Polyamide Fiber Reinforced Shotcrete for Tunnel Application

2018

This research aims to examine the impact of using natural and synthetic fibres as reinforcing materials, on the mechanical properties and water susceptibility of cold mix asphalt (CMA) including indirect tensile stiffness and resistance to rutting, cracking and moisture damage. Four different types of fibres were used: glass as a synthetic fibre, and hemp, jute and coir as natural fibres. Various samples of CMA, with and without fibres, were fabricated and tested. Traditional hot mix asphalt (HMA) was also used for comparison. The results indicate a significant improvement in the indirect tensile stiffness modulus, for all fibre-reinforced CMA mixtures, over different curing times. The improved tensile behaviour represents a substantial contribution towards slowing crack propagation in bituminous mixtures, while scanning electron microscopy analysis confirmed the fibre shape and surface roughness characteristics. The improved performance of the reinforced mixtures with both natural and synthetic fibres, facilitated a substantially lower permanent deformation than traditional hot and cold mixtures at two different temperatures (45 and 60°C). When using glass and hemp fibres as reinforcing materials, there was 2 a significant improvement in CMA in terms of water sensitivity. Resistance to surface cracking was also improved when fibres were incorporated. Based on the test results, 0.35% fibre content by mass of dry aggregate and 14mm fibre length are recommended to achieve the optimum performance output for indirect tensile stiffness.

Section: Itsmsupporting

confidence: 89%

A laboratory study of high-performance cold mix asphalt mixtures reinforced with natural and synthetic fibres

2018

“…According to Liu, et al [38], short fibres (10 mm) cannot properly reinforce mixtures that have a larger size of aggregate (maximum 14 mm) while long fibres (longer than the maximum size of the aggregate) can lead to loss in mixture strength because these fibres tend to lump together during the mixing process. The results found here were similar to those found in the literature [39]. Because of the use of an appropriate length of fibre (14 mm in this research), the placement and distribution of this fibre in the bituminous mixture, produced enhanced interlocking between the fibre and the paste, hence the lateral strain was delayed and the mixture strength improved [40].…”

Section: Fibres Optimisationsupporting

confidence: 89%

Predicting the rutting behaviour of natural fibre-reinforced cold mix asphalt using the finite element method

2018

This paper describes the development of a three-dimensional (3-D), finite element model (FEM) of flexible pavements made with cold mix asphalt (CMA), which has itself been reinforced with two different natural fibres: jute and coir. A 3-D finite element model was employed to predict the viscoelastic response of flexible CMA pavements when subjected to multiple axle loads, different bituminous material properties, tire speeds and temperatures. The analysis was conducted by the finite element computer package ABAQUS/STANDARD. The pavements were subject to cyclic and static loading conditions to test for permanent deformation (rutting). The accuracy of the developed model was validated by comparing the predicted results with those measured in the lab. Reinforced and unreinforced CMA mixture models were simulated in this research. The results indicate that the CMA mixtures reinforced with natural fibres, are effective in mitigating permanent deformation (rutting). These reinforcing materials can extend the service life of flexible pavements.

“…Short fibres perform as an expensive filler, while lone fibres tend to lump together leading to cause balling during the mixing process. This is in agreement with other studies for instance, work by Jeon, et al[50]. The appropriate fibres length and content provide best placement and distribution into the bituminous mixtures resulting improved interlock between the mixture and fibres[68].…”

supporting

confidence: 93%

A viscoplastic model for permanent deformation prediction of reinforced cold mix asphalt

2018

A reliable viscoplastic model of natural and synthetic fibres reinforced cold bitumen emulsion mixture is developed and applied to characterize the rutting behaviour of asphalt pavement by using finite element analysis. It is indicated that the traffic load parameters such as temperature, static loading condition and vehicular speed not only affects the rutting depth, it accelerates the rutting rate, causing the pavement earlier enter into rutting failure with shortened service life. Several finite element models (FEM) have been developed to simulate the behaviour of hot mix asphalts (HMAs), but none exists for cold mix asphalt (CMA) reinforced by natural and synthetic fibres. This research presents the first three dimension (3-D), finite element model (FEM) to assess the viscoplastic behaviour of reinforced CMA mixtures. The model is also able to predict rutting (permanent deformation) of asphalt mixtures under different traffic and environmental loadings, traditional HMA used as a comparison. The enhancement of the performance of CMA mixtures against permanent deformation using finite element software (ABAQUS) was validated by comparing the models' predictions with measurements from wheel-tracking tests at different temperatures (45°C and 60°C). A very good level of agreement 2 was found between the rutting predicted by the model and the experimental test. The results show that the finite element model can successfully predict rutting of flexible pavements under different temperatures and wheel loading conditions. Finally, the natural and synthetic fibres reinforced CMA mixtures are much more effective at resisting permanent deformation damage than conventional cold and hot asphalt mixtures.