Performance Evaluation of Cold Bituminous Mix Reinforced with Coir Fibre

Cold bituminous mix (CBM), which is a mixture of bitumen emulsion and aggregate that is mixed together at ambient temperature, has several advantages like energy savings, easiness in preparation, environmental benefits, and high production at low investment. But there are certain limitations of CBMs like inferior mechanical properties, high air voids, weak early life strength, long curing time and poor coating that hinder its extensive usage. The possibility of improving mechanical performance of CBMs by the addition of coir fibre is attempted in this study. The objectives of the study are to assess the improvement in performance of CBM due to addition of coir fibre and to identify the optimum length and optimum content of coir fibre for CBMs. Three coir fibre contents and three coir fibre lengths were used in this study. Performance evaluation of CBM modified with coir fibre was done through Retained Marshall Stability (RMS) test and Hamburg wheel tracking test. Coir fibre was added to the aggregates and mixed before the addition of pre-wetting water and emulsion, to achieve uniform distribution and to avoid balling of coir fibres. When coir fibre was added to the mix, Marshall Stability increased up to a certain level of coir fibre content depending on fibre length. Highest Marshall Stability value was obtained at 0.2% content (by weight of total mix) of coir fibre of 15 mm length. Resistance to moisture damage was assessed by RMS test. It was observed that the addition of coir fibre improved the RMS value. From the Hamburg wheel tracking test, it was observed that the addition of coir fibre improved rut resistance. For all fibre lengths, CBM with 0.2 % coir content showed the highest rut resistance, with 10 mm fibre length showed the best performance. Hence, coir fibre is recommended as a feasible additive for mechanical performance improvement of CBMs.

Evaluation of polyaminoamide as a surfactant additive in hot mix asphalt

The phenomenon of breaking the bond between the aggregates and the bitumen is known as stripping. Strip-ping of asphalt films from the surface of aggregate particles results in premature failure of asphalt pavement. This causes weakening of pavement resistance to rutting and fatigue. Furthermore, moisture damage increases the susceptibility of pavement to reveling, a distress that causes the loss of skid resistance on surface of the road and deterioration of pavement. Surfactant additive or adhesive agent is a surface-active agent that changes (lowers) the surface tension of rock materials. Introduction of surfactant additive results in increased strength of adhesive bond between bitumen and the rock materials surface preventing stripping throughout the service life of the asphalt concrete. Polyaminoamide is an organic water soluble compound that allows waterproofing mineral aggregate surfaces and acts as a bonding agent to bitumen. The objective of this research is to study the effect of polyaminoamide based and pholiphosphoric acid based liquid additives on stripping, moisture susceptibility, rutting and fatigue performance of asphalt concrete. In this paper, boiling water test was used to determine the percentage of stripped aggregates after boiling. The moisture susceptibility of asphalt mixtures was investigated by means of testing the retained indirect tensile strength after water immersion using Marshal stability test method. Wheel tracking test was also conducted on asphalt slabs prepared in the laboratory to determine rut resistance. Asphalt concrete with commonly used mineral filler was chosen as a control mixture. It was found that the adhesion additive not only improves stripping resistance, but also slightly improves asphalt rut resistance.

Effect of Mineral Powder on Performance of Unaged and Aged Asphalt Mortar

In order to analyze the effect of mineral powder on the high-temperature rut resistance and fatigue cracking resistance performance of unaged,short-term and long-term aged asphalt mortar, Dynamic Shear Rheometer (DSR) was used to study different powder/bitumen ratio of asphalt mortar. The results indicate that increasing mineral powder content can improve high-temperature rut resistance performance of asphalt mortar, but decrease its fatigue cracking resistance performance. As the experiment temperature rises, high-temperature rut resistance performance of different asphalt mortar will decrease, on the contrary, rising fatigue cracking resistance performance.

Evaluation of Rut Resistance of Polymer-Modified Asphalt Concretes

The rutting is a significant damage mechanism showing longitudinal furrows along with both wheel paths on asphalt pavement surface. To prevent the rutting under heavy traffic condition, polymer-modified asphalt (PMA) concretes were introduced in asphalt pavement industry. To measure rut resistance of asphalt concretes, the asphalt pavement analyzer (APA) and the deformation strength, SD, were used in this study. The SD was measured by Kim Test, a simple static-loading test, on the 150 mm-diameter cylindrical specimens at 60oC and APA test was performed for the same material. The PMA concretes were found to show improvement in SD and APA rut resistance by more than 50% and 60%, respectively. The SD and APA rut depth showed a relatively high correlation (R2 = 0.81) each other at 60°C. Therefore, it was possible to estimate rut tendency of normal asphalt and polymer-modified asphalt concretes by SD.