Limestone and Silica Powder Replacements for Cement: Early-Age Performance

Area of Science:

• Materials Science
• Civil Engineering
• Sustainable Construction

Background:

• The 21st-century sustainability movement prioritizes reducing ordinary portland cement (OPC) in concrete mixtures.
• While some OPC alternatives have limited supply, limestone and silica powders are abundant.
• Understanding the impact of these fillers on cementitious material properties is crucial for sustainable development.

Purpose of the Study:

• To investigate the chemical and physical effects of limestone and silica powders on cement-based materials.
• To analyze their influence on rheology, hydration, and setting properties.
• To evaluate their potential as sustainable replacements for OPC.

Main Methods:

• Experimental analysis of cement-based materials incorporating limestone and silica powders.
• Three-dimensional microstructural modeling to visualize hydration and nucleation processes.
• Rheological measurements, hydration studies, and setting time assessments.

Main Results:

• Both limestone and silica particles act as nucleation sites for cement hydration products.
• Limestone's solubility contributes to carboaluminate formation.
• Up to 50% replacement of OPC by volume minimally impacts initial setting time, with some pastes setting within 24 hours.

Conclusions:

• Limestone and silica powders are effective, sustainable alternatives to OPC, particularly for applications requiring controlled setting.
• While setting behavior is similar, rheological properties differ significantly between limestone and silica powder pastes.
• These fillers can be incorporated at significant levels, offering functional benefits for tile adhesives, grouts, and renderings.