Revealing the fate of superplasticizers in blended cements

Predicting the performance of superplasticizers in modern blended cements remains a “black box” due to the complex physico-chemical interactions between polymers and heterogeneous mineral surfaces. This study deconstructs the timeline of admixture function in blends of Ordinary Portland Cement (OPC) and Limestone (LS) through three integrated quantitative approaches: the “Direct and Delayed Dosing” (D3) methodology to quantify early admixture loss, “Pore Solution Matching” (PSM) to resolve admixture distribution in the blend, providing a realistic assessment of how admixtures partition between OPC and limestone. Finally, a mass-balance model calculates the specific fractional surface coverage (θ) on individual phases. Results demonstrate that both hydration retardation and rheological behavior up to the onset are governed by the specific fractional surface coverage (θ), following a linear “surface poisoning” relationship. By isolating these local interactions from the global dosage, this research provides a robust physical description of admixture efficiency in sustainable binders. These insights culminate in guidelines for architecting Polycarboxylate Ethers (PCE) for modern low-clinker cements.