不同化学改性方法提高玉米芯骨料混凝土的性能

Improving the properties of corn cob aggregate concrete by utilizing different chemical modification methods

玉米芯具有较低的导热系数,可以作为天然的保温材料,用于混凝土砌块中。然而,由于玉米芯的多孔结构,导致玉米芯骨料混凝土的抗压强度偏低,亟需进行改性。为了推广玉米芯的规模化利用,该研究以玉米芯为原料改善混凝土砌块的性能,通过红外光谱、拉曼光谱和扫描电镜等测试手段,探讨了3种不同改性技术对玉米芯骨料混凝土水化产物化学键、分子结构、界面过渡区微观结构、抗压强度和导热系数的影响。结果表明:与环氧树脂改性相比,陶粒法改性和裹浆法改性不仅增加了玉米芯骨料混凝土界面过渡区的水化硅酸钙凝胶含量,同时也降低了界面过渡区的厚度,优化了混凝土砌块的微观结构、提高了混凝土砌块的抗压强度、降低了混凝土砌块的导热系数。其中,陶粒法改性技术的效果尤为明显。界面过渡区厚度水化硅酸钙特征峰由大到小顺序分别为陶粒法改性、裹浆法改性、环氧树脂改性。经过陶粒法改性、裹浆法改性和环氧树脂改性后,玉米芯骨料混凝土的界面过渡区分别为无明显界面过渡区、55~66 μm和93~101 μm之间。和未改性玉米芯骨料混凝土相比,掺30%陶粒法改性玉米芯骨料混凝土的抗压强度的导热系数分别降低了51.5%和32.2%。当掺入不超过15%的改性玉米芯骨料时,混凝土砌块满足国家标准GB/T8239-2014中对抗压强度的要求。为了改善玉米芯骨料混凝土砌块的综合性能,建议掺入不超过15%的陶粒法改性玉米芯骨料。研究结果为玉米芯在混凝土砌块中的大规模利用提供了依据,同时也为进一步改善混凝土砌块的相关性能提供了参考。

China is a major agricultural country,emitting a large amount of corn cob solid waste annually,yet its comprehensive utilization rate is relatively low.Corn cobs have a lower thermal conductivity and can be used as natural insulation materials in concrete blocks.However,due to the porous structure of corn cobs,the compressive strength of corn cob aggregate concrete is relatively low and urgently requires modification.In order to promote the scaled utilization of corn cob and use them to improve the properties of concrete blocks,this study explored the effects of three different modification techniques,such as epoxy resin modification,the modification methods of ceramide and coating,on the chemical bond and molecular structure of hydration products,microstructure of interfacial transition zone,compressive strength and thermal conductivity of corn cob aggregate concrete by infrared spectroscopy,Raman spectroscopy,and scanning electron microscopy.The results showed that compared with epoxy resin modification,the modification methods of ceramide and coating not only increased the content of calcium silicate hydrate gel in the interfacial transition zone of corn cob aggregate concrete,but also reduced the thickness of interfacial transition zone,optimized its microstructure,improved the compressive strength,and reduced the thermal conductivity of concrete blocks.Among them,the effect of ceramide modification method is particularly significant.The order of characteristic peak of calcium silicate hydrate gel in the interface transition zone was the modification methods of ceramide,the modification methods of coating,epoxy resin modification.After ceramide modification,coating modification,and epoxy resin modification,the thickness of the interfacial transition zones of the corn cob aggregate concrete were no distinct interfacial transition zone,between 55~66μm,and between 93~101μm,respectively.Compared with concrete with original corn cob aggregate,the thermal conductivity and compressive strength of concrete with 30%ceramide method modificated corn cob aggregate decreased by 51.5%and 32.2%,respectively.When the proportion of modified corn cob aggregate did not exceed 15%,the concrete blocks met the national standards MU20~MU30 for compressive strength.To improve the overall performance of corn cob aggregate concrete blocks,it is recommended to incorporate no more than 15%of corn cob aggregate with ceramide modification method.This research provides a theoretical basis for the large-scale utilization of corn cobs in concrete blocks,and provides a reference for the further improvement of the relevant properties of concrete blocks.