Up until very recently the proper method of completing the installation of brick or concrete pavers was to place very fine silica sand between the joints. The primary purpose and function of the silica sand was to enhance the structural integrity of the concrete pavers as a whole, by providing continuity between one brick paver and the brick paver adjacent to it. A sealer, in most cases, would then be applied over the brick pavers and hence, the sealer would harden the layer of silica sand closest to the surface. This in turn would help to prevent infestation from ants, germination of weeds and grasses and would help to prevent the base that the brick pavers were laid on from water ingress and washout.
The problem with basic fine silica sand is that it is subject to washout during heavy rainfall and because only the upper surface of the sand is hardened by the sealer, which will wear off, it does allow the germination of weeds and grasses and the infiltration of ants.
In order to prevent washout and to provide better protection against the germination of weeds and grasses manufactures have begun to add polymers to the silica sand, creating
polymeric sand. Unlike basic silica sand, polymeric sand does not depend on the sealer to create a hard surface as the polymeric sand hardens from the top through to the bottom of the fill. It also adheres or bonds to the sides of the concrete or brick pavers. Secondarily, because of this hardening and bonding the polymeric sand provides protection from water getting below the brick or concrete pavers. One of the biggest causes of shifting of concrete or brick pavers is water that resides between the bottom of the pavers and the base materials that the pavers are laid on. With water ingress all but eliminated the integrity of the brick pavers remains intact for much longer than would be the case with just silica sand between the brick or concrete paver joints.
Note: Polymeric sand also works extremely well as a fill between flagstones. Additional information on using polymeric sand with the installation of flagstones.
Polymeric sand is a generic term and does not define the specific properties of any one manufacturer. There are many manufacturers of polymeric sand and each has a developed a proprietary blend of chemicals or organics that they believe to be the best. Some manufacturers also add portland cement to their polymeric sand. In all cases the polymeric sand is activated by applying water to the product, after it is placed in the joints of the concrete, brick pavers or flagstone. The water activates the polymers that have been added, creating an impregnable surface and the bonding action.
Chemical versus Organic Polymeric Sand:
There are basically two primary types of polymeric sand:
- Synthetic or chemical based polymeric sand,
- Organic (Eco-sand) polymeric sand.
In order to choose which type of polymeric sand is best for you, it is important that you understand the differences between the two types of polymeric sand as the performance of the two products is substantially different, although, the installation of both types of polymeric sand is identical.
The synthetic based polymeric sands use a variety of different chemical polymers as the sands bonding agent. The chemicals do not, for all intent purposes, have a limited life. Once activated by water they produce a solid fill between the brick or concrete pavers. In general, they will survive extreme weather conditions and will provide resistance to weed and grass germination and infestation of ants for a very long period of time. However, the negative is that if the brick or concrete pavers do shift, for whatever reason, the hardened polymeric sand has to be removed, in some cases using chisels or other mechanical equipment in order to re-lay the concrete or brick pavers.
Organic based polymeric sand uses plant material that has been pulverized as the bonding agent. While this is undoubtedly more environmentally friendly than using chemicals as the bonding agent it does, in the writers opinion, have some drawbacks. One of the key selling points for organic polymeric sand is that the sand softens every time it gets wet. Because of this, the sand will when wet, reshape itself to fill new voids between the concrete or brick pavers. So, if there is some shifting, in theory, the organic polymeric sand will automatically fill the crevices created after being hosed down or after the next rainfall. However, because they soften when wet, the organic polymeric sands resistance to weed and grass germination is dramatically less than a chemical based polymeric sand that does not soften. As well, the organic matter has a limited life and over time it will not provide the necessary bonding between the grains of sand and will have to be removed and replaced with new polymeric sand.
Note: It is not wise to use an organic based polymeric sand around swimming pools or live ponds. If the organic material used as the bonding agent, should enter the swimming pool or pond water it could easily through off the balance of the chemicals or natural eco-balance in the case of a pond, used to keep either of those pools of water at their optimum level.
Figure 1 - Polymeric sand
Polymeric Sand Cost:
You will require the same amount of polymeric sand as the basic silica sand. Some manufacturers sell it based on volume while others sell if by weight, in either case the price of the polymeric sand is three to four times the price of basic silica sand. If you factor the on-going costs that are inherent in using basic silica sand – killing weeds and grasses that grow in the joints, killing ants, replacing washed out sand and the having to rework the installation due to water ingress below the brick pavers, the added cost of the polymeric sand is well worth the expense.
Availability of Polymeric Sand:
You should not have any problem is finding polymeric sand; all of the yards that sell brick or concrete pavers are now carrying the products. As well, the big box home improvement stores all carry polymeric sand and it can be ordered on-line from Amazon.com, as shown in Figure 1.
Note: Some manufacturers have produced polymeric additives that are designed to be blended with basic silica sand and hence create polymeric sand. For concrete or brick paver installations by home handymen we do not recommend the use of these polymeric additives as it is very difficult to get a homogenous blend of the polymer with the sand without commercial mixing equipment. As well, the silica sand must be completely dry when being mixed with the polymer or the polymer will begin to activate during the mixing process and you will end up with a big lump of hard sand!
Polymeric Sand Colors:
Initially polymeric sand was only available in tan and grey. As more and more individuals and contractors begin to use the polymeric sands, manufacturers are increasing the available colors. If you need colored polymeric sand in order to match masonry or colored mortars you will, possibly with some shopping effort be able to find darker colors and shades of tan. Remember that there is no industry standard when it comes to colors, so changing the manufacturer will most likely change the color. Hence, it is important to use the same manufacturer of polymeric sand for the entire project. Changing the manufacture of the polymeric sand in the middle of a project could be visually noticeable.