Mechanical Properties and Microscopic Characteristics of Lime-Fly Ash-Solidified Saline Soil

doi:10.16552/j.cnki.issn1001-1625.2026.0212

Abstract

Abstract:

To investigate the mechanical properties of lime-fly ash-solidified saline soil in the Hangzhou Bay area， this study conducted unconfined compression tests and direct shear tests， the influences of salt content and curing age on the solidification effect of lime and fly ash were analyzed. Furthermore， the scanning electron microscopy （SEM） and mercury intrusion porosimetry （MIP） tests were employed to reveal the microstructural characteristics of lime-fly ash-solidified saline soil （lime-fly ash soil）. The results show that the unconfined compressive strength， tangent modulus， and strain energy density of saline soil all initially increase and then decrease with the rise of salt content. Therefore， it can be inferred that there exists an optimal salt content regarding the influence of salt content on the mechanical properties of saline soil. The mechanical properties of lime-fly ash soil are significantly improved after the incorporation of lime and fly ash. They generally increase with rising salt content and curing age， however， a salt content exceeding 1% （mass fraction） does not lead to a further significant enhancement of these properties. Based on the microscopic test results， it is found that lime and fly ash can effectively improve the pore structure characteristics of saline soil. The pore volume， median pore diameter， average pore diameter， porosity， and fractal dimension of lime-fly ash soil are all lower than those of saline soil， and the bulk density of soil increases from 1.41 g/cm³ to 1.47 g/cm³. These parameters provide a better understanding of the relationship between the microstructural characteristics and macroscopic mechanical properties of lime-fly ash soil. The research results can provide a scientific reference for the application of lime-fly ash soil in practical engineering in the Hangzhou Bay area.

Key words: lime, fly ash, saline soil, salt content, curing age, mechanical property, microstructural characteristics

CLC Number:

TU448

CHEN Fei, ZHAO Hongting, WU Xiaopeng, LI Xiaolin, WAMG Fei. Mechanical Properties and Microscopic Characteristics of Lime-Fly Ash-Solidified Saline Soil[J]. BULLETIN OF THE CHINESE CERAMIC SOCIETY, 2026, 45(9): 3151-3162.

Figures/Tables 23

Fig.1 Particle size distribution curve of soil sample

Table 1 Basic physical properties of soil sample

Category	Liquid limit/%	Plastic limit/%	Maximum dry density/（g·cm^-3）	Optimum moisture content/%	Plasticity index
Silty clay	37.51	23.06	1.69	19.56	14.45

Table 2 Main chemical composition of soil sample

Composition	SiO₂	Al₂O₃	Fe₂O₃	K₂O	MgO	Na₂O	TiO₂	P₂O₅	SO₃	Other
Mass fraction/%	67.56	17.19	5.10	2.60	2.51	1.59	0.80	0.18	0.18	2.29

Table 3 Soluble salt content determination results of soil sample

Ion	Na⁺	K⁺	Mg²⁺	Ca²⁺	Cl^-	SO $4 2 -$	HCO $3 -$
Content/（mg·g^-1）	0.03	0.02	0.03	0.15	0.03	0.10	0.29

Table 3 Soluble salt content determination results of soil sample

Ion	Na⁺	K⁺	Mg²⁺	Ca²⁺	Cl^-	SO $4 2 -$	HCO $3 -$
Content/（mg·g^-1）	0.03	0.02	0.03	0.15	0.03	0.10	0.29

Table 4 Physical properties of slaked lime

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Salt content/%	Unconfined compressive strength/kPa	Tangent modulus/MPa	Strain energy density/（kJ·m^-3）
0	144.60	7.27	2.80
1	184.55	9.70	3.03
2	182.40	9.35	2.71

Salt content/%	Unconfined compressive strength/kPa	Tangent modulus/MPa	Strain energy density/（kJ·m^-3）
0	144.60	7.27	2.80
1	184.55	9.70	3.03
2	182.40	9.35	2.71

Salt content/%	Fitting formula	R²	Cohesion/kPa	Internal friction angle/（°）
0	τ=33.33+0.50σ	0.99	33.33	26.57
1	τ=35.97+0.49σ	0.99	35.97	25.99
2	τ=38.60+0.36σ	0.99	38.60	19.78

Salt content/%	Fitting formula	R²	Cohesion/kPa	Internal friction angle/（°）
0	τ=33.33+0.50σ	0.99	33.33	26.57
1	τ=35.97+0.49σ	0.99	35.97	25.99
2	τ=38.60+0.36σ	0.99	38.60	19.78

Salt content	Variation in unconfined compressive strength/kPa
Salt content	3 d	7 d	14 d
From 0% to 1%	63.41	373.53	809.44
From 1% to 2%	62.57	51.50	16.58