火山石与偏高岭土对UHPC立方体抗压性能影响

Effect of volcanic rocks and metakaolin on cube compressive properties of UHPC

为了探究火山石与偏高岭土(MK)对超高性能混凝土(UHPC)立方体抗压强度的影响,通过设置火山石粒径和MK掺量2个参数考察了其影响规律,同时采用SEM、XRD和TG微观分析方法,揭示了材料微观形貌变化、物相组成、物质组成以及矿物成分结晶度对UHPC抗压性能影响机理.结果表明:火山石孔洞与砂浆形成机械锁嵌效应结构可有效改善UHPC-火山石界面抗剪性能;在9.5~31.5 mm的火山石粒径范围内,UHPC立方体抗压强度随着火山石粒径增大而增大;当MK掺量小于等于4%时,UHPC立方体抗压强度和UHPC内CaCO_(3)、水化硅酸钙(C-S-H)凝胶以及钙钒石(AFt)的含量随着MK掺量的增加而增大;28 d龄期时,相比于掺量为1%的MK,添加4%的MK将UHPC基体中C-S-H凝胶和AFt的生成量提高了24.82%;当MK掺量为4%时,UHPC内CaCO_(3)、C-S-H凝胶以及AFt的结晶度更高,MK促进CaCO_(3)大量结晶为方解石,可为UHPC提供更高的强度;火山石粗骨料的掺入一方面使得CaCO_(3)的结晶度增加,另一方面也使得CaCO_(3)晶体更加稳定;4%掺量的MK和火山石共同作用会显著促进CaCO_(3)的结晶.

In order to explore the influence of volcanic rocks and metakaolin(MK)on the cube compressive strength of ultra-high performance concrete(UHPC),the influence rules of volcanic rocks particle size and MK content are investigated.At the same time,SEM,XRD and TG microscopic analysis methods are used to reveal the influence mechanism of material microscopic morphology changes,phase composition,material composition and crystallinity of mineral composition on the compressive performance of UHPC.The results show that the mechanical locking effect structure formed by the holes of volcanic rocks and mortar can effectively improve the shear resistance of UHPC-volcanic rocks interface.In the range of 9.5-31.5 mm of volcanic rocks particle size,the cube compressive strength of UHPC increases with the increase of volcanic rocks particle size.When the MK content is less than or equal to 4%,the cube compressive strength of UHPC,the contents of CaCO_(3),calcium silicate hydrate(C-S-H)gel and vanadite(AFt)in UHPC increase with the increase of MK content.At the age of 28 d,compared with 1%of MK,the addition of 4%of MK increases the production of C-S-H gel and AFt in UHPC matrix by 24.82%.When the MK content is 4%,the crystallinities of CaCO_(3),C-S-H gel and AFt in UHPC are higher.MK can promote the crystallization of CaCO_(3)into a large amount of calcite,which can provide UHPC with higher strength.On the one hand,the addition of volcanic rocks coarse aggregate increases the crystallinity of CaCO_(3),on the other hand,it also makes CaCO_(3)crystal more stable.The crystallization of CaCO_(3)can be significantly promoted by the combined action of 4%of MK and volcanic rocks.