H.I. Al-Abdul Wahhab

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.

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.

Improving slurry seal performance in Eastern Saudi Arabia using steel slag

Abstract Harsh climate, heavy traffic and, most importantly, use of low-quality aggregates have resulted in unsatisfactory slurry seal performance in the eastern region of Saudi Arabia. On the other hand, blast furnace steel slag, a superior aggregate type with excellent strength and surface properties, is being wasted as a by-product during the steel manufacturing process. This research was carried out to assess and improve the performance of slurry seal mixtures in the laboratory using the Aggregate Blend Improvement Technique by incorporating steel slag aggregate. Aggregate blends consisting of slag and limestone were evaluated to form an improved slurry seal mixture that will generate simultaneously greater wear-resistance and improved bonding characteristics with bitumen. Results indicate that significant improvements in mixtures are guaranteed through improved aggregate blending of slag with limestone.

Performance of recycled plastic waste modified asphalt binder in Saudi Arabia

Abstract The amount of solid plastic waste generated from material packages like plastic bottle and similar utilities within the kingdom of Saudi Arabia has skyrocketed. This is as a result of the increased level of industrial packaging due to rapid industrialisation and fast urbanisation in the country. The associated cost of managing these solid wastes has also multiplied as the task become difficult and enormous. The effect of polypropylene, high- and low-density polyethylene (PP, HDPE and LDPE)-recycled plastic wastes (RPW) on the viscoelastic performance of the local asphalt binder has been investigated. The recycled plastics were obtained by shredding and grounding the RPW to a desirable size for easier blending with the asphalt binder. All the RPWs result in an improved rutting performance. The RPW-modified asphalts upper PG limit increase by at least one level for each 2% increase in the RPW content, in most cases. An increase of 55, 19 and 9% in resilient modulus (MR) was observed for PP-, HDPE- and LDPE-produced asphalt concrete (AC), respectively. Correlation between the MR of the AC and non-recoverable creep compliance (Jnr) of the asphalt binder was established. The obtained viscoelastic properties of the RPW-modified binder was utilised to model a typical pavement section using AASHTO mechanistic empirical pavement design guide (ME-PDG) software. The predicted distresses of the modelled pavement shows significant rutting and fatigue performance improvement for pavement produced with the RPW. Elastomeric type of polymer is required to supplement these RPW to enable them meet the AASHTO TP 70 elastic recovery requirement.

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.

Storage stability and high-temperature performance of asphalt binder modified with recycled plastic

Huge amounts of generated non-degradable plastic wastes constitute a major global environmental nuisance. The combined annual municipal solid waste (MSW) generation of Saudi Arabian Kingdom (KSA) exceeds 14,000,000 tonnes, with an average per capita of 1.4 kg/day. Plastic wastes constitute up to 10% of these MSW. The local asphalt can only perform satisfactorily without polymer modification in an environment with a maximum pavement temperature below 64°C. But the 7-day maximum pavement temperature ranges between 64°C and 76°C within the Kingdom. Dynamic storage stability, high-temperature performance, non-recoverable creep compliance (Jnr), and strain recovering tendency of recycled high- and low-density polyethylene (RHDPE and RLDPE), and recycled polypropylene-(RPP) modified asphalt binders in combination with styrene–butadiene–styrene (SBS) and polybilt (PB) were presented in this study. Improved high-temperature performance was observed. Even though the recycled plastic waste-modified binders lack sufficient strain recovering ability, RLDPE and RHDPE could be utilised along with an elastomeric SBS to achieve a higher recovery and strain resistance, than that which could be achieved if the same amount of SBS alone is used. RPP content above 2% will lead to an unstable modified asphalt binder. The RHDPE content below 4% and the RLDPE content below 6% whether containing either SBS or PB have shown good storage stability trait under mild agitation, in terms of both time degradation and separation.

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.

Strain recovery rate and absolute per cent recovery of polymer-modified asphalt binders

ABSTRACT Multiple Stress Creep and Recovery (MSCR) test was conducted on four different types of polymer-modified asphalt (PMA) with three different performance grade (PG) levels, at two stress levels (0.1 and 3.2 kPa) and four temperatures (58°C, 64°C, 70°C and 76°C). Strain recovery rates, absolute per cent recovery and creep compliance recovery rate of the PMAs at near instantaneous (NI) and near steady-state (NSS) regions were estimated and analysed. Higher levels of applied stress and temperature have induced a correspondingly higher rate of strain recovery both at NI (RRNI) and NSS, due to additional rebound energy accompanying more sustained deformation. Similar but mild strain recovery rate trend was observed with increasing PG. The strain recovery rate is inversely proportional to the per cent strain recovered, for a given temperature and applied stress, both at NI and at NSS region. An absolute per cent recovery at NI (%RNI) and NSS (%RNSS) was estimated in terms of the strain recovery rates. The %RNI is relatively constant for all rest periods, and can be obtained within the first 2 seconds of the creep-recovery cycle. Finally, even though the conventional MSCR parameters (i.e. Jnr and R) showed statistically significant correlation with the AC rutting, some strain recovery rate base parameters (%RNI and %RNSS) demonstrate a statistically better correlation with the AC rutting.

Design and maintenance criteria for Saudi bituminous concrete mixes

Abstract Premature rutting has occurred on a number of highways recently built in Saudi Arabia. The Ministry of Communications, in an effort to solve the problem, has initiated a number of studies and started to replace affected pavements. The aim of this study is to identify possible factors which may relate to rutting and to recommend maintenance and repair criteria for existing rutted pavements. The study covers nineteen sections of eleven major highways. Results indicate a direct relationship between rutting and the percentage of air voids; the percentage of voids in mineral aggregate; the percentage of voids filled with asphalt, resilient modulus at 25°C; and bitumen viscosity. These properties were used as bases for maintenance criteria as well as criteria for the design of mixes to resist rutting on Saudi roads.