b) La cultura gitana es protegida por la Constitución

The friction angles of sand composites with and without additives at the failure point are shown in Figure5- 14. The results were divided into three main categories, including five composites per group, containing 0%, 10% and 20% rubber addition (i.e., ST, STR10, and STR20, respectively). Overall, the composite containing rubber exhibited a greater value in the LDS test than in the SDS results, except SC0R10.

Further, the addition of only 10% rubber decreased the internal friction of sand by 3°.

Although the lowest friction angle was assigned to SC0R10, compared with the small box, most of the composites exhibited higher internal friction at the failure point. This behaviour was quite different from that observed in the SDS test: the decrease in the friction angle of sand resulted in the addition of rubber. Thus, the scale effect revealed the mechanical properties of rubber.

Despite of few differences, which might be observed due to the effect of rubber particles, the scale effect comparison was revealed a fairly similar trend in both scales.

For instance, in the LDS test, the maximum friction angle was assigned to the SS5R10 composite, while the addition of only 10% cement generated a composite with the highest internal friction angle in the SDS test. Considering the general similarity of result, therefore, the additional analysis has been conducted in further sections by focusing on the large direct shear box results. The importance of direct shear box dimension to show the influence of rubber particles is also analysed and presented in following sections.

In contrast, as in the SDS test, sand reinforcement with only the cementitious material led to an increase in the internal friction angle of pure sand. A comparison of the stabiliser material revealed the same results as those obtained in the case of the small box. Using the cementitious materials only for sand reinforcement, we found that the same percentage of slag was more effective than cement. The maximum friction angle of pure sand was improved by approximately 0.2° per percentage point

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of cement addition. The corresponding improvement for the slag–sand composites was three times higher. Further, considering the importance of the curing time, we found that the addition of slag for sand stabilisation generated a composite with a higher shear strength than sand containing cement within a short period.

Figure5- 14. Friction angle of sand and the treated samples for the peak shear stress in the large direct shear test, compared with the results of the small direct shear test.

The application of rubber only shows an incremental improvement trend for the friction angle of sand. Dissimilar to the SDS data, the addition of 20% rubber not only did not generate the lowest internal friction in the pure sand but also exhibited a similar result to that of the SC5R0 composite (i.e., more than 38°). The minimum improvement was obtained by the application of 10% rubber only. The friction angle of the SC0R10 samples was approximately 3° lower than that of the pure sand;

however, it significantly increased to between 5° and 9° upon the addition of 5% and 10% cementitious material, respectively, for example. Moreover, the combination of slag with 10% rubber almost generated a composite with a higher friction angle than that of cement. The slag suggested the existence of the optimum proportion of additives. Note that in both scales, an upward trend was detected by increasing the

1-SC0R0 4-SC5R0 44-SS5R0 5-SC10R0 55-SS10R0 2-SC0R10 6-SC5R10 66-SS5R10 7-SC10R10 77-SS10R10 3-SC0R20 8-SC5R20 88-SS5R20 9-SC10R20 99-SS10R20

30 32 34 36 38 40 42 44

φp (degree)

φp-SDS

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stabiliser content and the samples had a more similar range of the maximum friction angle in the SDS test.

The composites of the STR20 category exhibited a considerably similar friction angle. Regarding the reasonable improvement in the friction angle of SC0R20, a lower difference was observed after the addition of stabilisers. However, the addition of a stabiliser to sand with 20% rubber increased the friction angle by 2°. The results of the large-scale test were similar to those of the small-scale tests. As in the case of the small scale, the addition of 5% slag was found to be more effective than that of 5% cement, with a minor change in friction angle reduced by increasing the

proportion of slag. Moreover, the friction angle of SC5R20 improved even after doubling the proportion of cement added to sand with 20% rubber, which generated the highest friction angle among the composites of the SRT20 category. The STR10 and STR20 composites exhibited a similar trend on both the considered scales and in the case of the larger scale, the composites demonstrated the effects of the use of rubber in sand reinforcement.

BRIEF SUMMARY…

The results were divided into three main categories by the proportion of rubber added: 0%, 10% and 20% added rubber (i.e., ST, STR10, and STR20, respectively).

Overall, the composite containing rubber obtained a greater value in the LDS test than in the SDS test, except SC0R10. The application of only 10% rubber reduced the internal friction of sand by 3°.

The use of cementitious materials only for sand reinforcement yielded the same results as the small box. Note that on both scales, an upward trend was detected by increasing the stabiliser content, and the samples had a more similar range of the maximum friction angle in the SDS test. A comparison of the stabiliser material also revealed that the same percentage of slag was more effective than cement. Moreover,

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an increase in the proportion of added rubber for stabilising sand showed an incremental improvement trend for the friction angle of sand. The STR10 and STR20 composites exhibited a similar trend on both scales, and on the larger scale, the composites demonstrated the effects of the use of rubber in sand reinforcement.

Regarding the reasonable improvement in the friction angle of SC0R20, a lower difference was observed after the addition of stabilisers.