Another WFO in the UK - 42" Pompeii

[rwiegand]

It seems to me that any time a brick, stone or piece of tile is sucking water out of mortar that's a Bad Thing. My understanding is that cements and mortars attain maximum strength if kept wet throughout the curing process. Having the brick or tile take up water often results in a small separation between the brick and mortar, surely not good. Wet mixes of portland cement containing concretes and mortars aren't as strong as drier ones. I think it is prudent and a more controlled process to thoroughly wet the bricks then use a mortar mix at the right consistency to stick rather than using an overly wet mixture in hopes of compensating for dry bricks.

[Gulf]

I agree that the mortar needs to be at the correct consistency and that the brick should not be powder house dry. However, I question what "thoroughly wet the bricks" means. If that means soaking them in a bucket, or flooding them with a water hose, I disagree. Brick must be able to pull some mositure from the mortar to enable the bond. For firebrick, (on the hottest, dryest day) I have not seen any extra moisture needed other than a quick mist from spritz bottle. Set it for a fine mist and lightly spray the brick just before laying. If fthe water soaks imediately in to the brick, your ok with the spritz bottle. If it takes over 2 to 3 seconds to soak in, put the bottle to the side and just lay the brick without spritzing.

[brad mole]

Ok thanks for the info guys, i was soaking them for a few minutes then leaving them out for a few minutes to dry a little on the surface, i like the idea of the mist spray and i think i will lay a wet cloth over at the end of each session to keep things moist underneath. As for the consistency i was aiming for 'peanut butter' consistency which is what i had read on here, is that correct? im doing a homebrew mix of 3 (sand) to 1 (lime) 1 (cement) 1 (fireclay) mixing dry then adding water until its just right

[Gulf]

I have seen what appeared to be the mortar pulling away when it was actually only happening near the surface. That sometimes will happen when the mortar is sliced flush with the brick immediately after it is layed. That leaves the outer edge exposed to air. If it is hot, I will have a fan blowing on me which compounds the problem of the joint surface drying too quickly. My advice is to leave the flash that squeezes outside, undesturbed for about 15 to 20 minutes. Then tool (press) it back into the joint. That said, a brick has to be placed immediately after the mortar is spread. If it is moved after a few seconds of laying, the cohesion is lost. It then must be removed and fresh mortar applied.

[JRPizza]

I started going for "peanut butter", which for the kind of PB I eat was way too dry. I ended up pulling out my first layer of bricks as the mortar was too dry and it pulled away from the bricks. I found if I mixed the mortar wet and added dry mix to where if I ran my trowel through the bucket the mortar would just start to hold ridges it worked well. At that point it is way wetter than peanut butter.

[SableSprings]

Another thing I had to watch for on my bricks was dust/dirt. I used salvaged and new bricks, obviously I cleaned off the salvaged bricks but was surprised that most of my new bricks had enough dust on them to keep the mortar from adhering properly. Some of it was truly just dust and some was residue from cutting the bricks. I ended up just taking a wet brush and cloth to the bricks followed by a quick dip in a bucket of clean water. I usually just cleaned enough bricks for the work I intended for that session. The mortar stuck pretty well to those clean and moist brick surfaces.

If you think your mortar is the correct consistency as noted by the above posts and it's still not appearing to stick...make sure the bricks are cleaned of any surface contaminants that might be interfering with the bonding process. My brother in law (who was a professional brick layer) told me that often times if they were having trouble with a batch of mortar sticking, they could trace it back to someone using dirty water when they mixed that batch. Solution - throw out that batch of mortar and make a new one with clean water.

