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Reclaimed asphalt pavement (RAP) is the deteriorated pavement material, containing aged binder and aggregates. A rejuvenator is normally added to the mixture to reduce its stiffness, by blending wi...

Environmental, economic, and social benefits are encouraging the incorporation of reclaimed asphalt pavement (RAP) in stone matrix asphalt (SMA) mixtures. However, RAP-incorporating mixture...

The need for incorporation of Reclaimed Asphalt Pavement (RAP) in the Stone Matrix Asphalt (SMA) mixtures is becoming a priority in the pavement industries. The RAP offers several benefits such as the reduction in usage of bitumen, and natural aggregates, and reduction in the landfills, emission into the environment and cost. SMA is known for its success in improving rutting resistance, durability and cracking resistance and to utilize the benefits of both RAP and SMA, it seems a logical purpose to incorporate RAP in the SMA mixtures. However, RAP contains an aged binder, which increases the stiffness of the mixtures and a rejuvenator is added to improve the rheology of the aged binder. In this study, Waste Vegetable Oil (WVO) is used as a rejuvenator in the RAP incorporated SMA mixture. In order to determine the maximum RAP content and optimum WVO dosage, four RAP contents (10, 20, 30, and 40% by weight of the aggregate) and four WVO dosages (0, 3, 6, and 9% by weight of bitumen content) are used to prepare the SMA mixtures. The laboratory tests were conducted to evaluate drain down, volumetric properties, Marshall characteristics, stripping behaviour, Retained Marshall Stability (RMS), and Tensile Strength Ratio (TSR) and they are compared statistically to each other and to the control mixture. The results indicate that RAP incorporated SMA mixtures have a substantial positive effect on the volumetric properties and it enhanced the Marshall Stability (MS), stripping resistance and RMS, however, reduced the TSR value. To the contrary, the addition of the WVO improved the TSR value to a great extent and increased the RAP content. The statistical analysis, Analysis of Variance (ANOVA) results, showed that the RAP content and WVO dosage have a significance on the properties of the SMA, and the main effect plot results concluded that it is possible to incorporate 40% of RAP content with 6% WVO in the SMA mixtures.

Early deterioration of flexible pavements, due to increased traffic volume, environmental conditions, poor maintenance and construction quality, causes difficulties to road users, all around the wo...

Plastic is a major source of continuing pollution and poisons the environment. Environmental hazards due to waste plastics can be addressed to a large extent by using them effectively in road construction. The incorporation of different types of virgin or recycled polymers improves the performance of asphalt concrete. In dense graded mixtures they act as a modifier to improve the mixture properties, namely, Marshall characteristics, resistance to moisture action, rutting, etc., thus ultimately improving the pavement life. In case of gap and open graded asphalt concrete mixtures, some suitable stabilizing additive may be required due to their aggregate structure. Instead of the costly polymers and other commercial stabilizers, waste and recycled plastics can be used, which act as an effective stabilizer material and also provide economical and environmental benefits. The incorporation of plastics to asphalt mixtures can be accomplished either by mixing it with asphalt binder (known as wet process) or by adding directly to aggregates (known as dry process). Many researchers observed dry process as a better method compared to wet process, and considered it as practically more viable. Still, if proper mixing of plastics with asphalt binder, by using high power stirrers, is ensured, wet process also provides a good plastic-modified asphalt. This chapter discusses on the need of stabilization of asphalt concrete, different stabilizer materials that can be adopted, and the possibility of using recycling plastics instead of costly virgin polymers. Suitable methods for incorporating waste plastics, advantages of each, and performance of waste plastic added mixtures are discussed in detail with a brief information on some field evaluations. Considering the availability, economy, and environmental benefits, waste plastics or recycling plastics (after processing) can be recommended as an efficient stabilizer and modifier in asphalt concrete to enhance the mixture stability performance.

