Inorganic Acid Resistance Performances of Magnesium Phosphate Cement: A Two-Year Observation

Area of Science:

• Materials Science
• Chemical Engineering
• Civil Engineering

Background:

• Magnesium phosphate cement (MPC) is a cementitious material known for its acid-base reaction hardening.
• Limited studies exist on the durability of MPC in acidic environments.
• Understanding MPC's acid resistance is crucial for its application in corrosive settings.

Purpose of the Study:

• To systematically evaluate the acid resistance of MPC in common inorganic acid solutions.
• To investigate the mechanisms and influencing factors of MPC's acid resistance.
• To compare MPC's performance against different acids (H2SO4, HCl, H3PO4) at various pH levels.

Main Methods:

• Measuring compressive strength changes of MPC under acidic conditions.
• Quantifying mass loss and observing apparent changes in MPC specimens.
• Analyzing pH variations and microstructure evolution of MPC in acid solutions.

Main Results:

• MPC exhibited superior resistance to H2SO4 and HCl compared to H3PO4 at pH 1.0-2.0.
• At pH > 2.0, MPC showed robust resistance to all tested acids, with 68.9%-86.9% compressive strength retention.
• Acidic conditions led to NH4/P loss from struvite and redissolution of corrosion products, increasing porosity and reducing mechanical strength.

Conclusions:

• Magnesium phosphate cement demonstrates good acid resistance, particularly in environments with pH above 2.0.
• While acidic conditions can reduce mechanical strength due to porosity increase, MPC's performance is superior to other cement-based materials.
• MPC is suitable for applications requiring enhanced resistance to acid corrosion.