JOURNAL OF TRANSPORTATION INFRASTRUCTURE ENGINEERING (JTIE)
Year:2019 | Volume:5 | Issue:2 (18) |Papers Count:8

Crude oil and its derivatives infiltrate into the soil in the communities where oil exploration activities are prevalent. The leakage of crude oil, in addition to negative environmental effects such as groundwater contamination, causes changes in the geotechnical characteristics of the soil. In granular soils, these changes occur mostly in physical properties while in fine-grained soils, the texture and structure of the soils are mainly altered. It is important to note that these changes in characteristics of the soil layer could reduce the bearing capacity and increase the overall and relative the settlement of the foundation underneath the structures and may lead to an ultimate collapse. This research work aimed at experimental investigation into the effect of crude oil contamination on Atterberg limits, specific gravity, compaction, strength and permeability of Kaolinite clay soil. Numerous Soil samples were prepared from contaminated soil having various percentages of crude oil and were tested subsequently. The results of the experiments showed that the liquid and plastic limits and plasticity index decreased with increase in crude oil content. Also, as the crude oil content in the contaminated soil increased, the maximum dry unit weight of the soil increased while the optimum moisture content decreased. In addition, increasing contamination caused the permeability coefficient of contaminated soils to decrease. Increasing the amount of oil had also a different effect in the uniaxial test of contaminated soils. It was observed that increase in contamination content up 2% would cause the uniaxial strength to increase. However, more increase in the contamination content, 4% and 6%, reduced the rate of increase in the uniaxial strength of soil. Soil contaminated with crude oil is essential be stabilization or modified before use in construction.

Warm mix asphalt (WMA) is used as innovative method of asphalt production that have several economic and environmental benefits. However, some ambiguities have been reported with regard to its performance against low-temperature cracking. In this work, Semi-Circular Bending (SCB) test that is used for fracture mechanics analysis of asphalt mixes was employed to study performance of WMA against low-temperature cracking. Hence, SCB testing was applied at three different temperatures (namely, 0,-10 and-20 ° C) on pre-notched specimens. The results showed that WMA mixes produced using chemical additives were more resistant to low-temperature cracking compared with mixes produced using organic additives and foam bitumen technology. In addition, WMA specimens produced using foam bitumen technology was the weakest compared with other methods of production. Finally, it can be stated that performance of different types of WMA mixes at low-temperature conditions strongly depend on the adopted technology and the mix production circumstances (i. e. mixing temperature, additive contents and experimental conditions).

Because of important role of pavement quality on the safety and comfort of road users and reducing the operation period costs, the researchers have paved the way for asphalt pavement to produce improved asphalt, to increase its strength and durability against traffic load and conditions Weather. Today polymers are also bituminous modifying additives that are widely used in asphalt. In this study, three polymer with names Styrenine-Butadiene-Styrene, Styrene-Butadiene-Rubber and PolyStyrene were used to improve moisture and rutting asphalt resistance. Styrene-butadiene-styrene has a favorable experience in repair of pavement damage, but imported and due to its price dependence on political occasions, the researchers sought to combine the production of internal polymers efficiently and at reasonable prices Replace it. In this regard, two polymers of styrene-butadiene-styrene and polystyrene were mixed in 25/75, 50/50 and 75/25 combination ratios and 3 and 5% by weight of bitumen in asphalt mixtures. Marshall Stability, Indirect Tensile Strength, Resilient Modulus and Rutting tests were performed on modified specimens. The results showed that the use of polymer blends is much more efficient than the use of polymers individually, and a polymer blend containing 75% styrene butadiene, along with 25% polystyrene, can produce moisture and rutting resistance equal to styrene butadiene styrene.

