Influence of experimental procedure on d-spacing measurement by XRD of montmorillonite clay pastes containing PCE-based superplasticizer

This study investigates the influence of the experimental procedure on determining the cl-space enlargement of montmorillonite clay (MNT) produced by the absorption of polycarboxylate (PCE) based superplasticizers. d-Spacing alterations registered by in situ X-ray Diffraction (XRD) analysis on fresh clay pastes have been compared against the results obtained when clay pastes are previously centrifuged and dried (reference methodology reported in bibliography). Data from experiments show relevant differences between the two methodologies. While MNT clay d-spacing present limited expansion when recorded on samples previously separated and dried, direct XRD for fresh clay pastes shows much larger expansion of inter-laminar space. Clay expansion evolves with the increase of PCE dosage up to 3 times larger than typical data recorded when samples previously dried. The results shown here indicates that information collected following the typical experimental procedure based on sample drying could not be representative of MNT clay interference on dispersion mechanism of PCE soperplasticizers.