Why road surface stability matters for dust control in hyper-arid mining operations

Moisture can temporarily prevent these particles from becoming airborne. But unless the road surface itself becomes more resistant to mechanical degradation, new dust-generating material continues to form. This distinction between temporarily retaining fines through moisture and reducing the formation of loose fines through surface stabilisation is particularly important under hyper-arid mining conditions. 

This distinction formed the basis of research led by Bind-X chemist Jan-Philip Merkl at a mine site in the Atacama Desert. By examining both moisture-based dust suppression and surface stabilisation under hyper-arid conditions, the study provided valuable insights into how different approaches perform when evaporation and traffic continuously challenge the road-surface integrity.

Water is widely used for dust suppression because it is immediately effective and can be applied using equipment already available at most mine sites.

Once applied, water wets fine particles and temporarily increases cohesion at the road surface. This reduces the amount of material that becomes airborne under the influence of traffic and wind. However, this effect provided by water is quickly lost as the surface dries.
The testing with road material from the Atacama region observed drying times of approximately 30 to 45 minutes. Maintaining continuous surface moisture would have required an estimated 15 to 20 litres of water per square metre per day.

For most mining operations, maintaining this level of application across extensive road networks would be operationally and economically unrealistic.

Under increasingly hot, dry and windy conditions, this effective window becomes shorter, while haul traffic disturbs the surface between applications. The result is a recurring cycle of water use, water-truck movements and temporary dust reduction rather than sustained dust suppression.

Magnesium chloride is commonly used on mine roads to extend the period during which moisture remains available at the road surface. It can absorb and retain moisture from the surrounding environment, allowing a treated road surface to dry more slowly than one treated with water alone. This can reduce watering frequency under suitable conditions.

However, this mechanism depends on the relationship between the salt and the surrounding or subsequently added humidity.

Merkl explains that magnesium chloride has an equilibrium relative humidity of approximately 29–33%. At this point, the material is neither gaining nor losing moisture overall. When relative humidity falls below this range, the treated material is more likely to release moisture and dry.

That behaviour explains why chloride treatments require repeated application in hyper-arid climates, even though they retain moisture longer than plain water.

Chloride-based treatments also introduce operational trade-offs. Merkl discussed equipment corrosion, long dilution times, and slippery road conditions as common operational challenges that mine operators must manage. As a result, some mines prohibit chloride-based treatments entirely or restrict their use in certain areas.

More importantly, moisture retention can reduce the road material’s resistance to breakdown. Traffic can continue to wear the surface, creating new loose fines that eventually become available for dust generation. Added water usually increases soil plasticity and thus facilitates surface deformation.

Beyond these operational trade-offs, Merkl raised a longer-term question during the Atacama study: why do hygroscopic salt treatments require repeated reapplication over many years if their moisture-retention mechanism is an intrinsic chemical property that remains unchanged?

The hygroscopic properties of magnesium chloride are an intrinsic chemical characteristic and do not simply disappear over time. Yet many mining operations continue to apply large quantities of chloride-based products throughout the life of a haul road.

According to Merkl, this raises an important question about the long-term behaviour of these salts within the road structure. If chloride remained concentrated in the upper surface layer where dust suppression is required, significantly lower reapplication rates should be expected.

Instead, chloride is widely understood to migrate within the road body under the influence of water movement and traffic. Merkl hypothesises that the continued accumulation of hygroscopic salts in deeper road layers may gradually create what he describes as a “hygroscopic sponge” within the road structure.

Under this hypothesis, hygroscopic salts that migrate into deeper road layers may draw and retain moisture below the surface rather than in the upper layer where dust suppression is most effective. Over time, this redistribution could contribute to faster drying of the upper road layer, even as the total salt content within the road continues to increase.

Focused research is needed to quantify this effect and its significance under different operating conditions. However, the concept illustrates the complexity of relying solely on moisture-retention mechanisms for long-term dust control in hyper-arid environments.

Regardless of the long-term behaviour of hygroscopic salts within the road structure, one challenge remains unchanged: haul traffic continues to generate new loose fines. This shifts the discussion beyond moisture retention to a more fundamental question: how can mine roads be made more resistant to the mechanical processes that create dust in the first place?

A mine road is exposed to repeated dynamic loading. Heavy vehicles apply pressure to the surface while acceleration, breaking and turning generate horizontal forces that displace and break down road material. 

Where the surface has limited resistance to these stresses, aggregates gradually deteriorate and fine material accumulates in the upper road layer. 

This means dust is not only caused by dry material. It is also the result of the road surface continuously generating loose particles. Moisture-based treatments primarily influence what happens to fines after they are present. A surface-stabilisation treatment takes a different approach by increasing the resistance of the treated material to mechanical wear. 

The relevant question for hyper-arid operations is therefore not only how long moisture can be retained at the road surface, but also how effectively the surface can resist the mechanical forces that generate new loose fines.

To evaluate this distinction, Merkl and the Bind-X research team tested road material from Chuquicamata Mine in the laboratory and validated the findings under field conditions.

The tests in the lab were designed to assess how the treated material responded to mechanical stresses relevant to mine-road operation.

Magnesium chloride treated soil did not show any increase in measured breaking point in the abrasion test compared to water treated soil. This highlights the absence of substantial cohesive forces in the material.  Bio-based binder treatments became progressively more resistant as the treatment level increased, reaching a breaking point of up to 2,500 grams, indicating resistance to typical stress conditions in Chuquicamata.

The vibration tests showed a similar distinction between moisture retention and mechanical stabilisation. Magnesium chloride reduced material loss by around 85% compared with the water-treated reference, despite providing little mechanical strength. The bio-based treatment reduced material loss by around 99.5%.

Magnesium chloride therefore provided a substantial improvement over water in retaining the material. However, the bio-based treatment demonstrated considerably greater resistance to mechanical material loss under the applied test conditions.

These results illustrate the difference between retaining fines through moisture and increasing the material’s resistance to mechanical degradation. On a haul road, tyres continually roll, brake and turn across the surface. Greater resistance to this wear can reduce the amount of loose material available to form dust.

A field trial was conducted on an access road at Chuquicamata in March 2026 to determine whether the stabilisation effect observed during laboratory testing could be transferred to operating conditions.

A hardened surface layer formed within hours of application. It remained stable throughout the documented three-day period of continuous operation and continued to demonstrate stability beyond this initial observation period.

The significance of the field trial was not only the measured reduction in airborne particles. The physical condition of the road surface also changed. By increasing cohesion between particles and improving resistance to traffic-induced breakdown, the treatment reduced the availability of loose fines at the surface.

Bind-X’s bio-based treatment forms hybrid mineral-organic bridges between particles in the road material. 

These bonds create a stable surface matrix and hardened upper layer. Once this structure has formed, continued dust-control performance is no longer dependent on keeping the road permanently wet.

Water is still required during the initial application, but its role is to distribute and activate the treatment rather than to provide the lasting dust-control mechanism. This distinction is particularly relevant in hyper-arid environments. Watering suppresses dust while sufficient moisture remains available; hygroscopic products extend moisture retention; and surface stabilisation increases the material’s resistance to the mechanical processes that generate loose fines.