Lime or cement mortar?

[meow2222]

Lime putty is sometimes made from quicklime (producing warm mortar), but usually its slaked to produce hydrated lime, distributed, then water is addded again to produce the putty.

NT

[Weatherlawyer]

Cement properties are rarely understood, there is no doubt a loss of quality control between research laboratories and bricklayers who have been working for decades. Both think they know it all. Een so clled experts tend to overlook the types of cements.

That quick setting stuff that used to be used in precast huge structures such as swimming pool beams and motorway bridges for example, took everyone by surprise.

I wonder if a little lime might have supported things a bit better.

[Stuart Noble]

How about dry ice?

[meow2222]

Where can we read more about types of cement? IIRC theres opc, hac, sulphate resisting, weld cement, no doubt more too.

NT

[Weatherlawyer]

In recent years, the market for packed cement products has become much more sophisticated. New standards have introduced the opportunity to develop more durable cements to meet the needs of the market.

To align our product offering with the needs of the end user an extensive national research programme was carried out. The research was carried out during 2004 and 2005 and covered hundreds of interviews, focus groups, usage and attitude surveys and conjoint analysis with merchants and end users including product demonstrations and selection processes.

The results of the study together with further investigation of which products should be included in our packed cement range of choices have led to our '3 cement product range'.

cement is the most common type of cement in general usage, as it is a basic ingredient of concrete, mortar and most non-speciality grout. It is a finely-ground powder produced by grinding Portland cement clinker (more than 90%), about a maximum of 5% gypsum which controls the set time and up to 5% minor constituents (as allowed by various standards).

As defined by the European Standard EN197.1, Portland cement clinker is a hydraulic material which shall consist of at least two-thirds by mass of Calcium silicates (3CaO.SiO2 and 2CaO,SiO2), the remainder consisting of aluminium- and iron-containing clinker phases and other compounds.

The ratio of (CaO/SiO2) shall not be less than 2.0. The magnesium content (MgO) shall not exceed 5.0% by mass. (the last two requirements were already set out in the German Standard, issued in 1909).

Portland cement clinker is made by heating, in a kiln unit, an homogenous mixture of raw materials to a sintering temperature, which is about 1450=B0C for modern cements.

The aluminium oxide and iron oxide are present as a flux and contribute little to the strength properties of Portland cement. For special cements, such as Low Heat (LH) and Sulfate Resistance (SR), it is necessary to limit the amount of tricalcium aluminate (3CaO.Al2O3) formed.

The major raw material for the clinker-making is limestone (CaCO3). Normally, an impure limestone which contains SiO2 is used - the CaCO3 content can be as low as 80%.

Secondary raw materials depend on the purity of the limestone. Some of the secondary raw materials used are: sand, shale, iron ore, bauxite, fly ash and slag. When a kiln is fired by coal, the ash of the coal becomes a secondary raw material.

In the 19th and early 20th century, clay was a common secondary raw material, particulary in the wet process which is no longer used. In the 21st century, it would be rare for clay to be used in a raw mix, because it gives handling problems and contributes unnecessary aluminium oxide.

Cement plants as alternatives to conventional waste disposal or processing

Due to the high temperatures inside the cement kilns, combined with the oxidizing (oxygen-rich) atmosphere and long residence times, it has proven to be an excellent processing option for various types of waste streams. The waste streams often contain combustible material which allows the substitution of part of the fossil fuel normally used in the process.

Waste materials used in cement kilns as a fuel supplement: [8]

1. Car and truck tires; steel belts are easily tolerated in the kilns 2. Waste solvents and lubricants. 3. Hazardous waste; cement kilns completely destroy hazardous organic compounds 4. Bone meal; slaughter house waste due to bovine spongiform encephalopathy contamination concerns (in Europe) 5. Waste plastics 6. Sewage sludge 7. Rice shells 8. Sugar cane waste

Industrial by-products used as a raw material:

1. Blastfurnace slag (granulated, water quenched) 2. Fly ash (from power plants) 3. Silica fume (from steel mills) 4. Synthetic gypsum (from desulfurization) ash is the finely divided mineral residue resulting from the combustion of powdered coal in electric generating plants. Fly ash consists of inorganic, incombustible matter present in the coal that has been fused during combustion into a glassy, amorphous structure. Coal can range in ash content from 2%-30%, and of this around 85% becomes fly ash. (The remaining 15% is called bottom ash and isn't lifted up by the flue gases.)

