混凝土外加剂原理及应用技术

混凝土外加剂原理及应用技术MechanismandApplyingTechniqueofConcreteAdmixtures孙振平(同济大学材料科学与工程学院，上海200092）Email：Tel:惠州，2009.10.21KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation主要内容•混凝土外加剂作用机理•混凝土外加剂基本性能•混凝土外加剂应用技术•混凝土坍落度损失机理及控制技术•混凝土外加剂与水泥/掺合料适应性及解决措施KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation一、外加剂作用原理•减水剂------表面活性剂•引气剂------表面活性剂•早强剂------盐类、有机物•缓凝剂------盐类、有机物•速凝剂------盐类KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation一、外加剂作用原理1.表面活性剂指能显著降低液体表面张力或二相间界面张力的物质，如洗衣粉的主要成分十二基烷苯磺酸钠，肥皂的主要成分硬脂酸钠等都是表面活性剂独有的降低二相间界面张力，提高分散体系稳定性的作用KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation一、外加剂作用原理2.表面活性剂的分子结构CH3CH2…..CH2------COOH,OH或---SO3Na等憎水基团亲水基团表面活性剂的分子结构示意图KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation3.水泥颗粒在水分散介质中凝聚(絮凝)的原因•布朗运动，边角碰撞•粒子之间的范德华力•水泥颗粒带电，同性相吸C3A、C4AF等铝酸盐在水化初期带正电C3S、C2S等硅酸盐矿物在水化初期带负电•水泥水化初期产生凝胶KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation一、外加剂作用原理4.水泥浆絮凝体的形成水泥颗粒游离水水泥浆体絮凝状结构示意图KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation一、外加剂作用原理表面活性剂的分类分类方法按照能否解离出离子进行分类按照解离出离子的电性进行分类表面活性剂解离示意图代表性物质阴离子型表面活性剂+H2O-+羧酸盐(RCOOMe)烷基磺酸盐(R--SO3Me阳离子型表面活性剂+H2O+胺盐离子型表面活性剂两性离子型表面活性剂+H2O++氨基酸(R-NH-CH2COOH)表面活性剂非离子型表面活性剂/乙二醇、多元醇KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation一、外加剂作用原理几种类型减水剂的特性减水剂掺量/%界面张力/mN.m-1减水率/%纯水/70.2/高浓型FDN萘系减水剂0.5068.518聚羧酸系减水剂0.2043.026氨基磺酸盐系减水剂0.5052.022KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation固体颗粒表面活性剂离子相互排斥水溶液表面活性剂离子在悬浮体系内固体颗粒上的吸附KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation一、外加剂作用原理减水剂的吸附分散----作用掺加减水剂的浆体中絮凝状结构的解体游离水游离水水泥颗粒水泥浆体絮凝状结构的形成絮凝结构解体后，包裹水被释放，浆体流动性改善KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation一、外加剂作用原理凝聚凝聚分散分散•减水剂的润滑作用水泥颗粒气泡掺加减水剂的浆体中水泥颗粒与极性微气泡之间的相互作用KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation一、外加剂作用原理减水剂作用原理•吸附----分散作用•湿润作用•润滑作用KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation一、外加剂作用原理•混凝土配合比：C:S:G=330:749:1171，高效减水剂SPF-1抗压强度(MPa)混凝土SPF掺量W/C坍落度减水1d3d7d28d(%C)(cm)(%)基准/0.6208.0/10.7/10016.9/10024.4/10032.5/1001#0.750.4788.022.916.3/15226.0/15436.0/14841.5/1282#0.750.62022.0011.0/10318.3/10825.6/10533.1/1023#0.750.55014.011.314.2/13323.2/13730.5/12537.4/115•将混凝土配合比中水泥用量减少：C:S:G=285:707:12584#0.750.4808.5/13.218.025.133.0KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation二、外加剂基本性能•C=k,Slump=kW/C,R•C=k,W/C=kSlump•fcc,0=k,Slump=kC•C=k,Slump,W/CR,SlumpKeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation二、外加剂基本性能减水剂的品种普通减水剂高效减水剂高性能减水剂KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation二、外加剂基本性能普通减水剂•糖钙•木质素磺酸盐(钠、钙、镁、胺)KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation二、外加剂基本性能高效减水剂•萘磺酸盐系高效减水剂（Sulphonatednaphthalenebasedsuperplasticizer）•磺化三聚氰胺系高效减水剂（Sulphonatedmelaminebasedsuperplasticizer）•氨基磺酸盐系高效减水剂（Sulphonatedaminophenolbasedsuperplasticizer）•以蒽油为原料的聚次甲基蒽磺酸盐高效减水剂（Sulphonatedmethyl–authracenecondensatessuperplasticizer）•脂肪族系高效减水剂•改性木质素磺酸盐高效减水剂（Modifiedlignosulphonatessuperplasticizer）•聚羧酸系高性能减水剂（Hydroxylatedcarboxylicacidbasedsuperplasticizer）KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation二、外加剂基本性能木钙减水剂掺量对混凝土坍落度的影响0246810121416182000.10.20.30.40.51木钙掺量(%C)坍落度(cm)掺加减水剂对新拌混凝土性能的影响二、外加剂基本性能KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducationSPF高效减水剂掺量与混凝土坍落度之间的关系0246810121416182022242600.20.40.60.811.21.4SPF掺量(%C)坍落度(cm)二、外加剂基本性能KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation木钙掺量对混凝土含气量的影响0123456700.10.20.30.40.50.60.70.8木钙掺量(%C)含气量(%)MDF、MF高效减水剂掺量与混凝土含气量的关系012345600.250.50.751掺量(%C)含气量(%)FDN(机械振捣)FDN(人工捣实)MF掺加木钙减水剂对混凝土泌水率的影响012345670123456时间(小时）泌水率(%)0.25%0二、外加剂基本性能KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation木钙掺量对矿渣大坝水泥所配制混凝土的凝结时间的影响(同水泥用量,同坍落度)010203040506000.20.30.40.5掺量(%C)凝结时间(小时)初凝终凝二、外加剂基本性能KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation萘系高效减水剂对混凝土凝结时间的影响(同水泥用量，同坍落度)凝结时间(h:min)减水剂名称及掺量(%C)水灰比坍落度(cm)初凝终凝00.438-128-911-12FDN高效减水剂0.50.368-129-1012-1300.6123.85:559:200.50.5935.06:309:15UNF高效减水剂1.00.5764.55:558:4000.708.56:158:30SN-II高效减水剂1.00.549.06:308:30二、外加剂基本性能KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation掺外加剂对混凝土凝结时间的影响•当木钙减水剂超量掺加时，将导致混凝土严重引气和缓凝，甚至发生长时间不凝结现象，并且对混凝土强度产生较大的副作用。而当高效减水剂超量掺加时，也会使混凝土缓凝，早强降低•温度对混凝土凝结时间也有较大的影响。混凝土的凝结时间随混凝土拌和物的温度降低而延长，所以在温度较低情况下施工用的混凝土，木钙掺量不宜过大，夏季高温天气施工用的混凝土，为延长混凝土的凝结时间，可适当增大木钙减水剂的掺量，如采用0.30%C二、外加剂基本性能KeyLaboratoryofAdvancedCivilEngineeringMaterials(TongjiUniversity),MinistryofEducation使用减水剂对混凝土水化热的影响•水泥水化热对于大坝