Refractory Cement / Mortar which type to use?

[SvH]

Hi All,

I am new here and I have been reading a lot of posts the last 2 weeks. I am living in Thailand and I want to build a pizza oven that will last a long time. I will build it under a roof so during rainy season it will be dry however the climate here is tropical so a lot of sun, heat and very high humidity.

I used the build one before (6 or 7 years ago) using refractory cement but that one did not last long... the cement did not adhere to the bricks, cement did crack and it was still soft after weeks so when you touched it, it went back to dust... maybe that type of cement should have dried under a high temperature??

I will be using fire bricks and there is only 1 size available here which is 6.4 x 11.5 x 22 cm.

Most of you use the home brew with Portland but it is very easy here to get really all kinds of refractory materials (castable, insulation materials, refractory plastics, mortar, etc) but I have no idea after reading the last couple of weeks what I should use.... Should I do a home brew or use refractory?

The Portland home brew seems more difficult here because most of the people here are not technical enough and have for example no idea what Powder Clay / Fire Clay is or Hydrated lime (Calcium Hydroxide). Even the sales people of the refractory company could not give good complete answers to the questions I had. I understand some of you go for the cheaper solution but the price for me is not that important... It is more about the materials I have access too.

I want a dome that I can use for a long time in the climate (tropical humidity) where I am....
I need some advise please, below some specifications and the question is what is the best option (or should I go for the Portland mix).....

Type 30AM (Air Setting)
This is a wet type and a pre-mix version that is ready to use.
Silica 55%
Alumina 37%
Iron Oxide 1.8%
This is not 100% in total but that is all the info I got from the manufacturer....
Orton Cone: 30
Modulus of rupture after drying at 110 C - kg/cm2: 25

Type 30AMD (Air Setting)
This is the dry type of the above and I need to add water myself (and maybe other things?)
Silica 45%
Alumina 43%
Iron Oxide 2%
This is not 100% in total but that is all the info I got from the manufacturer....
Orton Cone: 28-29
Modulus of rupture after drying at 110 C - kg/cm2: 20

The company does advise that the joints between bricks should be 2 mm which is almost impossible to make when I need to cut the bricks in shape. Would there be any problem making the joints bigger (example 1 or 1.5 cm?)

I worry because of the joint size they advise and.... would it dry and adhere to the bricks without heating up the oven above 500 or 600 degrees? or will it adhere even without any heat?

Hope to get some help of you!
Sven

[UtahBeehiver]

Didn't you post this question earlier and Vince gave a fairly detailed answer?

[SvH]

Dear Russell,

My question to Vince was not the same as I did not gave the specifications exactly at that time. Yes I wrote to Vince and yes he gave very good info back how he made his dome. However his dome is new and when my previous dome was new all looked good but over a short period of time it started to crumble. This happened during the rainy season and at the moment we are in the middle of the dry season here.

Maybe its was the type I did use at that time or maybe I am doing something wrong. The type I have questions about now is from a different supplier and they did gave the specifications while the previous supplier didn't. However all suppliers here give limited info, I do not know why they do but its a common thing here in Thailand.....

By giving the specifications I hope to get feedback that one of the types will or will not work and if it will work how I need to apply it.

So if any forum members can help I appreciate that a lot.
Happy Xmas to you all !!

Sven

[fox]

From my experience with using refectory cement I would not recommend it or at least not the types I have used.
Hight temperature cement sets really fast , like 30 minutes or so and I don’t think that is a good idea for sticking bricks together.
On the other hand, home brew is great for the job.
finding dry clay powder was the most difficult thing for me too but I got some in the end ... from a pottery.

[david s]

Sven,
See my reply to yours in visitor messages.
Dave

[SvH]

After all your advise I will go for the Portland Home Brew mix... however I need some advise when it comes to the Portland Cement Type 1. It seems that the Portland Cement here might be different...
According to my search the USA does follow the ASTM C150-07 standards. Enclosed an image of the test / specification report of the Portland I can get here called "Rajasri Red". Can someone please confirm this is the right Portland I need to use for the Home Brew Mix.

Sand is easy to find here so that is solved.
Calcium Hydroxide (Lime) Industrial grade I also found.
Dry Clay or Fire Clay is a little more difficult... I found one clay / pottery supplier (need to call them after new year) and they have 3 types all in 50KG bags.
- Low Earth Powder - Suitable until 1100 Degrees C. around 18 USD
- Terracotta Body Casting - Suitable until 1100 Degrees C. around 15 USD
- Terracotta Body Molding - Suitable until 1100 Degrees C. around 17 USD

Update will follow ;-)

[david s]

After all your advise I will go for the Portland Home Brew mix... however I need some advise when it comes to the Portland Cement Type 1. It seems that the Portland Cement here might be different...
According to my search the USA does follow the ASTM C150-07 standards. Enclosed an image of the test / specification report of the Portland I can get here called "Rajasri Red". Can someone please confirm this is the right Portland I need to use for the Home Brew Mix.

