PERFORMANCE EVALUATION OF BITUMINOUS CONCRETE WITH DIFFERENT FILLERS

Abstract

First step in the design of a bituminous concrete mix is the selection of the appropriate materials and proper mix design. Materials normally required for the paving mix are coarse aggregate, fine aggregate, mineral filler and binder. Mineral filler consists of inert, non-plastic particles passing through 75 ti sieve size. Commonly used fillers in the bituminous concrete mix are stone dust, lime, ordinary Portland cement, kiln dust, baghouse fines, glass fibres and industrial waste products like fly ash, marble dust and granite dust. Use of appropriate type and quantity of filler improves overall performance of the bituminous mix and life of the flexible pavement. Desirable properties of good bituminous mix are sufficient durability, stability, workability and skid resistance as well as low susceptibility to aging, rutting and moisture. Simple Performance Tests (SPT) are conducted such that the test results determine the ability of the mix to resist pavement distresses like permanent deformation or rutting, fatigue cracking, thermal cracking, moisture susceptibility and skid resistance. Five types of fillers namely stone dust, marble dust, granite dust, fly ash and lime were used in the present study with an objective to explore possibility of use of industrial wastes in bituminous construction. The filler content in the mix was varied from 4 to 8.5% in steps of 1.5%. Optimum binder content (OBC) was determined for all proportions of these fillers in bituminous concrete mix by using Marshall method of mix design. OBC as determined was used to prepare bituminous mixes for conducting performance tests namely Indirect Tensile Strength Test (ITS, AASHTO 322), Moisture Susceptibility Test (Modified Lottman Test, AASHTO T 283-89) and Static Unconfined Creep Test (BS 598: Part 3). A total of 210 Marshall specimens (Marshall Test-80, ITS and Moisture susceptibility Tests-120, Static Crep Test-10) were prepared for conducting these tests. It was observed from Marshall Test that maximum Marshall stability of 16.2 KN was at 6.9% stone dust. ITS Test results showed that 7-8.5% marble and granite dust are better for use in cold region where low-temperature cracking failure occurs in the pavement due to the development of tensile stresses. Maximum value of Tensile Strength Ratio (1.398) was at 7% marble dust. From Creep Test, it is evident that permanent deformation is the least (0.024 mm) and recoverable strain is maximum (87.03%) at 5.5% marble dust.