CRACK TREATMENT OF THE ASPHALT BINDER COURSE

 

Main Break Water(MBW) access road occurs several cracks on the asphalt binder course. The road cracks are monitored and investigated with specialist from RDA Research & Development. This report describes the reason and remedial method of the cracks based on the investigation and consultation.

MBW access road structure consists of fallowing cross section and the core samples have been taken on the cracks.

According to core sample data, can be observed that the crack was started from CBM and reflected to the binder course surface. CRACK INVESTIGATION The crack survey carried out for the entire road and investigation detail summarized as an attached sheet. Core samples were taken from the jointly selected locations with the engineer. MBW access road cracks were categorized into two types based on crack surface appearance. Transverse cracks Longitudinal cracks Transverse cracks Transverse cracks were occurred as a perpendicular to the road center line. These cracks are reflecting from the CBM layers. According to core sample data, can be identified the fallowing crack types was happened. Some of cracks were occurred from CBM 2st layer and reflected to the binder course surface. Other cracks are started from CBM bottom layer (1st layer) and reflected to the binder course. Longitudinal cracks Longitudinal cracks were occurred as a parallel to the road centerline and which was happened due to the reflection of the CBM longitudinal joint. PROPOSAL FOR REPAIR OF CRACK Proposal of the crack repairing method is introduced by specialist from RDA Research & Development. Three conditions for reflection cracks on CBM : Cracks in the base layer must be wide enough to generate stress conditions in the asphalt surface. There is no method available to relieve the stress concentrations. The asphalt is brittle enough to crack due to upwards propagation of the stress concentration. In most cases, reflection cracks are narrow (less than 3mm) and will not adversely affect the performance of the pavement. But all the cracks on MBW access road will be treated to prevent from the possibility of propagation. As per the specialist’s proposal, Geo-Fabric material will be applied along the cracks of the binder course before laying the wearing course in accordance with manufacturer’s instructions. CRACK REPAIRING Proposed Material Polyfelt (PGM-G 50/50) to be used, material details is in Appendix Manpower Supervisor Skilled Labours Unskilled Labours Sequence Methodology Identify the crack locations and properly cleaning by air compressor. Bring the notification to the site representative of the Engineer. The binder surface is thoroughly cleaned and free from all the traces of dust and any of unsound materials. Cut the Ploy paving Fabric (PGM 50/50) for required length of the crack and 0.5m offset from the crack as following the sketch.

Apply the tack coat on the dry surface of the binder course. More details are attached the appendix document.

Install the Polyfelt PGM 50/50 and tensioning of the paving fabrics to prevent wrinkles.

Immediately after PGM installation and apply the second tack coat for asphalt wearing course.

Laying the asphalt wearing course.