Understanding variability in performance of type il cements: insights from Raman imaging

Portland-limestone cement (PLC), designated as Type IL under ASTM C595, has emerged as a lower-carbon alternative to ordinary Portland cement (OPC). By replacing up to 15% of clinker with finely ground limestone, PLC reduces calcination-related emissions and offers an average greenhouse gas reduction of more than 8%. Although this environmental benefit has accelerated the adoption of PLC across North America, significant performance variability has been reported in the field, including reductions in 28-day strength, increased water demand, and inconsistent set behavior. The origins of this performance variability remain insufficiently understood because commercial PLCs differ in both clinker phase composition and fineness. This thesis investigates twelve commercial Type IL cements to quantify their performance variability and understand how their physical and chemical properties influence it. Multimodal characterization was applied, combining compressive strength testing and open porosity measurements (at 1, 3, 7, and 28 days of hydration), isothermal calorimetry, and rheology of fresh paste, with laser diffractometry, X-ray diffraction (XRD), and Raman imaging. A key contribution of the work is also the development of an automated Raman imaging algorithm that improves reproducibility by relying on objective criteria for Raman band and peak-top band selection. Performance testing revealed substantial differences across the 12 PLCs. Early-age compressive strength varied between 2000 to 3800 psi at 1 day (mean: 3000 ± 465 psi), while calorimetry showed a range from 180 – 230 J/g in cumulative heat at 1 day (mean: 200 ± 18 J/g) and a 2.5 hour difference in set times. Rheological measurements also differed significantly, with dynamic yield stress varying between 16 to 59 Pa (mean: 34 ± 9.8 Pa) and the plastic viscosity of the stiffest cement being 0.61 Pa.s while that of the most compliant one was 0.12 Pa.s. Open porosity at 28 days ranged between 24% to 32% (mean: 28 ± 2.3%), and strong relationships were observed between porosity reduction and compressive strength (R2 = 0.75, RMSE = 12.7%). Bulk particle size analysis indicated wide variability in fineness, with D50 ranging from 9.8 – 12.3 m (mean: 11.2 ± 0.8 m) and a range of 2 – 4 m in D10 across cements (mean: 3 ± 0.7 m). The D10 showed the strongest correlation with early hydration heat at 1 day (R2 = 0.65, RMSE= 5.0%) and 3 days (R2 = 0.67, RMSE= 3.2%), confirming that ultrafine particles dominate early dissolution, nucleation, and reactivity. Chemical analysis using XRD showed large differences in clinker phase composition as well. Raman imaging played a key role in linking chemistry and fineness at the phase level. The automated algorithm developed in this thesis produced Raman-based phase quantification that agreed closely with XRD, with a RMSE of 3.22% and most phase measurements within 5%. More importantly, Raman imaging enabled extraction of phase-specific PSDs revealed substantial differences in the fineness of individual phases that were masked in bulk PSD measurements. A composition coefficient (C_"c" ) that uses Raman phase composition and a phase-specific PSD factor (F_"psd" ) that represents the geometric mean of phase-D50 values were both correlated with hydration heat. When combined as the product (C_"combined" ), the predictive capability improved further, achieving the strongest correlation with 3 day cumulative heat (R2 = 0.71, RMSE= 3.0%). These results show that performance variability in commercial Type IL cements arises from the combined effects of clinker phase composition and the fineness of reactive phases. By integrating laser diffractometry, XRD, and Raman imaging, this thesis provides a more complete framework for understanding PLC variability and offers quantitative tools for predicting hydration and strength. The automated Raman imaging approach developed here also advances the technique toward more routine use in industrial characterization and performance control.

Name thesis:degree_name

M.S.

Level thesis:degree_level

Thesis

Discipline thesis:degree_discipline

Civil Engineering

Grantor

University of Illinois Urbana-Champaign

Year dc:date

2025

Author dc:creator

• Garg, Yaman

Contributors dc:contributor

• Garg, Nishant

• Portland-Limestone Cement
• Type IL Cement
• Raman Imaging
• Cement Variability

Statement dc:rights

• Copyright 2025 Yaman Garg

Language dc:language

en

Handle dc:identifier

https://hdl.handle.net/2142/132809

OAI identifier oai:identifier

oai:www.ideals.illinois.edu:2142/132809