Amin Noushini

Drying Shrinkage Behaviour of Fibre Reinforced Concrete Incorporating Polyvinyl Alcohol Fibres and Fly Ash

The current study assesses the drying shrinkage behaviour of polyvinyl alcohol fibre reinforced concrete (PVA-FRC) containing short-length (6 mm) and long-length (12 mm) uncoated monofilament PVA fibres at 0.125%, 0.25%, 0.375%, and 0.5% volumetric fractions. Fly ash is also used as a partial replacement of Portland cement in all mixes. PVA-FRC mixes have been compared to length change of control concrete (devoid of fibres) at 3 storage intervals: early-age (0–7 days), short-term (0–28 days), and long-term (28–112 days) intervals. The shrinkage results of FRC and control concrete up to 112 days indicated that all PVA-FRC mixes exhibited higher drying shrinkage than control. The shrinkage exhibited by PVA-FRC mixes ranged from 449 to 480 microstrain, where this value was only 427 microstrain in the case of control. In addition, the longer fibres exhibited higher mass loss, thus potentially contributing to higher shrinkage.

Detecting the Presence of Chloride in Hardened Mortar Using Microwave Non-Destructive Testing

Concrete durability is to a large extent governed by the concrete resistance to the penetration of aggressive substances. One such aggressive substances, present predominantly in marine or coastal environments, is the chloride ion. Chloride in presence of water and oxygen cause corrosion and the measurement of chloride content is an important factor in the detection of early corrosion damage induced by chloride attack. However, there is currently a lack of a reliable nondestructive method to examine the chloride content of the structure in practice. This paper presents the results of an experimental study to investigate the viability of Microwave Non-Destructive Testing (MNDT) to monitor the ingress of the chloride into the concrete. The variations in the electromagnetic properties of mortar specimens with variations in their chloride contents are measured to identify correlations between chloride content and two main electromagnetic properties of mortar; viz. dielectric constant and loss factor. EMPs are measured through two-port measurement performed using a vector network analyzer and S-band rectangular waveguide. The existence of correlations between chloride content of mortar and its electromagnetic properties is confirmed by the preliminary results, highlighting the potential for development of an MNDT technique to monitor the chloride content of concrete in practice.

Ductility and Damping Characteristics of PVA-FRC Beam Elements

The structural behaviour of reinforced concrete beams incorporating polyvinyl alcohol (PVA) fibres is investigated in this study. A total of 10 reinforced concrete beams have been tested in order to investigate how the structural characteristics (i.e. ductility, energy dissipation capacity and damping ratio) of concrete beam elements are affected by addition of a certain amount of PVA fibres into the concrete. The structural properties and behaviour of PVA-FRC beams were assessed under the action of both monotonic and cyclic loads. Four-point static flexural, three-point cyclic and impact resonant frequency tests were conducted on PVA-FRC beams and results of which are compared with conventional reinforced concrete (RC) beams. Experimental results show that PVA fibre addition to the mix, generally, improves the ductility and damping ratio of the elements. Furthermore, PVA-FRC beams showed higher stiffness degradation rate and higher capacity to maintain their stiffness during the test.

Rheological properties and compressive strength behaviour of polyvinyl alcohol fibre-reinforced concrete

AbstractComprehensive experiments were carried out to assess the effects of uncoated polyvinyl alcohol (PVA) fibres of two geometric lengths (6 and 12 mm) on the fresh and hardened properties of concrete. Fly-ash was also used as partial replacement of Portland cement in all mixes. Based on total concrete volume, four fibre fractions of 0.125%, 0.25%, 0.375% and 0.5% were evaluated for their effect on slump, compacting factor, air content, mass per unit volume, compressive strength, relative strength with age and mode of failure in PVAfibre-reinforced concretes (FRCs). PVA fibres were observed to decrease the slump and mass per unit volume of FRC, while increasing the compressive strength up to 56 days ageing. With regards to workability and compressive strength, optimum fibre addition was establishedfor 0.25% PVA-FRC incorporating 6 mmfibres with a 12% increase noted in compressive strength compared to the control concrete at 28 days ageing.