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Obligatory first-time-mortar-concerns post

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  • Obligatory first-time-mortar-concerns post

    I mortared my first bricks last night (pairs together, for later transport to the hearth) and then the first courses today. I used Lars' 6:4:2:1 recipe with about 4 to 4.5 parts water.

    I have four questions: behavior over time, recipe, sand, watered consistency.

    First, after twelve hours, and again this evening (about twenty-four hours) -- admittedly not very long yet -- the mortar seems very tacky and small globs break off easily (not chipping like old concrete, but like dried glue. Despite extremely ginger care when transporting brick-pairs to the hearth, admittedly a few were abused and easily fell apart...which I then bar-clamped together and left to sit, although I'm not sure if a break after twelve hours can simply be pushed back together or if it is too late at that point.

    Question one: is this behavior from the mortar acceptable? I thought it should act like concrete and be impressively hard the next day. Admittedly, numerous posts on FB confirm that this might be okay, so I'm trying not to worry about it, but it seems a little odd to me that is stays soft for so long.

    Question two: There seem to be almost as many recipes as oven-builders. I am NOT asking which recipe people blindly recommend, FB already has no shortage of such posts. What I would greatly appreciate, however, is an understanding of what effect variations of the recipes should have. For example, Lars' increased the fireclay and decreased the lime relative the James'. Many other recipes do something similar. What does each change do? What does increasing the fireclay do? What does decreasing the lime do? Many recipes increase the sand. Some completely dismiss lime entirely. How should these changes affect mortar? I could experiment, except that I wholly admit I don't even know what to look for, which makes "playing around" rather unproductive. Experimenting is only useful if you know what you're shooting or.

    Question three: I bought the white silicate sand available at Home Depot (100 Lb. #30 Silica Sand - 362201999 at The Home Depot), image attached (the image shows "settled" sand, the smallest grains after shaking it level. There are slightly larger grains below the surface I'm afraid.). My mortar has a gritty consistency, as one would expect from such sand. I find this at odds with the numerous "peanut-butter" recommendations, although I admit that that is w.r.t. water, not sand. Is everyone's mortar gritty?

    Question four: Water. I know the peanut-butter mantra, but I'm not sure I "get" it. The mortar is very unlike peanut-butter due to the sand, so any advice on this topic would be appreciated. What I used today was 6:4:2:1:4-1/2 (sand, fireclay, portland, lime, water). I felt that 4 parts water was too dry and 5 parts was pushing runny...but I just don't know what to shoot for...sigh.

    If you read this far, thank you.

    Cheers!
    Attached Files

    Website: http://keithwiley.com
    WFO Webpage: http://keithwiley.com/brickPizzaOven.shtml
    Thread: http://www.fornobravo.com/forum/f21/...ttle-7878.html

  • #2
    Re: Obligatory first-time-mortar-concerns post

    hey keb..

    What type of portland are you using ? n, s, ?

    The peanut butter thing, I didnt use the home brew, Used the Heat Stop. It may not be the same for the home brew...

    Part of your problem could be the hand mixing, you may not be getting a good consistency that way...

    sorry im not answering your questions directly as i dont have the answers, just trying to get some more thought on it and Im not being critical of you just trying to help..

    also dont forget you are moving the bricks, In a dome situation they are under constant pressure holding them in place and keeping pressure until your bond forms and cures,

    dmun pre joined his cut bricks for his dome, but he also used Heat stop 50,, Maybe the home brew just cant acclomplish a joint properly this way...

    Hope my thoughts arent making you more nuts

    Cheers
    Mark

    are you keeping your joints moist after they start to dry...

    Comment


    • #3
      Re: Obligatory first-time-mortar-concerns post

      Originally posted by ThisOldGarageNJ View Post
      hey keb..
      What type of portland are you using ? n, s, ?
      I got the standard stuff from HD, labled type 1 and 2.: 94 Lb. Lafarge Portland Cement - 352903999. I don't know if it's N or S. The lime is type S however.

