Detection of the Content Nitrogen-Containing Compounds by the Potentiometric Method in Admixtures for Concrete

ABSTRACT

The article reflects the identified features of the first experiment for determining the content of nitrogen-containing compounds by the potentiometric method in additives for concretes according to the procedure proposed in Amendment No. 1 to STB1112–98 (date of introduction 01.10.2016).

There were cases of ammonia smell appeared in the constructed buildings, both preventing their normal operation and being toxic where found in the building practice. This technique, as well as the imposed requirements that limit the content of nitrogen-containing compounds in concrete additives, are designed to reduce the risk of such a phenomenon.

The article gives an analysis of the issues that using of ammoniumselective electrode ECOM-NH4 for the research of concrete additives led to. Analysis of the results obtained allows to suggest a significant influence on them of the presence of interfering ions in additives. The need for a more precise formulation of the algorithm for calculating the final result of measurements with allowance for the aggregate state of additives (liquid, dry). The established norm of the content of ammonium ions in the investigated additives (100 mg/kg) is practically the lower range of this ammonium-selective electrode, and it’s inevitably raises the risk of error in assessing the suitability for this indicator.

The results of the study of a number of widely used additives for concrete showed an excess of the established standard. At the same time, ammonia emission issues were not observed among tested additives. The main reason for such results is assumed to be the effect of interfering Na and K ions.

Dosages of various additives in concrete can differ by more than an order of magnitude, and concrete can harden under different conditions, including high temperature in the factory. Taking it into account along with the results obtained, it can be concluded that the investigation with samples of concrete or concrete mixes is more correct at this time.

Keywords: concrete, admixtures, ammonia, ammonium ions, potentiometric method.

For citation: Kalyska A., Drozd A. Detection of the Content Nitrogen-Containing Compounds by the Potentiometric Method in Admixtures for Concrete. In: Contemporary Issues of Concrete and Reinforced Concrete: Collected Research Papers. Minsk. Institute BelNIIS. Vol. 9. 2017. pp. 219–231. https://doi.org/10.23746/2017-9-14

Full text in Russian:



References:

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