用超滤法将萘磺酸甲醛缩合物（FDN）按分子量大小进行了超滤分级,采用质谱仪和元素分析仪测定了各个级分的分子量分布及磺化度,考察了不同分子量FDN对水泥净浆及砂浆分散增强性能影响。结果表明,高分子量FDN较低分子量更有利于改善水泥净浆和砂浆的流动性能,截留分子量大于30000级分在掺量为0.5%时砂浆减水率已达16%,比未提纯FDN提高4%;其砂浆7 d压缩强度较空白样提高了30%,弯曲强度提高了23%,减水增强性能明显优于未超滤的FDN。SEM测试结果表明,掺高分子量FDN的硬化水泥水化早期易形成均匀致密的杆状钙钒石。
Four naphthalene sulfonate formaldehyde condensate（FDN） fractions with different molecular weights were obtained by fractionation using ultrafiltration and their Molecular weight distributions and the contents of sulfonic group were tested separately by mass spectrum and element analysis.The effects of four FDN fractions on the property of cement and mortar were studied.It is found that FDN with higher molecular have better workability.When the mass dosage of FDN gotten through 30000 member size is 0.5%,the water-reducing ratio of mortar is up to 16%,increases by 4% than that of original FDN.At the same time,the compressive strength of responded mortar is rised by 30% compared with blank sample after 7 days,accompanying with flexural strength increases by 23%.FDN with higher molecular has some retarding effect comparing with the lower,and can help the formation of uniform and densely thin rod-shaped ettringite during cement hydration early by scanning electron microscope（SEM）.
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