SU834516A1 - Sand content in concrete determination method - Google Patents

Description

one

This invention relates to methods for determining the composition of concrete with assistance, the absorption spectrum of a sample of infrared rays.

There is a known method for determining the clinker content in cement by measuring the x-ray intensity of the analytical line of a specific mineral in the sample under examination and reference samples l.

The disadvantage of this method is the complexity and low accuracy in determining the content of sand in concrete.

Closest to the proposed method for determining the amount of sand in concrete, including the separation of large aggregate concrete from a sample and the subsequent measurement of the content of silica sand in the remaining part of the sample. This method uses a chemical method for determining the composition of concrete, based on different solubilities of silica sand and cement in acids 2.

The disadvantage of this method is the complexity and duration, due to the need for multiple heat treatment of the sample and chemical exposure to it.

In addition, the accuracy of the analysis is unsatisfactory, since the fine sand fractions partially dissolve in acids (which introduces an error in the determination of the sand content.

The purpose of the invention is to increase accuracy and reduce the duration and complexity of the determination.

The goal is achieved by the fact that in the method of determining the amount of sand in concrete, including the separation of large aggregate concrete from a sample and the subsequent measurement of the content of quartz sand in the remaining part of the sample, the infrared absorption spectrum of the remaining part of the sample is taken from the ratio of the intensities of the absorption band of quartz sand with an oscillation frequency of 800 cm and the absorption bands of silicates with an oscillation frequency of 970 cm-2 judge the amount of sand in concrete.

Claims (2)

This method of determining the content of quartz sand is based on the dependence of the intensity of the absorption band of quartz on its content. This dependence is experimentally obtained in the form of a graph constructed using standards — artificially prepared samples of concrete of known composition. To improve the stability of the analysis results. Graph builds | not by the absolute intensities of the band 800, but by the ratios of the intensity of this band to the intensity of the band 970 cm (silicate band). The graph is non-linear, therefore reliable determination of sand content is possible in the limit of 35-90% and involves the use of at least 6 reference samples in this interval. To capture infrared spectra, you can use a domestic infrared spectrophotometer type IKS-14 or any other, the design of which provides the ability to work in the range of vibration frequencies 700-1000 cm. The analyzed sample is calcined at (1-2 h), stirred, dried at 110 ° C, and mixed with optical potassium bromide in the ratio of 1:50 (1 h of sample, 50 parts of potassium bromide). The mixture is pressed at a pressure of 10,000 to 20,000 kg / cm to obtain a tablet. The total weight of the mixture and the crushing tablets depend on the design of the spectrophotometer (the tablet must cover the beam of rays incident on the measuring channel of the spectrophotometer). When working with the X-14 spectrophotometer, 10–12 mg of the sample is taken, mixed with 600 m of potassium bromide, and pressed to obtain a round tablet with a diameter of 20 mm. The label is set in the measuring channel. If the spectrophotometer is a two-beam one, a similarly prepared tablet from a single kgcea bromide (without an analyzed sample) is installed in the comparison channel. The spectra measure the ratios of the intensities of the absorption bands with an oscillation frequency of 800 cm (the exact frequency is selected so that it corresponds to the absorption maximum of the corresponding band). Samples of concrete of known composition or artificially prepared mixtures that are subjected to the same treatment as samples are used as standards. The standards are plotted in coordinates: the percentage of sand content is the ratio of the intensity of the bands. According to the graph, the sign of the ratio of the intensities of the bands in the sample, the desired sand content is determined in it. Claims A method for determining the amount of sand in concrete, including separating large aggregate concrete from a sample and then measuring the content of quartz sand in the remaining part of the sample, characterized in that, in order to improve the accuracy of reducing the duration and laboriousness of the determination, the infrared absorption spectrum of the remaining part of the sample and with respect to the intensity of the absorption band of quartz sand with a vibration frequency of 800 cm and the absorption band of silicates with a vibration frequency of 970 cm are judged by the amount sand in concrete. Sources of information taken into account in the examination 1. The author's certificate of the USSR. 374530, cl. G 01 N 33/38, 1971. 2. Recommendations for analyzing hardened concrete and mortar to determine their initial composition. M., Publishing house of literature on construction. 1969, p. 12 (prototype).,