Investing in the future: Building 100-year pavement foundations
Modern roadway failures, especially potholes, are often the result of overlooked subsurface issues. Among them, excess moisture is a primary culprit. In pavement structures built on unsaturated soils, common in roads and runways, water behaves in surprising ways. Rather than moving through the soil by gravity, moisture in unsaturated zones travels via capillary action. This mechanism, combined with insufficient drainage, can result in significant structural damage over time. Fortunately, advanced moisture control technologies such as moisture wicking geotextiles are transforming how engineers address this challenge.
In this blog, we’ll explore how moisture management geotextiles, particularly those using capillary wicking technology, can prevent road failures and serve as an effective pothole prevention solution - especially in climates with seasonal freeze-thaw cycles or expansive clay subgrades.
Unlike saturated soil where water moves under gravity or hydraulic gradients, unsaturated soils conduct moisture through capillary action. This subtle, lateral movement of water is often underestimated but can accumulate significantly over time, especially under impermeable pavements where evaporation is minimized.
Most roads are constructed over unsaturated soil, making subgrade moisture regulation a critical design factor. Unfortunately, conventional geotextile solutions, whether woven or nonwoven, are often non-absorbent. They act as capillary barriers, preventing vertical moisture migration. This unintended effect causes moisture to accumulate above the geotextile, eventually saturating the subgrade and reducing its shear strength and load-bearing capacity.
Figure 1 illustrates this barrier effect, where trapped moisture softens the subgrade, increasing compressibility and decreasing strength (Figure 2). This deterioration often leads to pavement rutting and ultimately, potholes.
To combat this, engineers are now turning to moisture wicking geotextiles—advanced fabrics engineered with wicking yarns that draw and transport water through capillary wicking technology. These geotextiles behave differently from traditional fabrics in several key ways:
Anti-capillary barrier behavior: As soon as these fabrics meet moisture, the wicking fibers begin to draw it cross-plane or laterally through the fabric.
High specific surface area: The internal structure of wicking yarns creates higher matrix suction than the surrounding soil, pulling water into the geotextile system (see Figure 3 and 4).
Figure 3
Figure 4
Directional drainage: Moisture moves from wet zones to dry zones, promoting balanced subgrade moisture levels and allowing water to exit the pavement structure when the geotextile terminates in a drainage layer or vegetated soil cover (Figure 5).
This geotextile solution for water-damaged roads dramatically reduces moisture buildup, helping preserve subgrade integrity and pavement performance.
In regions with distinct seasonal changes, moisture in roadways can freeze, expand, and then thaw - creating damaging heaves and subsequent depressions. Capillary wicking technology helps mitigate this by keeping pavement water infiltration to a minimum. By maintaining a drier subgrade, moisture wicking geotextiles reduce the expansion potential during freezing and limit contraction during thawing (Figure 6).
This consistency not only improves pavement performance but also extends road lifespan - reducing maintenance costs and safety risks caused by frost-related failures.
Expansive clayey subgrades are notoriously difficult to stabilize due to their tendency to swell when wet and shrink when dry. This repeated movement often results in longitudinal edge cracking, which progresses into severe pavement damage over time.
Wicking geotextile fabric offers an elegant solution by equalizing the moisture content within the subgrade, thereby limiting the differential movements that cause stress cracks (Figure 7a and 7b). Over time, this stabilizes the entire pavement structure and reduces the need for costly reconstruction.
For civil and geotechnical engineers, integrating wicking geotextiles into roadway design is a strategic decision. These materials can be used:
Under asphalt pavements in new construction or rehabilitation projects.
Within railway embankments, airport runways, and low-volume roads where moisture sensitivity is high.
In seasonal or monsoon-prone regions where rainfall infiltration can severely impact road performance.
As a long-term pothole prevention solution in municipal road networks, reducing maintenance burdens.
To maximize effectiveness, engineers should ensure the geotextile:
Has proper termination points for moisture exit (drains or vegetated zones),
Is installed in direct contact with the subgrade, and
Is compatible with existing subsurface drainage systems.
Moisture-related damage remains one of the leading causes of pavement deterioration. Yet with today’s innovations in geotextile drainage solutions, engineers now have tools to manage this challenge more effectively than ever before.
By leveraging moisture management geotextiles, particularly those equipped with capillary wicking fibers, it’s possible to create roadways that are stronger, more resilient, and less prone to failure. These technologies aren’t just about reducing potholes—they’re about building a smarter future for infrastructure.
