Home brew problems

[antwlo]

I have been using Heat Stop so far, and everything was ok. I decided to switch to a home brew mix with ratio of (3:1:1:1) 3 parts sand: 1 part portland cement: 1 part lime: 1 part fireclay.

I mixed everything and did my first application today with the new mix. Something is wrong!! the mix is not holding together. It's crumbling and not sticking on the firebricks. I made the mix a bit more "liquidy" by adding more water. I just tested an area that dried off, and the mix basically crumbled in my hand.

What am I doing wrong?

Please help

[justsan]

Sounds to me like you're using WAY too much water.

Go buy a 5 gallon Spiral mixer at home depot and attach it to a cordless drill and mix with that. I used the same exact recipe and with that mixer and just a little water my peanut butter mix even held the dome bricks upside down. Also, maybe you are trying to mix too much at a time...I used a red solo cup for a measurement tool.

*Tip - put all the dry ingredients together, mix, then add a little water at a time.

[deejayoh]

Hmmm... crumbling/not sticking sounds like not enough water to me - my experience is that it should be more like oatmeal than peanut butter. The excess moisture soaks into the bricks. It may still be crumbly after a day - as it is still setting up, that is not an issue.

My tip is that when you mix it dry - using a cup or container as justsan suggests - make a bunch of it at once. More than you'll need (like half of a 5 gal bucket). That way you have a supply and you can add mix/water until you get the consistency right. Mix it in small batches (I used a drywall compound tray) - that way you don't need a mixer, you can just use your trowel to get a good consistency. It it seems a little off, add a trowel or two of mix or a splash of water until it seems right.

[Gulf]

........................ I just tested an area that dried off, and the mix basically crumbled in my hand..........

I want to concentrate on this one statement. Portland based products require "curing" time to develope their strength. Curing and drying are two different things. Portland based mortar can dry out on the side of a mortar board in just a few minutes. But, it will crumble easily under your fingers. It hasn't cured. That takes time and some residual moisture to happen. Depending on the mix and the conditions, it can take 24 to 48 hours to get to a little over half of it's final strength. Which, is about 28 days.

[SableSprings]

As Gulf noted, Portland cement needs water to cure to harden (and stick) properly. If your bricks are too dry, they will pull the water out of your mortar mix and the concrete may dry...but it will NEVER cure without adequate moisture. I used a mixture that was a bit firmer than peanut butter...but not a lot..I think the texture of oatmeal (without the lumps ) is as good as any for the starting point. I would apply it to the bricks and you could actually see it stiffen up as the bricks absorbed some of the water. I could butter my bricks easily with the mix, use the trowel to trim the mortar edges back a bit, and apply the brick to the brick chain/layer below. As Deejayoh & Justsan noted, premixing dry ingredients first is a good technique. Small amounts of water worked into a small amount of the dry mix (what you intend to use in the next 20-30 minutes) is important. The cement actually cures by building a crystalline structure (with the available water) within the mass...that's the main reason it is recommended to keep a slab covered and moist for 3-4 weeks to achieve maximum strength. Too dry a mix and no internal crystals form so no strength or hardness develops.

Remember getting the mix consistency takes a little experimenting, but a little more water or a little more dry mix to achieve the consistency is OK. You may end up with a little more than you originally planned on mixing...but you can apply it to the chains and gaps on the parts you have done.

Don't want to insult here...but you are using Portland cement, not a pre-mix...right... Hope all these answers will give you some confidence to hang in there and keep trying...it DOES work!

[david s]

All good advice, but I'd caution against mixing the ingredients dry and then storing it for use later. When you buy sand it is invariably damp, in fact where I buy it they often use a sprinkler to keep the dust down. This means the sand will stay pretty damp for months if left in a pile. While the top may look dry, digging down a little usually reveals damp sand. If you want to dry mix a quantity ensure that your sand is perfectly dry or the water contained in it will quickly react with the cementious material mixed with it as described above and your mix will be useless. I have bins of sand which contain sieved dry sand, sieved slightly damp sand and the unsieved damp stuff from the building supplier. I constantly move this stuff around to dry and grade it.

[deejayoh]

All good advice, but I'd caution against mixing the ingredients dry and then storing it for use later. When you buy sand it is invariably damp, in fact where I buy it they often use a sprinkler to keep the dust down. This means the sand will stay pretty damp for months if left in a pile. While the top may look dry, digging down a little usually reveals damp sand. If you want to dry mix a quantity ensure that your sand is perfectly dry or the water contained in it will quickly react with the cementious material mixed with it as described above and your mix will be useless. I have bins of sand which contain sieved dry sand, sieved slightly damp sand and the unsieved damp stuff from the building supplier. I constantly move this stuff around to dry and grade it.

Ah - I bought bagged fine sand from my concrete vendor (using fine sand is another great tip, IMO) that was totally dry. But good point.