Mechanistic quantification of performance loss of PCE superplasticizer in carbonate-enriched cementitious suspensions

The dispersing efficiency of polycarboxylate ether (PCE) superplasticizers is substantially compromised in alkali-activated cementitious systems containing carbonate ions (e.g. alkaline carbonates as activators), even in the absence of solubility constraints. This loss of plasticization performance mainly stems from competitive adsorption of carbonate ions (CO32−) at particle surfaces and conformational collapse of PCE macromolecules. To distinguish and quantify their respective impacts, we employed the YODEL (Yield Stress mODEL) and symbolic regression on limestone suspensions containing systematically varied K2CO3 and PCE dosages. Results reveal that K2CO3 induces an exponential decrease in surface coverage of PCE by blocking effective adsorption sites, while simultaneously causing a linear reduction in the viscosimetric size of PCE macromolecules. Importantly, the yield stress across the K2CO3 concentration range (<190 g/L) is predominantly governed by reductions in effective surface coverage rather than steric hindrance losses from collapse of PCE macromolecules.