Sustainable foam lightweight soil (FLS) with the introduction of solid waste-based binders and dredged mud has shown high engineering and environmental value in expressway reconstruction and extension projects. Accelerated testing through high-temperature curing is considered a crucial method for early-stage assessment of sustainable FLS construction quality. This study aims to explore the curing temperature effect on the strength development of the FLS with different mix proportions and the applicability of accelerated curing method. Strength tests were first conducted on kaolin clay-based FLS with three wet densities and three water contents under different curing temperatures (T), and the strength of the dredged mud-based FLS was also tested to broaden the applicability. Results indicate that higher T and increased wet density significantly enhance the strength of clay-based FLS at any curing age, while higher water content reduces it. The wet density and water content of the proposed FLS recommended in this study considering the strength and lightweight requirements are 800 kg/m3 and 100%, respectively. Moreover, the effectiveness of the accelerated aging method for clay-based FLS is demonstrated by the fact that no dramatic strength loss occurs due to foam expansion and collapse at elevated T of up to 50 degrees C. On this basis, a strength prediction model based on the concept of activation energy is proposed for both kaolin clay-based and dredged mud-based FLS considering the temperature effect. Changes in wet density have a minimal impact on model parameters, but variations in soil type and water content require updating these parameters to ensure prediction accuracy. Finally, an early quality control method is introduced for applying the sustainable FLS in field projects.

The bond-slip behavior of stiffened deep cement mixing (SDCM) piles-which is crucial for their bearing capacity-evolves continuously with curing age. In the study reported here, 20 element tests were conducted on the interface between cemented soil and a stiffened core, analyzing the bond-slip behavior affected by curing temperature and age, and then ensemble learning methods (XGBoost, random forest) were used to establish models for the evolution of the bond-slip behavior considering thermal effects. The constructed models can predict the peak shear strength (tau(max)), the residual shear strength (tau(res)), and the interfacial shear modulus (G). The test results show that the shear strength of the stiffened-core-cemented-soil interface grows with the increasing curing temperature and age, with faster growth at 0-14 days compared to 60-90 days. To lessen the reliance on ineffective brute-force searching, Bayesian optimization with a tree-structured Parzen estimator is used to select the hyperparameters of the established models. The results demonstrate the superior performance of the chosen approach, with R-2 > 0.93 for the training set and R-2 > 0.81 for the test set. The results of the XGBoost model are best for tau(max), with a mean absolute percentage error of less than 5 %, thereby enabling accurate predictions of the mechanical parameters of the stiffened-core-cemented-soil. This research enhances the understanding of the mechanical properties of SDCM piles and provides valuable guidance for projects involving such piles.

The influence of curing temperature on the strength development of cement-stabilized mud has been well documented in terms of strength-increase rate and ultimate strength. However, the strength development model is not mature for the extremely early stages. In addition, there is a lack of studies on quality control methods based on early-stage strength development. This paper presents a strength model for cement-stabilized mud to address these gaps, considering various curing temperatures and early-stage behaviors. In this study, a series of laboratory experiments was conducted on two types of muds treated with Portland blast furnace cement and ordinary Portland cement under four different temperatures. The results indicate that elevated temperatures expedite strength development and lead to higher long-term strength. The proposed model, which combines a three-step conversion process and a hyperbolic model at the reference temperature, enables accurate estimate of the strength development for cement-treated mud with any proportions cured under various temperatures. With this model, a practical early quality control method is introduced for applying cement-stabilized mud in field projects. The back-analysis parameters obtained from a 36-h investigation at temperature of 60 degrees C demonstrated a sufficient accuracy in predicting strength levels in practical applications. (c) 2024 Institute of Rock and Soil Mechanics, Chinese Academy of Sciences. Published by Elsevier B.V. This is an open access article under the CC BY-NC-ND license (http://creativecommons.org/licenses/by-nc-nd/ 4.0/).

Magnesium oxychloride cement (MOC) is an environment-friendly cement often used for stabilizing soft soils because of its exceptional mechanical properties. In this study, the influence of curing temperature on the strength development of MOC-solidified clay is explored, considering different MgO/MgCl2 molar ratios. Different tests were carried out to study the corresponding effects. The results show that the effect of curing temperature on the strength of MOC-solidified clay differs greatly from that of cement-solidified soil. Increasing the curing temperature leads to strength reduction, whereas decreasing the curing temperature increases the corresponding strength. Scanning electron microscope (SEM) and X-ray diffraction (XRD) analyses indicate that the variation in type and amount of hydration products of the solidified soil account for the strength development difference between MOC-solidified and cement-solidified soils. A model based on the experimental results is proposed to characterize the relationship between strength development and curing time. The strength influence factor (eta T) and the strength expedite factor (K) were introduced to demonstrate the relationship between strength development at a specific curing temperature as well as at room temperature.