针对内蒙古锡盟地区粉煤灰堆存量大、利用率低以及当地土壤荒漠化严重等系列问题，本工作提出利用粉煤灰改良荒漠土壤的新思路。首先用硫酸对惰性的粉煤灰进行表面活化改性，采用SEM和XRD等分析测试手段研究粉煤灰结构变化，采用XPS和TG分析方法分别对粉煤灰表面羟基定性分析和定量计算，以期明晰粉煤灰表面羟基化效果；其次，使用改性前后粉煤灰分别作为土壤加固剂，以现场采集沙土为加固对象，研究改性粉煤灰对砂土稳定性的影响。结果表明，使用1.5 mol/L的硫酸溶液预改性后，颗粒表面羟基数量较原始粉煤灰增大4倍。按质量比1:9将酸改性前后的粉煤灰分别与沙土复配并静置15天后对复配土的力学强度进行测定，结果显示原始沙土间的黏聚力为0.29 kPa，改性前粉煤灰-沙土复配土的黏聚力为0.88 kPa，而改性后粉煤灰-沙土复配土的黏聚力提高到3.51 kPa。

Aiming at a series of problems such as large amount of fly ash (FA), low utilization rate and serious desertification of local soil in Ximeng Region of Inner Mongolia, this work put forward a new idea of using fly ash to improve desert soil. Firstly, the inert fly ash was activated by sulfuric acid. Scanning electron microscope (SEM) and X-rays diffraction (XRD) were used to study the structural changes of fly ash. X-ray photoelectron spectroscopy (XPS) and thermogravimetric analysis (TG) were used to analyze the surface hydroxyl of fly ash qualitatively and quantitatively, so as to clarify the surface hydroxylation effect of fly ash. Secondly, the influence of modified fly ash on the stability of sand soil was studied by using fly ash before and after modification as soil reinforcement agent. The results showed that the number of hydroxyl groups on the surface of the particles increased by 4 times compared with the original fly ash after pre-modification with 1.5 mol/L sulfuric acid solution. According to the mass ratio of 1:9, fly ash before and after acid modification was mixed with sand and stood for 15 days, respectively, and the mechanical strength of the mixed soil was measured. The cohesion between the original sand was 0.29 kPa, and the cohesion between fly ash and sand before modification was 0.88 kPa. However, the cohesion of the modified fly ash-sand mixture was increased to 3.51 kPa. The fly ash-sand composite soil prepared by adding modified fly ash and sand soil had the functions of sand fixation, water retention, nutrient supply and soil aggregate structure reconstruction.