      Originally posted by ThisOldGarageNJ View Post
      hey keb..
      Part of your problem could be the hand mixing, you may not be getting a good consistency that way...
      I'll buy a drill mixer from HD tomorrow. It's $13 instead of $4 (from HF), but I don't want to drive to HF.

      Originally posted by ThisOldGarageNJ View Post
      hey keb..
      sorry im not answering your questions directly as i dont have the answers, just trying to get some more thought on it and Im not being critical of you just trying to help..
      No no. I appreciate the feedback. Thanks.

      Originally posted by ThisOldGarageNJ View Post
      hey keb..
      also dont forget you are moving the bricks, In a dome situation they are under constant pressure holding them in place and keeping pressure until your bond forms and cures,

      dmun pre joined his cut bricks for his dome, but he also used Heat stop 50,, Maybe the home brew just cant acclomplish a joint properly this way...
      An excellent point, worthy of consideration. That part's pretty much done anyway. I was only doing that for the first three flat courses. I had considering making my inner arch separately and transporting it in one piece, but now, maybe not.

      Originally posted by ThisOldGarageNJ View Post
      hey keb..
      are you keeping your joints moist after they start to dry...
      Hmmm, I can easily mist it on occasion, as I did with the concrete at earlier stages. Thanks for the tip.

      Cheers!

      Website: http://keithwiley.com
      WFO Webpage: http://keithwiley.com/brickPizzaOven.shtml
      Thread: http://www.fornobravo.com/forum/f21/...ttle-7878.html

      Comment


      • #4
        Re: Obligatory first-time-mortar-concerns post

        Originally posted by ThisOldGarageNJ View Post
        What type of portland are you using ? n, s, ?
        The HD website says it's pressure rating is "N/Apsi". Is that what you mean?

        Website: http://keithwiley.com
        WFO Webpage: http://keithwiley.com/brickPizzaOven.shtml
        Thread: http://www.fornobravo.com/forum/f21/...ttle-7878.html

        Comment


        • #5
          Re: Obligatory first-time-mortar-concerns post

          Mortar Cements

          Type N Cement
          For Exterior, Above-Grade Walls.
          Type N is a medium compressive-strength cement. Type N is recommended for most exterior, above-grade walls exposed to severe weather, including chimneys.

          Type S Cement
          High Strength Non-Shrink Grout.
          Type S is sometimes specified for masonry at or below grade, but offers another quality. S has high compressive strength, but adds high tensile bond strength.



          Portland Cement Association
          Type 1 - Normal portland cement. Type 1 is a general use cement.

          Type 2 - Is used for structures in water or soil containing moderate amounts of sulfate, or when heat build-up is a concern.

          Type 3 - High early strength. Used when high strength are desired at very early periods.

          Type 4 - Low heat portland cement. Used where the amount and rate of heat generation must be kept to a minimum.

          Type 5 - Sulfate resistant portland cement. Used where the water or soil is high in alkali.

          Types IA, IIA and IIIA are cements used to make air-entrained concrete. They have the same properties as types I, II, and III, except that they have small quantities of air-entrained materials combined with them.



          Water to Cement Ratio: The #1 Issue Affecting Concrete Quality
          A low water to cement ratio is the number one issue effecting concrete quality.

          The ratio is calculated by dividing the water in one cubic yard of the mix ( in pounds) by the cement in the in the mix (in pounds). So if one cubic yard of the mix has 235 pounds of water and 470 pounds of cement- the mix is a .50 water to cement ratio.

          If the mix lists the water in gallons, multiply the gallons by 8.33 to find how many pounds there are in the mix.

          Low water cement ratio impacts all the desired properties of hardened concrete listed in desired properties of concrete.
          Use a maximum .50 water to cement ratio when concrete is exposed to freezing and thawing in a moist condition or to deicing chemicals per the 1997 Uniform Building Code. (Table 19-A-2)

          Use a maximum .45 water to cement ratio for concrete with severe or very severe sulfate conditions per the 1997 Uniform Building Code (Table 19-A-4)

          Water permeability increases exponentially when concrete has a water cement ratio greater than .50.

