This paper presents the experimental investigation into the effect of salinity on the strength behavior of cement-stabilized dredged clays as fills at high initial water contents. One source of dredged clay was dredged from Baima Lake of China. Specimens were prepared having different porewater salinities by blending the air-dried clays with NaCl solution at different salt concentrations. The prepared saline dredged clay specimens were thereafter adjusted to different initial water contents and blended with cement with different amounts. Unconfined compression tests were performed on cement-stabilized dredged clay specimens after 28-day curing. All tested specimens show strain softening behavior where the axial strain corresponding to the peak stress varies with amount of cement. Stress-strain curve for the specimen with lower salinity lies above on that of higher one. Initial water content has a negative effect on the strength of cement-treated clays while cement has a positive effect on the development of strength for cement-treated dredged clays due to the pozzolanic reactions. The presence of salt has an adverse influence on the obtaining of strength for cement-treated dredged clays because salt can inhibit cement from generating C-S-H and C-A-H. Unconfined compressive strength almost linearly decreases with the increasing salinity. A quantitative expression was presented to calculate the unconfined compressive strength for cement-treated saline dredged clays concerning the effects for initial water content, porewater salinity and amount of cement.

This study presents an experimental investigation on the effects of cyclic loading waveform and cyclic stress ratio (CSR) on dynamic behaviors through laboratory tests on a source of soft clay under cyclic loading in drained condition. Test results showed that under different cyclic loading waveforms at a given frequency (f = 1 Hz) and CSR = 0.6, the axial strain increases significantly at a relatively lower number of cycles (N) and then became stable, while the axial strain consistently decreases with the increasing N and tend to be stable. At a given N, specimen under sine wave cyclic loads shows a higher axial strain rate than that under triangle wave or square cyclic loads. Test results also indicated that at different CSRs, the axial strain increases rapidly at a relatively lower N and then gradually tends to be stable with the increasing N at lower CSR yet there is no stable trend for specimens at higher CSR, which indicates there is a critical value of CSR. It is recommended to apply the cyclic loading in sine waveform with CSR close to and less than the critical value to get a better treatment effect.

When using supplementary cementitious materials to replace cement partially, the carbon emissions of cement products can be reduced, but it often leads to reduced strength. This study explores the application potential of carbide slag (CS) and calcined coal gangue (CCG), byproducts of acetylene production, to partially replace cement. The effects of these two materials on the macroscopic properties and microstructure of cement-based materials were analyzed through systematic experiments. The compressive strength, ultrasonic pulse velocity, and electrical resistivity test results showed that replacing 20% of cement with CCG did not cause significant changes in the test results of the specimens. An X-ray diffraction (XRD) analysis showed that these two materials can produce additional hydration products. Scanning electron microscopy images (SEM) further revealed that CCG produces hydration products to fill microscopic pores. Thermogravimetric analysis (TG) results after 28 days showed that with the addition of supplementary cementitious materials, calcium hydroxide (CH) in CS reacts with CCG, resulting in the consumption of CS. Finally, the environmental impact of CS and CCG was assessed. It was found that CS is more favorable for reducing carbon emissions compared to CCG. However, when considering the effect of cement replacement on compressive strength, combining these two materials is more advantageous for sustainable development. Overall, the use of CS and CCG demonstrated good performance in promoting sustainable development.

This paper presents an improved method for predicting the bearing capacity of single jacked pile based on piezocone penetration test (CPTu) data which contain tip resistance (q_t), side friction (f_s) and excess dynamic pore water pressure (u₂). Firstly, the average value of q_t was determined to calculate the pile unit base resistance according to the influence zone of the logarithmic spiral concerning the effect of soil types. Secondly, f_s and u₂ were used to calculate the pile unit shaft resistance considering the effect of friction fatigue. The pile jacking force was obtained in terms of unit base resistance and unit shaft resistance. The ultimate bearing capacity was finally determined using pile jacking force multiplied by a force ratio denoted as R_f. The ultimate bearing capacities calculated for two case projects show a good agreement with the measured results, which indicates that the proposed method is feasible and effective. Reliability assessment was carried out on the proposed method and other five estimation methods with respect to the reliability index obtained by advanced first-order second-moment (AFOSM) method. Comparison result showed that the method proposed in this study has a higher reliability index over other five existing methods. Therefore, the proposed method can be used as a reliable alternative to predict the bearing capacity in the engineering practice of jacked pile foundation.

Using industrial byproducts to replace cement is an important way to reduce carbon emissions from the cement industry. In this study, the effects of two industrial byproducts, fly ash (FA) and quartz powder (QZ), as supplementary cementitious materials (SCMs) on the macroscopic properties and microstructure of cement-based materials were experimentally investigated. The results of the compressive strength and ultrasonic pulse velocity experiments showed that QZ significantly mitigated the decrease in strength and ultrasonic pulse velocity caused by the reduction in cement dosage in the early stage. Moreover, the 28-day compressive strength of the FA group was comparable to that of the control group, and regression analysis indicated a negligible effect of FA addition on 28-day compressive strength. X-ray diffraction and Fourier transform infrared spectroscopy experiments showed that QZ can promote the hydration reaction in the early stage. Scanning electron microscopy images revealed that a layer of hydration products can form on the surface of FA after 28 days of hydration. Hydration heat experiments indicated that FA significantly reduces the release of hydration heat, while QZ promotes the formation of ettringite through nucleation effects in the early stage of hydration, thereby accelerating the release of hydration heat. Thermogravimetric analysis after 28 days showed that the amount of hydration products and calcium hydroxide produced decreased with the addition of cementitious materials. Finally, the use of FA and QZ was analyzed for carbon emissions and energy consumption. The results showed that using these two cementitious materials significantly reduces carbon dioxide emissions and energy consumption.