膨胀剂和含水率对预拌补偿收缩混凝土微观结构的影响  

Effects of expansive agents and water contents on microstructure of ready-mixed shrinkage-compensating concrete

作　　者：张阳阳[1] 马芹永[1] 

机构地区：[1]安徽理工大学矿山地下工程教育部工程研究中心,安徽淮南232001

出　　处：《中国科技论文》2015年第13期1535-1538,1562,共5页China Sciencepaper

基　　金：高等学校博士学科点专项科研基金资助项目(20133415130001)

摘　　要：为研究膨胀剂和干拌混合料含水率对预拌补偿收缩混凝土微观结构的影响,进行了贮存期为7d,5种膨胀剂掺量(0%、4%、6%、8%和10%),3种含水率(0.5%、1.0%和1.5%)情况下的预拌料混凝土微观结构试验。结果表明:当膨胀剂掺量为0%到6%时,随着膨胀剂掺量的增加,针棒状钙矾石AFt晶体在混凝土内部的孔洞和微裂缝中不断生长,且和C-S-H凝胶逐渐搭接在一起形成相互交错的网状结构,C-S-H凝胶和Ca(OH)2晶体间构成的微界面及内部大量空隙被填实,混凝土孔隙率减小,形成了较为均匀密实的连续体;当膨胀剂掺量为8%和10%时,在混凝土内部除致密的胶凝连续体和原有的裂缝外,会产生由于膨胀性能过大引起的新微裂缝,且随膨胀剂掺量的增加,新微裂缝的尺寸也有所增大,导致混凝土的孔隙率增加。随着干拌混合料含水率的增加,混凝土中凝胶数量相对减少,且和Ca(OH)2晶体的黏结性逐渐下降,孔洞的数量和尺寸增加,导致孔隙率增大,密实度下降。In order to study the effect of the expansive agent dosages and the sand moisture content of dry-mixed materials on the microstructure of the ready-mixed shrinkage-compensating concrete,an experiment was conducted on samples with the storage period of 7 days including 5 kinds of expansive agent dosages (0%,4%,6%,8% and 10%)and 3 kinds of sand moisture con-tents (0.5%,1.0% and 1.5%).The results show that,needlelike crystals of ettringite (AFt)constantly grew in the holes and micro cracks within the concrete and gradually lapped together with the C-S-H gel to generate an interlaced network structure with the increase of expansive agent dosages from 0% to 6%.The micro interface between the C-S-H gel and Ca(OH)2 crystal and large numbers of internal voids in the micro interface were filled,leading to decreasing porosity of the concrete and generating a relatively uniform homogeneous matter.When the expansive agent dosage was equal to 8% or 10%,apart from the dense gel continuum and initial cracks in the concrete,new micro cracks were induced due to too much expansive property in the concrete. Moreover the size of these new cracks increased gradually with the increasing expansive agent dosages,which resulted in the in-crease of the porosity and the decrease of the compactness.With the increase of the sand moisture content in dry-mixed materials, the quantity of the gel decreased relatively,and cohesiveness between the gel and Ca(OH)2 crystal declined gradually,while the number and size of the holes increased,which leaded to the increase of the porosity and the decrease of the compactness.

关 键 词：补偿收缩混凝土 预拌料混凝土 膨胀剂 含水率 微观结构 孔隙率 

分 类 号：TU528[建筑科学—建筑技术科学]