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A two-lift gradient design for airport pavements has been proposed to mitigate the functional degradation, especially the salt-frost (S-F) damage induced by deicing slat fluids. Herein, this study focuses on elucidating the mechanism and improvement of incorporating mineral admixtures in the development of a novel S-F resistant surface concrete material, which is of great significance for delaying the functional deterioration of pavement surface in northern China. The results indicated that the filling effect and secondary hydration reaction between the fly ash (FA) and silica fume (SF) and cement hydration products results in a dense spatial network structure, effectively reducing porosity and optimizing pore structure. It was found that SF can effectively improve the frost resistance and salt corrosion resistance of cement mortar, while the influence of FA depends on its content and environmental conditions. The incorporation of FA and SF significantly enhanced the structural density of cement concrete and reduced chloride ion permeability. The improvement in impermeability is most pronounced when both FA and SF are used in combination. In addition, a fitting equation between the admixture content and chloride ion permeability has been established, demonstrating good fitting results. In non-frozen saline soil areas, a large amount of FA or SF could be incorporated; in seasonally frozen areas, the priority should be given to SF to ensure salt corrosion resistance and frost resistance. The findings of this study provide a scientific basis for sustainable airport pavement construction in northern China.

期刊论文 2025-07-18 DOI: 10.1016/j.conbuildmat.2025.141882 ISSN: 0950-0618

Geopolymer-based cementitious materials known for their robust durability and lower environmental impact make them an ideal choice for sustainable construction. The main focus of this study is to understand the influence of chemical admixtures which plays a pivotal role in improving the properties of geopolymer mortar (GM). This research integrates various chemical admixtures, including calcium chloride, sodium sulphate, sodium hexametaphosphate, and MasterGlenium SKY 8233 (SKY) which falls under the category of either accelerators, retarders, or superplasticisers. Assessments were conducted on the fresh and hardened states of flyashbased GM mixes with varying proportion of river sand (RS), laterite soil (LS) and copper slag (CS), encompassing flowability, setting times, compressive strength, durability study in aggressive environmental conditions and microstructural analyses after 56 days of ambient curing. Findings reveal that calcium chloride and sodium sulphate efficiently decrease the initial and final setting times of the geopolymer paste, highlighting their roles as accelerators, with calcium chloride showing greater efficacy than sodium sulphate. On the other hand, sodium hexametaphosphate serves as a retarder, substantially extending the initial setting time of the geopolymer paste. Introducing the modified polycarboxylic ether (PCE) based superplasticiser SKY into the mortar matrix caused the initial setting time to be extended and resulted in a slight drop in compressive strength compared to the other mixes. Durability tests confirmed the superior resistance of GM mixes to harsh environments like acid, sulphate, and marine water exposure. These findings highlight the potential for tailoring geopolymer blends to achieve desired properties under ambient curing conditions using chemical admixtures.

期刊论文 2025-02-21 DOI: 10.1016/j.conbuildmat.2025.140135 ISSN: 0950-0618

A capillary barrier cover (CBC) is a geotechnical structure which a coarse-grained soil layer covered by a fine-grained soil layer. A CBC can retain downward water infiltration, increase water storage capacity and lateral diversion, and prevent capillary rise. Geotextiles are usually set up as isolation layers between fine-grained and coarse-grained layers to prevent fine particles entering the coarse-grained layer, resulting in a decrease in downward water infiltration and water storage capacity. However, crustal stress, farming, animal, plant activities, and other factors may cause damage to the isolation layer. At present, there is no reliable and accurate method to determine the location and degree of damage to the isolation layer. The existing methods search for the damage location by excavating the whole fine layer, which incurs high maintenance costs. If the damaged position of the CBC isolation layer can be accurately obtained, it can reduce maintenance costs. Therefore, this study investigated the influence of a coarse-grained layer mixed with different particle sizes and proportions of fine particles on water storage capacity through laboratory soil column experiments. The results are as follows: (1) Fine particle mixing into the coarse-grained layer will reduce water storage capacity, and there is a worse admixture ratio that minimizes water storage capacity. (2) The CBC enhances the fine-grained layer volumetric water content (VWC), but the enhancement degree decreases as the distance from the fine-coarse interface increases. (3) A method has been proposed to determine the location and degree of damage to the isolation layer. When the VWC at the fine-coarse interface reaches a stable level during breakthrough, the CBC effect exists, the higher the VWC at the fine-coarse interface, the stronger the CBC; when the VWC at the fine-coarse interface is unstable during breakthrough, the CBC effect disappears, and the median diameter of the fine particles mixed into the coarse-grained layer is finer than or equal to the fine-grained particles' median diameter.

