According to the Recommendation for the Design and Construction of UHSFRC Structures (JSCE Guildeline for Concrete No.9), the characteristics tensile strength ( ) shall be determined using standard split-cylinder tests with electronic transducer attached to the specimens. The recommendation define the first cracking strength as a stress level in the UHPdC associated with a point in the stress-strain (of displacement) curve where the assumption of linear elasticity is no longer applicable, which is the point where maximum stress developed in the UHPdC after the first crack has formed (refer to figure 1a). Therefore, the specimen should be either attached with strain gauges or LVDTs on the surfaces of both ends, perpendicular to the direction of the tensile force, in order to continually observe the load and strain (or displacement) relationship (refer to figure 1b). Figure 2 shows the frequency distribution of splitting cylinder test result, performance by using 100 mm diameter cylinder of the standard UHPdC. The test results show the average split tensile strength was 8.1 MPa, with a standard deviation of 1.53 MPa at 28 days.

First Cracking Strength (BS EN 12390-6:2000)

Figure 1: (a) Example of displacement measurement in split cylinder and (b) test setup.