Measurement of a Cement Admixture by a TOC Solid Sample Measurement System

Importance of the Topic

Accurate quantification of organic admixtures in cement-based materials is critical for assessing the durability and performance of concrete structures. Conventional extraction methods for total organic carbon (TOC) can introduce bias and require lengthy sample preparation. The use of a solid sample TOC analyzer streamlines analysis, reduces variability from extraction, and accelerates measurement time.

Objectives and Study Overview

This work demonstrates the direct determination of cement admixture content in pulverized concrete using a TOC solid sample combustion system. The study compares two concrete samples treated under different conditions and evaluates the system’s ability to measure total carbon (TC), inorganic carbon (IC), and calculate TOC by subtraction.

Methodology and Instrumentation

The analytical approach involves the following steps:

• Sample Preparation: Coarse concrete fragments are ground to a fine powder in a vibrating mill.
• TC Measurement: Approximately 100 mg of powder is placed in a ceramic boat and combusted at 980 °C in the TOC furnace (combustion catalyst oxidation).
• IC Measurement: About 70 mg of powder is mixed with phosphoric acid in a ceramic boat and heated at 200 °C in the IC furnace to release CO₂.
• TOC Calculation: TOC is obtained by subtracting IC from TC.
• Calibration: A one-point calibration using glucose powder (40 % C) for TC and sodium carbonate powder (11.3 % C) for IC.

The system comprises a TOC-L CPH total organic carbon analyzer coupled with an SSM-5000A solid sample combustion unit.

Key Results and Discussion

Two concrete samples (A and B) yielded the following carbon contents:

• Sample A: TC 0.861 % C, IC 0.636 % C, TOC 0.225 % C
• Sample B: TC 0.859 % C, IC 0.756 % C, TOC 0.103 % C

Results indicate that concrete treatment conditions impact the residual organic carbon content. The direct solid measurement minimizes variability due to extraction inefficiency and provides reproducible TOC values.

Benefits and Practical Applications of the Method

• Reduced sample preparation time by eliminating solvent extraction.
• Improved accuracy and repeatability of organic admixture quantification.
• Applicability to quality control in cement and concrete production.
• Enhanced reliability for forensic analysis of existing structures.

Future Trends and Potential Applications

Advancements may include:

• Integration with automated sample feeders for high-throughput analysis.
• Expansion to other construction materials and complex matrices.
• Coupling with speciation techniques to distinguish different organic admixture classes.
• Development of standardized protocols for regulatory compliance in construction quality assurance.

Conclusion

The TOC solid sample measurement system offers a streamlined, accurate approach for quantifying organic admixtures in pulverized concrete. By bypassing extraction steps, the method reduces potential biases and expedites analysis, supporting improved quality control and structural evaluation.

References

Shimadzu Corporation. Application No. O56: Measurement of a Cement Admixture by a TOC Solid Sample Measurement System. First Edition, April 2016.