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粉煤灰改性高水材料力學性能試驗研究及機理分析

Experimental study and analysis of the mechanical properties of high-water-content materials modified with fly ash

  • 摘要: 為解決礦山高水充填材料成本較高、粉煤灰等工業廢料大量剩余造成資源浪費、環境污染等問題,借助微機控制電子萬能試驗機(ETM)力學試驗系統、掃描電鏡掃描裝置和X射線衍射分析儀,研究粉煤灰摻量對高水材料物理力學性能的影響規律,并通過物相和微觀結構分析探討其影響機理.結果表明:隨著粉煤灰摻量的增加,高水材料的凝結時間逐漸延長,含水率逐漸降低,容重基本不變;摻雜粉煤灰前后高水材料均是一種彈塑性材料,其變形破壞過程可以分為孔隙壓密階段、彈性階段、屈服階段和破壞階段;高水材料的峰值強度、彈性模量和變形模量均隨粉煤灰摻量的增加略有降低,殘余強度卻有所提高;綜合考慮高水材料的強度、模量和成本,粉煤灰摻量a為15%是最優摻量,此時峰值強度、彈性模量和變形模量僅分別降低了25%、8.6%和10%,殘余強度卻提高了50%.物相和微觀形貌分析結果表明:粉煤灰的摻量影響了β-C2S的水化進程,導致鈣礬石生成量減少,其他水化產物生成量增多,進而破壞了鈣礬石結構的整體性和均勻性,最終降低了高水材料的抗壓強度.

     

    Abstract: High-water-content materials are a new type of inorganic cementitious material. They have been widely used in the mining of underground mined-out areas in recent years. However, the higher filling cost has always been the key limiting factor in their further development and application. Meanwhile, large volumes of industrial waste, such as fly ash, has become a serious environmental problem as well as a wasted resource, at a time when the rational repurposing of industrial waste is of great significance to the developed world. To solve the problems of the high cost of mine-filling material, the wasting of a useful resource, and the environmental pollution caused by large surpluses of industrial waste like fly ash, the physical and mechanical properties, microstructure, and chemical components of high-water-content materials of varying fly ash content were studied. An engineering test model (ETM) mechanics test system, scanning electron microscopy (SEM) scanning device, X-ray diffraction (XRD) diffraction analyzer, and a fly ash modification mechanism were discussed based on the microscopic and phase analysis results. The test results show that:(1) with increasing fly ash content, the setting time of high-water-content materials gradually increases, water content decreases, and bulk remained relatively unchangs; (2) high-water-content materials, with or without fly ash, are elastoplastic materials, and their deformation and failure progress could be divided into pore compaction stage, elastic stage, yield stage, and failure stage; (3) the peak strength, elastic modulus, and deformation modulus of high-water-content materials are reduced with increasing fly ash content, although residual strength is improved; and (4) the most reasonable dosage of fly ash is 15% when strength, modulus and cost are considered. Peak intensity, elastic modulus, and deformation modulus of high-water-content material are reduced by only 25%, 8.6% and 10% at this fly ash dosage, respectively, and the residual strength increased by 50%. Phase and morphology analyses show that the amount of fly ash affects the hydration progress of β-C2S, resulting in reduction of ettringite and an increase in other hydration products. Thus, the homogeneity and integrity of the structure of ettringite are destroyed at different levels, leading, eventually, to a reduction in the compressive strength of high-water-content materials.

     

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