Amer Ali Al-Rawas

A comparative evaluation of various additives used in the stabilization of expansive soils

This paper looks at the effectiveness of using cement by-pass dust, copper slag, granulated blast furnace slag, and slag-cement in reducing the swelling potential and plasticity of expansive soils. The soil used was brought from a location where structural damage was observed. The experimental program first dealt with determination of the chemical, mineralogical, and geotechnical characteristics of the untreated soil. The soil was then mixed with stabilizers at 3, 6, and 9% of the dry weight of the soil. The treated samples were subjected to liquid limit, plastic limit, swell percent, and swell pressure tests. Furthermore, the cation exchange capacity, exchangeable cations, and pH of the treated samples were also measured. This work showed that copper slag caused a significant increase in the swelling potential of the treated samples. Other stabilizers reduced the swelling potential and plasticity to varying degrees. The research further indicated that cation exchange capacity and the amount of sodium and calcium cations are good indicators of the effectiveness of chemical stabilizers used in soil stabilization.

The factors controlling the expansive nature of the soils and rocks of northern Oman

The factors controlling the expansive nature of the soils and rocks in Northern Oman were studied. Basic geotechnical data from over 40 sites were collected and using empirical relationships, swelling potentials were identified. A laboratory testing program was carried out using undisturbed samples from these swell pressures up to 3.5 MPa, and swell percent values up to 30 were measured. The clay minerals and cations of these samples were determined and Na-smectite was identified as being the main clay-mineral present. Microfabric studies showed generally dense clay matrices. However, these swelling materials exist as impersistent bands with non-swelling soils and rocks which makes prediction of the ground heave problematic.

Geological and engineering characteristics of expansive soils and rocks in northern Oman

The geology and former climate of northern Oman favoured the formation of smectite clay minerals in certain materials which are implicated in ground heave problems. Investigations have shown that the smectite content of these expansive materials was developed in Oligocene, Miocene and Pliocene times. No evidence of a significant content of smectite was found in pre Eocene strata or in Quaternary strata, except for Desert Fill. It is shown that the main types of expansive materials in northern Oman are bentonitic mudstones, marls and silty mudstones, argillaceous dolomitic limestone, altered conglomerates and the desert fill derived from these. These swelling materials exist as impersistent bands within the bedrock Tertiary conglomerates and limestones. A geotechnical testing program was carried out on undisturbed samples from Sultan Qaboos University staff housing areas where building damage had occurred, to evaluate mineralogical composition, cation content and swelling characteristics. The test results characterized these soils/rocks as highly expansive type with Na-smectite as the dominant clay mineral.

Properties of Omani artificial pozzolana (sarooj)

Artificial pozzolana (sarooj) has been used in Oman in various engineering structures for hundreds of years but its use is now limited to the restoration of castles and forts. This paper reports on the status of a major research project on Omani sarooj being undertaken at Sultan Qaboos University. Clays were collected from five sites in Northern Oman (Wadi Al-Mawal, Bahla, Al-Hamra, Birkat Al-Mouz and Qurayat) which were known for the production of sarooj in the past. A detailed program covering geotechnical, mineralogical, thermal, chemical and physical tests was carried out. It was found that the sarooj produced by Al-Hamra clays was superior to those of other sites. From the results, it was evident that the chemical composition, calcination temperature and duration of burning are the main factors for producing suitable sarooj.

Construction problems of engineering structures founded on expansive soils and rocks in northern Oman

Abstract Construction problems due to expansive soils and rocks are evident in Al-Khod (northern Oman). The geological and climatic conditions in northern Oman favoured the formation of smectite clay minerals in certain materials which are causing ground heave problems. The paper describes the fundamental aspects covering the geological background, site investigation, laboratory soil test results, mineralogy and damage. A detailed description of the damage which occurred to various elements of certain structures is provided. Distress to a typical residential house, a store house and an asphalt road is investigated in detail. The width of the cracks developed in these structures varies from hairline to very severe (of the order of 150 mm). Finally, based on the case study investigation, a number of remedial measures to eliminate or minimize ground heave problems are outlined.

Stabilization of oil‐contaminated soils using cement and cement by‐pass dust

Purpose – To investigate the effect of cement and cement by‐pass dust (CBPD) as a stabilizer on the geotechnical properties of oil‐contaminated soils resulting from leaking underground storage tanks, or soils surrounding petroleum refineries and crude oil wells.Design/methodology/approach – Oil‐contaminated soil (untreated soil) and a soil treated by bio‐remediation (treated soil) as well as a natural soil were obtained from Northern Oman. These soils were stabilized with cement and cement by‐pass dust at 0, 5, 10, 15 and 20 percent, by dry weight of the soil, and cured for seven, 14 and 28 days. Compaction, compressive strength, direct shear, permeability and leaching tests were carried out on the stabilized soils.Findings – The results indicate that cement and cement by‐pass dust improve the properties of oil‐contaminated soils. Traces of arsenic, barium, cadmium, chromium and lead were found in the oil soils, but none of them exceeded the EPA limits.Practical implications – Reuse in construction applic...

