辉绿岩混凝土的强度与界面特征研究

结合襄十高速公路的实际情况，对辉绿岩作混凝土集料进行了深入的研究。通过与石灰石集料的对比研究发现，辉绿岩作集料配制出的混凝土无论在坍落度，还是在强度等方面均优于石灰石混凝土。同时，还结合SEM方法对比研究了辉绿岩混凝土和石灰石混凝土的界面粘结情况，进一步解释了辉绿岩混凝土强度高于石灰石混凝土的原因。  

机制砂对高强混凝土体积稳定性的影响

采用对比的方法,研究了天然砂、机制砂及机制砂中的石粉质量分数对高强混凝土的工作性、抗压强度、弹性模量、干缩和受压徐变的影响。结果表明:机制砂中适量(7%—10.5%)的石粉并不会劣化混凝土的工作性能,甚至可以改善混凝土的工作性能,且随石粉质量分数的提高,机制砂混凝土的抗压强度逐渐增大;石粉质量分数较低(小于7%时)的机制砂混凝土弹性模量接近于天然砂混凝土的弹性模量,但当石粉质量分数较高时,机制砂混凝土的弹性模量降低;石粉质量分数对机制砂高强混凝土干缩的影响与干缩龄期密切相关,石粉质量分数较高的机制砂混凝土的前7 d龄期干缩值比河砂混凝土大,而后龄期干缩值相差不大,同时,掺入粉煤灰使机制砂混凝土各龄期的干缩值减小;石粉质量分数为7%的机制砂混凝土徐变度、徐变系数与天然砂混凝土较为接近。  

石粉含量对C80机制砂混凝土性能的影响

针对机制砂的石粉含量对混凝土抗渗性及体积稳定性的影响进行了相应研究。实验表明,C80机制砂混凝土的氯离子扩撒系数均较低,随石粉含量的增加,氯离子扩撒系数呈线性增长;弹性模量随石粉含量的增加有下降的趋势,5%含量以下时高于河砂混凝土;在早期,机制砂混凝土的干燥收缩随着石粉含量的增大而增大,而在60 d以后5%石粉含量混凝土的干缩最小,试验证明,石粉含量在7%以下时,机制砂混凝土耐久性与体积稳定性较好,与河砂混凝土相当,一定量的石粉不会对混凝土渗透性与体积稳定性产生不利影响。  

Influence of MB-value of manufactured sand on the shrinkage and cracking of high strength concrete

The relation between methylene blue (MB) value of MS and its limestone dust content and clay content was investigated. The effects of MB value ranging from 0.35 to 2.5 on the workability of fresh concrete and crack propagation characteristics at the age of 24 hours, and effects on the mechanical properties, dry shrinkage of the harden concrete were tested. The experimental results show that the MB value is not related with the limestone dust content of MS, but in direct proportion to clay content. With the increase of MB value, the concrete workability decreases, and the flexural strength and 7 d compressive strength reduce markedly, whearas the 28 d compressive strength is not affected. When the MB-value is less than or equal to 1.35, the change of the MB-value has a little influence on early plastic cracking and dry shrinkage property of concrete, but when the MB-value is more than 1.35, the tendency of plastic cracking and dry shrinkage is remarkable. Funded by the Nationd West Communication Construction Technology Project(No.200331881106)  

Effects of the Lithologic Character of Manufactured Sand on Properties of Concrete

Six representative parent rocks of sand, including limestone, quartzite, gneisses, granite, Basalt and Marble were selected to conduct a systematical research on the effects of various lithologies of manufactured sand on the workability, mechanism properties, volume stability and durability of manufacturedsand concrete. The experimental results show that the strength of manufactured-sand concrete is slightly higher than that of natural-sand concrete. Furthermore, substituting 15% cement of the concrete mixture with equal quantity of the six different lithology stone powder respectively, the data indicated that they can improve the concrete's workability, postpone the plastic cracking time, enhance the anti-cracking grade, and have no obvious effect on the properties of antifreeze and sulfate attack resistance but reduce the capability to resist chloride ion penetration. Moreover, the differences in concrete's workability, mechanism properties, volume stability and durability caused by various lithologies of manufactured sand and stone powder were not significant and the influence of lithology variety on the macro properties of concrete could be neglected eventually.  

基于紧密堆积理论的环氧混凝土配合比设计

基于紧密堆积理论，采用MAA模型和Fuller最大密度理论选出了砂石骨料的最优级配，应用正交试验方法确定了环氧混凝土的最佳配合比，并进行了力学性能评价和微观分析。结果表明：砂石骨料经级配优化后，紧密堆积空隙率明显降低，最紧密堆积空隙率仅为22.23％。骨胶比对环氧混凝土劈裂抗拉强度具有显著性影响，水泥适合作为填料掺入环氧混凝土中。环氧混凝土的立方体抗压强度随龄期的增长而略有增长，且与环氧树脂的固化程度紧密相关，当环氧树脂完全固化时，环氧混凝土的立方体抗压强度基本不再随龄期而变化。经级配优化后，环氧混凝土的力学性能得到改善，立方体抗压强度有所提高。通过SEM微观测试分析发现，级配优化后的环氧混凝土内部有害缺陷明显减少，体系密实均匀，内部黏结力更强。