This study examined the possibility of using PET aggregates as a partial substitute for natural fine-grained aggregates in Roller Compacted Concrete Pavement (RCCP) mixtures. To enhance the performance of RCCP, the mixtures were also modified by using pozzolanic Metakaolin (MK) as a partial substitute for cement and adding steel fibers obtained from the recycling of worn vehicle tires. The response surface methodology (RSM), which is capable of predicting the variations of a response value in the variations range of independent variables, was used to cover all possible mix compositions. Using this method, 20 mix designs were prepared, which allowed for significant time and cost saving in experiments without sacrificing thoroughness. The behavior and characteristics of RCCP specimens in terms of water absorption, ultrasonic pulse velocity and compressive strength at the age of 7 and 28 days were investigated. The obtained responses were used to develop statistical models, which were then utilized in the optimization of mix design with the help of analysis of variance. The results showed that the use of PET aggregates increased water absorption and decreased the compressive and flexural strength of the RCCP specimens. Partial replacement of cement with MK generally improved the performance of the specimens. The effect of shredded recycled steel fibers (SRSF) was generally dependent on other components of the mixture. The optimal mix design obtained from the statistical models involves replacing 29vol% of fine aggregate with PET, replacing 20wt% of cement with MK powder, and adding 2wt% SRSF to the mixture. The proposed mix design contributes to clean recycling of PET and conservation of natural resources and reduces the cost and carbon footprint of RCCP construction with considering the standard requirements for pavement structures.

Nowadays, WMA technology is known as an efficient way to reduce the cost of production of asphalt, fuel consumption and environmental pollution. In contrast to its numerous advantages, stripping phenomenon comes as a disadvantage for the industry. One of the ways to improve the resistance of asphalt concrete and adhesion between bitumen and aggregates, is to use chemical and organic additives. Zycotherm as a nano-chemical additive, plays a bilateral part: as an anti-stripping agent and as an additive for the production of WMA. To better understand the phenomenon of stripping as a result of weak adhesion, several mechanisms have been used to describe the adhesion between the components of asphalt mixtures. Since adhesion between two different phases depends on mechanical and chemical reactions, cohesion the theory of free surface energy, the mechanisms controlling adhesion failure between the components of asphalt mixture are complicated. The main objective of this laboratory study is to evaluate the effect of aggregate type on functional properties of WMA modified with nano-chemical additive named zycotherm as a warm mix and anti-strip agent in terms of water susceptibility tests according to the newest national and international codes such as modified Lottman test and boiling water test. To do this, IDT test was also carried out. Image processing of boiling water test and analyzing the results of water susceptibility tests betoken that zycotherm has a poor performance as a warm mix agent on both limestone and silica materials but has a remarkable effect on improving resistance to moisture damage of silica materials.

In cases where the soil normally has undesirable properties and it is not possible to replace the soil, it is necessary to use methods such as compaction, injection, stabilization, reinforcing and other methods for soil improvement. Recently, due to the advancement of engineering science and since many soils and minerals are among the nano materials, their chemical reactions occur at nano scale. In this regard, nano materials are used to improve the geotechnical properties of the soil. Also, the self-healing of clay as one of the positive properties of clay in recent years has been considered by researchers. In this study, in order to investigate the effect of iron oxide nanoparticles on the behanior of clayey-sand soil, three soil types were selected for laboratory tests, including soils with 10, 20 and 30 percentage of clay. The results show that the peak strength of soil stabilized with iron oxide nanoparticles is increased especially sandy soil with lower percentage of clay. Also, the effect of curing time was obvious on the strength development in the restoration process of the soil. The effect of nanoparticles on the peak strength and self-healing characteristics of clayey sand has been shown with a series of SEM images.

Flexible Pavement has the most share for road construction in most countries. Iran also follows this rule. In most asphalt pavements design methods, there is less focus on base and subbase layers and most of the researches are focused on the asphalt layer. Since the behavior of these materials is different in the short and long term due to the elastoplastic properties, it’ s so important to examine their behavior before using in the pavement layers and also behavioral comparison between different types of materials. This leads to the choice of the best type of pavement materials and the best conditions for grading, moisture and compaction. In results, it is important to select the test conditions that can accurately simulate the actual stresses on the pavement. Light weight deflectometer (LWD) test is usually used to determine the bearing strength of the unbound layers of the pavement. The purpose of this study is to examine simultaneously the role of the effective factors associated with the base layer on the behavior of this layer using of LWD test. The selected effective factors include compaction, thickness, and moisture content of the layer. The results show that increasing of compaction from 87% to 97%, and layer thickness from 20 to 40cm, the surface modulus of layer is significantly increased and deflection is reduced. Also, the results show that the changes in the moisture content of the layer did not have effect on the modulus and deflection of the layer.