Determination of Polymer Type and Content in Concrete Materials by FTIR and TGA

Importance of the Topic

The incorporation of polymers such as ethylene vinyl acetate (EVA) into cement formulations enhances workability, adhesion, curing performance, mechanical strength and durability of mortar and concrete. Accurate determination of polymer type and content in polymer-modified concrete is critical for quality control, product optimization and ensuring that target performance attributes are met in construction applications.

Objectives and Study Overview

This study evaluates the use of Fourier transform infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA) to identify and quantify polymers in cement-aggregate mixtures. Key goals include qualitative identification of EVA copolymer and associated inorganic components, development of chemometric calibration models for multicomponent quantification by FTIR-PLS, and validation of polymer content measurement by TGA.

Applied Methodology and Instrumentation

• Sample Preparation: Sixteen EVA–cement–aggregate mixtures were prepared with nominal EVA contents ranging from 0 to 20 % by Admaterials Technologies (Singapore). Polymer extraction from selected mixtures employed tetrahydrofuran (THF).
• FTIR-ATR Analysis: Shimadzu IRTracer-100 with Specac Quest ATR diamond crystal. Spectra collected from 4000 to 420 cm-1 at 4 cm-1 resolution, 45 scans, Happ-Genzel apodization, DLATGS detector.
• FTIR-DRS and Chemometrics: Diffuse reflectance accessory on IRTracer-100; spectra from 4000 to 400 cm-1 used for PLS calibration. Second derivative preprocessing (order 2, seven points) and autoscaling applied to improve resolution. Calibration models built with five PLS factors.
• TGA Analysis: Shimadzu DTG-60 simultaneous DTA-TGA. Samples (20–30 mg) heated from ambient to 600 °C at 20 °C/min under nitrogen (50 mL/min). Polymer content determined from mass loss between 200 and 600 °C.

Main Results and Discussion

FTIR-ATR spectra of raw EVA revealed characteristic EVA absorptions along with kaolin and calcium carbonate signatures. Extracted polymer spectra after THF removal matched EVA reference, confirming polymer identity. FTIR-DRS spectra of mixed samples, despite broad cement/aggregate signals, yielded robust PLS models for EVA, cement and aggregate content. Calibration yielded R2 values above 0.995 and validation recoveries within ±10 %.

TGA curves displayed distinct mass loss between 200 and 400 °C (acetic acid loss) and 400–600 °C (polymer degradation). EVA reference showed 80.7 % mass loss in this range. Polymer contents measured by TGA in mixtures correlated linearly with nominal EVA content (R2 = 0.9993), with reproducibility below 3 % and recoveries between 95 and 105 %.

Benefits and Practical Applications

• Rapid qualitative identification of polymer and inorganic additives in raw and modified materials by ATR-FTIR.
• Simultaneous quantitative analysis of polymer, cement and aggregate in complex mixtures using FTIR-PLS, minimizing sample preparation.
• Accurate polymer content determination by TGA, suitable for quality control and material screening.

Future Trends and Potential Applications

Further work may extend to other polymer types and concrete formulations, integration of coupled TGA-FTIR systems for evolved gas analysis, and advanced chemometric algorithms for enhanced prediction accuracy. Inline or at-line monitoring in production environments could also leverage these techniques for real-time quality assurance.

Conclusion

The combination of FTIR (ATR and DRS) with chemometric PLS enables reliable identification and quantification of polymers, cement and aggregate in modified concrete. TGA provides a complementary quantitative measure of polymer content. Together, these methods offer robust tools for research, QA/QC and industrial analytics in construction materials.

Reference

1. Ohama Y Handbook of Polymer-Modified Concrete and Mortars Noyes Publications 1995 Pages 31–32
2. ASTM E1131 Standard Test Method for Compositional Analysis by TGA Vol 14.02 1997
3. Tokura T Lim J Chua AM Ohta M Naganishi A Takeuchi S Analysis of Gaseous Products by DTA/TGA-FTIR System Shimadzu Review 71(3-4) 2015 Pages 129–133