Experimental Study On Tensile Properties Of Fiber Reinforced Cementitious Composites Under The Condition Of High Fiber Volume Fraction

In this thesis, an experimental investigation was conducted under the condition of high fiber volume fraction to study the influences of different types of fiber on compressive properties, flexural properties and tensile properties of high performance fiber reinforced cementitious composites (HPFRCC). In tensile research, various factors were taken into account such as water-cement ratio, fiber volume fraction, fiber types, age and admixtures. The fiber types concerned include:aramid fiber (Aramid), two kinds of polypropylene fibers (PP) and three kinds of polyvinyl alcohol fibers (PVA).The experiment results showed that:The flexural strength, compressive strength and tensile strength of HPFRCC decrease with the increase of water-cement ratio. Fibers could improve the flexural strength of HPFRCC, but reduce the compressive strength.Compared with the control groups, with the increase of water-cement ratio, aramid fiber exerts a more and more dramatic influence on the increase of flexural strength and the decrease of compressive strength of HPFRCC; W-PVA fiber of HPFRCC compressive strength weakening was more obvious. S-PVA fiber of HPFRCC flexural strength enhancement and compressive strength weakening were more obvious. Kuraray PVA fiber of HPFRCC compressive strength weakening was more obvious.Without mineral admixtures in the matrix, the tensile strength of HPFRCC decreases with age increasing. If mineral admixtures are used in the matrix, the tensile strength of HPFRCC increases with age increasing.If Kuraray PVA fiber is used in the matrix, higher fiber volume faction results in higher flexural strength and lower compressive strength. When water-cement ratio is0.27, higher fiber volume faction results in worse tensile properties. When water-cement ratios are0.36and0.45, higher fiber volume faction results in better tensile properties.Influence of PP#fiber diameter on the increase of compressive strength and flexural strength of HPFRCC is not obvious. When the fiber volume faction increases from2.8%to3.1%, the flexural strength of HPFRCC is increased. When fiber volume faction was2.8%, there was no obvious difference between the flexural strength of experimental groups and that of control groups.When aramid fiber, S-PVA fiber, Kuraray PVA fiber or PP$is used in the matrix, strain hardening and multiple cracking phenomena were observed in uniaxial tensile tests. When W-PVA fiber or PP#fiber is used in the matrix, strain hardening phenomenon was observed but multiple cracking phenomenon did not appear.When aramid fiber, S-PVA fiber or Kuraray PVA fiber is used in the matrix, specimens were saturated with cracks, whose widths were less than100μm. HPFRCC exhibits self-controlled crack widths under increasing load. When PP$fiber is used in the matrix, the number of cracks were very few, crack widths were greater than200μm and the tensile deformation was greater than3mm.