Stone Matrix Asphalt (SMA) is a gap-graded bituminous mixture characterised with its improved rut resistance and durability. It has comparatively higher proportion of coarse aggregates and binder mastic with bituminous binder and mineral filler. Drain down of mastic content at various stages of construction is a common issue with SMA, and generally, some fibre additives are used to stabilise the mixture or a modified bitumen is used as the binder material. In this study, shredded waste plastics (SWP) are used instead of other stabilising additives, to prepare SMA mixtures with conventional viscosity graded (VG) 30 bitumen. Mixtures were prepared with four different levels of SWP content, and another mixture without any stabilisers was also prepared using polymer-modified bitumen (PMB). Specimens were prepared in superpave gyratory compactor (SGC) for all mixtures at different bitumen contents to determine volumetric and Marshall properties, and optimum bitumen content (OBC) was calculated for each mixture...

Subgrade is one of the important layers of any pavement. It must be able to support loads transmitted from pavement structure without excessive deformation under adverse climatic and traffic conditions. In this investigation, laboratory studies were carried out to evaluate the influence of a commercial electrolyte lignin stabilizer (ELS), fly ash (FA) and a combination of both, on black cotton (BC) soil procured from North Karnataka region in India. Basic geotechnical and engineering properties like unconfined compressive strength (UCS), California bearing ratio (CBR), etc. were determined for both untreated and treated soil. Dynamic repeated load test was conducted to examine the fatigue behaviour of the soil. Durability of the soil was checked by wet-dry (WD) and freeze-thaw (FT) cycle tests, and swelling properties by free swell index test. From the studies, it was observed that consistency limits, dry density, UCS and CBR values were improved for treated soil, with curing periods of 1, 7 and 28 days. Weight loss in FT test was less than 14 % for 12 cycles, which ensures that the stabilized soil has become durable. But none of the samples were observed to be withstanding above five cycles in wet-dry test. Soil stabilized with ELS and FA showed better results compared to soil with only ELS. Swelling was reduced to a great extent with 28 days curing period for the former one. From the experimental results, it can be concluded that this chemical can be used as a stabilizer for existing BC soil in site to enhance its subgrade strength.

Moisture damage is one of the most common reasons for the premature deterioration of Hot Mix Asphalt (HMA) pavements. Over the years, extensive research has been carried out by scientists and engineers on this subject; however, pavements still succumb to early failure from infiltrating moisture. A very popular method of minimizing the moisture susceptibility of asphalt pavements is by the use of anti-stripping agents. These additives are chemical substances that alter the physicochemical properties of the asphalt by making it more hydrophobic. This study focuses on the effect of anti-stripping agents on the moisture susceptibility of Bituminous Concrete (BC) mixture. The anti-stripping agents used were hydrated lime and Zycosoil. Three mix types were studied, namely: BC mix without additive, BC mix with hydrated lime and BC mix with Zycosoil. Viscosity Grade (VG) 30 bitumen was used in all three groups of samples. Marshall mix design method was adopted and specimens were prepared at bitumen contents 4.5, 5.0, 5.5, 6.0, 6.5 and 7.0% by weight of mixture. Volumetric properties and Marshall characteristics were determined for each specimen, and using them, the Optimum Binder Content for each mixture was obtained. Moisture susceptibility of mixtures was assessed using Tensile Strength Ratio, Retained Stability and Stripping Value. From the experimental results, it is observed that the addition of anti-stripping agents had a significant positive influence on the results of the test properties being evaluated in each test.

After publication of this work [1], we noted that we misspelled the Corresponding author’s name Saravanan K. Kothandaraman and has now been updated. We are publishing this erratum to update the Corresponding author’s name as Saravanan Kothandaraman.

