Trace additions of grinding aids and strength enhancers are recovering 3–28 day strength in lower‑clinker cements—while lifting mill output and cutting power—according to lab trials and supplier data.
As cement makers push down the clinker factor to cut cost and CO₂, early strength takes a hit. Supplementary cementitious materials (SCMs—pozzolanic or latent‑hydraulic add‑ins such as slag, fly ash, and limestone filler) slow early hydration and weaken early strength. Specialty chemical grinding aids and performance enhancers—often polycarboxylate/amine blends, alkali salts, or accelerators—are stepping in to counter the tradeoff by optimizing particle dispersion and hydration chemistry, boosting both early‑ and late‑age strength (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov).
In one study, just 0.03% of a new polycarboxylate‑based grinding aid (polycarboxylate ether, or PCE) cut mean cement particle size by ≈3.7 µm (micrometers) and raised 3‑day and 28‑day compressive strength by 6–8 MPa (megapascals) (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). Major suppliers report similar effects in practice: Sika’s SikaGrind‑870 and ‑874 stress “increased early strength, improved powder flow” and claim higher 3‑day and final strengths even as fineness rises (pak.sika.com) (vnm.sika.com). Indonesian distributors market NEXCEM products specifically to “increase strength (Early & Late)” by reducing agglomeration and optimizing particle size (nexco.id).
Grinding aid mechanism and fineness control
Grinding aids—commonly PCE polymers blended with alkanolamines—adsorb on fresh cement surfaces to neutralize charges and keep particles separated. The result: higher mill efficiency (lower kWh/t), finer and more uniform Blaine fineness (a standard index for cement fineness), and fewer “overground” clumps; finer particles accelerate hydration and strength gain (vnm.sika.com) (nexco.id). In trials, combining polycarboxylate with triethanolamine (TEA) or triisopropanolamine (TIPA—both alkanolamines) reduced average particle size by ~4.2 µm and improved the hydration microstructure (pmc.ncbi.nlm.nih.gov). Those compounded PCE+alkanolamine mixes “enhance the early and late strength of cement” far more than PCE alone (pmc.ncbi.nlm.nih.gov).
Lab hydration studies corroborate the chemistry: the right aid catalyzes aluminate and C3S (alite) dissolution and C–S–H (calcium‑silicate‑hydrate) formation—boosting early ettringite and C–S–H without changing the final mineralogy (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov). These effects are achieved at trace dosages—often 0.02–0.1% by weight of cementitious—requiring accurate, stable addition at the mill; many plants pair the additive package with a dedicated dosing pump for repeatability at hundred‑ppm levels.
Strength enhancers: amines and salts
Performance enhancers include accelerators and specialty additives dosed during grinding or batching: alkanolamines (TEA, TIPA, THEED), alkali sulfates (K₂SO₄, Na₂SO₄), and calcium salts (Ca(NO₃)₂, Ca(HCOO)₂). They accelerate hydration reactions or supply nucleation sites. Sika cites that tri‑isopropanolamine “enhances the dissolution of C₄AF (ferrite), thereby increasing the alite surface area” and boosting strength (zaf.sika.com). In practice, 0.1–0.3% of such amines often improves 1–3 day strength by tens of percent (cement‑chemistry dependent) while still benefiting 28‑day strength; a lab study with a combined alkanolamine/alkali additive raised 7‑day strength by ~16% (pmc.ncbi.nlm.nih.gov) (pmc.ncbi.nlm.nih.gov).
Calcium nitrate or sulfate‑type accelerators can “fire‑harden” blended cements. In a high‑volume fly‑ash clinker mix, Ca(NO₃)₂ + NaSCN (sodium thiocyanate) increased 7‑day compressive strength by ≈68% and 28‑day by ≈10% over the untreated mix, with modest increases in ettringite (link.springer.com). Nanoscale additives also matter: swapping silica fume for 5–8% nano‑silica in a fly‑ash mixture yielded an additional 7–9% gain in 7–28 day strength, essentially offsetting inert fly ash (link.springer.com) (link.springer.com).
Pilot data and mill economics
Small doses, measurable gains: a Chinese study found 0.03% PCE grinding aid raised 3‑day strength by 6–7 MPa and 28‑day by 6–8 MPa (pmc.ncbi.nlm.nih.gov). Another campaign showed that an early‑strength accelerator (ESA) calcined at 800°C gave 60% slag cement (IPO 60%) concrete 1‑day and 3‑day strengths equal to 100% OPC (Ordinary Portland Cement) (pmc.ncbi.nlm.nih.gov). Supplier data point the same way: Sika reports 5–15% gains in 3‑day mortar strength for typical Portland‑limestone cements using its additives (see Fig. ahead), with additive dosages often at 0.02–0.1% by weight and compatible with any concrete water‑reducing admixture.
