were looking for something to do. So whatever the quality of the mix, it was evidently adequate! I was quite pleased with another discovery while mixing the castable. Because it was such a dry mix the dust was filling the atmosphere as the little mixer went round and I found that a black plastic bin liner bag would just stretch over the mouth of the machine and contained the dust a treat. Alan Quote Link to comment Share on other sites More sharing options...
Frosty Posted July 15, 2016 Share Posted July 15, 2016 Mixing mud for the block layers, I did that briefly when I first moved to Alaska. Mortar is a whole different flavor mud. No, splatter is probably a better description for what you were experiencing. Castables are inherently wetter than you want soils for compacting. Water is incompressible so a sharp impact with a flat object tries to move the mix but it can't compress the water under the hammer so the only way it can go is sideways and it splatters. What kind of furnace have you been using for the last 25 years? Is that an AP Green refractory? Good products. I hated dry mixing in a mixer at the lab, dust got on everything and Portland cement burns my skin worse than most folk. We HAD to follow the procedure though and it required we mix the dry material for 5(?) minutes before adding the water. A measured amount of water and we were supposed to add it in a steady gradual stream. One of the guys thought of using a bug sprayer and we could mist the water in instead. A few comparisons between the bug bottle and a poured stream showed insignificant differences and really held the dust down. He was a soils lab hero. Frosty The Lucky. Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted July 25, 2016 Share Posted July 25, 2016 High John, I finally got the contact information for the casting group, and rememberered it was you it needs to reach: Bill Ross 1661 E Thomas Rd Grapeview, WA 98546 360-427-4122 billwross@aol.com Quote Link to comment Share on other sites More sharing options...
John in Oly, WA Posted July 27, 2016 Author Share Posted July 27, 2016 As always, great info and discussion here. I'm learning a lot about a lot of different interesting subjects. Mikey, thanks for the contact info on the casting group. I'll contact Bill and see when the next meet up will be. Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted August 2, 2016 Share Posted August 2, 2016 John, Look forward to seeing you there. Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted August 7, 2016 Share Posted August 7, 2016 So, John showed up, and we found that only minor tweaks would be needed to give his forge a big boost. Others are also welcome. Quote Link to comment Share on other sites More sharing options...
John in Oly, WA Posted August 9, 2016 Author Share Posted August 9, 2016 Mikey, thanks for the invite to the metal casting meet up. And more thanks for all the great info on tweaking my burner and forge for better performance. This weekend I'll make the modifications to the burner and heat some more metal. Quote Link to comment Share on other sites More sharing options...
Mikey98118 Posted August 16, 2016 Share Posted August 16, 2016 John, I enjoyed seeing your forge, and especially enjoyed looking at the burner design you came up with. Because I am forced to dis the typical "every thing but the kitchen sink" burner that comes from guys who don't do any study before jumping in, it is natural to think I'm hostile to new attempts at burner innovation; in fact I have waited for years for just that very thing. Usually I see my ideas inclued on foreign burners; a very left-handed compliment... Quote Link to comment Share on other sites More sharing options...
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