磺化麦草碱木质素的结构特征及其作为混凝土减水剂的性能

研究了碱法制浆副产物麦草碱木质素的磺化产品磺化碱木质素(SWSL)作为混凝土减水剂使用的性能,掺量(相时于水泥的质量分数,下同)为0.25%时,掺SWSL的混凝土减水率达13.5%,较掺木质素磺酸钙(CLS)的(10.2%)高,混凝土3天和7天龄期抗压强度比仅为113%和105%,较掺CLS的(134%和125%)低.SWSL在水泥浆碱性溶液中具有较好起泡性和泡沫稳定性,有较高的减水率,但泡径较粗且分布不均匀,最大泡径为2 mm,导致硬化砂浆密度减小,孔径小于0.01 mm的气孔比例相对较少,孔径在0.01～0.05 mm范围的较多,抗压强度下降.SWSL的磺化度为1.1 mmol/g,重均相对分子质量(MW)为4 424,较木钙(11 370)低.较低的磺化度使SWSL的分散性能比木钙差.

Structural Characteristics of Sulfonated Wheat Straw Lignin from Alkali Pulping and Its Performances as Concrete Water-reducer

The performances of sulfonated wheat straw lignin(SWSL),which is a sulfonated product of wheat straw lignin extracted from alkali pulping,used as concrete water-reducer were studied.When the dosage is 0.25 %(based on concrete),the water-reducing ratio of SWSL reaches 13.5 % which is higher than that of calcium lignosulfonate(CLS)obtained from sulphite pulping;but the 3 and 7 d compressive strengths of concrete are only 113 % and 105 % respectively,which are lower than those of CLS.Further researches indicate that,in the alkali solution of cement paste,SWSL has good foaming property and foam stability,which result in high water-reducing ratio.However the foam of SWSL solution is large and non-homogeneous,with the largest bubble diameter of 2 mm,which leads to decrease of the density of hardened mortar blended with SWSL.The content of pores with a diameter less than 0.01 mm was relatively low;while the content of pores with a diameter between 0.01-0.05 mm was high.Thus the compressive strength of hardened concrete was reduced.The sulfonation degree of SWSL is 1.1 mmol/g and its molecular weight is 4 424 only,which are all lower than those of CLS.The relatively low sulfonation degree is the reason that the dispersibility of SWSL is not comparable with CLS.