碱激发下粉煤灰-市政污泥固废基混凝土抗冻融性能

为改善市政污泥对混凝土抗冻融性能的劣化效果，在氢氧化钠及水玻璃的复合激发下，用经生石灰改性后的市政污泥取代10%细骨料，粉煤灰分别取代10%、20%与30%水泥，制备了混凝土。分析了不同冻融循环次数下，混凝土的表观现象、相对质量、相对动弹性模量、相对抗压强度及微观结构随粉煤灰掺量与碱当量的变化规律，分别以相对动弹性模量与相对抗压强度为损伤变量建立了不同的冻融损伤模型。研究结果表明：随冻融循环次数增加，混凝土表观损伤愈发严重，内部孔隙增多，相对动弹性模量及相对抗压强度显著降低；与对照组相比，粉煤灰及碱激发剂的加入可以改善市政污泥对混凝土冻融耐久性的劣化效果，降低混凝土在冻融循环作用下的质量损失、动弹性模量损失及抗压强度损失；当粉煤灰掺量10%、碱当量4%时，粉煤灰可在碱激发剂及改性污泥中残余碱的联合作用下被较充分地激发，可消纳改性污泥中的残余碱，减弱市政污泥对混凝土抗冻融性能的劣化效果，此时混凝土水化程度最高，在冻融循环作用下的质量损失、动弹性模量损失及抗压强度损失最小，且服役寿命最长，约为16a以上；相对动弹性模量与相对抗压强度相关性良好，分别以两者为损伤变量的冻融损伤模型与试验结果均吻合良好。

Freeze-thaw Resistance of Concrete based on Fly Ash and Municipal Sludge under Alkali Excitation

Under the compound excitation of sodium hydroxide and sodium silicate, municipal sludge modified by quicklime was used to replace 10% fine aggregate, and fly ash was used to replace 10%, 20% and 30% cement, respectively, to improve the deterioration effect of municipal sludge on freeze-thaw resistance of concrete. The changes of apparent phenomena, relative mass, relative dynamic elastic modulus, relative compressive strength and microstructure of concrete with fly ash content and alkali equivalent under different freeze-thaw cycles were analyzed. Different freeze-thaw damage models were established with relative dynamic elastic modulus and relative compressive strength as damage variables. The results showed that with the increase of freeze-thaw cycles, the apparent damage of concrete was more serious, the internal pores were increased, and the relative dynamic elastic modulus and relative compressive strength were significantly reduced. Compared with the control group, the addition of fly ash and alkali activator can improve the deterioration effect of municipal sludge on the freeze-thaw durability of concrete, and reduce the loss of mass, dynamic elastic modulus and compressive strength of concrete under the action of freeze-thaw cycle. When the fly ash content was 10% and the alkali equivalent was 4%, the fly ash can be fully excited under the combined action of the alkali initiator and the residual alkali in the modified sludge, which can absorb the residual alkali in the modified sludge and weaken the deterioration effect of municipal sludge on the freeze-thaw resistance of concrete. At this time, the hydration degree of concrete was the highest. Other, the mass loss, dynamic elastic modulus loss and compressive strength loss under freeze-thaw cycle were the least, and the service life was the longest, which was more than 16a. The relative dynamic elastic modulus had a good correlation with the relative compressive strength, and the freeze-thaw damage models with the two as damage variables were in good agreement with the experimental results.