| The Yellow River flows through the Loess Plateau carrying large amounts of sediment to the Lower Yellow River, which results in the riverbed of downstream constantly elevation. Undoubtedly, this kind of situation becomes a serious hidden danger to residents living on both sides of the lower Yellow River, and also brings about serious environmental problems. In order to alleviate social and environmental stress, the research and practice of realizing resources utilization the sediment, primarily focused on building materials, ceramics and geotechnical applications, are started in succession. Some results have been achieved, in facts, most of these products prepared by sintering and pressing process and consumed low volume sediment. Therefore, these have become a barrier for utilization of sediment with low energy consumption.This paper aims to realize resource utilization of the Yellow River channel sediment. Degradable stabilized earth concrete with suitable mechanical properties and durability was prepared from the Yellow River sediment. Activation mechanism of the sediment and the discussion of its products regarding the formation process and degradation mechanism of the strength network system were analyzed principally. And the mechanical properties, microstructure, moisture transport mechanisms and durability of stabilized earth concrete were conducted in-depth study. Moreover, this thesis is financially supported by National Natural Science Foundation of China under Grant No.50972099. The main progresses are as follows:1. The Yellow River sediment of in different channel of the lower reaches was characterized by physical, chemical and engineering properties. The results indicate that all the sediment show weak alkaline and contain silicon, aluminium and calcium in chemical composition. The particles are mainly concentrate in0.075-0.005mm silty soil (>80%), which is composed of quartz, feldspar and carbonate and active ingredient is very low. All characteristics of the Yellow River sediment result in shortcomings at compactibility, plasticity and stability, which determine and restrict the field of its engineering applications. 2. Activity characterization methods, activating technique and activation mechanism of the Yellow River sediment were discussed. The results show that mechanical polishing improves compactibility and plasticity of the Yellow River sediment significantly. NaHSO4, accelerates the process of soil formation of feldspar by acid hydrolysis and chemical weathering. Free Si4+and Al3+and generating layered secondary minerals are released from feldspar which leads to pozzolanic activity index (PAI) and reactive rate increase from0.51and1.18to0.64and5.20, respectively. The sediment is further activated and strengthened by Ca(H2PO4)2·H2O through complexation reactions and specific adsorption of H2PO4-on the cosmid surface. The PAI of the Yellow River sediment reaches0.68.3. According to the materials and structural design of stabilized earth concrete, three sets of strength network system design concept and structure model was established in this paper, and these were verified by microstructure and interacted mechanism among various components. Studies have shown that, a continuous network of inorganic hydration product consolidates sediment through physical filling and chemical enhancement, which is the support component of the strength and water resistance of stabilized earth concrete. Interpenetrating network is formed by an organic polymer network with inorganic hydration network, strengthening stabilized earth concrete in a semi-continuous network. The plant fiber three-dimensional disorderly distributed in stabilized earth concrete and build strong physical bond with the inorganic hydration network playing a role in the consolidation the sediment particles. Three sets of strength network supplement and cooperate with each other. By means of optimization of preparation process and mix proportion, stabilized earth concrete was prepared from the Yellow River sediment. Its28d compressive strength is14.4MPa, flexural strength is3.54MPa, the softening coefficient is0.87, the thermal conductivity is0.38W/(m-K).when mixture ratio of activated silt/cementitious binder/sand is65/25/10supported by1.8wt.%modified polyvinyl alcohol and1.2V%plant fibers.4. The evolution of the structure and properties of stabilized earth concrete under different environmental conditions were studied, and its long-term moisture transport mechanism and performance degradation mechanism were explored. The results show, the capillary absorbent capacity is proportional to the square root of time from stabilized earth concrete in contact with water to water saturated. The capillary absorption coefficient is42.08g/m2·s1/2, water surface inflow velocity and t0.01is linearly related. There is a large number of needle-like ettringite in the large holes and cracks after freezing and thawing. The volume of harmful pore (50-200nm) increases20%. The results of carbonation experiment show that compressive strength and carbonation depth is linearly related with y=-0.23x+15.1. According to the experimental results of the freeze-thaw cycle and carbonation, compressive strength degradation calculation model of stabilized earth concrete was derivated: fcuk≈-0.86(?)·(φn/φ0)0.9+15.1. The formation of stabilized earth concrete experienced30freeze-thaw cycles disintegrated after being soaked in10wt.%(NH4)2SO4solution for150days. The wheat planted can emergence and grow smoothly when specimen debris and soil are mixed with a ratio of3:7. |
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