Measurement of Water Absorption of Recycled Aggregate

Area of Science:

• Civil Engineering
• Materials Science
• Sustainable Construction

Background:

• Recycled aggregate (RA) has high absorption capacity, impacting concrete properties.
• Accurate measurement of saturated-surface-dried water absorption (W_SSD) is critical for the water-to-binder ratio in recycled aggregate concrete.

Purpose of the Study:

• To comprehensively review existing methods for measuring W_SSD of RA.
• To identify limitations and inaccuracies in current W_SSD measurement techniques.
• To propose optimizations for developing a more accurate and convenient W_SSD measurement method.

Main Methods:

• Review of ten W_SSD measurement methods: Wiping, Slumping, Centrifugation, Infrared, Evaporation, Airflow drying, Conductivity, Pycnometer, Hydrostatic balance, and Extrapolation.
• Emphasis on the physical principles and operability of each method.
• Analysis of the accuracy and limitations of each technique.

Main Results:

• All reviewed methods demonstrated unsatisfactory accuracy in measuring W_SSD.
• Specific issues identified include water retention in pores (Centrifugation), delayed temperature changes (Airflow drying), and pre-absorption of water (Hydrostatic balance).

Conclusions:

• Existing W_SSD measurement methods for RA are inadequate.
• Suggestions for improvement include combining Evaporation and Airflow drying, optimizing liquid selection for Hydrostatic balance, and incorporating mixers in centrifugation.
• Further development is needed for an accurate and convenient W_SSD measurement method for RA.