Development of a New Environmentally Friendly Glass Fibre Reinforced Cold Mix Microasphalt with High Resistance to Cracking and Deformation.

Nowadays, the pavement industry plays an important role in the global transportation infrastructure and stimulates economic growth in both advanced and emerging countries. Nevertheless, most of these transportation infrastructures are paved with using hot mix asphalt (HMA) technology. Apropos to this, the use of cold bituminous emulsion mixtures (CBEMs) for road maintenance is increasingly gaining interest. These mixtures offer advantages in several ways: environmentally friendly, energy saving, cost effectiveness, safety and enhanced production processes. Today in the UK, the use of cold mix attracts less interest, as these mixtures show low strength to resist traffic loading due to rainfall. Microasphalt is a cold mix applied wearing course which is deemed as an important player in the maintenance of the nation’s roadways. This research was designed to investigate the cracking and deformation resistance properties of microapshalt both with and without a novel glass fibre applied. The effect of varying the length of glass fibres (aspect ratio) and varying the percentage of quantity of glass fibres (volume fraction) in the microasphalt mix was probed. The investigation was divided into three main areas of study. They were i) the physical, ii) chemical characterisation of glass fibres, aggregates, bitumen emulsion, primary & secondary filler, and iii) mechanical testing of control microasphalt, glass fibre reinforced cold mix microasphalt and green cement filler microasphalt. Chemical testing involved a regime to show the affinity between aggregates and bitumen emulsion in the presence of water. Chemical composition of glass fibres and secondary filler was also examined. Physical testing included the common tests for demonstrating the properties of glass fibres. These tests included the tensile testing and scanning electron microscopy (SEM) test. Microasphalt was chosen as a suitable road material for testing the effects of the glass fibre to retard the reflective cracking and rutting pavement distresses in a bituminous emulsion material as it is a uniformly graded stone matrix mixture and is currently enjoying increased acceptance Europe-wide as a high-quality surfacing material. Tests applied included the semi-circular bending (SCB) and wheel tracking tests. All necessary equipment was available to the researcher at Liverpool John Moores University (LJMU). Observations made during the testing programme showed that for the first time the glass fibres displayed a useful improvement in the cracking and deformation properties of microasphalt over the control microasphalt. This was also validated through mass production prototyping of glass fibre reinforced cold mix microasphalt in road trial sections. In addition, paper sludge ash (PSA), cement kiln dust (CKD) and rice husk ash (RHA) were used as a novel secondary filler to; i) replace ordinary Portland cement (OPC) currently used for replacing limestone filler and ii) improve the mechanical properties and durability of cold mix microasphalt (CMM). The blended secondary filler (PSA, CKD and RHA) played a vital role in accelerating the hydration process of the microasphalt paste and thus produced a resilient thin surfacing material. Microanalysis techniques, namely SEM and x-ray florescence (XRF), were used to investigate the role and mechanism of active fillers in CMM. The newly developed material was subjected to seasoned testing protocols and showed an achievement of 15% and 33% in the tensile strength of reinforced microasphalt at maximum load failure and ultimate failure respectively compared to the control microasphalt based on the results of the three-point bending test and an improvement of 83% in the deformation for reinforced microasphalt from the wheel track test compared to the control microasphalt. The results obtained in this research work which also covers a study using finite element modelling (FEM), appear to open up a new era of CMM and are based completely on sustainable techniques for both light and heavily trafficked road and highway pavements