A new method to analyze copolymer based superplasticizer traces in cement leachates

Area of Science:

• Materials Science
• Analytical Chemistry
• Environmental Science

Background:

• Polymeric admixtures, particularly PolyCarboxylate-Ester (PCE) copolymers, enhance concrete properties but can leach into water.
• Existing analytical methods lack the sensitivity and specificity to detect trace amounts of PCE and free polyethylene oxide (PEO) in mineral-rich cement leachates.
• Accurate detection is crucial for concrete structures interacting with drinking water supplies.

Purpose of the Study:

• To develop and validate sensitive analytical methods for detecting superplasticizer traces in cement paste leachates.
• To quantify free PEO and PCE copolymer content in leachates from CEM I cement paste.
• To address limitations of current techniques in analyzing complex cementitious material leachates.

Main Methods:

• Matrix-Assisted Laser Desorption/Ionization Time-Of-Flight (MALDI-TOF) mass spectrometry was used to determine free PEO content.
• Pyrolysis coupled with Thermally Assisted Hydrolysis and Methylation (THM) followed by triple-quadrupole mass spectrometry (QqQ-MS) was employed for PCE detection.
• Analysis focused on leachates from hardened CEM I cement paste formulated with superplasticizers.

Main Results:

• MALDI-TOF MS effectively quantified free PEO in the cement paste leachates.
• The combination of pyrolysis and THM-QqQ-MS demonstrated high sensitivity and good performance for detecting PCE copolymer traces.
• This approach overcomes limitations of traditional methods for analyzing high molecular weight, polymolecular copolymers in challenging matrices.

Conclusions:

• Sensitive detection of superplasticizer compounds (PCE and free PEO) in cement leachates is achievable using advanced mass spectrometry techniques.
• Pyrolysis-THM-QqQ-MS offers a robust solution for identifying and quantifying PCE copolymers, even with their complex structures.
• These methods are essential for assessing the environmental impact of superplasticizers in concrete applications, particularly concerning water quality.