question on cultured stone and cement - Contractor Talk - Professional Construction and Remodeling Forum

enforcer · 09-25-2009, 07:24 PM

i saw a few posts lately and my curiousity got the best of me.
i notice cultured stone has to be at least 4" above the ground so water does'nt hit it; it absorbs moisture. if thats the case,what about a foundation,thats made of concrete,why could that be exposed to water?

concretemasonry · 09-25-2009, 08:25 PM

Different type/quality of concrete and possible different types of aggregates and admixtures.

Captainsls · 09-26-2009, 12:04 AM

Mortar has a tendency to wick moisture thus popping off the stone during a freeze thaw. Ice buildup under the stone alone is enough to break the bond. A foundation on the other hand…. Is less than likely to pop off your house.

concretemasonry · 09-26-2009, 09:38 AM

Actually, many types of cultured stone are intentionally made to have higher absorption, lower strength than concrete or block and have a lower density to reduce the weight. - Less weight means lower shipping costs because the cultured stone plants are widely spaced, lower weight means less weight for the mortar to hold up and lower labor and handling costs. The higher absorption can also make construction faster.

Some types of manufactured stone are made to different standards.

Bottom line is that cultured stone standards are different than either concrete or block standards because of the different manufacturing methods and product requirements.

enforcer · 09-26-2009, 02:30 PM

concrete absorbs less water than stone or mortar? someone asked why can't mortar sit near the ground or by water when the foundation is basically the same material and that goes into the ground?

concretemasonry · 09-26-2009, 04:46 PM

It is not all the same material. Block is produced in highly automated, controlled plants. Cultured stone is normally manufactured. These all usually have controlled curing conditions. Ready-mix is plant proportioned, but is subject to additions and contractor practices for placement and curing. They all have cement in them plus they all have some sort of aggregate (sand to rock or even porous type rock of different sizes). Some have too much water to make costs lower and placement easier.

Manufactured concrete products can have wildly different methods and properties. There are many different mix designs (water, cement, aggregate types and gradations) different types of placement, molding and compaction. Some are in a mold as little as 7 seconds whiles other may have to be in the mold for 24 hours or so.

As an example, a minimum strength concrete block must be 1900 psi (usually is 3000 psi because low strengths are not economical to produce) but can be pushed up to over 8500 psi if necessary (the aggregate type, water amount and gradation is critical). For wet cast concrete (many cultured stones) the time in the mold increases the investment and selling price. Ready mix concrete is a wet mix with too much water that is used to make placement easier and shrink more (shrinkage cracks) that is placed with little control, but it is difficult to get below 3000 psi, but placement and curing can change the durability. All factory produced materials use controlled accelerated curing which eliminates the variable that plagues poured concrete.

Mortar is a totally different animal since it really has not absolute proportions (really a blend of proportions) that is subject to the moisture content and the mixing time. If you talk about mortar strength you can get 4500 psi block prisms using 2500 psi mortar because mortar has a minimal effect. The specifications recommend using the weakest mortar necessary to carry the loads, since other properties are more important.

You are trying to split hairs since the recommendations are based on experience and performance of products when used as a wall system in the real world.

Tscarborough · 09-26-2009, 06:09 PM

BBQ sauce and Cake both have sugar as an ingredient, would you compare the two for physical properties?

enforcer · 09-27-2009, 07:48 AM

cement/concrete is made to withstand water? mortar is also but just not as much? same with stone?

thermax · 09-27-2009, 08:05 AM

i thought that adding ingredients to concrete and mortar,they can become water proof thereby reducing the absorbtion rate significantly.

concretemasonry · 09-27-2009, 09:24 AM

Chemicals and admixture can only improve the water resistance of a concrete mix to a small degree and they are not necessarily long lasting, except for water reducing agents that get the job done immediately during placement. The main properties are the percentage of compaction, the mix matrix and the properties of aggregate. Also aggregate shape also is a factor in many uses.

