摘要
【目的】为提高粉煤灰和煤矸石的利用率、减少天然碎石的开采,研究高掺量粉煤灰对水泥稳定煤矸石基层性能的增强机制,为高掺量粉煤灰在水泥稳定煤矸石基层中的应用提供理论依据。【方法】用煤矸石全部替代天然碎石作为骨料、并掺入适量粉煤灰替代骨料,制备水泥稳定煤矸石基层混合料;通过无侧限抗压试验、劈裂试验、抗压回弹模量试验、水稳定性试验、冻融试验研究混合料的力学性能和耐久性能;研究不同粉煤灰掺量(质量分数)下混合料的强度形成机制。【结果】粉煤灰质量分数为4%、8%时,水泥与粉煤灰发生火山灰效应,生成新的水化产物填充胶凝材料内部孔隙,提高了混合料的力学性能;粉煤灰质量分数为12%时,混合料的抗压回弹模量最大,荷载作用下混合料的变形量最小;粉煤灰掺量为16%时,粉煤灰在混合料中的微集料效应充分发挥,28 d龄期无侧限抗压强度和劈裂强度有明显提升,但抗压回弹模量减小。【结论】在不同粉煤灰掺量下,随着粉煤灰掺量的增加,混合料的无侧限抗压强度、劈裂强度逐渐增大,抗压回弹模量先增大后减小;粉煤灰掺入后,混合料的水稳定性能和抗冻性能略有降低。
Objective With the global emphasis on environmental protection and resource conservation,improving the utilization rate of industrial waste and reducing the exploitation of natural resources have become research hotspots.Fly ash and coal gangue are the major wastes from thermal power generation and coal mining processes.Their large-scale accumulation not only occupies valuable land resources,but also pollutes the environment.Therefore,this study aims to explore the enhancement mechanism of high-content fly ash on the performance of cement-stabilized coal gangue base.It provides a new way for the effective utilization of industrial waste while reducing the exploitation of natural gravel,thereby achieving the dual goals of environmental protection and resource conservation.Method In this study,high-quality coal gangue was selected as the aggregate to replace traditional natural gravel.Appropriate amounts of cement were selected as the bonding material,and different proportions of fly ash(4%,8%,12%,16%)were mixed.Through accurate calculations and optimized design,the composition of the mixture with different proportions was determined.To evaluate the mechanical properties of the mixture,unconfined compressive strength tests,splitting tests,and compressive rebound modulus tests were carried out.These tests comprehensively reflected the key mechanical indicators of the mixture such as compressive strength,splitting strength,and elastic modulus.To evaluate the durability of the mixture,water stability tests and freeze-thaw tests were carried out.The water stability tests simulated the performance changes of the mixture under water immersion,while the freeze-thaw test simulated the performance changes after freeze-thaw cycles in cold areas.The study also discussed the strength formation mechanisms of mixture with different fly ash content.Result When fly ash was added to the cement at a content of 4%and 8%,a pozzolanic reaction occurred between the cement and fly ash,producing new hydration products.These newly generated hydration products were very fine and could effectively penetrate into the internal pores of the binding materials,serving to fill and reinforce them.This filling not only enhanced the compactness of the mixture,but also significantly improved its overall strength,providing a more stable foundation for construction.As the fly ash content further increased to 12%,the properties of the mixture changed significantly.Under external loads,the mixture showed excellent deformation resistance,with the deformation amount reaching its minimum.This indicated that at a specific fly ash content,the stability of the mixture was significantly improved,enabling it to withstand greater external pressure and changes.When the fly ash content increased to 16%,the micro-aggregate effect of fly ash began to show its unique advantages.This effect ensured that the fly ash particles were more evenly distributed in the mixture,enhancing their cohesion and thereby greatly improving the mechanical properties of the mixture.Experimental data showed that at this content level,the unconfined compressive strength and splitting strength of the mixture were significantly improved after 28 days of curing.Conclusion This study showed that with the increase of fly ash content,the unconfined compressive strength and splitting strength of the cement-stabilized coal gangue base mixture gradually increased,while the compressive rebound modulus first increased and then decreased.This indicated that an appropriate amount of fly ash can improve the mechanical properties of the mixture,but an excessive content may lead to a decline in its performance.In addition,although the incorporation of fly ash slightly reduced the water stability and frost resistance of the mixture,it still met the overall engineering requirements.By analyzing the hydration reactions and microstructural changes of the mixture,it was found that the addition of fly ash promoted the hydration reaction of the cement,generating more hydration products.These hydration products filled the gaps between aggregates and improved the compactness and strength of the mixture.Moreover,the addition of fly ash also improved the pore structure of the mixture and reduced the number of large and interconnected pores.Therefore,the application of high-content fly ash in cement-stabilized coal gangue base has broad prospects.It not only increases the utilization rate of industrial waste and reduces the exploitation of natural resources,but also provides high-performance building materials for road engineering and other fields.
作者
张博杰
俞莉
张东生
张文博
杨秋宁
ZHANG Bojie;YU Li;ZHANG Dongsheng;ZHANG Wenbo;YANG Qiuning(School of Civil and Hydraulic Engineering,Ningxia University,Yinchuan 750021,China;Department of Civil Engineering,KU Leuven,Bruges 8200,Belgium)
出处
《中国粉体技术》
CAS
CSCD
2024年第4期43-50,共8页
China Powder Science and Technology
基金
国家自然科学基金项目,编号:51768058
宁夏回族自治区重点研发计划项目,编号:2021BEE03004。
关键词
煤矸石
粉煤灰
力学性能
耐久性
coal gangue
fly ash
mechanical property
durability
