# Study on Microstructure of Cemented Organic Soil in Dianchi Lake, China
## 4 Conclusions  
Based on the soil's actual humic acid (HA) content in Dianchi Lake, HA-containing cemented soil samples are prepared by adding HA and cement. After 28 days of curing, unconfined compressive strength (UCS), scanning electron microscopy (SEM), energy-dispersive analysis (EDS), and X-ray diffraction (XRD) tests are conducted on the samples. The strength development and microstructure changes of cemented soil containing HA are studied, and the following conclusions are drawn:  
1. With the increase in HA content, the UCS of cemented soil samples decreases to varying degrees. When the content of HA exceeds 15%, HA dramatically influences the UCS of cemented soil. Under the same HA content, the cemented soil UCS increases with the cement ratio.
2. SEM and EDS tests show that the incorporation of HA gradually weakens the cementation effect of hydration products on soil particles. With the increase in HA content, the connection between soil particles gradually changes from a surface-surface connection to a point-surface connection, point-edge connection, or point-point connection. The internal pore connectivity of cemented soil is apparent, and there is a large overhead structure. Its integrity gradually deteriorates. The presence of elements such as Ca, Si, and Al in the cemented soil indicates the existence of hydration products. Ca, Si, and Al spectral peaks all decrease, but their atomic mass fractions and HA content do not show apparent regularity. XRD testing shows that the intensity of the diffraction peaks of CSH and Ca(OH)\({}_{2}\) in cemented soil decreased gradually with increased HA content.
3. It can be seen from the above test that after adding HA, the internal pore connectivity of cemented soil is apparent, the integrity gradually deteriorates, and its strength gradually decreases. It is worth noting that when the HA content is more extensive than 15%, the effect of HA on cemented soil strength is more prominent. However, increasing the cement mixing ratio can weaken HA's negative effect on cemented soil's strength. When the cement mixing ratio is between 15% and 25%, the strength of cemented soil with high HA content can be effectively increased. However, this approach is not conducive to the protection of the environment. The strength of cemented soil is determined by HA content and cement mixing ratio.
4. The above research results show that when HA exceeds 15%, HA dramatically influences the UCS of cemented soil. The reason is that incorporating HA weakens the cementation effect of hydration products on soil particles. Based on previous studies, this paper focuses on the microcosmic study of the impact of humic acid on cemented soil. It more comprehensively demonstrates why humic acid inhibits the development of cemented soil strength. In addition, this paper shows that a 30% cement ratio can improve the mechanical properties of the soil. The technique can thus be promising. However, 30% cement is neither economical nor environmentally friendly. More work is needed to see if a target improvement can be reached using a smaller cement ratio.  
Conceptualization, J.C. and S.H.; methodology, S.H.; formal analysis, S.H.; resources, L.T.; data curation, Y.S.; writing--original draft preparation, Y.S.; writing--review and editing, H.L.; visualization, S.H.; project administration, Z.S.; funding acquisition, J.C. All authors have read and agreed to the published version of the manuscript.  
This research was funded by National Natural Science Foundation of China, grant number 41967035.  
**Institutional Review Board Statement:** Not applicable.  
**Informed Consent Statement:** Not applicable.  
**Data Availability Statement:** The data used to support the finding of this study are included in the article.  
**Conflicts of Interest:** The authors declare no conflict of interest.