生活污泥灰水化活性激发试验研究

Experimental study on activation of hydration activity of sewage sludge ash

为实现生活污泥灰的大规模资源化利用,研究了机械粉磨、微波辐照和外加剂对污泥灰活性的影响,采用激光粒度分析、X射线衍射、热重分析及扫描电镜等仪器对生活污泥灰及水泥复合试样进行表征。结果表明:与未处理的污泥灰相比,机械粉磨后的污泥灰体积密度峰值对应的颗粒粒径减小,比表面积增大,水化活性得以提高。微波辐照促使生活污泥灰发生熔融反应,生成以矽钙石(rankinite)和铝酸一钙为主的活性矿物,且污泥灰的水化性能大幅增长。复掺外加剂对生活污泥灰的激发效果优于单掺,当NaCl掺入质量分数为1.5%,三乙醇胺(TEA)掺入质量分数为0.03%时,污泥灰-水泥试样3 d抗压强度最大,相比空白样提高110%。复合外加剂的掺入促使更多生活污泥灰及水泥颗粒参与水化反应,并生成水化氯铝酸钙晶体包裹于层状的水化硅(铝)酸钙凝胶中,形成密实的微观结构,以提高污泥灰-水泥试样的早期抗压强度。

To utilize the resource of sewage sludge ash on a large-scale,the effect of mechanical grinding,microwave irradiation,and chemical reagent addition on the hydration activity of sewage sludge ash is investigated in this paper.Laser particle size analysis,X-ray diffraction phase analysis,and scanning electron microscopy are adopted to characterize the sewage sludge ash in the cement composite samples.The results indicate that,with the extension of grinding time,the particle size of the sewage sludge ash that has the peak volume density decreases,the specific surface area,and the hydration activity increase.Besides,a good gradation relationship forms between the sludge ashes and cement particles,which is conducive to the increase of the strength of the sample.The activation effect of mechanical grinding on sludge ash is gradually weakened with the extension of grinding time,and the best grinding time of sludge ash is 10 min,considering energy saving.Microwave irradiation promotes the melting reaction among minerals in sewage sludge ash to form new minerals-rankinite and calcium aluminate with certain hydrating activity.Both of them produce Ca(OH)2,C—S—H,and C-A-H gel through the hydration reaction.Also,the rankinite can react with CO2 in the air to form calcium carbonate and silica gel.All these reactions can further promote the hardening of the sludge ash cementing system.With the increase of microwave power and irradiation time,the hydration properties of sludge ash increase significantly.The activation effect of compound additives on the sewage sludge ash was superior to that of a single admixture.When the content of NaCl and TEA are1.5%and 0.03%,respectively,the compressive strength of the sludge ash-cement sample curing for 3 days achieves the optimum value,which is 110%higher than that of the control sample.The hydration degree of the cementitious system is improved with the addition of composite additives,promoting more sewage sludge ashes and cement particles to participate in the hydration reaction.The main hydration products include calcium chloraluminate hydrate(AFm),hydroxyapatite,calcium silicate hydrate,and calcium aluminate hydrate.The calcium chloraluminate hydrate crystals are wrapped in the layered hydrated silicon(calcium aluminate)gel,resulting in a dense microstructure and thus improving the early compressive strength of the sludge ashcement sample.