Sand is easy to find here so that is solved.
Calcium Hydroxide (Lime) Industrial grade I also found.
Dry Clay or Fire Clay is a little more difficult... I found one clay / pottery supplier (need to call them after new year) and they have 3 types all in 50KG bags.
- Low Earth Powder - Suitable until 1100 Degrees C. around 18 USD
- Terracotta Body Casting - Suitable until 1100 Degrees C. around 15 USD
- Terracotta Body Molding - Suitable until 1100 Degrees C. around 17 USD

Update will follow ;-)

The cement you have sourced will be fine. Regarding the lime, be sure that it is builders lime and not agricultural lime. The builders lime is hydrated ie it works like cement and goes hard with added water. The agricultural lime won’t. For the clay really any powdered clay will do, don’t worry about the temperature rating as you’ll never get it to 1100 C. The clay with the least shrinkage is best but those on offer will all be around the same. I’d go for the cheapest, the terracotta casting clay.

[SvH]

Hi David, Thank you so much !!!!

I understand you and others use terms like builders lime and agriculture lime but not all in all countries such terms are used. Hydrated Lime is used also in Agriculture according to the Graymont website, the Sciencedirect website and Wikipedia to name a few.

From my understanding is that I should NOT use Calcium Carbonate CaCO3 which is most often called Agriculture Lime in many countries.
Are you referring to Calcium Carbonate CaCO3 when you mention Agriculture Lime?

Where I am Agriculture Lime is Hydrated Lime Ca(OH)2 Calcium Hydroxide and NOT Calcium Carbonate CaCO3.
So the question is .... can I use Ca(OH)2 Calcium Hydroxide which is Hydrated Lime?

Happy new year to you and all others that read ;-)
Sven

[david s]

Hi Sven,
Strictly speaking it’s neither of those. It starts off as CaCO3 but is then calcined, that is heated up in kilns until the CO2 is driven off. It is then CaO. When water is added it will go hard like cement and it then becomes Ca(OH)2. Neither CaCO3 or Ca (OH)2 will behave like cement. Have a read about quicklime. The reason I said builders lime is that the stuff they use will go hard as a cementious material, whereas for agricultural purposes that characteristic is not required. So you need to be seeking lime specifically for use in mortar. If you are still unsure you could try to get a small sample and mix it with the same volume of sand, then add enough water to make a thick paste. If it’s good it should set to a hard lump in 24 hrs.

[SvH]

Hi David,

Oh my.... so the lime I need is not the standard Ca (OH)2 Hydrated Lime..... mmmmmm. Is there any other name for "Builders Lime"? It looks like it something typical to the USA... Are there any technical specifications I need to look for besides it becomes hard when water is added? What is builders lime exactly? I have been reading for hours today but so far I am stuck... all I can find here is white cement, gypsum and 47 types of other cement. I have read the post about Quickrete and this is a "hydrated lime type s" which can be used but that is a typical USA product. There should be a way to solve this... however hydraulic lime I can not find here as well... I cannot believe there is no lime here that I can use because also here its a natural source. A lot of cement that is made here does have Hydrated Lime inside but it might just be for making it easier to work with rather than having hardness properties?

Anyway I have learned a lot today which is always good, for me now... its late, tomorrow another day ;-)

Kind regards,
Sven

[david s]

This is the hydrated lime that I buy.

Download SDS
and here’s a little more on lime that may either provide clarity or confusion.
https://homeguides.sfgate.com/differ...ime-86906.html

[SvH]

Hi David,

Again... hours of reading.... its very interesting !! I am for sure not a scientist..... but I might build a house from Lime Mortar in the future making my own PUTTY, sounds fun!

About the MSDS you did send...
CAS number 1305-62-0
Calcium Hydroxide 90-95%

Its the same as I what I did sourced... I will request a small sample, test and let you know...
I need to wait until Jan 6 because everything is closed now.

I really wonder what the difference is between builders lime (which is Calcium Hydroxide) with cementious values and regular Calcium Hydroxide without cementious values....
It might be that cementitious materials in the builders lime are added? 5-10% pozzolans maybe? MSDS state "other non hazardous ingredients".

Anyway... I will test !

[david s]

Re-read post #9 It starts as calcium hydroxide, but then it is hydrated (H2O added) and calcined (heated to drive off CO2)
So if it is labelled as “hydrated lime” it should be the right stuff.

[SvH]

Hi David,

I got the sample of the Hydrated Lime and I made 2 samples.
1. Just the lime powder and add water to mix and let it dry.
2. Used the lime powder, sand and water to mix and let dry.
Version 1 and version 2 become hard.

Enclosed a photo of version 2.
When I take of of the 3 pieces and squeeze it between my fingers it does break apart, see the last photo.
Can you tell me if this is the right lime from the photos?

Thank you !!!

Kind regards,
Sven

[david s]

Yes, that’s it. Now mix 3:1:1:1 sand, cement, lime and powdered clay into a workable mix with water and you’ll have yourself a good mortar for oven use.