**2. Petroleum contaminants**

Over the last few decades there has been an increased public awareness of environmental issues, particularly when the contamination of sand, water, and air is involved. Worldwide, scientists and environmentalists are faced with the challenge of overcoming the detrimental effects of the contamination of sand, air, and water. The spillage of crude oil onto sand, leakages from pipelines, underground and surface fuel storage tanks, indiscriminate spills, and careless disposal and management of wasteand other by-products of society, constitute the major sources of petroleum contamination. **Figure 1** shows the final stage of produced water and the contaminated sand around the discharge disposal point, while **Figure 2** shows the oil spillage in one of the Libyan oil fields.

### **2.1 Sand contaminated with oil**

One of the most critical environmental impacts of the oil industry is the spillage of crude oil, which severely contaminates the sand. Remediating contaminated sand takes longer and costs much more than it does for water contaminated with oil. Hence, it is very important to investigate the properties of sand contaminated with oil [21] because crude oil has a significant effect on the physical and chemical properties of surround sand [22]. However, the severity of the effect is based on several factors such as the sand type and quantity of the crude oil spillage. **Figure 3** shows who the crude oil migrates down to the groundwater causing partial saturation of the sand and the pathway of the hydrocarbons as shown in **Figure 3**.

Several studies have already investigated the effect of crude oil on the geotechnical properties of the sands. For instance, Cook et al. [24] experimentally investigated the compaction, compression, and strength properties of uniformly graded sands contaminated by crude oil. They reported that although oil contamination had no significant effect on the compaction characteristics, it decreases the friction angle and considerably increases the compressibility of the sand. Similar results were obtained by Puri [25] and Meegoda and Ratnaweera [26] for sandy and clayey

**Figure 1.** *Oil contaminated sand caused by produced water Ghani field HOO [20].*

#### **Figure 2.**

*Oil contaminated sand caused by oil spillage Ghani field HOO [20].*

**Figure 3.** *Crude oil spillage and the leaching of light hydrocarbons to the aquifer [23].*

sands, respectively. Studies on the geotechnical characteristics of fine-grained sands have just recently gained momentum. Khosravi et al. [2] studied the geotechnical properties of the oil-contaminated clayey and sandy sands and found a reduction in strength, permeability, maximum dry density, optimum water content, and Atterberg limits of these sands. Singh et al. [27] found an increase of 35–50% in the consolidation settlement of fine-grained sands upon contamination with petroleum hydrocarbons. From the previous studies in can be considered that the uniformly graded sands, clayey sands, fine-grained sands showed similar results however, when clayey and sandy sands was used the strength, permeability, maximum dry density, optimum water content, and Atterberg limits were decreased. Although none of the previous studies were investigated the absorption test of crude oil, it is expected that the type of sands may play a great role properties of oil contaminated sand.

Hydrocarbon contamination has a direct effect on the erodibility of sand and water infiltration and may also cause fire on the ground. Furthermore, the

#### *Oil Contaminated Sand: Sources, Properties, Remediation, and Engineering Applications DOI: http://dx.doi.org/10.5772/intechopen.103802*

aggregation of fine particles, and the fusing of minerals, may lead to a reduction in the stability of the sand-organic matter aggregate. Whereas fire-induced or fireenhanced sand water repellence has often been cited as the major cause of post-fire enhanced runoff and erosion [28], hydrocarbon contamination can also affect the physio-chemical characteristics of sand [29].

A previous study by Rahman et al. [30] has shown that is not only the ecosystem that can be affected by the spillage of crude oil, but the safety of the civil engineering structures as well. Cleaning up contaminated sand is a complicated job due to the long period of time needed, and the high cost and limitations of disposing the excavated sand. Furthermore, proper environmental regulations are not available due to the lack of proper management in many developing counties such as Libya, which then leads to disused oil and illegal dumping of other hydrocarbon components, which could have helped to tackle the environmental issue, as well as the economy, in the form of construction materials such as sand. Moreover, oil contamination can adversely affect plants as well as contaminate ground water resources for drinking or agricultural purposes [31].

