Umesh Chandra Sahoo

Stabilization of a Clayey Soil with Fly Ash and Lime: A Micro Level Investigation

Pavement structures on poor soil sub grades show early distresses causing the premature failure of the pavement. Clayey soils usually have the potential to demonstrate undesirable engineering behavior, such as low bearing capacity, high shrinkage and swell characteristics and high moisture susceptibility. Stabilization of these soils is a usual practice for improving the strength. This study reports the improvement in the strength of a locally available cohesive soil by addition of both fly ash and lime. Analysis using X-ray diffraction, scanning electron microscopy, coupled with energy dispersive spectroscopy, thermal gravimetric analysis, zeta potential and pH value test was carried out in order to elucidate the stabilization mechanism. The micro level analysis confirmed the breaking of montmorrillonite structure present in the untreated clay after stabilization. In the analysis, it was also confirmed that in the stabilization process, pozzolanic reaction dominated over the cation exchange capacity.

Rheological, chemical and thermal investigations on an aged binder rejuvenated with two non-edible oils

The aged pavement material from a defunct pavement – commonly known as reclaimed asphalt pavement (RAP) – contains stiffened binder caused by loss of volatile materials and oxidation. Therefore, addition of a high amount of the RAP to asphalt mix, in case of pavement recycling, may make it prone to fatigue failure. Due to this reason, the addition of RAP to asphalt mixture in substantial amount has been a challenge so far. “Rejuvenators” are generally used to restore the properties of the aged binders in the recycled mixes. The present study deals with the assessment of two non-edible oils, that is, pongamia oil and composite castor oil (a composite rejuvenator having castor oil and coke-oven gas condensate) as asphalt rejuvenators to achieve 100% RAP recycling. The study mainly comprises rheological characterisation studies such as rutting behaviour, fatigue behaviour, dynamic mechanical analysis and creep-recovery studies of the rejuvenated binder specimens. Chemical investigations using infrared spectroscopy also affirmed use of these oils in effectively restoring the properties of aged binders. In addition, for assessment of the long-term performance in terms of thermostability of the rejuvenated binders, a thermal analysis was carried out using a simultaneous thermal analyser, which confirmed the adequate thermal stability of the rejuvenated binders. From the investigations taken up under this study, it was concluded that 5% oil (for both pongamia and composite castor oil) rejuvenated aged binder could show desirable rutting and fatigue behaviours and sometimes even better than the virgin binder. However, its confirmation can be laid only after suitable mix performance studies.

A rheological study on aged binder rejuvenated with Pongamia oil and Composite castor oil

Abstract Recycling of highway materials is an effort to preserve the natural environment, reduce waste and provide a cost-effective way for construction of highways. The reclaimed asphalt pavement (RAP) contains stiffened binder caused by loss of volatile materials and oxidation. Hence, the addition of high amount of the RAP to asphalt mix may make it prone to fatigue failure. Due to this reason, addition of RAP to asphalt mixture in substantial amount has been a challenge so far. Therefore, ‘rejuvenators’ which are supposed to restore chemical and physical properties of the aged asphalts are used effectively in asphalt mixture. In this study, two locally available oils, i.e. pongamia oil (locally known as Karanja oil) derived from the seeds of Pongamia pinnata and a composite rejuvenator made of castor oil and coke oven gas condensate have been explored for rejuvenating the aged binder. The rheological properties of aged binder and rejuvenated binders were studied using a dynamic shear rheometer. From the various rheological tests conducted, it was found that certain proportion of pongamia oil as well as composite castor oil was able to impart desirable rutting as well as fatigue performance for the rejuvenated binder samples. The thermal analysis carried out using thermogravimetric analysis ensured adequate thermal stability for the binder specimens treated with these oils. In terms of binder performances, it was found that these oils could be considered as suitable rejuvenators for effectively restoring properties of the aged binder. Performance studies on RAP mixes may be extended for recommending these two oils as rejuvenators for hot mix pavement recycling.

Effect of Slag on the Rheological and Strength Properties of Self-Compacting Concrete

This study deals mainly deals with the rheological and strength properties of self-compacting concrete (SCC) incorporating high volume replacements of slag. Plastic viscosity and yield stress were evaluated using ICAR rheometer. The effect of high range water reducing admixture (HRWR) dosage, the time to reach 500 mm diameter (T50), the final slump flow, V-funnel flow times and L-box blocking ratio were also investigated and studied in this research program. The results show that the plastic viscosity decreases with the increase of the percentage of slag and the yield stress was nearly zero for all the replacements studied. The compressive strengths determined for the SCCs demonstrate that high strength SCC of more than 100 MPa can be realized by using slag appropriately.

Long-Term Performance Evaluation of Rural Road Pavements in India

About 80% of the total road network in India is categorized as rural roads carrying traffic less than 450 commercial vehicles per day. A huge network of rural roads is being built under the countrys most ambitious prime ministers rural connectivity program (PMGSY) since its launch in December 2000. These roads are mostly designed as granular pavements with thin bituminous surfacing following the guidelines given in IRC:SP:20 (2002), which does not refer to any documented performance data. Collecting performance data on such pavements under different subgrade, climatic and traffic conditions is crucial for developing rational pavement design criteria and also for systematic maintenance management of the pavements. Moving a step in this direction, 19 rural road test sections were selected in the eastern part of the country for a long-term performance study, and this paper presents the data collected over a period of four and a half years. The reported performance data will be extremely helpful for developing rational design criteria and systematic management of rural roads. Also a performance criterion has been developed (considering vertical stress over subgrade) for thin surfaced rural roads using the limited data available under this study.

