METHOD FOR DETERMINING STRENGTH OF CONCRETE BY ACOUSTIC EMISSION METHOD Russian patent published in 2023 - IPC G01N29/14 

FIELD: construction; concrete mixtures.

SUBSTANCE: scope of the invention relates namely to the control of concrete mixtures of various compositions using the method of acoustic emission signals during the formation of their structure. A method for determining the strength of concrete with chemical and mineral additives using the acoustic emission method is disclosed, which includes determining the parameters of acoustic emission signals and recording the time of their appearance in real time. To implement the method, a deep waveguide with an attached acoustic emission transducer is placed in the concrete mixture. On concrete cubes of different compositions measuring at least 200×200×200 mm the structure formation is monitored, and each composition is duplicated two to three times, and for each composition monitoring is carried out continuously for at least twenty-eight days. Next, the strength characteristics of the concrete are monitored, and the strength of the control cubes is monitored on the 1st, 3rd, 7th, 14th and 28th days of curing. After this, the relationships and dependencies of the informative parameters of the acoustic emission signals between the strength characteristics of concrete are established. Then, the informative parameters of acoustic emission signals, which closely correlate with the strength of concrete, are considered, and the optimal time intervals for measuring acoustic emission are established, which makes it possible to most accurately predict the kinetics of further strength gain of concrete using the acoustic emission method. After this, acoustic emission pulses are recorded in real time, and three stages of structure formation are distinguished, characterized by varying degrees of acoustic emission intensity. The start and end times of the second period are specified in an automated mode, in which the Akaike information criterion is used

where AIC is the value of the Akaike criterion coefficient; – dependence of the number of acoustic emission pulses on time; N – duration of the observation interval; k – reference number. In this case, the change in the sign of the derivative of the Akaike function, which corresponds to the disorder of the process, is used as a detection criterion, and the moment when the criterion reaches a minimum is selected as the time. Within the framework of this algorithm, the Akaike criterion is applied twice - to determine the beginning and end of the second stage. Next, set the start and end times of each of the three stages, the parameters and are determined. The parameter is determined as the difference between the obtained values of the beginning and end of the second period, and the slope of the third perioddepending on the sum of acoustic emission pulses versus time. The parameter is determined by the least squares method in a time window, the beginning of which coincides with the beginning of the third stage, and based on the estimated parameters and . Then the strength of concrete is predicted in accordance with predictive models. SP-180 according to TU 20.59.59-003-26025492-2018 or CENTRIPOR TFM 411R are used as chemical additives, and ground and granulated blast furnace slag is used as a mineral additive.

EFFECT: ability to determine the strength of concrete with chemical and mineral additives using the acoustic emission method, and the relative error of using an automated algorithm when predicting strength does not exceed 4.0%.

1 cl, 12 tbl, 64 dwg