Influence of Carbonization Process on the Mechanical Properties of Nano-MgO Modified Cement Soil

Abstract

In order to explore the modification effect of carbonization time on nano-MgO-modified cement soil, unconfined compressive strength tests of nano-MgO-modified cement soil with carbonization times of 0 h, 6 h, 1 d, 2 d and 4 d were carried out. A method for normalizing the stress–strain curve was proposed, and the influence of nano-MgO content and carbonization time was investigated from the three aspects of compressive strength, peak strain and energy dissipation. The test results show the following: (1) The compressive strength of the modified cement soil can be significantly improved by adding 1.0% nano-MgO and after 1 d carbonization. (2) Under the same nano-MgO content, the peak strain of the modified cement soil after 2 d carbonization reaches the maximum, which can significantly increase its ductility. However, the nano-MgO content has little influence on the peak strain of the modified cement soil. (3) Under the same nano-MgO content, the energy dissipation rate of the modified cement soil after 1 d carbonization reaches the maximum, which can better resist the damage of external load.

Geotechnical Properties and Stabilization Mechanism of Nano-MgO Stabilized Loess

“…Furthermore, the fair fitting results also suggested that the ε frelation of NM-treated loess was not sensitive to NM and curing, which brought conv ience in engineering application. Figure 10 exhibits the data of nano-SiO 2 (NS)-and nano-MgO (NM)-treated clays extracted from the literature [22,31,37,53]. Twelve pairs of ε f and q u were fitted according to Equation ( 2), and the fitting results are exhibited in this figure.…”

“…It demonstrated that the 50 E of NM-treated loess was proportiona to u q , but in a nonzero-intercept way. Therefore, their relationship could be described as Figure 13 presents the E 50 -q u relationships of nanomaterial-stabilized clays extracted from literature [22,31,37,53]. Based on Equation (3), information about the parameters η and β could be obtained together with the determination coefficient R 2 : (1) For the NS (0~4%) stabilized clay with E 50 of 3~38 MPa and q u of 0.4~2.1 MPa, the fitting parameter η and β were 54.1 and −10.83, respectively; (2) For the clay treated with NS (0~1%) and polyester fiber (PF) (0~0.5%), the η and β were considered to be 16.4 and −3.1473, respectively;…”

“…In terms of soil stabilization, the effect of nanomaterials on geotechnical properties is a major concern. Recently, many researchers have devoted to this field and reported noticeable improvements, even with small amount of nanomaterials [15][16][17][18][19][20][21][22][23][24][25]. The more frequently utilized nanomaterials include nano-SiO 2 [16,17], nano-clay [18,19], nano-MgO [22,23], and nano-CaCO 3 [24,25].…”

“…Recently, many researchers have devoted to this field and reported noticeable improvements, even with small amount of nanomaterials [15][16][17][18][19][20][21][22][23][24][25]. The more frequently utilized nanomaterials include nano-SiO 2 [16,17], nano-clay [18,19], nano-MgO [22,23], and nano-CaCO 3 [24,25]. Among them, nano-MgO (NM) is normally produced by the sintering process of magnesite, performing under a relatively low temperature (700 • C), compared to that of cement (1450 • C), which makes it more energy-saving and eco-friendly in this field [26][27][28].…”

“…They observed that an increase in NM dosage up to 0.4% led to increases of dry density, optimum water content, and unconfined compressive strength (UCS). Wang et al [22] studied the influence of carbonization time on clayey soil treated with NM and cement. They found a sample with 1.0% NM, and 1 day carbonization gave the best improvement effect in UCS.…”