Effect of Wet-Dry Cycles on Mechanical Strength Properties of Cement Stabilized Granular Lateritic Soil

Scarcity of good quality stone aggregates has been posing a major challenge in sustainable development of roads in many developing countries including India. Granular lateritic soil is marginal material abundantly available in major parts of India and this needs to be stabilized for use in base and subbase layers. Traditionally durability is assessed through wet-dry durability test, where the specimens are subjected to alternate wetting and drying cycles, which is believed to simulate the natural weathering conditions. This work presented in this paper reports the effect of wet-dry (W-D) cycles on unconfined compressive strength (UCS), flexural strength (FS) and flexural modulus (FM) of a cement stabilized granular lateritic soil (CLS) collected from the eastern part of India. The strength and stiffness of CLS was found to be increasing with the number of durability cycles. This trend of increasing strength and stiffness is contradicting the general assumption that the W-D process reduces the material integrity and this may be attributed to the accelerated curing due to heating of samples, which negated the detrimental effect of wetting and also due to gradual strength gain with blended cements.

Use of waste polyethylene for modification of bituminous paving mixes containing recycled concrete aggregates

Recycling or waste utilisation in transportation construction industry is important for sustainability. Keeping this in mind, an attempt has been made in this study to explore the use of waste materials such as recycled concrete aggregates (RCA) and waste milk packaging polyethylene in bituminous paving mixes. In this study, dense bituminous macadam mixes were prepared with RCA as coarse aggregates and two different types of filler, i.e. cement and stone dust. For the purpose of comparison, paving mixes were also prepared using natural aggregate and other materials as above. It was observed that all the mixtures prepared with various combinations satisfy the requirements in terms of Marshall test parameters and moisture susceptibility specified by Ministry of Road Transport and Highways, India. Further, the use of waste polyethylene generally improves the engineering properties especially at a higher temperature, in terms of dynamic moduli value and rutting behaviour of mixtures.

Non-destructive strength and stiffness evaluation of cement-stabilised granular lateritic soils

Modulus of pavement materials is an important input parameter for the mechanistic design of pavements. As the bound layers such as cement-stabilised materials fail in flexure, flexural modulus (FM) is generally used as the modulus of stabilised material for the analysis of pavements. FM is determined from four-point bending tests under cyclic loading, but this process is a time-consuming exercise and therefore non-destructive method such as ultrasonic pulse velocity test (UPV test) may be employed for rapid determination of the modulus of elasticity of the material. In this study, ultrasonic pulse velocity of cement-stabilised granular lateritic soil (CLS) samples was determined using the UPV test and were correlated with the compressive strength, flexural strength and FM of 28-days cured stabilised specimens. It has been observed that the variation in pulse velocity determined from the UPV test shows good agreement with the variation of compressive strength and flexural strength of the stabilised lateritic granular soil samples considered in the study. Correlation was also established between the FM determined from the cyclic flexural test and constrained modulus determined from the UPV test on CLS beam samples.

Durability and shrinkage studies of cement stabilsed granular lateritic soils

ABSTRACT Cement stabilised materials are increasingly being used in pavement structural layers to solve the issue of scarcity of good quality stone aggregates and also to enhance the performance of the pavement. In addition to the strength and stiffness, the performance of pavements layers also largely depends upon the durability and shrinkage characteristics of stabilised materials used as base and subbase layers. The research reported in this paper focuses on the laboratory durability and shrinkage characteristics of cement stabilised granular lateritic soils (CLS). Wet–Dry (W–D) durability test and soaked UCS tests were conducted on CLS samples to evaluate the minimum dosage requirement of the binder. Preliminary studies were also done to assess the water absorption characteristics of CLS. Shrinkage properties of CLS were assessed through drying shrinkage tests. Effect of moisture content and cement content on ultimate drying shrinkage was also established in this study.

Strength and Stiffness Studies of Cement Stabilized Granular Lateritic Soil

A huge network of rural roads is being developed in India under the most ambitious Prime Minister’s rural connectivity programme, PMGSY (Pradhan Mantri Gramin Sadak Yojna). Under this programme, thousands of kilometers of rural roads are being constructed in the country, which require good quality pavement materials like crushed stone. The scarcity of natural aggregates has compelled to use marginal materials or locally available soils in structural layers of these pavements, which would reduced the cost of the project. Granular lateritic soils are widely available in many parts of India and presently, this is also used as sub-base material in different rural road projects, where it satisfies the code specifications. However, granular lateritic soils of some locations do not satisfy the strength and plasticity requirement of sub-base layer. But, they can probably be made suitable through stabilization. Though stabilization of soil by cement or lime is a well known process of improving the strength and stability of soil, the strength and stiffness parameters of stabilized lateritic soils in terms of modulus of rupture, resilient modulus, flexural modulus have very limited reference in literature. Therefore, in this study an attempt has been made to characterize the cement stabilized lateritic soils for use in sub-base and base layers in rural road pavements. A comprehensive laboratory testing programme has been conducted on cement stabilized granular lateritic soil samples collected from five different places of eastern India to study various strength parameters such as compressive strength, modulus of rupture and stiffness properties in terms of flexural modulus of cement stabilized granular lateritic soil. In this paper, strength and stiffness developments of cement stabilized granular lateritic soil in 7 days and 28 days have been studied and its suitability as a structural layer in rural roads has been investigated. Suitable modulus values of cement stabilized granular lateritic soils have been proposed which can be used as an input parameter for the input in mechanistic design of roads. Also relationships have been proposed to determine modulus of rupture and flexural modulus of cement stabilized granular lateritic soil from its compressive strengths.