SteamyTea

Isn't it simple harmonic motion. Punch in the material parameters i.e. mass, density, flex modulus, and the answer should come out, I actually missed the lecture about sound waves when at university (had to see the eye surgeon about my cataracts), so when I read the notes I seem to remember that because the ends are attached to a non moving part, they are modelled like a piano string i.e. only full or half waves allowed.

On another tread, I typed up a bit about Portland Cement. Now I am not a chemist at all, in fact I am rather dismissive of them. Having said that, 5 Chemists that I have chatted to informally have been very good at explaining what happens without relying on using memory test in Latin. One Chemist, a recent PhD graduate was working in sales and explained long chain polymers to me, they are really quite simple, repeating 'units' that attach to each other. Another one, again a PhD in chemicals, explained the electron orbits and how they are NOT 2D as drawn on paper, this is what governs, to a certain extent, the shape of molecules. Another, PhD again, sat me down in a lecture theatre and explained the polarity of molecules and why that causes CO2 to vibrate at certain frequencies and causes a disproportional amount of movement. This principle of polarity is why a small amount of some molecules can cause a large amount of heating. Then there was my old line manager, who also had a PhD in Chemistry who once said "when you design, or change a chemical formula to get the properties you want, you get what you are after, and something else". It is that something else that is important. Then there was our own @Jeremy Harris, who initially studied Chemistry then moved onto Physics. He was brilliant as he was a practical man and understood the limitation of the 'something else'. Now the above is just a way of asking if we have a decent chemist on here who can help out with a lot of the products used in the building trade, there must be at least one. So getting back to the title, I had a look at Portland Cement and then Lime because of a question that @saveasteading asked about releasing and absorbing CO2. After a bit of googling I found a long, but easy to read article explaining how Portland Cement is made and then used. http://matse1.matse.illinois.edu/concrete/prin.html Basically, from what I understand, is that during the roasting, free water is evaporated and then elevated temperature drives out CO2 that is attached to the calcium. When water is mixed back in, a reaction takes place that causes a rise in temperature, and the hydrogen and oxygen are split up and combine with the Di and Tri Calcium silicates and aluminate, with some Tetracalcium aluminoferrite and Gypsum thrown in. Di, Tri and Tetra I understand, the Ates and the Ites I don't, they need to be memorised. I was going to show the changes in formula when Limestone, Clay and Ferric Oxides are roasted, but I can't find a decent explanation (why we need a Chemist). The reverse hydration i.e. when water is added, is shown. Tricalcium silicate + Water--->Calcium silicate hydrate+Calcium hydroxide + heat 2 Ca3SiO5 + 7 H2O ---> 3 CaO.2SiO2.4H2O + 3 Ca(OH)2 + 173.6kJ And Dicalcium silicate + Water--->Calcium silicate hydrate + Calcium hydroxide +heat 2 Ca2SiO4 + 5 H2O---> 3 CaO.2SiO2.4H2O + Ca(OH)2 + 58.6 kJ If I understand the chemistry correctly, because the CaO is already attached to something the SiO2.4H2O chain and the Ca(OH2) there is nothing for the carbon in CO2 to attach to. So then I had a look at Lime, wanted to know what happened as way too many people seem to think that it is the bee's knees and will cure all ills in a building. I have been very dubious of those claims and can never find decent evidence to support it. So Lime is made in a similar way to Portland Cement. Get the right rocks, crush and heat them to change them: CaCO3 to CaO + CO2. Then the difference from Portland Cement happens, water is added, in the right proportion. CaO + H2O to Ca(OH2). Calcium Hydroxide. This forms a dry powder called Slaking. Also known as Hydrated Lime, add a bit more water and you get Lime Putty. Now, and this is where it is really different from Portland Cement, it absorbs both H2O and CO2 from the atmosphere as it wants to convert back to limestone CaCO3 (calcium carbonate). So come on Chemists, put me right and explain it better, maybe with a bit of basic theory as a grounding.

A builder would call that 'snagging'. We would call the builder something else. Glad the job is going OK. Must be strange going back to work after 4 months or so off, I only managed 2 months off, seems like I have never been away from it now.

I was thinking about you this morning, not in a peculiar way. You have started your new job now haven't you? How is it going.

Why that much, isn't the financial risk basically the price of materials. If the supplier tries to insure is running costs as a risk, then they should not be in business, and they are probably already having trouble getting credit.