[brad mole]

Thanks everyone for the great advice as always, it all makes sense wht you have said and i dont know why it didnt cross my mind when i was laying the bricks, i didnt clean the excess cutting dust off most bricks, i also wiped clean the surfaces straight after laying the bricks, maybe every 3 bricks or so, so this could explain the cracking like gulf has said, hopefully meaning the cracks are only on the outside, i give them a good wiggle and they seem pretty sturdy so i think im going to leave them as they are and learn from my mistakes what i will change from now on. clean water, scrub each brick clean, lay bricks within a few seconds of applying mortar, and dont clean joins until 15 mins or so after laying. I will also have a play with different consistencies of mix to see if any stick better.

Heres are some pics of the cracks, hard to see they are really quite small

[UtahBeehiver]

Very nice work on phase one. Here is a pic showing how to use the IT for cutting the taper inner arch. Remember, the cuts are "NOT" symmetrical and each brick is slightly different with the top dead center brick being the longest length brick. Although the pic is show a partial arch rather than a full arch, the concept is still the same.

[brad mole]

Today i managed to get the tapered arch bricks cut, feels great to have that done but it did take me all day just to cut the bricks!

Here is the first stage, cutting the side tapers on all arch bricks

I wrapped the base in cling wrap to protect it from water and stop the spread of nasty dust

[brad mole]

Thanks Russell, having a bit of trouble getting the pics to upload in the right order so i just deleted my post and posted it again, i have the rest of the arch cut so i will upload the rest of the pics now, shame i cant upload all at once!

So this shows the bricks with their first stage of cutting, then i laid them out on the arch template to mark up for the next stage (didnt get pictures on the arch template) using a piece of string asmongota suggested in my other thread about arch placement, holding each brick in its correct place on the arch and having the string run from the dome centre and past the brick, i marked the outer and inner radius on the string which i could then transfer these marks to my bricks to get my first line to cut in the second stage of cutting the arch bricks. As many people have already said, its easy to think that all of these bricks are the same, but they are not, every so slightly different each time, you can see after all are marked up and then laid out flat that there is a gentle curve in then back out


I then cut all bricks after i had all the individual markings, and popped them back on the arch template for stage 3 cuts which i used my pencil attachment set to my inner radius, i could then draw the line for the next cut, a pencil mark was made along the inner side of the arch template all the way around the arch to tell me which lines to join up, as soon as each brick had these two lines i could join the lines together to make the final cuts

[brad mole]

And now the final stage, the two lines i had made are joined together to give me a line to cut, really pleased with how this turned out in the end, worth spending the whole day on it, i would have liked to have mortared it too but il settle for that for a days work. Oh i did drop a brick from the arch which landed on my first ring and broke 2 joins so im going to have to pull those up to re lay them!

Im not sure i fancy laying all of these arch bricks in one go incase i unsettle some as i tap them into position, so i might just do one or two each time i mix up a batch of homebrew

[UtahBeehiver]

Tapered arch looks right on the button. Life will be good as you do the dome. I built my arch as I did courses but keeping the arch ahead of the dome course. Remember to make corrections on the dome near the front half of the dome. No one will see in this area.

[JRPizza]

The cuts on the arch do look nice indeed, but I have a question for you. In the attached picture you can see where the amount of brick "protruding" from the dome increases towards the top of the arch as the circumference of the dome gets smaller, which is why Russell said the TDC brick should be the longest. The prospective of the picture makes it look like my arch is leaning to the right, but that is an optical illusion. Have you placed a dome brick on top of your arch using the IT to make sure it all fits?

[mongota]

Brad, really nice job on the arch.

The arch geometry was a head-scratcher for me until I realized all I had to do was use the inside and outside radii of the dome as reference points and a ray projecting from the center of the dome to give the cut angle.

With the arch geometry figured out, you are going to get the courses of brick mortared up in no time at all.

Nice work!

[WarEagle90]

Tapered arch looks good, Brad. As Mongo pointed out, that may be the hardest part of the build to see in your head. Watch out for mortar creep (mortar joints getting to big or small, throwing the TDC brick out of place) as you lay the arch. Can't tell from the photos, but mark the placement of each arch brick on the outside of the form to help diminish the creep. Keep up the great work.