碱激发剂浓度及模数对碱矿渣胶凝材料抗压性能及水化产物的影响研究

采用水玻璃(复掺氢氧化钠调整模数)激发粒化高炉矿渣活性制备碱矿渣净浆试样.采用抗压强度测试、X-射线衍射(XRD)、综合热分析(TG-DSC)等技术手段研究了激发剂碱浓度(4%、6%、8%)及模数(0.75、1.00、1.50、2.00)对碱矿渣胶凝材料抗压性能及水化产物的影响.研究结果表明:激发剂模数较低时(0.75和1.00),碱矿渣胶凝材料抗压强度随着碱浓度的增加而呈下降趋势;激发剂模数较高时(1.50和2.00),试件强度在碱浓度为6%时达到最大值.在相同碱浓度下,激发剂模数为1.50时试件抗压强度值最大.碱矿渣胶凝材料主要水化产物为C-S-H凝胶,同时伴有C-A-S-H凝胶生成.另外观测到少量斜方钙沸石(CaAl2Si2O8· 4H2O)的生成.在部分配合比中还观测到水滑石(Mg6Al2(OH)16CO3· 4H2O)的存在.碱浓度较高的碱矿渣胶凝材料中生成了较多的C-S-H水化产物.激发剂模数较高时(1.50和2.00),更有利于碱矿渣中C-S-H水化产物的生成.碱浓度/模数较低时, C-S-H产物结晶度有所提高.相较于C-S-H凝胶结晶度,其生成量对碱矿渣胶凝材料抗压强度的影响更为显著.

Effect of Alkali Concentration and Modulus of Alkaline Activator on the Compressive Properties and Hydration Products of Alkali Activated Slag Cementitious Materials

Granulated blast furnace slag was activated by using water glass (sodium hydroxide was added in to adjust modulus) to prepare alkali activated slag paste specimens.Effect of alkali concentrations of 4%, 6% and 8% and moduli of 0.75, 1.00, 1.50 and 2.00 of the activator on the compressive properties and hydration products of alkali activated slag was studied by using compressive strength test, X-ray diffraction (XRD) and thermal analysis (TG-DSC) techniques.The results show that when a lower modulus was used, such as 0.75 and 1.00, compressive strength of alkali activated slag decreased with the increase of alkali concentration.While when the modulus used was higher, such as 1.50 and 2.00, the specimens could obtain the maximum compressive strength when alkali concentration was 6%.Under same alkali concentration, modulus of 1.50 could make the specimens get the maximum compressive strength.The main hydration products of alkali activated slag was C-S-H gels, certain amount of C-A-S-H gels was also formed simultaneously.Besides, small amount of gismondine (CaAl2Si2O8· 4H2O) was also detected in the system.Hydrotalcite (Mg6Al2(OH)6CO3· 4H2O) was found in some of the mixes. Larger amount of C-S-H gels was formed in the alkali activated slag system with higher alkali concentration.Use of higher modulus, such as 1.50 and 2.00, was beneficial for the formation of C-S-H gels in the system.When a lower alkali concentration/modulus was used, the C-S-H gels in alkali activated slag was more crystalline.Compared to the degree of crystallinity, amount of C-S-H gels was more influenced on the compressive strength of such system.