Water absorption property of cracked concrete and effect of water repellent treatment

Abstract

对小尺寸钢筋混凝土梁诱导了不同宽度的裂缝,通过吸水试验研究了带裂缝混凝土的吸水性能,以及混凝土表面涂覆硅烷和内掺硅烷对水分侵入的抑制效果.结果显示,带裂缝混凝土在吸水4 h内,其吸水量与时间平方根呈良好的线性关系;混凝土吸水系数随裂缝宽度的增大而增大,且呈"S"形状;经表面防水处理的混凝土,水分以气态形式沿裂缝进入混凝土,贯穿憎水区后逐渐凝结并最终与外界建立吸水通道,防水效果取决于憎水层厚度和裂缝宽度;内掺硅烷的混凝土整体憎水,即使裂缝宽度达0.4 mm,其防水效果仍保持不变. A series of small size RC beams were introduced with different crack widths and then treated with silane-based water repellent on the surface and inside the concrete.Their water absorption properties were then evaluated.The results indicate that a linear function of square root of time could describe well the water absorption for cracked concrete within 4 h of the test,the coefficient of water absorption increases with the increase of crack width following an "S" shape.For the cracked concrete with surface water repellent treatment,water vapor diffuses into concrete along the crack depth and then devaporates behind the hydrophobic layer,and finally a water absorption pathway with the outside is established.The efficiency of water repellent treatment depends on the thickness of hydrophobic layer and the crack width.While the internal water repellent concrete is integrally hydrophobic,the efficiency of treatment is well-maintained even the crack width is increased up to 0.4 mm.