海水珊瑚砂ECC的力学性能与裂纹宽度控制

Mechanical properties and crack width control of seawater coral sand ECC

  • 摘要: 为解决珊瑚混凝土的脆性与耐久性问题,采用岛礁地域性原材料制备了海水珊瑚砂高延性水泥基材料(Seawater coral sand engineered cementitious composites,SCECC)。试验研究了不同骨料种类、最大粒径和细度模数对ECC抗压、抗拉力学性能和裂缝控制能力的影响。结果表明:随珊瑚砂细度模数减小,SCECC抗压强度先增后降,最大粒径2.36 mm的特细砂SCECC达到最高(63.3 MPa);降低珊瑚砂最大粒径,SCECC拉伸性能参数不同程度地提升。最大粒径0.60 mm的SCECC拉伸性能最优,其初裂强度、抗拉强度和极限拉应变分别为2.29 MPa、4.11 MPa和5.15%,临近破坏时的平均裂纹宽度可控制在81 μm。相比于淡水石英砂ECC,SCECC抗压强度高且早期强度发展快(7天抗压强度可达28天的73%~78%)。两种ECC的骨料破坏和聚乙烯醇(PVA)纤维失效模式不同,SCECC拉伸强度、弹性模量及峰值应变附近的裂纹控制能力略低,但延性明显更优。

     

    Abstract: In order to address the brittleness and durability issues of coral aggregate concrete, seawater coral sand engineered cementitious composites (SCECC) was prepared by using the regional raw materials located in islands and reefs. The effects of different aggregate types, maximum grain size and fineness modulus on the compressive, tensile properties and crack control ability of ECC were experimentally investigated. The results show that with the decrease of the fineness modulus of coral sand, the compressive strength of SCECC first increases and then decreases, which maximizes (63.3 MPa) at SCECC with the maximum grain size of 2.36 mm. Reducing the maximum grain size of coral sand results in improved tensile performance to varying extents. SCECC with a maximum grain size of 0.60 mm exhibits the best tensile properties, and its initial cracking strength, tensile strength and ultimate tensile strain are 2.29 MPa, 4.11 MPa and 5.15%, respectively. Meanwhile, its average crack width approaching strain capacity is controlled at 81 μm. Compared with tap water-quartz sand ECC, SCECC possesses higher compressive strength and more rapid development of early strength (its 7 days compressive strength can arrive at 73%-78% of 28 days compressive strength). The failure modes of aggregate and polyvinyl alcohol (PVA) fiber in these two ECCs are different, resulting in slightly lower tensile strength, elastic modulus and crack control ability at peak strain, but significantly enhanced tensile ductility of SCECC.

     

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