          Durability increases the less permeable the concrete mix is.

          Strength improves with lower water cement ratios. A .45 water cement ratio most likely will hit 4500 psi (pounds per square inch) or greater. A .50 water cement ratio will likely reach 4000 psi or greater.
          Cement Types
          ************************************************** ********
          Hydrated lime is used as a component in building products such as mortars, plasters, whitewash and stuccos. For building lime products, two different types of hydrated lime products are defined in ASTM standards:


          Type N or Normal hydrated lime products are only partially hydrated and/or have poor workability. Additional additives and/or long soak periods are required for these products to perform effectively in building applications. At least a 24 hour soak period is required before Type N dolomitic hydrated lime can be used acceptably for masonry or plaster applications. High calcium hydrated lime products normally are classified as Type N hydrates due to their poor water retention. ASTM C270 (Mortar for Unit Masonry) states that if a portland cement/lime blend contains Type N hydrated lime, the blender must show through performance or testing that the Type N product is not detrimental to the soundness of the mortar.


          Type S or Special hydrated lime products are a combination of calcium and magnesium hydroxides. Type S hydrated lime products are characterized by their chemical purity, high level of hydration and water retention. In building applications, Type S hydrated lime products have high hydration levels and controlled plasticity (water retention). This allows for minimal soak periods prior to application. Though there are some high calcium Type S hydrated lime products, most building lime applications utilize Type S dolomitic hydrated lime.

          we all love Home depot, But sometimes thier lack of knowledge on certains things really sucks,, I would consider after reaading all this,, you can either call or stop by your local masonry supply, explain your situation and often these guys will be filled with good knowlege...

          Hope some of this if not helping, explains it more for you..
          Im also wondering if your sand is too grainy...

          When I mixed my Vermicrete, I measured everything with coffee cans and scraped the extra off the top.. How are you measuring ??

          Cheers
          Mark

          Comment


          • #6
            Re: Obligatory first-time-mortar-concerns post

            some more info:
            Soft sand (or Builders sand): a smooth sand, non-gritty, loamy and with cohesive properties, can be used for:

            Bricklaying mortar
            For bedding paving slabs
            For rendering walls


            Sharp sand: this has a gritty feel and is similar to that used to condition soils and potting composts, can be used for:

            Concrete
            For rendering floors and walls

            Comment


            • #7
              Re: Obligatory first-time-mortar-concerns post

              one more thought before I leave for work,, Lime, can act as an accelerator in the mortar, making it set too fast before it binds.. try a small batch without it.. Im thinking you could almost go without it...

              Good Luck... The drill mixer should help a lot too...
              Looking forward to hearing your progress later
              Mark

              Comment


              • #8
                Re: Obligatory first-time-mortar-concerns post

                Wow, thanks for all the great info. You commented on HD. Just to be clear, I got my fireclay and lime from a masonry supply, my Portland cement and silica sand from HD, so my current ingredients are:
                Your comment above suggests that smooth sand is good for certain mortars. I had read that you always want sharp-edged sand so the lime (and other powders?) grip and coat the sand securely. Thoughts?

                I also found this disturbing comment and then again about the fireclay on two different sites. I wonder what that means.

                I found a reference that describes the Lincoln fireclay as:
                • SiO2 52.29%
                • Al2 O3 32.55
                • Fe2O3 2.19
                • MgO 0.55
                • CaO 0.19
                • K2O 0.76
                • Na2O 0.33
                • L.O.I. 11.14
                • P.C.E. 30 31.5

                Gladding McBean, the distributor of Lincoln Fireclay 60 has an official tech sheet which doesn't differ too much from the numbers shown above.

                So, what do you think? Are those approximately the right ingredients? Should I replace any of it in my future mixes, perhaps the sand and/or fireclay?!! I think the Portland and lime are probably right, right? I posted a photo of the sand earlier in this same thread to show scale and texture.

                Thanks, as always.

