STUDY THE STRIPPING AND STABILITY OF AGGREGATE (KEY IJP************492)

• Sidhant Kumar,Pardeep

Abstract

The stripping value of aggregate is defined as the ratio of uncovered area observed visually to the total area of aggregates, expressed as percentage. Proper adhesion between aggregate and bitumen is one of the principal fundamental properties for good performance of bituminous pavement. This adhesion can be reduced by presence of water which may be caused by de-bonding of bitumen from aggregate. The phenomenon is known as 'stripping". Bituminous roads are greatly susceptible to moisture damage. Nowadays proper drainage facilities are lacking on the roads which is one of the main reasons for road damage due to stripping. Adequate drainage must be provided for prevention of damage of roads due to stripping as complete failure of the pavement can take place.Stripping is a complex problem comprising many variables, including the type and use of mix, aggregate and bitumen characteristics, environment, traffic, construction practice and use of anti-stripping additives.Contact of water with bituminous pavement is one of the main factors for stripping. The moisture affects physical properties and mechanical behavior of bitumen paving mixtures as aggregates that have a dry surface adhere better to bitumen and have a higher stripping resistance than wet aggregate. The water can be in the form of ground water, surface water or rain water. Presence of water on the road, if not properly managed, may cause deterioration of road more rapidly as it reduce the potency of bond between bitumen and aggregate which provides strength to the mix and ultimately leads to failure of pavement. For prevention of such damage, adequate drainage must be provided.The physical and chemical characteristics of aggregates have a significant effect on the bonding between aggregate and bitumen. In addition, aggregate surface texture. aggregate porosity and pore pressure are also known to affect stripping. A deficiency in properties of aggregates reduced the strength of bond and leads bitumen-aggregate mixture towards stripping. Stripping may further cause rutting, raveling, bleeding, cracking and formation of potholes and culminate with complete failure of pavement.Hence, to prevent pavement from these failure, we need to thoroughly investigate various factors which affect the stripping of aggregates. This study presents various influencing factors, their effect and possible remedies to the problem. The stability test provides the performance prediction measure for the Marshall Mix design method. The stability portion of the test measure the maximum load supported by the test specimen. Load is applied to the specimen till failure, and maximum load is designed as stability.The indirect tensile strength test is used to determine the tensile properties of bituminous mixture which can be further related to the cracking properties of the pavement. Low temperature cracking, fatigue and rutting are three distress mechanisms. The resistance of bituminous mixture to fatigue cracking is depending upon its tensile properties, notably its tensile strength and extensibility characteristics. The layers of flexible pavement structure are subjected to continuous flexing as a result of the traffic loads that they carry. resulting in tensile stresses and strains at the bottom of the bituminous layers of the pavements. The magnitude of strain is dependent on the overall stiffness of the pavement. Indirect tensile strength test is an indicator of strength and adherence against fatigue, temperature cracking and rutting.