KH550改性SiO2气凝胶及其掺杂对砂浆性能的研究

目的提高SiO_2气凝胶颗粒与砂浆的相容性,降低砂浆的导热系数。方法以质量分数为5%的KH550硅烷偶联剂为改性剂,先对SiO_2气凝胶颗粒进行表面改性,并以改性后的SiO_2气凝胶颗粒为替换骨料,采用等体积替换法制备SiO_2气凝胶砂浆,再用SEM、XRD、傅里叶红外光谱(FTIR)和接触角测量仪对原材料性能和砂浆的微观形貌进行表征,并研究不同替换比例的SiO_2气凝胶颗粒对砂浆密度、力学性能、收缩性能以及导热系数等性能的影响。结果采用KH-550硅烷偶联剂对SiO_2气凝胶进行表面改性,改性后的SiO_2气凝胶能够稳定地镶嵌于砂浆中,与无机胶凝材料的结合较为紧密,填补了砂浆中的孔洞,使得砂浆内部结构更为均匀,形成较为稳定的复合体系;随着SiO_2气凝胶颗粒替换比例的增大,SiO_2气凝胶砂浆的密度、力学性能以及导热系数逐渐降低,收缩率逐渐变大,当替换率达到60%时,密度由最初的2014.1 kg/m3降至1231.4 kg/m3,28天抗压和抗折强度分别降至2.15 MPa和0.45 MPa、导热系数值从0.6039 W/(m·K)降至0.1524W/(m·K),自收缩率增大到2729×10-6。结论从使用性能、材料成本、以及保温性能等方面综合考虑,当替换比例为50%时,为最优体积掺量,此时,其密度、抗压和抗折强度、自收缩率以及导热系数分别为1387.1kg/m3,8.3 MPa和2.23 MPa,1928×10-6,0.2248 W/(m·K)。

Influences of KH550 Modified SiO2 Aerogel on Mortar Property

Objective To improve compatibility between SiO2 aerogel and mortar and reduce the thermal conductivity of mortar.Methods SiO2 aerogel mortar was prepared by equal volume replacement method using the modified SiO2 aerogel particles which were modified by the mass fraction of 5％ KH550 silane coupling agent as modifier to replace sand.Properties of raw materials and microstructure of mortar were characterized via SEM,XRD,FTIR and contact angle gauge.Effects of different aerogel contents of SiO2 aerogel particles on the density,mechanical properties,shrinkage performance,thermal conductivity,etc.were also investigated.Results The SiO2 aerogel which was modified by silane coupling agent of KH-550 could be set in the mortar stably.It was more closely combined with inorganic gelled material and it could make up holes in mortar,make internal structure of mortar more uniform,and form relatively stable composite system.As replacement rate of SiO2 aerogel particles increased,density,mechanical properties and thermal conductivity of SiO2 aerogel mortar decreased and shrinkage rate increased gradually.When the replacement rate reached 60％,the density decreased from the original 2014.1kg/m3 to 1231.4kg/m3,the compressive and fracture strength of 28 days dropped to 2.15MPa and 0.45 MPa respectively.The value of thermal conductivity fell from 0.6039 W/(m·K) to 0.1524 W/(m·K),and the shrinkage increased to 2729× 10-6.Conclusion Under the comprehensive consideration of usability,material cost and insulation performance,etc.,the optimal volume fraction is achieved when the replacement rate is 50％.At this point,its density,compressive strength,rupture strength,shrinkage rate and thermal conductivity coefficient are 1387.1 kg·m-3,8.3 MPa,2.23 MPa,1928 × 10-6 and 0.2248 W/(m.K) respectively.