Fly ash material is solidified while suspended in the exhaust gases and is collected by electrostatic precipitators or filter bags. Since the particles solidify while suspended in the exhaust gases, fly ash particles are generally spherical in shape and range in size from 0.5 =B5m to 100 =B5m.

They consist mostly of silicon dioxide (SiO2), aluminium oxide (Al2O3) and iron oxide (Fe2O3), and are hence a suitable source of aluminum and silicon for geopolymers. They are also pozzolanic in nature and react with calcium hydroxide and alkali to form cementitious compounds. Fly ash also contains some heavy metals.

pie in the sky about asphalt replacing cement in roads: thought that was a substance alreay in use.)

((And anyway transport costs could be decimated (maybe even cementimated) with the use of neither, if more canals were made using clay as the waterproof liner the way that they were made 200 years or so back. That would cut out modern water problems too; as well as supplying drought stricken areas, the creation of more and larger canals would be the creation of resevoirs at the same time.))

Then there are geopolymers:

about that ancient process reminds me of the silly ideas our scientific monkeys have about ancient copper and lead mines in this archipelago. I suspected that there must have been some sort of crushing machine at the brochs and other long lost mining sites. And why would they not also be utilised in the production of lime, cement and pottery as well as ore milling?

Digging huge caverns with bones and antlers. As if!

slightly off topic:

Ray Mears in one of his survival programmes, remarked that ancient Britons consumed vast quantities of shelfish at the water's edge. That we know this from the vast heaps of shells from the eaten fish that have been found and dated to the long ago.

Thinking about that concept leads me to believe how unlikely it is. Just supposing a clan held togehter long enough to consume that amount actually at the beach or riverside - even over a period of years, makes me wonder why they saw fit to collect the residue togehter in neat stacks.

You just wouldn't do it. First of because the tribe would just gravitate to a newer harvest site. Secondly the waste heaps would stink and thirdly, the chances of their waste being piled in places that they would survive intact for all time at, is ridiculous.

The piles were obviously stored in a secure location from the tide and the weather. But what for? I had supposed for fertilising acid clay soils. But also they would have been part og the lime cache that these brochs would have crushed.

(Yes I know that the full use of the ancient buildings remains unknown. But the DO seem like windmills to me.)

And slipping further still:

Several semi historical shows on the TV have attempted to demonstrate how a blacksmith might have produced an iron sword. OK the method of welding red hot iron bars byt smiting them together on an anvil is the most likely way of doing it.

But with wind or water power the ancients could have drop forged a sword in a couple of smacks with a hammer lifted by a powered axle. Likewise a coin would have been fairly easy to mint.

And the same process would have been used -maybe the same mill, if they wanted to crush ore or baked clay as well as pulverise limestone or shell. Of course the transportable and least durable pars of a mill would not survive the centuries. But somewhere in the mud of copper producing regions, there may yet be found some preserved centreposts. Who can say?

[John Stumbles]

That he did what?

From my limited recollection of that 'source' it is silent on the question of where God came from.

Just supposing I did believe that fossil fuels came from the tooth fairy, easter bunny, Father Xmas or God, how would that be a case of circular reasoning?

Not that I don't already know, of course.

Of course.

[Guy King]

The message from Stuart Noble contains these words:

Supercritical CO2 has been used for hardening concrete. It's expensive, so guess who gets to use it? Yup, the military!

[meow2222]

reservoir of informatoin snipped

Thanks, and I'll check out lafarge when I get time.

NT

[The Natural Philosopher]

My impression is that lime pointing does it worse actually.

Old bricks are soft and porous and crumbly, they need a soft crumbly porous mortar like lime. Modern bricks are not like that.