China is a major agricultural country that produces a large amount of corn straw every year, and there is an urgent need to improve its comprehensive utilization rate. The residue of corn straw incineration has potential volcanic ash activity and is expected to improve the performance of concrete. However, corn straw ash contains certain impurities, which are not conducive to the relevant performance of concrete and require modification treatment. In order to reduce the influence of impurities, corn straw ash was subjected to citric acid soaking treatment, and the action mechanism of original corn straw ash (OCSA) and acid-soaked corn straw ash (ACSA) in cement-based materials was compared and analyzed. The results show that the use of citric acid modification technology can effectively reduce impurities in corn straw ash and improve the strength of cement-based materials. As the content of corn straw ash increases, the peak area of hydrated calcium silicate in matrix of sample first increases and then decreases, while the Ca/Si ratio of hydrated calcium silicate at the interfacial transition zone first decreases and then increases. At the same time, the porosity of samples continues to increase, and the compressive strength first increases and then decreases. When the content of corn straw ash is 15wt%, the compressive strength of samples reaches its maximum. Compared with samples with OCSA, samples with ACSA have a higher peak area of hydrated calcium silicate in the matrix, and the Ca/Si ratio of hydrated calcium silicate at interfacial transition zone reduces by 15.25%-26.72%. In addition, the most probable pore diameter of samples is finer, and the compressive strength increases by 2.53%-12.86%. This research can reduce the adverse effects of impurities in corn straw ash on the relative properties of concrete, and provides a theoretical basis for the application of corn straw ash in concrete.
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