Dynamic Tensile Properties of Ultra-High Ductile Concrete Under Different Strain Rates
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摘要:
超高延性混凝土具有优异的应变硬化和多裂缝开裂特性,在抵抗冲击荷载等方面具有巨大的应用潜力. 为研究超高延性混凝土(UHDC)拉伸性能的应变率效应,在从准静态到冲击状态范围内的11种应变率(
0.0001 ~189.0700 s−1)条件下进行直接拉伸试验,分析应变率对UHDC拉伸应力-应变曲线形态、裂缝开裂模式以及拉伸性能指标的影响,进一步建立拉伸性能指标动态增长因子关于应变率的表达式;此外,分析拉伸速率对纤维-基体界面黏结性能的影响,从而进一步解释UHDC拉伸性能的应变率效应. 结果表明,UHDC变形能力随应变率的增加呈下降趋势,但在应变率达到102.0000 s−1时,依然具有显著的应变硬化和多缝开裂能力,拉伸应变可达4%;平均裂缝宽度基本不随应变率变化,保持在100 μm左右,显示出UHDC优异的裂缝控制能力;拉伸性能指标动态增长因子与应变率的关系曲线呈现明显的两阶段特性.Abstract:Ultra-high ductile concrete (UHDC) has excellent strain hardening and multi-cracking characteristics, and it has great potential in impact load resistance. Direct tensile tests were conducted under 11 strain rates (0.000 1–
189.0700 s−1) ranging from quasi-static to impact states to investigate the strain rate effect on the tensile properties of UHDC. The influence of strain rate on the shape of the tensile stress–strain curves, cracking pattern, and tensile performance indicators of UHDC was analyzed. The expression of the dynamic increase factor of tensile performance indicators regarding strain rate was established. In addition, the influence of the tensile rate on the fiber–matrix interface bonding performance was analyzed to further explain the strain rate effect on the tensile properties of UHDC. The results show that the deformation capacity of UHDC decreases with the increase in strain rate. When the strain rate is 102.000 0 s−1, UHDC still has significant strain hardening and multi-cracking pattern capacity, with the tensile strain capacity up to 4%. The average crack width, which keeps a constant value of 100 μm, does not vary with the strain rate change, exhibiting the excellent crack control capacity of UHDC. The relationship curves between the dynamic increase factor of the tensile performance indicators and strain rate show a clear two-stage characteristic. -
表 1 UHDC配合比
Table 1. Mix proportion of UHDC
材料 水泥 粉煤灰 石英砂 水 外加剂 纤维 配合比 936.7 401.4 401.4 360.1 4.2 19.4 表 2 PE纤维的性能参数
Table 2. Performance parameters of PE fibers
参数 长度/
mm直径/
μm抗拉强度/
MPa弹性模量/
GPa延伸率/
%密度/
(g•cm−3)取值 24 25 2900 116 2.42 0.97 表 3 不同应变率下拉伸试件的裂缝信息
Table 3. Crack information of tensile specimens under different strain rates
应变率/s−1 Nc/条 wc/μm sc/mm 0.0001 89 104.6 0.90 0.0010 76 104.8 1.06 0.0100 70 103.0 1.14 0.0500 69 96.9 1.15 0.1000 67 92.8 1.28 1.2500 66 108.0 1.21 13.2000 63 103.3 1.26 58.5600 44 102.4 1.83 102.1400 36 98.0 2.22 123.9100 32 93.9 2.52 189.0700 24 93.7 3.33 表 4 UHDC各应变率下的拉伸参数
Table 4. Tensile parameters of UHDC at various strain rates
应变率/s−1 σtc/MPa σtu/MPa εtu/% gse/ (kJ•m−3) Et/GPa 0.0001 2.74 (0.66) 5.70 (0.29) 11.68 (0.66) 531.5 (46.28) 15.75 (2.75) 0.0010 3.04 (0.64) 6.50 (0.27) 9.93 (1.81) 451.9 (73.97) 16.06 (3.09) 0.0100 3.43 (0.90) 6.60 (0.28) 9.02 (1.44) 448.5 (55.33) 14.72 (1.87) 0.0500 3.91 (0.78) 7.80 (0.52) 8.28 (0.50) 492.1 (53.77) 19.75 (0.56) 0.1000 4.03 (0.26) 8.06 (0.74) 7.84 (1.00) 534.4 (110.69) 18.70 (5.49) 1.2500 4.20 (1.75) 8.41 (1.14) 7.79 (1.97) 417.6 (195.01) — 13.2000 5.09 (1.27) 9.77 (0.71) 6.79 (0.52) 425.3 (211.58) — 58.5600 6.65 (0.63) 10.10 (0.96) 4.41 (0.75) 289.4 (58.68) — 102.1400 6.21 (0.83) 11.65 (0.24) 3.94 (1.37) 107.8 (85.24) — 123.9100 7.43 (1.21) 12.88 (1.04) 2.38 (1.15) 154.6 (93.6) — 189.0700 8.01 (1.26) 15.07 (0.48) 1.31 (0.39) 112.9 (98.60) — 注:括号内数值为相应的标准差. 表 5 各类ECC拉伸参数的对比
Table 5. Comparison of various ECC tensile parameters
文献 峰值应
力/MPa峰值应
变/%应变能/
(kJ•m−3)应变率/
s−1ECC
类型文献[9] 5.5 0.80 45.2 0.0100 PVA-ECC 文献 [14] 8.6 0.80 68.8 0.1000 PVA-ECC 文献[15] 17.5 3.00 525.0 0.1000 PE-ECC 文献[18] 3.5 4.00 140.0 0.1000 PVA-ECC 文献[17] 5.5 3.90 217.9 0.0100 PVA-ECC 文献[24] 5.9 3.80 224.2 0.1000 PVA-ECC 文献[24] 4.2 3.20 134.4 0.1000 PE-ECC 本文 6.6 9.02 448.5 0.0100 UHDC 8.1 7.80 534.4 0.1000 10.1 4.40 289.4 58.5600 表 6 UHDC各应变率下的动态增长因子
Table 6. Dynamic increase factors of UHDC at various strain rates
应变率/s−1 ftc ftu fε fE 0.0001 1.00 1.00 1.00 1.00 0.0010 1.11 1.14 0.85 1.02 0.0100 1.25 1.16 0.77 0.93 0.0500 1.43 1.37 0.71 1.25 0.1000 1.47 1.41 0.67 1.19 1.2500 1.53 1.48 0.67 13.2000 1.86 1.71 0.58 58.5600 2.43 1.77 0.38 102.1400 2.27 2.04 0.34 123.9100 2.71 2.26 0.20 189.0700 2.92 2.64 0.11 表 7 单纤维拔出试验结果
Table 7. Single fiber pull-out test results
加载速率/
(mm•min−1)脱黏位移/
mm脱黏力/
N峰值位移/
mm峰值力/
N5 0.095 0.390 0.382 0.469 50 0.116 0.409 0.505 0.488 200 0.524 0.522 500 0.871 0.527 -
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