Direct shear mechanical properties and damage evolution of coral seawater sea-sand concrete after high temperature
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摘要: 为探究高温后珊瑚海水海砂混凝土(CSSC)直剪力学性能及其损伤本构关系,以经历最高温度T、恒温时长H为变化参数,设计并完成了高温后CSSC直剪试验。通过试验观察了高温后CSSC直剪破坏形态,获取了相应的应力-位移曲线,得到了T、H对CSSC剪切强度、体积膨胀及质量损失的影响规律,对比分析了高温后CSSC损伤演变过程。研究结果表明:高温导致CSSC内部出现不均匀温度场,并出现表面龟裂、边角崩裂等现象;随着T及H的增加,CSSC剪切承载力逐渐降低,体积膨胀率和质量损失率逐渐增大。当T > 400℃后剪切强度下降速率加快;T = 800℃时CSSC直剪强度仅为常温下的39%。最后,提出了高温后CSSC直剪强度计算方程及其损伤演化过程。Abstract: In order to explore the direct shear mechanical properties and constitutive relationship of coral seawater sea-sand concrete (CSSC) after high temperature, the direct shear test of CSSC after high temperature was designed and completed with maximum high temperature T and constant temperature duration H as changing parameters. The failure mode and stress-displacement curve of CSSC under direct shear were observed, and the effects of T and H on the shear strength, volume expansion and mass loss of CSSC were obtained. Then the damage evolution process of CSSC after high temperature was analyzed and compared. The results show that the high temperature leads to non-uniform temperature fields, surface cracks and corner cracks in CSSC. With the increase of T and H, the shear strength of CSSC decreases gradually while the volume expansion rate and the mass loss rate gradually increase. When T > 400℃, the decrease rate of shear strength accelerates. When T = 800℃, the direct shear strength of CSSC is only 39% of that at room temperature. Finally, the direct shear strength calculation equation of CSSC after high temperature and its damage constitutive model are proposed.
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表 1 珊瑚粗骨料(CA)物理性能
Table 1. Physical properties of coral coarse aggregate (CA)
Property Water absorption/% Moisture content/% Bulk density/(kg·m−3) Apparent density/(kg·m−3) Value 12.79 0.67 879.90 1667.00 表 2 珊瑚海水海砂混凝土(CSSC)试验设计及其抗压强度
Table 2. Test design and compressive strength of coral seawater sea-sand concrete (CSSC)
Number T/℃ H/h fcu T/MPa T25 25 — 30.43 T200-H1 200 1 27.08 T300-H1 300 1 26.66 T400-H1 400 1 22.38 T400-H2 400 2 23.94 T400-H3 400 3 22.12 T500-H1 500 1 19.57 T700-H1 700 1 10.47 T600-H1 600 1 14.38 T800-H1 800 1 8.93 Notes: fcu T—Cubic compressive strength of CSSC after high temperature; T—High temperature; H—Constant high temperature duration. 表 3 CSSC的配合比
Table 3. Mix ratio of CSSC
kg·m−3 W/C Coral Sea-sand Cement Seawater Additional seawater Water reducing 0.4 655.8 760.1 535.0 214.0 75.1 1.4 Note: W/C—Water-cement ratio of CSSC. 表 4 高温后CSSC直剪强度数据对照
Table 4. Comparison of CSSC direct shear strength data after high temperatures
T/℃ fcu T/MPa τ1/MPa τ2/MPa τ3/MPa τA/MPa Standard deviation Variance Coefficient of variation τ Τ/MPa τA/τ Τ 200 27.08 3.66 2.94 3.13 3.24 0.37 0.14 0.12 3.27 0.99 300 26.66 2.69 2.96 3.23 2.96 0.27 0.07 0.09 3.12 0.95 400 22.38 2.99 2.47 2.74 2.73 0.26 0.07 0.10 2.84 0.96 500 19.57 2.12 1.71 2.52 2.12 0.41 0.16 0.19 2.38 0.89 600 14.38 1.65 1.49 1.78 1.64 0.15 0.02 0.09 1.83 0.90 700 10.47 1.51 1.08 1.48 1.36 0.24 0.06 0.18 1.32 1.03 800 8.93 1.03 1.13 — 1.08 0.07 0.01 0.07 0.92 1.17 Notes: τ1, τ2, τ3 —Shear test values of CSSC after high temperature; τA—Mean shear test value of CSSC after high temperature; τ Τ—Mean shear theory value of CSSC after high temperature. -
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