#### **2.2 Mechanical properties of oil contaminated sand**

Sand is a naturally occurring material, which is considered to be an engineering material. Thus, its physical characteristics can be determined by experiments, which then may enable these properties to be used to predict their expected behaviour under working conditions, which in turn raises the possibility for its potential beneficial use to be determined [32]. The advantages of examining the mechanical properties of sand are that it permits a greater accuracy of measurements, so that any changes in conditions can be simulated to represent the conditions during and after construction, and the sand parameters can be derived within a reasonable time scale. Therefore, understanding mechanical properties of sand is beneficial to an engineer in terms of reducing the uncertainties in the analysis of foundations and earth work and the creation of structures, and in the use of sand as a construction material. In this application, the mechanical properties such as shear strength is investigated.

#### *2.2.1 Shear strength*

The shear strength of sand is one of the most important parameters in civil engineering applications. The safety of any mechanical engineering structure is based on the shear strength of the underlying sand [33]. All constructions, when in or on the land, impose loads on the sand that supports the foundations of that particular construction or building. The load imposed on the sand may cause shear failure of the underlying sand, which occurs when the shear stress imposed on the sand mass exceeds the maximum shear resistance (shear strength) that the sand can offer [34]. The shear strength of the sand is considered to be an important aspect in many foundations, such as in the bearing capacity of shallow foundations and piles, the lateral earth pressure on retaining walls, and the stability of slopes of dams [35]. Hence, understanding the shear strength can play a great role in terms of the entity classification of the sand [36], which in turn can assist engineers to derive the critical aspects of the overall sand mechanics in a specific environment.

The shear strength of common engineering materials, such as steel, from a continuum mechanics viewpoint, is governed by the molecular bonds that hold the material. The higher the shear strength of a material, the stronger the molecular

structure [35]. Nevertheless, the shear strength of sand operates under a different set of principles. Sand is a particulate material, so shear failure occurs when the stresses between the particles are such that they slide or roll past each other. Due to the particulate nature of sand, unlike that of a continuum, the shear strength depends on the interaction of anti-particles (is it a particle of the opposite charge), rather than the internal strength of the sand particles themselves [36]. Sand derives its shear strength from two sources: cohesion between particles and frictional resistance between particles. Cohesion is the cementation between sand grains or the electrostatic attraction between sand particles [34].

#### **2.3 Stabilisation of oil contaminated sand by mixing with cement**

Several studies have investigated the mechanical properties of concrete utilising oil contaminated sand and have evaluated their potential use in construction. These studies are presented in this section, as well as the current usage of oil contaminated sand in construction.

#### *2.3.1 Effects of oil contamination on the properties of mortar and concrete*

Hamad and Rteil [37] revealed that oil acted like a chemical plasticiser, improved the fluidity, and doubled the slump of the concrete mix, while maintaining its compressive strength. A similar study was conducted by Hamad et al. [10] who added engine oil to a fresh concrete mix and found that its effect was similar to adding an air-entraining chemical admixture, which enhanced some of the durability properties of concrete. Additionally, the potential use of sand contaminated with petroleum in highway construction was investigated by Hassan et al. [38], and they concluded that it could be used for this purpose.

In a recent study by Ajagbe et al. [3] the effect of crude oil on compressive strength of concrete was investigated, and they concluded that 18–90% of its compressive strength was lost due to 2.5–25% contamination with crude oil. Ahad and Ramzi [9] indicated that there was a significant reduction in the compressive strength and about an 11% reduction in the splitting-tensile strength of concrete soaked in crude oil. **Table 1** summaries the effect of oil contamination on the mechanical properties of concrete. Nevertheless, there are still disagreements about the effect of crude oil and its produced content on the properties of produced concrete.

