# Influence of the Diatomite Specie on the Peak and Residual Shear Strength of the Fine-Grained Soil
## 4 Conclusions  
In this research, the influence of diatomite species and content in peak and residual shear strength of diatomite-kaolin mixtures was analyzed using the annular shear strength test. Scanning electron microscopy and Afterberg limits were also carried out as additional tests to explain the interlocking effect between the microfossils and the kaolin. Based on the experimental results, the following conclusions are drawn:  
* According to SEM images, both diatomite species have larger voids content due to the pores disposed along their surfaces. The presence of these pores can be related to aspects such high water retention that influences the results of tests such as the Afterberg limits. For both species, the higher the diatomite content was, the higher the liquid limit and the plastic limit values were. However, diatomite-kaolin mixtures manufactured with Mexican species displayed greater values, suggesting that this diatomite has larger porosity in its structure.
* For the annular shear strength test, the results show the increment in the peak and the residual strength as the normal stress increased. A linear behavior was observed  
Figure 10: Correlation between peak and residual friction angle.  
in almost the totality of the mixtures. Comparing the results from both diatomite species, the peak shear strength was much higher when modifying the kaolin mixture with Mexican diatomite instead of Colombian diatomite, especially when the confined vertical pressure was higher and with diatom contents superior to 60%. Regarding residual shear strength, Mexican diatomite also denoted higher values of residual shear strength, especially with diatom contents equal to or higher than 60% as was observed in the peak shear strength as well.
* The increase of diatomite content in the samples polarized their behavior towards materials similar to compacted sands. Likewise, when the specimens had a higher proportion of clay, their response was contractive, analogous to a normally consolidated clay.
* With respect to the friction angle results, as the diatom content increased, the peak friction angle was also higher. That phenomenon was observed in both species. Nevertheless, the Mexican diatomite revealed higher values compared with Colombian diatomite species. Regarding the residual friction angle, mixtures manufactured with Mexican diatomite also displayed higher values when compared to mixes with Colombian diatomite. In addition, the difference between peak and residual friction angle was higher in Mexican diatomite mixes.
* As has been observed, diatomite has large porosity, low density, and interlocks well with other particles, increasing the shear resistance. Due to these properties, future research is recommended to study the influence of these microfossils in other composites such as concrete or bituminous mixtures.  
Conceptualization, C.J.S.-A., D.A.Z.-A., J.C.R. and D.C.-F.; methodology, C.J.S.-A. and D.A.Z.-A.; formal analysis, C.J.S.-A. and D.A.Z.-A.; resources, C.J.S.-A. D.A.Z.-A. and D.C.-F.; writing--original draft preparation, C.J.S.-A., D.A.Z.-A. and J.C.R.; writing--review and editing, D.C.-F.; funding acquisition, D.A.Z.-A. All authors have read and agreed to the published version of the manuscript.  
This research was funded by Centro de Investigaciones-Escuela de Ingenieros Militares (ESING), budget item A-02-02-02-008-001, Ejercito Nacional de Colombia.  
Not applicable.  
The authors declare no conflict of interest. The funders had no role in the design of the study; in the collection, analyses, or interpretation of data; in the writing of the manuscript, or in the decision to publish the results.