Research Of Exploiting Sulfonated Starch As A New Water Reducing Admixture

The technology, properties and mechanism of using sulfonated starch asWRA(Water Reducing Admixtures) is systemically illustrated in this article. Theresearch is performed in order to develop sulfonated starch as a new superplasticizeradmixture and achieve industrialization finally. The project shows great significanceand prosperity in solving many problems existed in the field of WRA in China andunfolding a new applied field for natural polymer-starch.Sulfonated starch is prepared by introduce –SO3H to the molecular chain ofstarch. And it was extensively used in the fields such as food, pharmacy andpetroleum.etc,. WRA is one kind of the most important cement admixtures. Now,Lignin sulfate and sulfonated naphthalene formaldehyde (SNF) are most commonlyused in China. The two kinds of WRA both have their own disadvantages;therefore, Itis urgent to exploit new kinds of WRA. Sulfonated starch has been proved to reducewater in theory, yet no concerned research has been reported in literatures. In thisarticle, sulfonated starch of a certain DS (degree of substitution) is verified that itcan reach a high rate of water reducing. Meanwhile, the research shows thatsulfonated starch set retarding of cement intensively. So sulfonated starch can beexploited as a new type of set retarding and superplasticizer admixture. In addition,the applied range of sulfonated starch could be broadened by mix hardeningaccelerating admixtures.The overall results as follows:1, To meet the demand of water reducing, sulfonated starch is prepared by makingcorn starch react with ClSO3H, and ClCH2CH2Cl is used as the solvent. Furthermore,the influencing factors and the optimal technology of sulfonation is studied byorthogonal experiments. The research shows that the ratio of ClSO3/Starch is the maininfluencing factor of sulfonation, whereas, the reaction temperature and the reactiontime have little effect on sulfonation. When the DS of –SO3H is designed to 0.8, theactual DS reach the max. of 0.25 approximately in the temperature range of 10～40℃and the time range of 1～4 h, but reaction efficiency is about to drop. Meanwhile, inorder to simplify the technology and reduce the cost, sulfonated starch is alsoprepared by half dry method using CH2Cl2 as a dispersant.2, In this article, the performance of water reducing of sulfonated starch of differentDS has been tested. Results show that the ratio of water reducing increase with theincrease of DS in a certain range, and sulfonated starch set retarding of cement. Usingsulfonated starch prepared by half dry method and the designed DS is 1.0, the totaltesting standards meet GB 8076—1997 of set retarding and superplasticizer admixtureunder the fixed amount of 0.3 % (wt%), the testing standards include the ratio ofwater reducing and normal setting time of cement paste and the compression strengthof mortar(3d and 28d). when adding sulfonated starch and TEA together to the cementpaste, the total testing standards meet GB 8076—1997 of superplasticizer admixtureunder the fixed amounts of 0.3% (sulfonated starch, wt%) and 0.12%(TEA, wt%).3, sulfonated starch influence the hydration, concreting and induration of cementremarkably when it adds to the cement paste as a WRA. The testing results of XRDand SEM show that sulfonated starch slow the hydration of early stage of cementpaste for its performance of set retarding. After a long period of hydration such as onemonth, the effect of set retarding to the cement paste almost disppear, nevertheless, theflocculent structure of cement has been destroyed for the performance of water reducing ofsulfonated starch, which makes the cement paste hydrate fully, and the structure ofhardened cement paste become more uniform and compact than that of the controlsample, and the compression strength also be more high than the control ones.