Strain hardening behavior of lightweight hybrid polyvinyl alcohol (PVA) fiber reinforced cement composites

Experimental results on the strain hardening and multiple cracking behaviors of polyvinyl alcohol (PVA) fiber reinforced cementitious composites under bending are reported in this paper. Different hybrid combinations of PVA fibers with different lengths and volume fractions are considered to reinforce the mortar matrix. Among different hybrid combinations, the composite containing 2% thicker PVA fibers of 12 mm length and 1% thinner PVA fibers of 6 mm length and the composite containing 2% thicker PVA fibers of 24 mm length and 1% thinner PVA fibers of 6 mm length showed the best performance in terms of highest ultimate load, largest CMOD (crack mouth opening displacement) at peak load and multiple cracking behavior. The effects of four types of light weight sands on the strain hardening and multiple cracking behavior of hybrid fiber composites are also evaluated in this study. It has been observed that the ultimate load and CMOD at peak load for all light weight hybrid fiber composites are almost the same irrespective of volume fractions of light weight sand. The composites containing finer light weight sands exhibited higher ultimate load than those containing coarser light weight sands. It is also observed that the hybrid fiber composite containing normal silica sand exhibited higher ultimate load than the composites with light weight sands

Thermal and mechanical properties of hemp fabric-reinforced nanoclay-cement nano-composites

The influence of nanoclay on thermal and mechanical properties of hemp fabric-reinforced cement composite is presented in this paper. Results indicate that these properties are improved as a result of nanoclay addition. An optimum replacement of ordinary Portland cement with 1 wt% nanoclay is observed through improved thermal stability, reduced porosity and water absorption as well as increased density, flexural strength, fracture toughness and impact strength of hemp fabric-reinforced nanocomposite. The microstructural analyses indicate that the nanoclay behaves not only as a filler to improve the microstructure but also as an activator to promote the pozzolanic reaction and thus improve the adhesion between hemp fabric and nanomatrix

Strain hardening behaviour of polyethylene fibre reinforced ambient air cured geopolymer composite

This paper presents experimental investigation on strain hardening and deflection hardening behaviour of polyethylene (PE) fibre reinforced ambient air cured geopolymer composite. Comparison is also made with its counterpart ordinary Portland cement (OPC) based composite. The effect of different volume fractions of PE fibre on compressive strength, strain hardening and deflection hardening behaviour of above two composites is evaluated and a critical volume fraction of PE fibre for strain hardening and multiple cracking behaviour is identified. Results show that ambient air cured geopolymer composites exhibited better strain hardening, deflection hardening and multiple cracking behaviour than its counterpart OPC based composite containing same volume fraction of PE fibre. Compressive strength of OPC composite is higher than that of geopolymer composite. PF fibre volume fraction of 0.75–1.0% exhibited optimum fibre content for strain and deflection hardening behaviour of both composites

Ductile fibre reinforced cementitious composites (DFRCC) for improved corrosion durability of reinforced concrete columns

This paper reports the results of an experimental program on the effectiveness of ductile fibre reinforced cementitious composites (DFRCC) in retarding the corrosion of steel, corrosion induced damage and post-corrosion structural behaviour of reinforced concrete (RC) columns. Two series RC columns are included in this program. The first series consists of ordinary RC columns that are subjected to an accelerated corrosion regime. The second series consists of two columns that are similar to first two series in every aspect, except that the ordinary concrete in the column is replaced with a ductile DFRCC material. Two types of DFRCC materials are considered: a hybrid-fibre DFRCC containing 1.5 vol.% PVA fibers and 1 vol.% steel fibers and a mono-fibre DFRCC containing 2.5 vol.% PVA fibers. Specimens of the second series are also subjected to a regime of accelerated corrosion. Corrosion damage, including the possible development of spalling and/or delamination, is monitored in each specimen using a specially-fabricated mechanical expansion collar. Based on the collective findings from theoretically-estimated steel losses, visual recordings of corrosion damage, and measurements of the tendency of cover delaminate, it was concluded that the steel reinforced DFRCC columns had a remarkably higher resistance against reinforcement corrosion compared to the ordinary RC columns. The corrosion damaged DFRCC columns also exhibited about 23-64% higher failure load than that of corrosion damaged RC columns and no sign of spalling of cover of columns in the structural test

Effect of Cracking on Corrosion of Steel in Concrete

© 2018, The Author(s). It is generally recognized that cracks provide easy access to ingress of chlorides in concrete and hence, the initiation of corrosion of steel in cracked concrete occurs at early stage. However, wide variety of results on the effect of crack widths on corrosion of steel in concrete are reported in many studies. Apart from crack width, the crack depths, cracking frequency and healing of cracks also influence the corrosion of steel in concrete. This paper presents a comprehensive review and summarised the results on the effect of cracking on corrosion of steel in concrete. The effect of crack widths on the diffusion of chlorides ions and carbon-dioxide is also discussed in this paper. Among all available results, a correlation between the corrosion current and the crack widths up to 0.3 mm can be established, however, no distinct trends are observed beyond that crack width. Conflicting results on the effect of crack widths on chloride ion diffusion are also reported. The longitudinal crack causes more severe corrosion of steel in concrete than transverse cracks of same width. Cracked concrete containing supplementary cementitious materials exhibited superior corrosion resistance than cracked ordinary Portland cement concrete of same width of transverse as well as longitudinal cracks. The same is also true in the case of lower water–binder ratios of cracked concrete. The increase in crack depth increased the chloride diffusion; however, the corrosion test shows an opposite trend. Conflicting results on the effect of crack frequency on corrosion of steel are also reported