期刊论文 2025-01-01 DOI: 10.3390/w17020183

Various problems are often encountered during the backfilling process of deep foundation pits. The development of low-cost and efficient solidified materials for the preparation of fluidized solidified soil is currently an ideal solution. This article used industrial solid waste (granulated blast furnace slag, fly ash, carbide slag, etc.) as the main raw material to study the hydration hardening properties of solidified materials and the construction feasibility of fluidized solidified soil prepared from solid waste materials. The results are as follows: Compared with cement-based materials, solid waste-based solidified materials had lower early activity. The cumulative heat release within 72 h was less than 200 J/g. Different solid wastes, such as fly ash and carbide slag, had different effects on the properties of solidified materials. Overall, they had the potential to prepare fluidized solidified soil. The prepared fluidized solidified soil had a fluidity greater than 350 mm, a 28d compressive strength greater than 3 MPa, and exhibited good workability and excellent mechanical properties. Hydration products such as CS -H and AFt were filled in the soil structure. The 28d compressive strength well above the design requirements of general engineering projects. Meanwhile, the prepared fluidized solidified soil had good adaptability to conventional water reducers (fluidity could be increased by more than 40%) and early strength agents (1d compressive strength could be increased by more than 60%).

期刊论文 2024-04-12 DOI: 10.1016/j.conbuildmat.2024.135900 ISSN: 0950-0618

Expansive soil exhibits significant swellings and shrinkages, which may result in severe damage or the collapse of structures built upon it. Calcium-based admixtures, such as lime, are commonly used to improve this problematic soil. However, traditional chemical additions can increase significant environmental stress. This paper proposes a sustainable solution, namely, the use of lignin fiber (LF) from the paper industry to partially replace lime as an amendment for expansive soils. Both the macroscopic and microscopic characteristics of the lignin fiber-treated expansive soil are extensively studied. The results show that the mechanical properties of expansive soil are improved by using lignin fiber alone. Under the condition of an optimal dosage of 8%, the compressive strength of lignin fiber-modified soil can reach 193 kPa, the shear strength is increased by 40% compared with the untreated soil, and the water conductivity is also improved with the increase in dosage. In addition, compared with 2% lime-modified soil, the compressive strength of 8% lignin fiber- and 2% lime composite-treated expansive soil increased by 50%, the cohesion increased by 12%, and the water conductivity decreased significantly. The microstructure analysis shows that at an 8% lignin fiber content, lignin fibers interweave into a network in the soil, which effectively enhances the strength and stability of the improved soil. Simultaneously, the fibers can form bridges across the adjacent micropores, leading to the merging of pores and transforming fine, dispersed micropores into larger, connected macropores. Lime promotes the flocculation of soil particles, forming larger aggregates and thus resulting in larger pores. The addition of fibers exerts an inhibitory effect on the flocculation reaction in the composite-improved soil. In conclusion, lignin fibers are an effective addition used to partially replace calcium admixture for the treatment of expansive soil, which provides a sustainable and environmentally friendly treatment scheme for reducing industrial waste.

期刊论文 2024-04-01 DOI: 10.3390/app14083393

To achieve value-added recycling of slurry -like mud (MS) and resolve the shortage issue of construction fill materials, physicochemical combined methods (PCCMs), which integrate flocculation, solidification, and vacuum preloading (optional), have been proposed to enhance the engineering properties of MS. The optimization of chemical admixtures, which consist of solidification and flocculation components, is crucial in ensuring the effectiveness and cost -efficiency of PCCM in practical application. In this study, a number of solidification model tests are performed to optimize the solidification components for PCCM via determining the optimal mixing ratio in each of the two GGBS-based binders. Subsequently, surcharge preloading deposition tests and vacuum preloading model tests, with different types/dosages of flocculant, are conducted to determine the appropriate flocculation components. The results indicate that OPC-GGBS exhibits remarkable effectiveness in strength improvement, and the use of a combination of organic and inorganic flocculant, particularly CaO-PAM, can significantly enhance the efficiency of PCCM. Moreover, increasing the dosage of the composite flocculants enhances the dewatering process, but the benefit becomes less significant when the dosage exceeds a threshold value of 0.16%. Additionally, this study provides a preliminary understanding of the key mechanism involved in synergizing flocculation, solidification and preloading to enhance the performance of MS. These findings contribute to the optimal design and application of PCCM for the treatment of MS.

期刊论文 2024-03-15 DOI: 10.1016/j.conbuildmat.2024.135434 ISSN: 0950-0618
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