The Omani Artificial Pozzolans (Sarooj)

Sarooj is a local Omani term for artificial pozzolana produced by calcining clays. Calcined clay mixed with lime and water has been used as a cementing material for a long time. It has been used widely in hydraulic structures due to its good hydraulic properties and in military defensive installations due to its durability. This project focuses on the exploration of potential clay areas in Oman for the production of sarooj. A large number of samples have been collected from different sites in the country and were subjected to an extensive program of testing involving chemical, mineralogical, thermal, and physical analyses. This paper presents some of the results obtained for samples tested from five locations in Northern Oman (Al-Khod, Soor Al-Haboos, Al-Fulaij, Al-Hamra, and Al-Awabi). It was found that the sarooj produced by Al-Fulaij clays has higher strength than those of other sites. It was also found that the total content of silica, alumina, and iron oxide together with the burning temperature and the duration of burning have significant effect on the physical properties of the sarooj produced.

A Comparative Quantitative Study of an Omani Soil Using X-Ray Diffraction Technique

Two methods for the quantification of clay minerals using X-ray diffraction techniques: the Constant Mineral Standards Method and the Constant Clay Method were applied to soil samples from Al-Khod (Northern Oman). The first method was based on the addition of different concentrations of clay to constant mineral standards while the latter was based on the additions of known internal standards to the clay sample. The clay investigated in this study contained montmorillonite, palygorskite, illite and kaolinite. The areas of the reflection peaks were found to relate linearly with additions of different proportions of clay or mineral standards. Using the two methods, the concentrations of the different components and their experimental errors were determined. From the errors and self consistency of the results obtained, and the practicality of sample preparation, it is proposed to use the Constant Mineral Standards Method.

The use of brackish and oil-contaminated water in road construction

This paper discusses the use of non-freshwater, including brackish groundwater and oily production water, in road construction. Non-freshwater was obtained from four major oil production fields in Oman. First, chemical analyses were carried out on nine non-freshwater types, including tap water, obtained from the four sites. These water types were then used with well-graded sand (WGS), high-plasticity silt (HPS), and a road base material to evaluate water effect on material properties. Atterberg limits, compaction, California Bearing Ratio (CBR), swell percentage, swell pressure, and direct shear tests were performed. Results show that there is a slight decrease in the liquid limit when non-freshwater is used. Non-freshwater resulted in a slight decrease in optimum moisture content and a slight increase in maximum dry density in WGS, whereas with HPS it caused slight decreases in optimum moisture content and maximum dry density values. There was an increase in CBR when non-freshwater was used with WGS and HPS soils. However, the use of production water caused a decrease in CBR values for WGS. For the road base material, the use of non-freshwater generally caused a decrease in CBR. The swell pressure tends to increase when non-freshwater is used with HPS. For the road base material, there is a decrease in cohesion and an increase in friction angle when non-freshwater is used in lieu of tap water. Promising laboratory results indicate the potential use of brackish and oily water types in road construction.

Use of Tank Bottom Sludge to Construct and Upgrade Unpaved Roads

Tank bottoms are the liquids and residue, such as heavy hydrocarbons, solids, sands, and emulsions, that collect at the bottom of the treating vessel or that remain at the bottom of storage tanks after a period of service. Sludge composition is 50% to 65% crude oil, 20% to 35% water, and 5% to 20% solids. Disposal of tank sludge is a significant item of tank maintenance costs. Results are presented on the use of tank bottoms as a binder to construct and upgrade unpaved roads. Various sludge samples were initially characterized for chemical and physical composition, then three mixtures were prepared by using blends of aggregates and tank bottoms. No bitumen was used in the mixes. The mixtures include hot mix (aggregate and sludge were both heated), heated sludge and cold aggregate mix, and cold mix (no heat was applied). The Marshall mix design (ASTM D1559) was followed in the preparation and testing of the specimens. Results indicate that tank bottoms act as a binder to the aggregate and can provide significant strength. Heating both the sludge and the aggregate resulted in the highest stability value of 11.9 kN. An optimum sludge content of 6.5% by total weight of the mixture satisfied the requirements for low (3.3 kN) or medium (5.3 kN) trafficked surfaces or base layers according to Asphalt Institute specifications. Other mix properties, such as flow, air voids, voids in mineral aggregate, and voids filled with asphalt, were acceptable.