淀粉基减水剂对水泥及混凝土性能的影响

Effect of Starch-Based Water Reducer on Properties of Cement and Concrete

以玉米淀粉为生物基原材料,双氧水(H_(2)O_(2))为绿色氧化剂,阳离子季铵盐为醚化剂,通过氧化-醚化反应制备了一种新型绿色淀粉基减水剂(SWR)。为评价SWR对水泥水化性能的影响,利用红外光谱分析(FT-IR)SWR制备过程中官能团的变化;对比SWR、聚羧酸减水剂(PWR)、萘系减水剂(NWR)三种减水剂对水泥减水率、Zeta电位、净浆流动度、胶砂强度、混凝土抗压强度性能的影响。结果表明,SWR分子链上引入了羧基与醚键。随减水剂掺量的增加,SWR的减水率逐渐增大,且较PWR、NWR有更优异的减水效果,以水泥质量为基准,SWR折固掺量的质量分数为1.0%时,减水率可达33%。Zeta电位分析表明,三者具有相近的电位绝对值,但SWR具有最大的经时电位绝对值。当减水剂掺量的质量分数低于0.6%时,三者的水泥净浆流动度较为相近,但继续增加减水剂用量,NWR的水泥净浆流动度更为突出。SWR胶砂试件的7 d与28 d抗折强度、抗压强度基本介于PWR与NWR胶砂试件之间;SWR混凝土7 d抗压强度最低,28 d时抗压强度最高,达49.6 MPa,表明SWR起到缓凝作用。综合分析,SWR减水剂具有较好减水与缓凝作用,同时可保证混凝土的强度性能,推荐SWR折固掺量的质量分数为1.0%。

A new green starch-based water reducer(SWR)was prepared by oxidation-etherification reaction using corn starch as biological raw material,hydrogen peroxide(H_(2)O_(2))as green oxidant and cationic quaternary ammonium salt as etherifying agent.In order to evaluate the effect of SWR on cement hydration performance,the change of functional groups in the process of SWR preparation was analyzed by FT-IR.The effects of SWR,PWR and NWR on water reducing ratio,zeta potential,fluidity of cement paste,strength of mortar and compressive strength of concrete were compared.The results show that carboxyl group and ether bond are introduced into SWR molecular chain.With the increase of water reducer content,the water reducing rate of SWR increases gradually,and it has a better water reducing effect than PWR and NWR.Based on the cement quality,when the mass fraction of SWR is 1.0%,the water reducing rate reaches 33%.Zeta potential analysis shows that the three have similar absolute potential values,but SWR has the largest absolute potential over time.When the mass fraction of water reducer is lower than 0.6%,the fluidity of cement paste of the three is similar,but the fluidity of NWR cement paste is more prominent when the content of water reducer continues to increase.The flexural strength and compressive strength of SWR sand specimens at 7 d and 28 d are basically between PWR and NWR sand specimens,the compressive strength of SWR concrete at 7 d is the lowest,and the compressive strength at 28 d is highest,up to 49.6 MPa,indicating that SWR plays a role in retarding setting.Comprehensive analysis shows that SWR water reducer has better water reducing and retarding effects,and guarantee the strength performance of concrete.The recommended mass fraction of SWR is 1.0%.