Optimizing grout formulations for post-tensioning using pozzolanic and filler blends

Area of Science:

• Materials Science and Engineering
• Civil Engineering
• Construction Materials

Background:

• Post-tensioning (PT) technology is crucial for modern concrete structures requiring long spans and reduced depths.
• Conventional grout in PT systems faces issues like bleeding and segregation, leading to durability problems.
• High-performance grout (HPG) typically uses costly supplementary cementitious materials (SCMs) like silica fume and fly ash.

Purpose of the Study:

• To investigate limestone powder as an economical and locally available alternative to SCMs in HPG.
• To evaluate the performance of grout mixes with varying limestone powder, fly ash, and silica fume content.
• To determine the feasibility of using limestone powder in sustainable and cost-effective PT grout formulations.

Main Methods:

• Developed thirteen grout mixes with varied water-to-cementitious material ratios (0.27-0.45).
• Partially replaced cement with limestone powder (25%, 35%), fly ash (25%, 35%), and silica fume (2-10%).
• Assessed grout properties including bleeding, efflux time, and compressive strength.

Main Results:

• Increasing limestone powder content reduced bleeding but also decreased compressive strength and increased efflux time.
• Silica fume mixes demonstrated superior performance, achieving high compressive strength (40-55 MPa), low bleeding (<0.2%), and acceptable efflux times (23-26 s), meeting ACI/PTI HPG standards.
• Fly ash improved workability and long-term strength but did not effectively control bleeding.

Conclusions:

• Silica fume provides the optimal balance of strength, flowability, and durability for HPG.
• Limestone powder acts as a cost-effective filler that can moderately improve bleeding resistance.
• Limestone powder is a viable partial substitute for expensive SCMs in resource-limited regions, promoting sustainable and economical PT grout.