Assessing the Adoptability of Limestone Calcined Clay Cement (LC3) in Slab-like Elements
Date
2025-03
Authors
Journal Title
Journal ISSN
Volume Title
Publisher
Stellenbosch : Stellenbosch University
Abstract
The cement production industry significantly contributes to global CO2 emissions and consequently, to global warming. Replacing conventional Portland cement with limestone calcined clay cement (LC3) has been identified as a key strategy for reducing the environmental impact of the construction industry. However, the construction industry is laggard in adopting innovative technologies and materials, especially with cement and concrete. Lack of trust and in-depth
information on the handling and potential defects associated with such materials contribute to this laggardness. This research aims to holistically investigate the fresh properties, mechanical properties and plastic shrinkage cracking of LC3 from the perspective of a concrete floor contractor who is interested in its use.
CEM I was partially replaced with 30%, 45%, and 60% of commercially produced limestone and calcined clay (LC2) blend in concrete mixes to produce LC3 concrete. The flowability, rheology and fresh density of these mixes were evaluated, and their compressive and flexural performance were compared to the control. Plastic shrinkage cracking in the mixes was also examined under extreme and normal climatic conditions. Furthermore, the influence of superplasticiser on the LC3 concrete properties was investigated.
Results indicate that with 30% LC2 replacement in CEM I, the flowability of the mix decreased by approximately 41%, the yield stresses (static and dynamic) were more than double, while the fresh density remained similar. The compressive strength of the LC3 concrete at 30% LC2 replacement in CEM I is comparable to the control at 7 days but has a lower strength gain at 28 and 90 days, while LC3 concrete shows higher flexural strength gain over time compared to the control. Plastic shrinkage cracking in LC3 concrete containing 30% LC2 is more than twice that of the control, with cracking intensifying with increasing LC2 content in the mix. The addition of a moderate quantity of superplasticiser to the LC3 mixes significantly improved the flowability and rheology of the mix, while the fresh density (mix containing 30% LC2 and 0.35% superplasticiser) was reduced by about 3%. Regarding mechanical performance, the addition of superplasticiser led to about 3 MPa reduction in the compressive strength at 28 days across all percentage replacements, while no notable impact on the flexural strength of LC3 concrete was recorded. In mixes which required a higher dosage of superplasticiser (0.5% and 0.65%), plastic shrinkage cracking was reduced by about 30%.
In conclusion, to promote the adoptability of LC3 concrete, moderate use of polycarboxylate ether-based superplasticiser can effectively modify the rheological properties of the LC3 mixes. A replacement of up to 30% CEM I with LC2 appears suitable to achieve comparable mechanical performance to Portland cement. However, additional preventive measures are necessary to mitigate plastic shrinkage cracking, particularly in extreme climate conditions.
Description
Thesis (MEng)--Stellenbosch University, 2025.
CITATION: Abdrafiu, I.M. 2025. Assessing the Adoptability of Limestone Calcined Clay Cement (LC3) in Slab-like Elements. Unpublished masters thesis. Stellenbosch: Stellenbosch Univeristy [online]. Available: https://scholar.sun.ac.za/handle/10019.1/131995
CITATION: Abdrafiu, I.M. 2025. Assessing the Adoptability of Limestone Calcined Clay Cement (LC3) in Slab-like Elements. Unpublished masters thesis. Stellenbosch: Stellenbosch Univeristy [online]. Available: https://scholar.sun.ac.za/handle/10019.1/131995