助磨剂对粉煤灰流动性及水化活性的影响

Effect of Grinding Agent on Liquidity and Pozzolanic Activity of Grinding Fly Ash

采用硫酸钠与木质素磺酸钠为助磨材料磨细粉煤灰,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,3d和28d的活性指数分别提高10%和3%,而在固定流动度条件下则可分别提高约17%和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15kg/m^3,抗压强度提高约5 MPa;磨细过程在打散粘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。

Na_2SO_4 and sodium lignosulfonate were used as the grinding materials for grinding of fly ash(FA-G).According to the tests of net pulp,pure fly ash slurry,cement mortar,and concrete,respectively,the liquidity and hydration activity of raw fly ash(FA-R),mound fly ash and modified grinding fly ash(FA-G-M)were compared.The scanning electron microscopy(SEM)and the energy dispersive spectrometry(EDS)were used to observant and analyze the modification mechanism.The experimental results show that the modified measures significantly improve the fluidity and hydration activity of FA-G,and the water requirement reduces from 123% to 97 %.Under the condition of fixed quantity,the activity indexes of 3 dand 28 dincrease by 10% and 3%,respectively.In the cases of fixed fluidity,it increases by about 17 % and 15%,respectively,In the same mixture ratio and slump of C40 concrete,it reduces water consumption by 15 kg/m^3,and increases the compressive strength of 5 MPa.In the grinding process,the adhesion of particles are scattered,at the same time the partial spherical particles are also broken,which makes it easier for non spherical sponge particles suction.Finally,it results 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 improves the mechanical strength of hardened cement.