Ibrahim M. Asi

COMPARATIVE STUDY OF ASPHALT CONCRETE LABORATORY COMPACTION METHODS TO SIMULATE FIELD COMPACTION

Abstract The main objective of this study was to compare different laboratory compaction methods to field compaction and to select the laboratory method that was similar or close in compaction to that of the field. The candidate compaction methods were: (a) Marshall Automatic Impact Compaction; (b) Marshall Manual Impact Compaction; (c) California Kneading Compaction; (d) Gyratory Shear Compaction (angle of gyration 1.25°); and (e) Gyratory Shear Compaction (angle of gyration 6°). The evaluation of the five laboratory compaction methods was based on the similarity between the engineering properties of the laboratory compacted samples and the field cores. The engineering properties studied were resilient modulus, air voids, bulk density, and static creep behavior. The laboratory compacted specimens and field cores were also evaluated with the objective of identifying a promising laboratory compaction technique which would be able to produce mixtures with engineering properties closest to those of mixtures compacted in the field. Samples for this study were selected from four projects located at different locations in the Eastern Province of Saudi Arabia. The principal conclusion of the study was that the Gyratory Shear Compaction (angle of gyration 1.25°) method best represented the engineering properties of the field cores.

Stabilization of dune sand using foamed asphalt

Foamed asphalt technology has increasingly gained acceptance as an effective and economical soil improvement and stabilization technique, mainly because of its improved aggregate penetration, coating capabilities, and handling and compaction characteristics. This laboratory research program was carried out to investigate the feasible use of foamed asphalt technology in Saudi Arabia to improve the prevalent dune sands for possible use as a base or subbase material. Several variables were investigated to evaluate the relative improvement of dune sand as well as to permit the development of design procedures for the future use of foamed asphalt technology in the harsh climatic conditions of eastern Saudi Arabia. Statistical analysis of the results was employed to verify the effects of emulsified asphalt and foamed asphalt treatment, with and without the addition of Portland cement, on the strength characteristics of the treated mixes. The results displayed significant improvement in the performance of dune sand foamed asphalt mixes, as compared to that of the emulsified asphalt mixes.

PERFORMANCE AND CORRELATION OF THE PROPERTIES OF FLY ASH CEMENT CONCRETE

This investigation was conducted to evaluate the performance of fly ash cement concrete specimens made by cement replacement levels of 0, 10, 20, 30, and 40% with Specification for Coal Fly Ash and Raw or Calcined Natural Pozzolan for Use as a Mineral Admixture in Concrete (ASTM C 618) Class F fly ash. Compressive strength, pulse velocity, porosity, and water permeability were determined after 28, 90, 180, and 360 days of water curing. Reinforced concrete specimens were used to assess the corrosion-resistance of plain and fly ash cement concretes in chloride environments. The corrosion potentials on steel were measured at periodic intervals to determine the time-to-initiation of reinforcement corrosion. The data generated was statistically analyzed to ascertain the relationship between the various properties of plain and fly ash cement concretes. Results indicated a better performance by the 20% fly ash cement concrete than plain cement concrete and those made with other cement replacement levels. A good correlation between porosity, compressive strength, permeability, and porosity was observed.

Stabilization of an arid, saline sabkha soil using additives

Abstract This paper describes the results of an investigation on the effect of five stabilizing agents, namely limestone dust, marl, emulsified asphalt, cement and lime, on the properties of an arid, saline sabkha soil from eastern Saudi Arabia. Standard compaction and unconfined compressive strength tests were performed, the latter on wrapped specimens that had been allowed to cure for seven days. The results indicated that the density of sabkha mixtures could not be used as a primary criterion in any stabilization programme and the maximum strength of sabkha mixtures was attained at moisture contents much lower than the optimum. Despite the sabkhas coarsegrained nature, neither addition of marl nor of emulsified asphalt gave any significant improvement in the properties of sabkha and the effect of adding limestone dust was marginal. However, the addition of either lime or cement in the range of 2.5 to 100y weight of soil increased the strength between and 22 times.

Improvement of marl and dune sand for highway construction in arid areas

Abstract Major parts of the Eastern Province of Saudi Arabia are covered with windblown dune sand which is characterized as poorly-graded soil with high permeability. Also, marl, which is available in abundance in this region, has poor strength. It is usually required to use these materials as subgrade layers or as a backfill in base and subbase layers of roads and highways. Because of the low strength characteristics of these materials and the high water table in the region, some sort of stabilization is needed to improve the characteristics of these materials. In this research, slow-setting emulsified asphalt and medium-curing cutback asphalt were used to stabilize both marl and dune sand. Lime and Portland cement ( 2% and 4% ) were added to the stabilized soils to accelerate the curing process and to reduce stability loss due to water damage. It was found that the stabilizing agents improved both shear strength and resistance of the analyzed soils to water damage. It was observed that Portland cement was more effective than lime.

Stability of Vertically Bent Pipelines Buried in Sand

This paper discusses the stability of underground pipelines with preformed vertical bends buried in sandy soil. More specifically, the minimum cover height required to prevent the pipe from bowing under the action of forces due to temperature change and internal pressure is estimated. The variables considered include the pipe and soil materials, diameter, thickness, overburden height, bend radius, bend angle, internal pressure, fluid specific weight, and temperature variation. A comprehensive three-dimensional finite element analysis is carried out. The results are extracted from the output obtained. These results are put in a database which is used to develop general regression models to determine the relationships among the different variables. Different buckling modes are also considered. All of these results and models are entered into a computer software program for ready access.

Characterization of polymer modified Gulf asphalts

The rheological properties of polymer modified Arab asphalts were characterized using both routine test methods, such as penetration and softening point, and more rigorous methods, which included low temperature stiffness measurements using a bending beam rheometer, and dynamic mechanical analysis using dynamic shear rheometer. HP-GPC method of analysis was used to produce profiles of the molecular size distribution of the modified asphalts. Models were built to predict the rheological and performance-based properties from the HP-GPC profiles. The results indicated that polymer modification is capable and effective in improving the neat Arab asphalt binders rheological properties to meet and satisfy the performance requirements of the Gulf countries.

Physicochemical characterization of Gulf asphalts

ABSTRACT The neat asphalt samples collected from the different asphalt producing refineries in the Gulf countries were subjected to two aging processes to simulate heating, mixing and compaction, and in service aging. The asphalt samples of the different aging stages were subjected to physical and chemical tests. The measured physical and consistency properties were used to calculate various temperature susceptibility indices. Corbett analysis, Ion exchange chromatography, HP-GPC, and FT-1R analysis were used to study the effect of aging on the molecular nature of asphalts.

Cover Requirement and Stability of Horizontally Bent Buried Pipelines

The soil cover requirement for horizontally bent buried pipeline is discussed. The variables considered in this research include the pipe diameter and thickness, the radius and angle of the bend, the internal pressure, the fluid specific weight, the overburden height, the temperature rise, and the material used. A comprehensive threedimensional finite element analysis is run. The results obtained are utilized to develop regression models for the maximum allowed temperature change as well as the minimum overburden height. The relationships among the different variables are determined. To guard against elastic instability, several buckling mode are checked.