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To the lime skeptics here, I suggest a little more trying it out.
Re: Lime or cement mortar?
For an investment of £5 for a bag of builders lime you can experiment
for yourselves (and pound for a bucket, pound for some sharp sand - if
you don't have them lying about).
Find out for yourselves how easy it is to work with, experiment with
mixes, find out how long different sized lumps take to form a first and
second set and to gain most of it's strength.
And if you're not happy, you can rake it out again much more easily
(and if you are, you have the rest ready to use in a covered bucket).
Ooooh goodie an opportunity to wibble about lime ...
Re: Lime or cement mortar?
For some jobs
Dunno which jobs tho cos I wouldnt do this - bricklaying perhaps? Dont
risk it for external rendering
Homemade putty with bagged lime is much cheaper than bought putty
Labour costs are higher with lime cos more tending is needed due to
slower setting time and also cos there is a shortage of good lime
plasterers so they charge more
Better to use a well graded sand. My supplier sells it as 'plastering
sand'. For rendering I would try 3 sharp to 1 soft sand as a
substitute for well graded sand (um never have needed to tho ...) For
bricklaying a softer mix is better
TNP playing devils advocate again I see
Cement based mortars are better in continually damp stuations
There is a spectrum of products
Lime putty mortar
Weak hydraulic lime mortar
Strong hydraulic lime mortar
Cement mortar (concrete)
and you should choose the one appropriate to the situation, bearing in
mind that big business has been promoting the concrete and strong
hydraulic lime end of the spectrum for many years
Its not. I use hessian sheeting :)
With lime you dont need to leave expansion joints so it looks more
Difference of cement to lime putty is more impurities (silicon mostly)
and higher temperature of production
Lime putty cycle is:
Chalk or limestone + heat
Drives off CO2 and H20, producing quicklime (dangerous!)
Add H2O to produce lime putty
Take it out of the tub and put it on the wall
Add CO2 from the air and it becomes chemically equivalent to limestone
/ chalk once again
The cement cycle is the same with added twiddles
Processing lime uses less CO2 cos it is not cooked so much.
Transportation of lime uses more CO2 because there are less economies
of scale, unless you make your own quicklime (and loads of enthusiasts
More workable, user friendly. Cement mortar often has lime added
simply to make it fatter. Cement + Lime + sand is a cement mortar not
a lime mortar. These days FebXXX often gets used instead of lime
There we open up another can of worms. Lime mortar used to be used
both indoors and out. Nowadays cement mortar is used outdoors and
gypsum mortar / plasterboard is used indoors
Lime mortar with no cement sets OK
Cement mortar with no lime sets OK
Cement mortar with a little lime as a plasticiser sets OK
Lime mortar with a little cement added 'to help it set' may not set OK
Cement is very fine, fills up the pores in the mortar, CO2 cant get to
the lime so poor lime set. Not much cement so poor cement set and the
result is a poorly set mortar
Sadly many good and experienced builders do not know this. They know
lots about concrete but lime mortar is very poorly understood
~~ Anna Kettle, Suffolk, England
|""""| ~ Lime plaster repair and conservation
/ ^^ \ // Freehand modelling in lime: overmantels, pargeting etc
|____| www.kettlenet.co.uk 01359 230642
Re: Lime or cement mortar?
Anna Kettle wrote:
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.
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
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'.
Portland 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
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
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°C 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)
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
Cement plants as alternatives to conventional waste disposal or
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
Waste materials used in cement kilns as a fuel supplement: 
1. Car and truck tires; steel belts are easily tolerated in the
2. Waste solvents and lubricants.
3. Hazardous waste; cement kilns completely destroy hazardous
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)
Fly 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
µm to 100 µm.
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.
Some pie in the sky about asphalt replacing cement in roads:
(I 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:
Thinking 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!
Slipping 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
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?
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