                Website: http://keithwiley.com
                WFO Webpage: http://keithwiley.com/brickPizzaOven.shtml
                Thread: http://www.fornobravo.com/forum/f21/...ttle-7878.html

                Comment


                • #9
                  Re: Obligatory first-time-mortar-concerns post

                  Hey Keb..
                  silica sand
                  It's kinda odd, as your finding out the more you read the more contradictions you get.. As far as sand, the best I can determine is silica sand, washed 1-3 mm in size,,, smooth in texture for mortar use....
                  Home Depot LaFarge Type I & II Portland cement
                  Type I Portland Cement
                  Type I Portland cement is general purpose cement with no particularly special attributes. It is suitable for use in general applications, however it should not be used in applications where the cement will be in contact with the ground, or with ground water, as these substances tend to contain sulphates which can attack the cement and make it expand and distort out of shape.

                  Type II Portland Cement
                  Type II Portland cement has some sulphate resistance, and releases less heat during setting and hardening than Type I Portland cement. Type II cement is therefore suitable for construction projects which involve exposure of the cement to ground water, such as pavements and drainage systems. Type II cement can also be used for large scale work such as retaining walls and other such masses.

                  Im assuming this description is the same for Type 1 & 2 (combined) so so far I think your okay....

                  It sounds like you pretty much have it good..

                  My comments as follows

                  Mix a small batch and measure precisely,, level cups etc...
                  Use the drill and premix your dry ingredients
                  add the water and use the drill till thoroughly mixed..
                  you might want to lighten up on the lime to slow the setting some,
                  dip your bricks in water for a few before mortaring
                  butter the brick and use the trowel handle to tap it in place, will help it set in

                  if i think of anything else I will let you know...

                  Good Luck and keep me posted, Hope I helped
                  Mark

                  Comment


                  • #10
                    Re: Obligatory first-time-mortar-concerns post

                    A couple of things. Lime is a plasticizer, not an accelerant. It does not increase the set time, it decreases it. Portland is used in lime plasters to gauge them, i.e. give them a faster set FYI. The purpose of the lime is to improve workability, board life, and plastic cracking (it improves the water tightness of the mortar as well).

                    ThisOldGarageNJ, the information you posted about water is for CONCRETE not mortar and does not apply. For mortar you can mix it wetter and even add more water and re temper it. That is a big no-no for concrete. Since you are laying very non-absorbent firebrick, you will want the mortar to be drier than if you were laying your CMU, but it is not nearly as critical as it is with concrete.

                    Comment


                    • #11
                      Re: Obligatory first-time-mortar-concerns post

                      A couple of things. Lime is a plasticizer, not an accelerant. It does not increase the set time, it decreases it. Portland is used in lime plasters to gauge them, i.e. give them a faster set FYI.
                      So what your saying TS is that the portland regulates the lime, rather than the other way around.

                      The forum post have always been not to use too much lime as it will cause your mortar to "go off" quickly...

                      After reading Kebs post, What suggestions do you offer ?? Remember we are all here to help....

                      Cheers
                      Mark

                      Cheers
                      Mark

                      Comment


                      • #12
                        Re: Obligatory first-time-mortar-concerns post

                        Just for the record, we all use weird handles here...my name is Keith, just in case you didn't pick up on it. kebwi is a mangling of initials from my full name. keb is kindy catchy though, I don't mind. I find the handles distancing. It's too bad the forum interface doesn't encourage real-name-usage more easily, by including it somewhere that is easy to see.

                        One odd thing is, I remain a little unclear on the distinction between mortar and concrete. Other than the aggregate size, I don't see a difference.

                        Well, I'll keep plugging away, maybe trying less lime (I'm already at 1/13th, 6:4:2:1). I actually haven't felt that I had any trouble with the mortar setting too quickly...to the extent that I know what setting is when I see it. I have found my mortar to be fully workable for the twenty to thirty minutes that it takes me to use up a small batch.

                        Cheers!

