TY - JOUR
T1 - OHSI – Onset Heat Size Index
T2 - A new parameter to predict rheology of cement-calcined clay blends
AU - Iqbal, M. Farjad
AU - Garg, Nishant
N1 - This research was carried out in the Newmark lab facilities at the Department of Civil and Environmental Engineering and, in part, in the Materials Research Laboratory, Central Research Facilities at the University of Illinois at Urbana-Champaign. The authors acknowledge the various commercial calcined clay producers for supplying the materials used for this research. The authors acknowledge the support from Sangmin Kim and Muhammad Hasnain for lab experiments. Finally, the authors also thank the U.S. Department of State and U.S. Educational Foundation in Pakistan (USEFP) for supporting F.I. with a Fulbright fellowship.
PY - 2026/1
Y1 - 2026/1
N2 - Calcined clays (CCs) are promising supplementary cementitious materials given their potential for improving concrete durability and sustainability. However, they often cause high water demand and associated workability challenges. In this study, the rotational rheology of 16 cement and largely kaolinitic-CC blends was analyzed, revealing a wide range of dynamic yield stress (DYS) values (25–300 Pa). These DYS values strongly correlate with the ASTM C1437 paste flow, ranging from ∼30 % to 140 % (R2 > 0.9). Interestingly, calorimetry results indicated that the rheological properties are linked to the onset heat (OH). By combining 3 unique parameters: OH, and particle size distribution (PSD) outputs ( D 10 and D 50) a new parameter has been introduced, the onset heat size index (OHSI = OH/ D 10 ·D 50). This OHSI can reliably predict the DYS (R2 = 0.90, RMSE = 26 Pa), opening a pathway for employing widely adopted calorimetry and PSD measurements to simultaneously predict reactivity and rheology of cement-CC blended systems.
AB - Calcined clays (CCs) are promising supplementary cementitious materials given their potential for improving concrete durability and sustainability. However, they often cause high water demand and associated workability challenges. In this study, the rotational rheology of 16 cement and largely kaolinitic-CC blends was analyzed, revealing a wide range of dynamic yield stress (DYS) values (25–300 Pa). These DYS values strongly correlate with the ASTM C1437 paste flow, ranging from ∼30 % to 140 % (R2 > 0.9). Interestingly, calorimetry results indicated that the rheological properties are linked to the onset heat (OH). By combining 3 unique parameters: OH, and particle size distribution (PSD) outputs ( D 10 and D 50) a new parameter has been introduced, the onset heat size index (OHSI = OH/ D 10 ·D 50). This OHSI can reliably predict the DYS (R2 = 0.90, RMSE = 26 Pa), opening a pathway for employing widely adopted calorimetry and PSD measurements to simultaneously predict reactivity and rheology of cement-CC blended systems.
KW - Calcined clay
KW - Dynamic yield stress
KW - Onset heat size index (OHSI)
KW - Rheology
UR - https://www.scopus.com/pages/publications/105021802159
UR - https://www.scopus.com/pages/publications/105021802159#tab=citedBy
U2 - 10.1016/j.clay.2025.108044
DO - 10.1016/j.clay.2025.108044
M3 - Article
AN - SCOPUS:105021802159
SN - 0169-1317
VL - 279
JO - Applied Clay Science
JF - Applied Clay Science
M1 - 108044
ER -