# Study on Microstructure of Cemented Organic Soil in Dianchi Lake, China
## 3 Test Results and Analysis
### SEM and EDS Test Results and Analysis of Cemented Soil  
Figure 11 shows the cemented soil sample's SEM image (500\(\times\), 8000 times). The cement mixing ratio is 17.5%, and the content of HA is 0%, 15%, and 20%. Figure 12 is the EDS image of the fixed-point scanning of the cemented soil sample, and the ratio of elements in the sample is shown in Table 3.  
Figure 11: SEM image of cemented soil samples. (**a**) 0% HA content. (**b**) 15% HA content. (**c**) 20% HA content. Figure 10: Relation curve between UCS and HA content. Figure 11a shows that compared with the HA-cemented soil samples, the cemented soil without HA has fewer internal macropores. The particles have apparent agglomeration and better integrity. Figure 11b shows that when the content of HA is 15%, the internal pore connectivity of the cemented soil is apparent. The agglomeration effect of soil particles with the content of HA added by cement is not apparent, and the integrity of the cemented soil is not apparent. The differences between the two components are due to the fact that the CA is not a good indicator of the effect of soil particles. Figure 12: EDS diagram of cemented soil samples. (**a**) 0% HA content. (**b**) 15% HA content. (**c**) 20% HA content. becomes poor. Figure 11c shows that when the content of HA is 20%, the cemented soil's internal pores are connected, so there is a large overhead structure. The soil particles are loose, further deteriorating the integrity of the cemented soil. Overall, incorporating HA weakened the cementation effect of hydration products on soil particles. The connection mode between soil particles is gradually transformed from a surface-surface connection to a point-surface connection, point-edge connection, or point-point connection. The internal pore connectivity of cemented soil samples is apparent, and the integrity of cemented soil samples gradually deteriorates. Judging from the chemical properties of HA, the structural formula of HA contains many acidic groups, such as carboxyl and phenolic hydroxyl groups [33, 34, 35]. HA is slightly soluble in water and ionizes several hydrogen ions, making the pore water solution weakly acidic. The acidic environment leads to the consumption of alkali metal hydroxides and part of the gelling products in the cemented soil, resulting in poor integrity. Secondly, HA reacts with Ca(OH)\({}_{2}\) and other hydration products in cemented soil, which destroys the alkaline environment required for cement hydration and delays the progress of the cement hydration reaction. The filling effect of hydration products on pores is not apparent [36]. Tiny particles of HA are soluble in an alkaline liquid and insoluble in an acidic liquid. According to the actual measurement, the pH value of the distilled water immersion solution of the cemented soil rises to 9.7-11.0. The alkaline environment can dissolve the HA particles, which directly leads to the structural deterioration of the cemented soil. Figure 12 shows the main elements in cemented soil. Such as oxygen (O), sulfur (S), silicon (Si), calcium (Ca), aluminum (Al)), potassium (K), magnesium (Mg), titanium (Ti), and iron (Fe). After comparison, it is found that the spectral peaks of O, Mg, Al, Si, Fe, and Ca elements are high, and the spectral peaks of K and Ti are also apparent. Ca, Si, and Al elements exist in cement soil. Cemertitious products are calcium silicate hydrate, aluminate hydrate, and hydroxide. Compared with the cemented soil without HA, the spectrum peak and atomic mass fraction of Ca element in the cement decreased with the HA content. Although the peaks of Si and Al spectra decreased, the atomic mass fraction and the amount of HA did not show apparent regularity. ### SEM and EDS Test Results and Analysis of Cemented Soil  
Figure 13 shows the XRD diffraction patterns of the cemented soil samples with a curing age of 28d, a cement mixing ratio of 17.5%, and a humic acid (HA) content of 0%, 15%, and 20%.