Microstructure of ultra high performance concrete containing lithium slag

Area of Science:

• Materials Science
• Civil Engineering
• Environmental Science

Background:

• Lithium slag (LS) is an industrial byproduct requiring efficient recycling methods.
• Ultra-high performance concrete (UHPC) can incorporate supplementary cementitious materials (SCMs) like silica fume (SF).
• Investigating LS as a partial replacement for SF in UHPC is crucial for sustainability and resource conservation.

Purpose of the Study:

• To evaluate the impact of partially replacing silica fume (SF) with lithium slag (LS) on UHPC properties.
• To analyze the microstructural evolution of UHPC with varying LS content.
• To determine the feasibility of LS as a sustainable SCM in UHPC production.

Main Methods:

• Experimental study involving the preparation of UHPC with 0%, 5%, 10%, and 15% LS substitution for SF.
• Multi-technique analysis including mercury intrusion porosimetry, scanning electron microscopy, and nanoindentation.
• Assessment of compressive strengths and microstructural characteristics.

Main Results:

• LS addition initially degrades UHPC microstructure at early ages.
• Optimal LS content improves UHPC microstructure and hydration degree at later ages.
• LS enhances the elastic modulus of the interfacial transition zone (ITZ) in UHPC.
• Ultra-high density calcium-silicate-hydrate (UHD C-S-H) is the primary hydration product.

Conclusions:

• Lithium slag (LS) is a viable and promising substitute for silica fume (SF) in UHPC formulations.
• The use of LS in UHPC offers environmental benefits through waste material recycling.
• LS incorporation can lead to improved UHPC performance, particularly at later ages.