As it can be seen in **Table 1** that most of these researchers disagree on the effect of crude oil on the behaviour of concrete. The inconsistency of some of the factors such as type of crude oil, permeability of sand, sand properties, absorption, chemical composition, and spillage quantity [22, 39–41] were considered as the main reason beyond this lack of agreement. Thus, there is a need to further investigate the properties of oil contaminated sand and its effect on produced mortar and concrete.

#### *2.3.2 Beneficial use of mortar and concrete containing oil contaminated sand*

Range of remediation methods for sand contaminated with oil have been recommended but they are not cost effective [5]. The possibility of an end-use scenario of treated material or contaminated sand was addressed, based on the results of the compressive strength. For instance, less strength is required for landfill but a higher compressive strength is required to make bricks or for some other structural objectives. Based on the United States Environmental Protection Agency (USEPA)

*Oil Contaminated Sand: Sources, Properties, Remediation, and Engineering Applications DOI: http://dx.doi.org/10.5772/intechopen.103802*


#### **Table 1.**

*Effect of oil contamination on the properties of mortar/concrete properties.*

guidelines, the recommended compressive strength, at 28 days, for landfill disposal material is 0.35 MPa, while it is 1.0 MPa in France and the Netherlands [42]. A higher compressive strength of 3.5 MPa in a sanitary landfill is required according to the Wastewater Technology Centre (WTC) in Canada [43]. Based on the British standard for precast concrete masonry units (BSI, 1981) a higher compressive strength is required for blocks and bricks, of 2.8 and 7 MPa, respectively. Additionally, a minimum of 7 days cube compressive strength, which should vary between 4.5 and 15 MPa, is required for subbase and base materials, as regulated under the department of transport in the UK. This shows that there is high potential in using oil-contaminated sand in construction. However, an understanding of the details of its physical and mechanical properties is warranted.

## **3. Results and discussion**

#### **3.1 Effect of light crude oil contamination on shear strength**

The effect of oil contaminated sand with different percentages (0, 0.5, 1, 2, 4, 6, 8, 10, 15, and 20%) on shear strength was determined using the cohesion and frictional angle of fine sand contaminated with light crude oil, using the Mohr-Coulomb equation. **Figure 4** shows the sand shear strength as function of light crude oil contamination at an applied normal stress of 50 kPa. It can be deduced from the figure that light crude oil contamination affects the shear strength of fine sand.

The shear strength increased for fine sand with 1% oil contamination, which was due to the significant increase in the apparent cohesion of the fine sand contaminated with light crude oil [41]. In contrast, at a high level of crude oil contamination, the shear strength decreased significantly with a further addition of oil content beyond 1% of crude oil content in contaminated sand. Thus, it can be inferred that the presence of a high percentage of oil increased the viscosity, and as a consequence the sand particles started to be coated by the crude oil. By increasing the amount of oil content in particular sand, the chance of inter-particle slippage will also increase, and subsequently the shear strength of soil, will decrease [44]. This indicates that higher

**Figure 4.** *Shear strength of contaminated fine sand at 50 kPa normal stress.*

oil contamination resulted in lower shear strength values. Nevertheless, these results are contradicted by Khosravi et al. [2] finding, who concluded that the shear strength of kaolinite (clay) is not significantly influenced by gas oil. Furthermore, Puri [25], Shin and Das [45] both concluded that the shear strength of sand can be adversely affected by oil contamination. Moreover, Rahman et al. [44] have investigated the effect of hydrocarbons components on two types of soil, granitic soil and sedimentary soil. They concluded that the shear strength values of both soils significantly dropped from 0 to 4% of hydrocarbon content. Then, the shear strength values decreased slightly beyond 4% of hydrocarbon content. This implies that the sample will easily be slipped or sheared with higher oil content when the shear strain is applied. Moreover, Mashalah et al. [46] concluded in their study of the effect of crude oil contamination on three types of soils Lean clay, Silty sand and Poorly-graded sand (CL, SM and SP), that the shear strength decreased by increasing the crude oil content.