No. I have been reading up on it. It is a complicated process, both the roaring (4 stages) and the hydration a multi stage process depending on type. The typical makeup of Portland cement is. Cement Compound Weight Percentage Chemical Formula Tricalcium silicate 50 % Ca3SiO5 or 3CaO.SiO2 Dicalcium silicate 25 % Ca2SiO4 or 2CaO.SiO2 Tricalcium aluminate 10 % Ca3Al2O6 or 3CaO .Al2O3 Tetracalcium aluminoferrite 10 % Ca4Al2Fe2O10 or 4CaO.Al2O3.Fe2O3 Gypsum 5 % CaSO4.2H2O It is all about calcification and hydroxides which cause the crystallization. The curing is very interesting as time is important. Initially there is a rapid rise in temperature and the tricalcium silicate cures to give initial strength, then, over time, the dicalcium silicate comes into play and starts to cure, contributing to the final strength. While that is happening, some of the other compounds in it are reacting. As you know, concrete does not dry, it cures. The word drying should stopped being used in conjunction with cement products as it is misleading and causes misunderstanding of the processes (note plural). I grabbed the above from here, which is a long, but easy to follow description. http://matse1.matse.illinois.edu/concrete/prin.html You will see that energy units (kJ) appear often in the formula. That energy is what is doing the work of forcing molecules to bond. We often think that things getting hot is a nuisance, but in reality it is a vital part of the process. If you stop and think about it, a builder's labourer, who may have no experience in chemistry, should not really be allowed to mix up concrete, ever.

Well apart from the edge losses, and radiation losses. Though they are generally quite small. You can calculate the dew point from the temperature, relative humidity and air pressure quite well. But for these purposes then this will do. https://www.calculator.net/dew-point-calculator.html I think it uses: Td = T - ((100 - RH)/5.) where Td is dew point temperature (in degrees Celsius), T is observed temperature (in degrees Celsius), and RH is relative humidity (in percent).

There is a difference between cement and concrete. In 2021, cerement accounted for 1,672,592,400 tonnes of CO2 In the same year, the world produced 37,123,850,000 tonnes. Concrete was 4.5% of global CO2 emissions. https://ourworldindata.org/grapher/annual-co2-cement?tab=table&time=latest https://ourworldindata.org/co2-emissions#co2-emissions-by-region There is around 750 kg CO2/tonne for cement and around 1000 kg CO2/tonne for concrete emitted. Cement looks very bad in isolation. Concrete can last several hundred years and can be easily reused. CO2 from cement is not just the energy used (usually natural gas burners) but is also produced as part of the chemical change during roasting. If a house has a slab that is 10 tonnes of concrete, that is 10 tonnes of CO2. A good car these days produces around 0.1kg/CO2.km. So 100,000 km in a car is about the same. That is around 62k miles. My 16 year old car, newly MOTed at 240k miles, produces 0.143kg CO2/km, last year I drove 29,678 miles, that is 47,762 km, so it produced 6.83 tonnes of CO2 at the tail pipe. That is a mean of 3,452 tonnes/year so far over the life of the car. Another way to look at that is to compare it to my house, which uses around 4 MWh/year. It is all electric and CO2 emissions for electricity last year were around 200 kg CO2/MWh, so my house produced around 0.8 tonnes (maybe a little less as I think last year I only used 3.3 MWh and CO2 emissions are dropped quite rapidly last year).

Possibly, as long as it does not clash with anything else in my busy schedule.

I wonder how the person that started this topic is getting on.

I agree with you there. As a cheap work around, why don't designers project an image of their proposal onto a screen at the back of the plot. I know virtual reality is meant to do with, but it is still very artificial and depends on the accuracy of the initial plot survey.

Could make the jig a bit longer, drill two extra holes in it, and the wall to hold it level. Then drill the other holes in the right place. Oh hang on.

A single cylinder 4 stoke engine has 1 power stroke per 2 revolutions of the crankshaft. Never known anyone to stay below 7200 RPM. Still, come 2035 there will not be any new ICE machines on our roads, just the old noisy ones left.

This is straight drilling.

Yes. He touched on the price of building houses, said that the nice ones cost more then the nasty ones 100 years ago. Used that as justification to build expensive houses, ones that will last 1000 years.

There was a case of wire across the cycle path in Milton Keynes about a decade ago. Think there was a Sherlock Holmes story about it as well "The Ordinary Bicycle".

When I lived in France (1970's) a 14 year old on a Vespa was the main problem. Cheese wire string across the street at neck height was suggested at one stage by our French neighbour.

They are probably guessing. While I did not do any calculations when I secondary glazed my windows, intuition, backed by theory, meant I knew there would be a sizable improvement. The noise reduction was much better than I imagined. Thermally I probably benefited most because air leakage was reduced (I have 36 year old timber frames). Have you checked that all your windows close properly and the seals are sealing well? Can usually tell by dirt marks that have bypassed the seals.

Well that is a forgone conclusion, as he said (or was it someone else), you deal with a lot of people that have different ideas. Don't think ecologists where mentioned, they want nothing built anywhere. I am not sure that he is really the person to be talking about normal architecture.

4 secondary panes with the two middle ones hinged so that they double back onto the adjacent panes. I think you may be overthinking all this. It is never going to be invisible, so has to show the function in the best possible way.

Interesting listen, not really sure what his conclusion was. "Listen to me" I think. https://www.bbc.co.uk/sounds/play/m001r1b2

I bought one for an hour in Den Haag. Oh, Backhoe.

Now that would make for an interesting statistics project. Statisticians are allowed to be wrong, as long as the reasoning is right. Or is that economists.

Just make an imaginary one, you lot are good at that. Get them to make one. Applied mathematics is only using a simple rule, rather than complicated algorithms.

@Pocster is already 'out'.