EVALUATION OF BITUMINOUS CONCRETE WITH DIFFERENT INDUSTRIAL WASTES AS FILLER

Abstract

Road transport in India is carried by a vast network of about 3.3 million kilometers of roads, making it the second largest road network in the world. National Highways (NH) form the primary network of roads with a total length of about 67,000 km. National Highways (NH) carry 40% of the total road traffic but constitute only about 2% of the total road network. The whole road network is seriously capacity constrained and deficient, which has adversely affected the traffic movement. Realizing this fact, the Government of India took up National Highway Development Program (NHDP) in 2001 to provide high density corridors- multilane highways, expressways and two-lane roads with paved shoulders; to meet the present and future needs of growing traffic and to ensure the development of a rapid, efficient, safe, and well connected highway network. In Vision 2021 document of Indian Roads Congress, it is proposed to expand the existing National Highway network to 80,000 km by the end of 2021. Expansion, rehabilitation and maintenance of the transportation system are dependent on supply of aggregate and bitumen. Projected aggregate requirements for 2008 are more than six times the amount in 1966. Approximate estimates of the quantity of stone aggregates that will be required in India for road construction activities from the year 2001 to 2021 are 3500 million cubic metre. The demand for aggregates is increasing at a time when sources near urban and other high-use areas are depleting, and the quantity of available aggregates is at low level or becoming unavailable at certain locations because of mining restrictions, environmental protection regulations and appreciating land values. In view of the extensive and enormous road construction activities taking place in the country, which li consume substantial natural resources, there is a strong need to incorporate alternative materials or waste products in the construction. These newmaterials will conserve natural resources, which is also a must for maintaining the ecological balance. Granite dust and marble dust from stone industry and fly ash from thermal power plants are waste products produced in large quantities in India. Physical properties of these materials meet the requirements laid for fillers as per Ministry of Road Transport & Highways [MoRTH-2001], in India. Therefore, this study was conducted to explore the possible use of three industrial wastes; marble dust, fly ash and granite dust as filler in bituminous construction and their effect on strength and performance parameter of a mix. Hydrated lime and stone dust were also used to compare the results. Five types of fillers were characterized through different test procedures to study their characteristics such as particle size distribution, particle shape and texture, void content, clay content and mineralogical composition. Rheological properties of mastics formed with different fillers and filler/bitumen ratios were evaluated through viscosity measurements, softening point test and Dynamic Shear Rheometer. Bituminous Concrete (BC) is a commonly used wearing course in India on National highways. Bituminous concrete mixes were designed as per Marshall method of mix design (which is currently used in India), at four different percentages of fillers using these three industrial wastes along with stone dust and hydrated lime. Performance of bituminous concrete mixes with these wastes was studied through moisture susceptibility test, static creep test, indirect tensile strength test (IDT), flexural fatigue test and wheel tracking test. 111 Hydrometer analysis showed that the different filler materials have varying particle size distribution (minus 75 micron size). As a result, these fillers would behave very differently when used in bituminous mixes. Filler particles smaller in size than bitumen film thickness over aggregates, act as bitumen extender. Stone dust is the coarsest filler and hydrated lime is the finest filler material. Plasticity index value of marble dust is maximum but within permissible limits of MORTH-2001. Rigden voids are the highest in case of hydrated lime (~64 %) and the lowest in case of stone dust (=34 %), indicating that the mastic of hydrated lime would be very stiff as compared to that prepared with stone dust. Good correlation is obtained between the German filler test value and the Rigden voids, and hence these two tests can be used in complementary manner. Higher methylene blue values in case of stone dust and marble dust indicate that these materials should be more susceptible to moisture induced damage, as compared to other fillers. Presence of calcite mineral phase in marble dust makes this filler more resistant to stripping similar to hydrated lime whichis often used as anti-stripping agent in bituminous mixes. Viscosity and viscosity ratios are found to increase with the percent bulk volume of fines in the mastic. An increase in softening point by 12°C or a viscosity ratio of 10 is suggested as a guideline to avoid excessive stiff mastic and finally the mix. Nomographs are developed to decide the F/B ratio for a filler with a given Rigden voids to provide a mix which is not excessively stiff. Rutting resistance of mixes increases with the increase in filler/bitumen ratio and decreases with the increase in test temperature. Maximum values of rutting parameter (G*/sin5) was obtained in mastics with hydrated lime followed by granite dust, fly ash and marble dust. Minimum value of rutting parameterwas in the case of mastics with stone dust filler. IV It was found that the optimum binder content (OBC) of bituminous concrete decreases with the increase in content of these three industrial wastes. Same trend for OBC was seen in case of stone dust and hydrated lime also. OBC was minimum in case of marble dust filler, followed by fly ash, stone dust and granite dust. Maximum OBC was in case of mixes with hydrated lime. The three wastes showed good resistance to moisture induced damage as compared to stone dust and they can be optimally used up to 7.0%as filler in a bituminous mix. Rutting resistance of mixes showed an increase with increase in filler content for all the five fillers. Mixes with fly ash, granite dust and marble dust have almost 40 % more life in rutting when compared with stone dust filler. A mathematical relationship is developed between rut depth and bulk volume of fines in a mix at its OBC. Similarly another relationship is developed between fatigue life of a mix, at predefined stain level and horizontal tensile strain at failure in the IDT test. Such relationships will be extremely useful for estimating the life of a bituminous mix, either in rutting or in fatigue from simple tests like Rigden voids and indirect tension (IDT) test. Marble dust, granite dust and fly ash showed very good potential for their use as filler in bituminous mixes. Results suggest use of these materials as filler in bituminous concrete mixes up to 7.0 % filler content. Among the three industrial wastes, marble dust is the most promising filler and will prove to be very economical also, as mixes with marbledust have the lowest OBC. Rigden void and methylene blue value are two characterizations test for fillers that should be included in the Indian specifications, to have better understanding regarding their performance in a bituminous mix. The use of these industrial wastes will reduce the environmental pollution and solve their disposal problem partly. It will also help to reduce the consumption of resources of natural materials.