Soil stabilization is a technique to improve the weak soils and making them to meet certain requirements of the specific engineering projects. The type of soils available in Dakshina Kannada region of Karnataka State is laterite and Lithomarge clay. Its Plasticity Index is very high due to the presence of high percentage of silt and clay content. In the present investigation, an attempt is made to study the behaviour of laterite with and without adding chemicals. A chemical named Zycosoil, when added to water and mixed with soil alters its engineering properties that depend upon the type of the soil and dosage of chemical. These chemicals are liquid additives, which act on the soil to reduce the voids between soil particles and minimize adsorbed water in the soil for maximum compaction. In the present study, the effectiveness of Zycosoil in stabilizing the laterite soils of South Canara district is investigated through laboratory experiments. Various geotechnical properties are studied and correlations between different geotechnical properties and improvement in the soil properties with different percentages of chemical additions are derived. The important properties such as index properties, compaction characteristics, unconfined compressive strength parameters, California bearing ratio values and fatigue behaviour were studied. The results obtained indicate that there is an improvement in almost all properties with the addition of Zycosoil.

Stone Matrix Asphalt (SMA) is a gap graded asphalt mixture performing better than conventional dense graded mixtures. It contains high concentration of coarse aggregates, forming stone on stone contact between them, and high asphalt content. The coarse aggregate skeleton results better load distribution and the high asphalt content adds durability to the mixture. Due to the high mastic (filler and asphalt) content, there is possibility of drain down during various stages in construction. SMA mix should be prepared with suitable stabilizing additive to prevent the drain down of mastic material from the mixture. In this study, SMA mixtures are prepared in Superpave Gyratory Compactor (SGC) with shredded waste plastics, which are mixed with aggregates prior to the addition of Viscosity Graded (VG) - 30 asphalt. Mixtures are prepared with asphalt contents of 5.0 to 7.0 per cent (by weight of aggregates) and stabilizer contents of 0, 4, 8, 12 and 16 per cent (by weight of asphalt). Volumetric and Marshall properties, tensile strength, moisture susceptibility characteristics, etc. are determined. From the laboratory studies it is observed that addition of waste plastics in shredded form can be used instead of stabilizers by controlling the drain down and enhancing the performance.

Stone matrix asphalt (SMA) is a gap-graded bituminous mixture which can be used in surface layer of high volume pavements. The mixture has higher concentrations of coarse aggregates, providing strength and rut resistance to the mixture, and higher asphalt content giving durability. There must be a proper stone-to-stone contact between the coarse aggregates of SMA, and hence aggregate gradation is an important factor in this mixture. In the current study, two aggregate gradations, with nominal maximum aggregate sizes (NMAS) 16 and 13 mm were adopted to prepare SMA mixtures and their laboratory performances were compared. Polymer-modified bitumen (PMB) was used as the binder material and no stabilising additive was used, since drain down was within permissible limits for both mixtures with PMB. Conventional cylindrical specimens were prepared in superpave gyratory compactor with bitumen contents 5.0 %, 5.5 %, 6.0 %, 6.5 % and 7.0 % by weight of aggregates, and volumetric and Marshall properties were determined. Tensile strength, behaviour to repeated loading etc. were checked for cylindrical specimens prepared at optimum bitumen content, whereas specially prepared slab specimens were used to check the rutting resistance of SMA mixtures. From the laboratory study, it was observed that, out of the two SMA mixtures, the one with NMAS 16 mm performed better compared to the other. These improved properties may be attributed towards the larger coarse aggregate sizes in the mixture.

Stone Matrix Asphalt (SMA) is a gap-graded asphalt rich mix with a high concentration of coarse aggregates. In the present investigation, SMA mixtures were prepared with chemically treated aggregates and Crumb Rubber Modified Bitumen (CRMB), and were compared for various characteristics. SMA samples were prepared using conventional Marshall and Superpave Gyratory Compactor (SGC) methods. Volumetric and Marshall properties, Indirect Tensile Strength (ITS), rutting and moisture susceptibility, fatigue behaviour and permeability characteristics were determined for these mixtures. From the laboratory studies it is evident that, chemically treated aggregates with normal bitumen (Viscosity Graded (VG) 30) and CRMB with normal aggregates can be used in SMA to meet the drain down requirements. CRMB mixes were observed to be having an upper hand in performance, even though treated aggregates mixes showed better moisture resistance properties.