Plain water evaporates in hours; specialty additives keep roads and stockpiles damp for days, slash PM by up to 95% in tests, and cut total costs by tens of percent.
Industry: Cement | Process: Dust_Control_&_Air_Filtration
Indonesia already tells operators to keep dust down. Technical mine guidelines (Kepmen 1827/2018) require road watering and other measures, and companies must measure dust levels and “take corrective action” if limits are exceeded (greenchem.co.id). General occupational rules (Permenaker 13/2011) also set strict worker dust‑exposure limits (greenchem.co.id).
In practice, unpaved haul roads and stockpiles are kept wet by water trucks—think “checkerboard” or spot spraying (ro.scribd.com). The problem: water evaporates fast, especially in heat, so crews spray daily or even hourly (globalroadtechnology.com).
Those truck runs aren’t cheap. In dry climates, water can cost ≈$0.4/m³, while the biggest line item is the application itself; fuel and labor for continuously running trucks can be 5–10× the water’s purchase price (cypherenvironmental.com) (cypherenvironmental.com). One example: a mine using ~10^9 L/yr of water for dust control might also burn ~10^6 L of diesel annually (cypherenvironmental.com).
That’s why operators are looking past plain water to chemistry—and they’re finding gains by dosing surfactants and hygroscopic salts into the spray. For haul roads specifically, many programs standardize on a dedicated haul‑road blend such as a hauling road dust suppressant.
Regulatory baseline and water‑spraying status
Sprayed water binds dust only while liquid is present; the effect typically lasts a few hours. Industry guidance puts it bluntly: plain water “must be applied frequently to maintain adequate moisture” because it evaporates rapidly (globalroadtechnology.com). In arid operations, raw water has been cited at ~$385/Mℓ (Mℓ = megaliter) and application costs dominate (cypherenvironmental.com) (cypherenvironmental.com).
Surfactant wetting agents (mechanism and data)
Surfactants (surface‑active agents that lower water’s surface tension) help droplets spread across hydrophobic dust instead of beading up, improving adhesion and penetration (foundations.martin-eng.com) (beta.co.id). The result is better droplet retention and agglomeration of fine particles. Martin Engineering cites a typical cut in water usage by about half for the same level of dust control—e.g., ~5% water alone vs ~2.5% with a surfactant in one moistening example (foundations.martin-eng.com).
Laboratory data back this up. Adding a nonionic surfactant (Triton X‑100) cut sedimentation (wetting) time from 632 s with water alone to ~278 s; a calcium chloride solution, by comparison, was ~567 s under the same conditions (pmc.ncbi.nlm.nih.gov). An Indonesian industry explainer sums it up: “Surfactants reduce water’s surface tension, enabling better penetration into dust particles,” which yields “increased effectiveness and duration” (beta.co.id). Experiments show water + surfactant sprays can achieve good suppression with <50% of the moisture needed by water‑only spraying (foundations.martin-eng.com) (beta.co.id).
On the ground, additive dosing is straightforward: operators mix surfactants with spray water and meter them into the line using equipment such as a dosing pump. For sites standardizing chemical procurement, the consumables fall under a broad category of water and wastewater chemicals.
Hygroscopic chloride brines (CaCl₂, MgCl₂)
Hygroscopic salts (deliquescent agents that absorb moisture from air) like calcium chloride (CaCl₂) and magnesium chloride (MgCl₂) form persistent brines that keep the surface damp by pulling in ambient humidity (globalroadtechnology.com). Historical practice notes that roads treated with these salts stay “moist even under dry weather conditions,” because they “reduce evaporation” and allow the surface to “absorb water from the atmosphere” (globalroadtechnology.com).
Both salts also act as soil binders: solutes occupy pore space and increase inter‑particle cohesion via ionic bonding and flocculation, creating a harder crust and reducing dust. Studies note MgCl₂ tends to produce a slightly harder, more stable surface than CaCl₂, though both form highly hygroscopic films (globalroadtechnology.com) (gxcontractor.com). Effectiveness requires moderate humidity—MgCl₂ actively absorbs moisture when RH (relative humidity) ≳32% at 25°C, CaCl₂ at ≳29%—but even low‑level atmospheric moisture is often sufficient (globalroadtechnology.com). Chloride brines are most useful in dry or moderate climates; they are rapidly washed out by heavy rain, and care is needed regarding corrosion and environmental runoff.
Field and lab tests are striking. A hydrous MgCl₂ brine cut PM₁₀ (particulate matter ≤10 µm) emissions by over 95% across wind speeds versus no treatment (mdpi.com) (mdpi.com). Even at just 40–60% of the standard application rate, MgCl₂ still suppressed >90% of dust at high winds (mdpi.com). In mine‑road trials, CaCl₂‑ or MgCl₂‑treated areas stayed visibly moist with minimal rebound dust, while untreated surfaces remained dry and dusty.
