Abstract
The use of Portland Limestone Cement (PLC, Type 1L), a sustainable alternative to Ordinary Portland Cement (OPC), has gained traction in the United States as a means to reduce the carbon footprint associated with concrete production. Despite its environmental benefits, the inconsistent field performance, particularly with respect to strength development, durability, and admixture compatibility, has raised concerns about its application. This study aims to systematically evaluate the performance of PLCs in terms of material properties, mechanical behavior, durability, and microstructural characteristics, with the goal of informing optimized mixture designs and supporting broader implementation of PLC in infrastructure applications.
Three cement systems—one OPC and two PLCs—were characterized using quantitative X-ray diffraction (QXRD), thermogravimetric analysis (TGA), X-ray fluorescence (XRF), and particle size distribution analysis. Nine concrete mixtures were prepared using these cements, with and without two types of water-reducing admixtures (polycarboxylate-based and lignosulfonate-based), to investigate the influence of admixtures on fresh and hardened properties.
The results revealed variability in PLC performance, driven by differences in gypsum content, limestone content, particle size distribution, and alkali levels. PLC1, with the higher gypsum content, exhibited enhanced early-age strength and improved resistance to chloride penetration due to accelerated hydration and densified pore structure. However, its long-term compressive strength was lower than that of OPC and PLC2, attributable to its lower Belite content and higher CH (calcium hydroxide) concentration. PLC2 demonstrated higher flexural strength and a more favorable balance between early-age performance and long-term strength development.
Durability assessments, including resistivity, void content, water absorption, and rapid chloride penetration tests (RCPT), confirmed that PLC1 achieved the most refined microstructure but did not translate into superior compressive strength due to an accumulation of weak hydration products in the interfacial transition zone (ITZ). Advanced BSE-SEM image analysis of ITZ characteristics showed that while PLC concretes generally formed thinner ITZs due to the filler effect, the addition of water reducers paradoxically increased ITZ porosity, particularly in PLC1, where high CH accumulation diminished mechanical performance.
Overall, this study underscores the necessity of tailored mixture designs for different PLC sources to achieve optimal performance. The findings highlight that not all PLCs perform equivalently, and their compatibility with admixtures must be carefully considered. Recommendations include performance-based specifications for PLC usage and targeted SCM additions to stabilize long-term strength. This work provides a solid foundation for the implementation of PLC for constructing durable, low-carbon infrastructure and informs design practices aimed at maximizing both environmental and structural benefits.
Keywords
type 1L cement, interfacial transition zone (ITZ), water reducer, strength, durability
Report Number
FHWA/IN/JTRP-2025/27
SPR Number
4823
Sponsoring Organization
Indiana Department of Transportation
Performing Organization
Joint Transportation Research Program
Publisher Place
West Lafayette, Indiana
Date of Version
2025
DOI
10.5703/1288284318575
Recommended Citation
Sung, J., He, R., Lu, N., & Feng, Y. (2025). Systematic study of type 1L cement for mixture optimization and carbon reduction (Joint Transportation Research Program Publication No. FHWA/IN/JTRP-2025/27). West Lafayette, IN: Purdue University. https://doi.org/10.5703/1288284318575
SPR-4823 Technical Summary