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

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 55～66 μm, and between 93～101 μm, 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.