Replies

1. 
   Waters | Jan 30, 2009 03:42am | #1

   are you talking about casting your capstones in molds?  How many do you have?

   I would think concrete would be stronger.

   I'd build as many molds as I could (or needed) and do them all at once from as few batches of concrete as possible for consistency.

   what's type s cement, btw?

    

1. 
   gfretwell | Jan 30, 2009 04:24am | #2

   Type S is really mortar but it is basically sand mix concrete with a splash of lime and some additives. Portland products are like Mexican food. They all have the same basic ingredients (cement, water and aggregates of various sizes) it is just how you mix it and what additives you put in.
   If you are not using any reinforcement I think I would like some course aggregate (concrete) but I would still like some wire in it.

1. 
   brownbagg | Jan 30, 2009 04:53am | #3

   pea gravel

2. 
   Henley | Jan 30, 2009 04:58am | #4

   Yeah 14x24 could use some steel.

   Concrete definitely.

3. 
   Davo304 | Jan 30, 2009 05:24am | #5

   Definately go with concrete. As was already mentioned, Type S is really a high-strength mortar. Mortar is brittle, so if you make forms using this, your cap stones will fall apart.

   What usually works well is using Type III portland cement ( also known as high-early)with sand and pea gravel.  Because your forms are only gonna be 2 inches thick, 3/8 dia pea gravel is the right size for course aggregate. Larger aggregate is harder to blend in such a thin mix.

   Using a high-early allows you to break the stones out of the moulds sooner for re-use.

   From what I've been told , pre-mixed bags of Quickcrete 5000 (concrete mix)works pretty well for what you want. It will take approx one 45 lb. bag per cap stone.  You don't need to add any additional portland into this mix as the  pre-mixed ratios are really good. Just tear open the bag, and add water...but not too much...the less water the stronger the mix, but you need enough water so that you can pack and vibrate the form easily enough.

    

   Davo

4. 
   ponytl | Jan 30, 2009 06:30am | #6

   i cast tons of stuff...  tons is more than accuate... you want concrete... portland & rock... yes sand is a rock...  you don;t need steel if these are supported cap stones... you don't need rock .. just sand & portland... but if you use rock don't use pea... it's round and has no bite... use small course jagged rock...  if you use "golf course sand... and white portland... it will come out looking like  limestone ..(close ok)  

   p

1. 
   MBaybut | Jan 31, 2009 06:16am | #7

   Thanks all.
   Mike

5. 
   TGHepburn | May 28, 2012 11:35am | #8

   Cap Stone Finishing Mistery

   I know this post thread is old, but I'll post this here before making a new thread.

   I am doing the same cap stone project.  Thanks for all the great advice - it answered 90% of my questions

   The question:  How do you finish the concrete in the molds to get a "Sandstone" look?

   I've used colour agents in concrete before and am confident I can get the colour streaking required but the surface always comes out looking like...well... concrete.  Any tips would be great.  Thanks.

1. 
   gfretwell | May 28, 2012 08:51pm | #9

   If you tap the form with a mallet it will bring the cream out and make a smooth finish, assuming a smooth mold.

   You can always parge it with stucco mix to get whatever finish you want.

1. 
   TGHepburn | May 29, 2012 01:02pm | #11

   Form Material: tin or plywood

   I've used my reciprocating saw to vibrate the forms of other work I've done; it works well.  A quick touch with the side of the tool is all it takes.

   The cap stones are curved.  I was wondering if I should use tin to line the form so I get a smooth finish.  If I parge the stones I guess it doesn't really matter how they initially come out of the form.

   Another question:  Would anyone recommend using synthetic fibers to re-enforce the concrete cap stones.  I'm worried about the fibers sticking out.  Also, I have to buy a whole bag which is a little pricy for the small job I'm doing (14 lin. feet of capstones)

   Thanks for all the help.

1. 
   gfretwell | May 29, 2012 08:51pm | #13

   Round plastic tubs make great forms if you can get a shape you like. I made some bases for towel racks by the pool out of clear plastic flower pot "saucers".

   Fiber mesh will be fuzzy for a while and you don't want to be laying your bare arm on it.

   Mixing your own concrete with white portland and playground sand or course pool plaster sand (white crushed quartz) makes a nice molded piece. The quartz works well for doing a little aggregate exposure, just wash the cream off.

2. 
   DanH | May 28, 2012 09:59pm | #10

   Also remember that when the concrete is "green" it's quite soft, so you can easily abrade the surface if you wish, or wash it to reveal some of the sand/aggregate.  Obviously something that requires "technique", but with a few practice pieces you might work something out.

1. 
   TGHepburn | May 29, 2012 01:08pm | #12

   Washing

   I like your suggestion of  "washing".  I will definity have to practice on this technique to know when the concrete is firm enough.  I guess I'll add a few bags to my order. 

   Thanks!