改性磨细粉煤灰的流动性及水化活性

摘要

针对磨细粉煤灰流动性较差的特点,开发出新型粉煤灰改性材料并设计了工业改性方法;分别通过纯粉煤灰浆体和水泥净浆、砂浆、混凝土等试验,对比研究了原灰、磨细灰及改性磨细灰的流动性和水化活性,并通过扫描电镜(SEM)及能谱(EDS)观察和分析改性机理;结果显示,改性措施明显改提高了磨细粉煤灰的流动性和水化活性,需水比从123%降低至97%;在固定用水量条件下,3、28 d的活性指数分别提高10%、3%,而在固定流动度条件下则可分别提高约17%、15%,在相同配合比和相同坍落度的C40混凝土中,可减少用水量15 kg/m3,提高抗压强度约5 MPa;磨细过程在打散黏连颗粒的同时也打破了部分球形颗粒并使非球状的海绵体颗粒更容易吸水,导致粉煤灰流动性降低;附着在磨细灰颗粒表面的改性剂微粒,可通过"润滑"和缓凝作用,明显克服上述缺陷,并可使水泥水化产物钙矾石(AFt)晶体搭接粉煤灰颗粒与周围环境,进而提高水泥石的机械强度.%In view of the characteristics of the poor quality of grinding fly ash (FA-G),a novel modified material was developed and the modification method was designed for industrial manufacture.According to the tests of net pulp,pure fly ash slurry and cement mortar, concrete,respectively.The liquidity and hydration activity of raw fly ash(FA-R),mound fly ash and modified grinding fly ash (FA-G-M) was compared.The scanning electron microscope(SEM)and the energy dispersive spectrometer(EDS)were used to observant and analyze the modification mechanism.The results showed that the modified measures significantly improved the fluidity and hydration activity of FA-G,and the water requirement was reduced from 123% to 97 %.Under the condition of fixed quantity,the activity index of 3 d and 28 d increased by 10% and 3%,respectively.In the cases of fixed fluidity,it can increase by about 17 % and 17%,respectively,In the same mixture ratio and the same slump of C40 concrete,it can reduce water consumption by 15 kg/m3,and increase the compressive strength of 5 MPa.In the grinding process,the adhesion of particles were scattered,at the same time the partial spherical particles were also broke,and it make it easier for non spherical sponge particles suction.Finally,it resulted in the decrease of fly ash liquidity.The modifier particles attaching on the surface of FA-G particles can significantly overcome the defects by the lubricating gentle coagulation,and it can make the cement hydration products ettringite(AFt)crystal of cement lap of fly ash particles with the surrounding environment,then it improved the mechanical strength of hardened cement.