Problems of determination of compressive strength of bricks (clay brick, calcium silicate brick) are described, for example, in Aliabdo and Elmoaty , Brozovsky , and McCann and Forde .
Measurements were taken by direct sound transmission along the length of a calcium silicate brick in 5 measuring points (M.P.); see Figure 1.
Basic Characteristics of Calcium Silicate Bricks. The basic raw materials for the production of calcium silicate units are airy lime and silica sand.
Measurements were taken on two sets of calcium silicate bricks from various times of production; test results with nondestructive methods are influenced by technological factors (pressing force, density of the structure, and defects in the inner structure).
Calcium silicate bricks of the format 290 x 140 x 65 mm were used for experiments; they featured the following basic parameters:
(iii) number of calcium silicate bricks in a set--140.
Residual standard deviations of processed relationships (2)-(4) for the prediction of compressive strength of calcium silicate bricks obtained from the nondestructive test parameter are given in Table 2.
Based on the analysis obtained from the information and processed relationships needed for the prediction of compressive strength of calcium silicate bricks obtained from tests using the ultrasonic pulse method and the rebound hammer method, it is possible to state that the given methods are both separately and in combination applicable for the assessment of strength parameters of calcium silicate bricks.
Combined nondestructive testing SonReb reaches the highest accuracy of the value of expected compressive strength of calcium silicate bricks.
Practical applicability of the SonReb combined nondestructive method was established as a tool used for assessment of compressive strength of calcium silicate bricks, both for checking tests in the production plant and for determination of compressive strengths of bricks built in a structure (walling).
Setting of specifying coefficient is recommended for practical use of the basic calibration relationship for determination of expected strength of calcium silicate bricks from the measurement by means of the SonReb method (4) for particular production plant or for evaluation of calcium silicate bricks built in the structure.