The process payoff is non‑trivial. Better particle dispersion in the mill can lift production by 5–10% and trim power use by 2–4% (pak.sika.com). Plants typically monitor mill output, fineness, and both 1–7 day and 28‑day strengths to quantify the upside. Accurate micro‑dosing at the mill silo or feed line remains critical; many operators standardize on a dedicated dosing pump for long‑term control at hundred‑ppm levels.
Selection framework by SCM type
Fly ash–rich blends (low‑Ca, pozzolan‑rich): Class F fly ash has little free lime, so early strength suffers. Strong accelerators and amines are preferred. Calcium nitrate or alkali sulfates (K₂SO₄, Na₂SO₄) boost aluminate reaction; alkanolamines (e.g., TIPA/TEA) accelerate silicate hydration. Producers often add 1–3% Na₂SO₄ and 0.05–0.2% TIPA in high‑fly‑ash cements. Reports show such blends recovering >90% of normal OPC 7‑day strength. Nano‑silica (2–5%) or C–S–H seeding can further compensate by consuming Ca(OH)₂ fast. In practice, blends with ~30–50% fly ash often require ~0.05–0.2% accelerant (as solids) in mill or mix water to meet target strengths (link.springer.com) (pmc.ncbi.nlm.nih.gov).
Slag (GGBFS)–heavy cements: Slag is latent‑pozzolanic but slower than OPC. Accelerating aids such as Ca(NO₃)₂ or Ca(HCOO)₂ can jump‑start slag hydration; organic amines help dissolve slag components. For 50–70% slag, trials often use 0.1–0.5‰ TIPA (per mille) plus ~0.5–1.0% Ca‑salt by cement mass. Studies with 60% slag found that an 800°C calcined additive (with Ca and sulfate) restored 3‑day strength to 100% OPC levels (pmc.ncbi.nlm.nih.gov). If slag is ground coarser than OPC, PCE‑based grinding aids also help achieve suitable fineness.
Pozzolanic clays/calcined clay: Metakaolin and other high‑alumina SCMs react faster than fly ash but still slow early C–S–H formation. Alkanolamines (TEA, DIPA) are often effective here, leveraging aluminum‑complexing to speed strength; dosages around 0.02–0.1% are typical. Some makers add aluminate sources (e.g., lithium carbonate, sodium meta‑silicate). Given the fine particle size, less grinding aid may be needed, but dispersants help distribute fines uniformly.
Limestone/calcite (PLC): Finely ground limestone is mostly an inert filler (its nucleation can slightly boost early strength). The priority is optimized grinding and dispersion, not chemical acceleration. PCE‑based aids improve throughput and grading at 0.02–0.1% dosage; this helps the high specific surface of PLC‑blended cement avoid packing. Portland‑limestone cements (10–15% calcite) routinely use standard PCE grinding aids such as SikaGrind‑870 to hit target Blaine. If limestone exceeds ~15%, additional measures—like slower gypsum addition or specialized retarders—may be needed to control setting (vnm.sika.com).
Silica fume or nano additives: Very fine reactive silica can lift later‑age strength but may slow early set. Grinding aids are not typically required due to very fine grind, though concrete mixes benefit from high‑range superplasticizers (PCE). To reinforce early strength, some blends include Ca or alkali additives (e.g., ~3–5% nano‑CaCO₃ or CaSO₄) to seed C–S–H and offset C₃S dilution (link.springer.com).
Each SCM type interacts differently with additives. Decisions should rest on trial data and cost–benefit analysis—the “waste‑to‑benefit” calculus. For example, with 30% fly ash, expect ~50% lower 3‑day strength; a Ca‑nitrate/TIPA package that recovers half the loss may be worth ~$2–5/t of cement. For 50% slag, ensure at least one strength accelerator; the improved early cycle can speed form turnover. Suppliers often offer combination products (dispersant/amine blends) tuned to high‑alumina vs. high‑silica SCM chemistries. Precise addition—often 0.05–0.2%—is facilitated by stable metering through a dosing pump.
Market context and standards
Globally, SCM use is climbing: current cement mixes are ~24% SCM (www.mckinsey.com) and could rise further, making these specialty chemicals essential tools. Market analyses (McKinsey 2024) estimate SCM demand and the importance of performance enhancers (www.mckinsey.com) (www.mckinsey.com).
Indonesian producers are already using custom grinding aids and strength improvers to sustain productivity while lowering clinker ratios (text-id.123dok.com) (nexco.id). With the right additive strategy, lower‑clinker cements can meet standards for strength and setting (e.g., SNI 8912 Type HE) while reducing cost and carbon emissions.
Bottom line: chemical additives provide performance leverage in low‑clinker cements—tens of percent higher early strength or several MPa higher 28‑day strength at hundred‑ppm doses (pmc.ncbi.nlm.nih.gov) (text-id.123dok.com). Pilot test plans that track mill throughput, Blaine, and compressive strength at 1–7 and 28 days make the upside explicit—and help dial in the additive package for each SCM blend.