Some manufactured stone uses porous aggregates that have high absorption and a very difficult aggregate shape (for color and appearance) that make maximum density difficult. These products are made to the cost and visual demands of the market (higher absorption for installation and lighter for shipping/handling costs). Very high durability, high strength and low absorption can be acheived, but few people will pay that extra 100-200% for since it is rarely needed.

thermax · 09-27-2009, 10:16 AM

mortar can kind of degrade(from moisture) thereby delaminating the stone so to to speak.
as far as a foundation,i believe it should always be sealed with some sort of sealant from the inside.
i also read that you don't want concrete to lose its permeability either.
anyone want to expound on this? this is actually interesting since i know nothing about masonry.

stacker · 09-27-2009, 11:46 AM

when i was a kid,we climbed the highest trees and we are still alive.we drank from water hoses in the front yard and we are still here.if we did something bad,we were beat with a belt and lived to do it again.now days,kids cant climb trees because they might fall,the might get sick from the water hose,and dhs will remove you from your home if your parents discipline you.

i have laid plenty of cultured stone over the last 30 years.we have laid in to the ground level,laid it below ground level a few inches,and laid it to a concrete sidewalk or slab.and we have yet to have any problems with it.i think the same kind of thinking in the first paragraph of my post is what we have here.im not saying that it doesnt absorb moisture,but it's not a big enough problem to have to lay it 4 inches above the ground.

dakzaag · 09-27-2009, 01:29 PM

Quote:

i have laid plenty of cultured stone over the last 30 years.we have laid in to the ground level,laid it below ground level a few inches,and laid it to a concrete sidewalk or slab.and we have yet to have any problems with it.i think the same kind of thinking in the first paragraph of my post is what we have here.im not saying that it doesnt absorb moisture,but it's not a big enough problem to have to lay it 4 inches above the ground

While that is certainly your experience, it doesn't always translate to conditions and performance in a cold weather state such as Minnesota.

Not sure where Enforcer is from, but I would suggest that the 4" clearance is usually a good thing for life span of the wall, but the initial HO reaction will probably negate any long term possibilities.

Once again we have a poor substitute, culture stone, trying to replace a tried and true process of full depth masonry stone or brick. The adage "sometimes the short cut isn't so short" might apply in this situation.

Tscarborough · 09-27-2009, 01:55 PM

Adhered veneer should not be viewed or judged as a full thickness veneer. It should be considered as the final coat of a cementious stucco wall makeup. As such, it should not be in contact with the earth, no matter if it may or may not work. The design of the system dictates the usage, and the design for cementious stucco walls say no earth contact.

The reasoning has nothing to do with the absorption of the faux stone or any other single part of the system. It has to do with the design of the SYSTEM, and how that system works.

Concrete Tech · 09-27-2009, 09:42 PM

Actually there are two companies now producing internal waterproofing technology for block and mortar that are a silicone base that reduce absorptions below 2% consistently. Can't remember the name of the product but BASF produces one of them. Good luck

concretemasonry · 09-27-2009, 10:09 PM

Quote:

Originally Posted by Concrete Tech

Actually there are two companies now producing internal waterproofing technology for block and mortar that are a silicone base that reduce absorptions below 2% consistently. Can't remember the name of the product but BASF produces one of them. Good luck

I think the correct phrase is AS LOW AS 2%, depending on the rate of the untreated concrete. the effects are not permanent. For masonry there is the classic problem of hoe do you get a reduced absorption mortar to bond to a reduced absorption mortar. Names of the products have changed as the manufacturers changed hands through the years.

I know of concrete block made in 1952 that had absorptions less than 2% without any admixtures, but just good high quality production and quality control of materials. the expose block church is performing well (after 57 years) and is often described as being built out of cut stone.

Normally polymers (bigger $s) are better than the old silicone technology or stearates, but they are unreliable in the field under relatively uncontrolled conditions.