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Mechanism elucidation and constitutive laws of expansive concrete for durable and high performance concrete structures

耐久性高性能混凝土结构膨胀混凝土的机理阐明和本构规律

基本信息

批准号：
13450179
负责人：
KISHI Toshiharu
金额：
$ 9.66万
依托单位：
The University of Tokyo
依托单位国家：
日本
项目类别：
Grant-in-Aid for Scientific Research (B)
财政年份：
2001
资助国家：
日本
起止时间：
2001 至 2002
项目状态：
已结题

项目摘要

Crack resistant mechanism of chemical prestressed reinforced concrete (CPRC) with expansive agent was studied in microscopic point of view as followings,(1) In cyclic loading of uni-axial test for CPRC unloading stiffness is gradually decreased and residual strain is remarkably increased up to cracking. Further, CPRC has higher deformability and tension stiffening effect after peak range is higher than normal RC.(2) A series of flexural test of CPRC with various specimen sizes were conducted. The deformability and cracking load of CPRC is higher in smaller cross section in which curvature becomes large. Not only ultimate load but also shear stiffness are enhanced by providing lateral reinforcement The effect of lateral shear reinforcement is more significant in larger cross section since plain concrete zone becomes larger in that situation.(3) Flexural test for CPRC was conducted where reinforcement ratio was varied under constant content of expansive agent It is shown that crack resistance is enhanced in accordance with not only chemical prestress but also chemical prestrain. Then, crack resistance of CPRC under long-term drying was also tested It was found that crack resistance of CPRC subjected to 1 month drying is decreased like normal RC, however it is recovered in 3 months drying.(4) A series of pull-out test of deformed bar embedded in massive concrete was conducted to check bond characteristic. Bond between expansive concrete and deformed bar is almost same as normal RC irrelevant of degree of lateral confinement Further, it was found in case where bar diameter is larger than maximum size of coarse aggregate, that very strange strain distribution appears in deeper zone of re-bar at very small stress level.Due to the above mentioned complicated governing mechanism of CPRC behaviors, formulations for crack width and constitutive laws for CPRC could not be yet established

从微观角度研究了膨胀剂化学预应力钢筋混凝土(CPRC)的抗裂机理：(1)CPRC单轴试验循环加载中卸荷刚度逐渐下降，残余应变显着增大直至开裂。此外，在峰值范围高于普通RC后，CPRC具有更高的变形能力和拉伸刚化效果。(2)对不同试件尺寸的CPRC进行了一系列弯曲试验。 CPRC 的变形能力和开裂载荷在曲率变大的较小截面中较高。通过提供侧向钢筋，不仅可以提高极限荷载，而且可以提高抗剪刚度。在这种情况下，素混凝土区域变大，因此侧向剪力钢筋的效果在较大的横截面中更为显着。（3）在膨胀剂含量恒定的情况下，对CPRC进行了弯曲试验，其中配筋率不同，结果表明，抗裂性不仅随着化学预应力的增加而增加，还随着化学预应变的增加而增加。然后，还测试了CPRC在长期干燥下的抗裂性。结果发现，经过1个月的干燥后，CPRC的抗裂性与普通RC一样有所下降，但在干燥3个月后又恢复了。(4)对嵌入大体积混凝土中的变形钢筋进行了一系列拉拔试验，以检查粘结特性。膨胀混凝土与变形钢筋之间的粘结几乎与普通钢筋相同，与侧向限制程度无关此外，我们发现，当钢筋直径大于粗骨料最大尺寸时，在非常小的应力水平下，钢筋较深区域会出现非常奇怪的应变分布。由于上述CPRC行为的复杂控制机制，目前还无法建立CPRC裂缝宽度的公式和本构定律