                        Website: http://keithwiley.com
                        WFO Webpage: http://keithwiley.com/brickPizzaOven.shtml
                        Thread: http://www.fornobravo.com/forum/f21/...ttle-7878.html

                        Comment


                        • #13
                          Re: Obligatory first-time-mortar-concerns post

                          Hey Keith, Keb....
                          I checked out your website,, you have some very cool stuff going on there... The Main reason I used heat stop 50 is that it removed a lot of variables for me.. The homebrew mortar here has been sucessfully used by so many,, I wish someone here with more experience with it can chime in and offer more suggestions for you..
                          One odd thing is, I remain a little unclear on the distinction between mortar and concrete. Other than the aggregate size, I don't see a difference.
                          Mortar is a cement/sand/water (and usually lime) mixture designed for laying up masonry units like cement block, stone or brick. Mortar is "sticky" so it adheres to the block, stone or brick. Concrete is designed to stand alone

                          Mortar and concrete are random composite materials, with the fine and coarse aggregate acting as the inclusions and the cement paste acting as the matrix. The only real difference between mortar and concrete is in the size of the aggregates used. Typically, the maximum aggregate diameter in a mortar is 1- 3 millimeters, while the maximum aggregate diameter in a commercial concrete is around 30 millimeters.

                          I think you hit the nail right on the head with your definition

                          Cheers
                          Mark..

                          p.s. Maybe Keb can be your altar-ego

                          Comment


                          • #14
                            Re: Obligatory first-time-mortar-concerns post

                            Keith, in your thread "parge recipe", I explained the differences between concrete, mortar, and stucco.

                            Lime mortar, that is mortar made with just lime and sand, will not take a set for hours (and this only because of the moisture absorbed by the masonry units), and will not cure for days to weeks. The reaction it relies upon to set is with carbon dioxide in the air to form calcium carbonate. Thus, lime mortar is not hydraulic.

                            Portland cement relies upon the water in the mix to hydrate. Thus it is hydraulic, i.e. the reaction is internal and does not rely on external ingredients (like carbon dioxide).

                            Adding lime to a mortar will increase the set time, but the most important reasons have to do with bond strength and workability.
                            Last edited by Tscarborough; 11-10-2009, 06:33 AM.

                            Comment


                            • #15
                              Re: Obligatory first-time-mortar-concerns post

                              Originally posted by ThisOldGarageNJ View Post
                              Mortar is a cement/sand/water (and usually lime) mixture designed for laying up masonry units like cement block, stone or brick. Mortar is "sticky" so it adheres to the block, stone or brick. Concrete is designed to stand alone

                              Mortar and concrete are random composite materials, with the fine and coarse aggregate acting as the inclusions and the cement paste acting as the matrix. The only real difference between mortar and concrete is in the size of the aggregates used. Typically, the maximum aggregate diameter in a mortar is 1- 3 millimeters, while the maximum aggregate diameter in a commercial concrete is around 30 millimeters.
                              Weeeellll, when I said I didn't understand the difference, I fully understood that concrete is that "stand-alone stuff" in driveways patios and that mortar is "brick-glue". What I meant was that, aside from aggregate size, I couldn't see the difference in components or approximate ratios within the margin of variety, so it seemed difficult for one to "be different" or to applied toward different goals than the other...since they are basically the same stuff aside from the aggregate.

                              Just as an example, you say that mortar is usually sticky...but they're the same stuff! That confuses me. I think I am picking up that it is lime that makes mortar sticky...so maybe you're saying mortar has more lime than concrete...but that seems completely at odds with what I've read about parging. I realize parge isn't the same as mortar, but it has to be sticky to hold to a vertical wall while at the same time most parge recipes have no lime at all...so, more confusion...but it's my problem. Really, don't worry about it. I'm obsessive, I admit it.

                              That's all I meant. Let's consider this dead-horse beat to a pulp. Thank you for entertaining the discussion, but I don't want to bother you.

                              Originally posted by ThisOldGarageNJ View Post
                              p.s. Maybe Keb can be your altar-ego
                              Wow, my alter-ego has an alter-ego.

                              Website: http://keithwiley.com
                              WFO Webpage: http://keithwiley.com/brickPizzaOven.shtml
                              Thread: http://www.fornobravo.com/forum/f21/...ttle-7878.html

                              Comment

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