Polymeric sand is a joint stabilizing material used in hardscaping projects to fill the spaces between pavers, bricks, or stone slabs. This product is a mixture of fine sand and synthetic polymer additives which, when activated by water, harden to lock the paving stones in place. This examination assesses the environmental concerns associated with its chemical composition, application process, and long-term ecological fate.
Chemical Composition and Raw Material Sourcing
Polymeric sand is composed of silica sand (85 to 95 percent by volume) and synthetic polymer binders. The extraction of this silica sand often involves open-cast mining, which leads to land degradation, topsoil loss, and ecosystem destruction. The mining process also consumes large volumes of water and can disrupt natural drainage systems, potentially lowering local groundwater tables. The binding agents are typically synthetic polymers derived from petroleum-based chemicals (e.g., acrylics, vinyl esters, or polyester resins), whose energy-intensive manufacturing contributes to greenhouse gas emissions and water pollution. Some formulations may contain traces of volatile organic compounds (VOCs), which present an inherent toxicity concern related to the raw ingredients.
Environmental Impact During Installation and Curing
The application of polymeric sand presents immediate environmental risks related to dust and runoff during the activation process. Dry sweeping the sand into paver joints releases fine crystalline silica dust into the air, posing a respiratory hazard to installers and nearby individuals. This dust must be thoroughly removed from the paver surface before wetting to prevent permanent staining, known as “poly-haze.” Wetting the sand to activate the polymers poses the greatest runoff risk; over-watering or applying the product before heavy rain causes the uncured polymer material to wash out of the joints. This washout results in a milky, white substance containing synthetic binders and additives that can enter storm drains, contaminating soil and nearby water bodies.
To mitigate this short-term pollution, best practices require the surface to be completely dry before application and for installers to use a controlled “shower” setting on the hose, minimizing excess water and runoff.
Long-Term Ecological Effects of Hardened Sand
Once fully cured, polymeric sand stabilizes the paver system, but the long-term presence of the synthetic material introduces several ecological concerns. The cured polymer forms a monolithic, non-biodegradable bond susceptible to natural weathering processes, including abrasion and UV exposure. Over years or decades, this breakdown results in the formation of secondary microplastics (fragments less than five millimeters in size). These microplastics, along with chemical additives present in the original polymer, can leach into the surrounding soil and eventually migrate into groundwater and surface water systems. Such additives can include chemical flame retardants and phthalates, compounds known for their persistence and potential toxicity in ecosystems.
The product is designed to repel water, significantly reducing water permeability. Traditional polymeric sand installations can reduce water penetration to as low as two to five percent. This reduction contributes to increased surface runoff and limits the natural infiltration of stormwater into the ground.
Sustainable Joint Stabilization Options
For those seeking to stabilize paver joints while minimizing environmental impact, several alternatives to traditional polymeric sand exist.
- Dense graded aggregate (DGA) or natural sand remains a basic, non-chemical option, though it is prone to washing out and allowing weed growth.
- Natural sand combined with organic stabilizers, such as plant-based binders, are fully biodegradable and avoid the use of synthetic polymers and the long-term risk of microplastic contamination.
- Specialized resin-based jointing compounds offer high durability and are often semi-permeable, allowing for greater water infiltration than fully hardened polymeric sand.
- Permeable pavers used with an open-graded base and clean, crushed stone aggregate allow for maximum water flow directly through the surface, prioritizing stormwater management.