Measured performance and maintenance outcomes
Compared with untreated or water‑only surfaces, chemical treatments last substantially longer. In side‑by‑side road trials, chloride‑treated sections needed about 75–80% fewer regrading events; a multi‑month study found untreated gravel needed ~8 regrades per year, versus ~2 for treated sections (gxcontractor.com).
Air quality improved in kind. Measured PM₂.₅/PM₁₀ levels (particulate matter ≤2.5/≤10 µm) dropped by roughly half to two‑thirds under salt or polymer treatments; in that study, dust suppressants (CaCl₂, MgCl₂, lignin) cut emissions 50–70% relative to no‑treatment, with MgCl₂ and CaCl₂ the most durable (gxcontractor.com). The net result was a 30–46% total cost reduction, including maintenance, for treated roads (gxcontractor.com).
The cost calculus: chemicals versus water trucks
Material costs do rise. One evaluation put commercial sodium/alkyl polyphosphate or organic wetting agents at roughly ¥2000–3000 per unit‑area versus water at ¥86—about 20× or more at recommended doses (pmc.ncbi.nlm.nih.gov). Calcium/magnesium chloride solutions also cost several times more per liter than water.
But the operations bill flips the ledger. Plain‑water programs rack up heavy equipment time, diesel, labor, and lost productivity from constant watering. Industry estimates cite raw water at ~$385/Mℓ in arid zones, with hauling costs 5–10× that amount (cypherenvironmental.com) (cypherenvironmental.com). In a comparative trial, chloride‑treated gravel roads cost only ~$9–11k per mile‑year versus ~$20k for untreated (water‑alone) roads—a ~45% cut after including the salt cost—by reducing grading and watering jobs from ~8×/yr to ~2×/yr (gxcontractor.com) (gxcontractor.com) (gxcontractor.com).
A Canadian aggregate producer reported ~$12,000 in annual savings after switching from daily water spraying to monthly polymer/chemical applications, extending maintenance intervals from weekly to monthly (ironbirdcc.com). The indirects matter too: suppressed dust can extend equipment life—one account cited 18% longer lifespan on filter‑protected engines (ironbirdcc.com).
Consider a large site using 1×10^9 L of water yearly for dust control (cypherenvironmental.com). At $0.0004/L for raw water, that’s ~$400k—before trucks. By contrast, CaCl₂ or MgCl₂ brine might total only a few percent of that volume (mix‑rate dependent), cutting water use by 90% or more. Even at $1000–2000 per ton of salt, the combined chemicals+blending+occasional re‑treatment can be far below water procurement plus application. There’s also material savings: liquid MgCl₂ or CaCl₂ reduced aggregate loss by 55–57% in one estimate, delivering ~36% lower total annual maintenance cost (innovativecompany.com).
Implementation and Indonesian context
Indonesian practice already encourages water spraying and, where dust persists, the use of additives (ro.scribd.com). For haul roads and stockpiles, operators can blend surfactants and chloride brines on site and meter them into the spray circuit—handled by utilities gear such as water‑treatment ancillaries and a dosing pump.
The choice is situational. MgCl₂ is often selected for wetter climates and CaCl₂ for very arid conditions, with both creating persistent moisture films (RH thresholds: MgCl₂ ≳32% at 25°C; CaCl₂ ≳29%) (globalroadtechnology.com). Field and wind‑tunnel data show brines can suppress >90% of PM₁₀ for days, versus only hours for plain water (mdpi.com) (gxcontractor.com), while surfactants routinely allow 30–50% less water for the same effect (foundations.martin-eng.com) (beta.co.id).
Annual budgets reflect the difference: although a single chemical treatment may cost a few times more than water‑only per area (pmc.ncbi.nlm.nih.gov), multi‑month comparisons show treated fields can end up ~50% less expensive per year, chemicals included, than repeated watering (gxcontractor.com) (gxcontractor.com). For procurement teams, that’s the case for shifting part of the spend from trucks to chemistry—sourced as water and wastewater chemicals or purpose‑built dust blends like a hauling road dust suppressant.
Sources: peer‑reviewed studies and industry reports on dust suppression, including field trials of surfactant and brine treatments (pmc.ncbi.nlm.nih.gov) (mdpi.com) (foundations.martin-eng.com), and economically minded analyses (gxcontractor.com) (cypherenvironmental.com). Indonesian regulatory and industry sources provided local context (ro.scribd.com) (greenchem.co.id).
