3.1.3. L-Box Test

Figure 12 shows the passing ability (PA) ratio of all mixtures. For the OPC-SCC control mixture, the PA ratio was 0.85, which meets the requirements mentioned in the standards [60]. SCC produced by replacing OPC with FA or GGBS with the constant amount of MS showed a higher passing ratio. The SCC mixtures showed the ability to reach equal depths for vertical section height and a horizontal section height of the L-box container. According to the European guidelines for self-compacting concrete [60], the conformity criteria for L-box are classified into two classes based on the number of steel bars installed in the L-box. The first class is PA1 (two bars with 59 mm gap), and the second class is PA2 (three bars with 41 mm gap). This classification is related to the number of smooth steel bars (12 + 0.2 mm) installed at the gate of the filling hopper of the L-box used in this investigation. This test represents the ability of concrete to flow in spaces and pass through steel reinforcing bars or tight openings without aggregate segregation or blocking; moreover, it represents the ability of concrete to flow without leaving voids at the time of casting. European guidelines showed that the passing ability ratio should be ≥ 0.75, whereas British Standards (BSI) showed that the passing ability (PA) ratio for SCC must be ≥ 0.8 and should not exceed 1.0. Figure 12 shows that all the SCC mixtures had a passing ability equal to 1.0 except for SCC with 35% GGBS (PA = 0.9); however, the PA ratio of SCC with 35% GGBS was higher than the OPC-SCC passing ability ratio. In general, the results in this investigation showed that the SCC mixtures designed with replacement levels from 20.43% to 71.16% GGBS/FA have the ability to be self-leveled horizontally when placed in formwork. Moreover, cementitious materials have participated successfully in producing SCC with an appropriate passing ability, and no segregation or blocking was observed for the mixtures [2,63].

**Figure 12.** L-box test results (passing ability ratio).
