Ahmed N. Bdour

One-dimensional hydrodynamic/sediment transport model applicable to steep mountain streams

A new one-dimensional (1-D) numerical model for calculating flow and sediment transport in steep mountain streams is developed. 3ST1D, which stands for Steep Stream Sediment Transport 1-D model, is applicable to unsteady flowconditions that occur over transcritical flowstream reaches such as flows over step-pool sequences. 3ST1D consists of two coupled components, the hydrodynamic and the sediment transport. The flow component is addressed here by solving the unsteady form of the Saint-Venant equations. The TotalVariation Diminishing Dissipation (TVD)-MacCormack scheme, which is a shock-capturing scheme capable of rendering the solution oscillation free, is employed here to approximate the hydrodynamic solution over transcritical flow stream reaches. The sediment component of the model accounts for multifractional sediment transport and incorporates a series of various incipient motion criteria and frictional formulas applicable to mountain streams. In addition, sediment entrainability is estimated based ...

Utilisation of waste marble powder in cement industry

Presently large amounts of slurry are generated in marble cutting plants with serious consequences on the environment and humans. This paper presents test results showing the feasibility of using waste marble powder (WMP) in cement industry as a substitute limestone. Also, it describes the formulation of new lime-based (CR II) cementitious materials derived from these industrial wastes. The characterisation included chemical composition, determined by X-ray fluorescence (XRF), thermal behaviour and particle size distribution. Also, physical parameters of milled powders such as the specific surface area and the percent of weight retained in a fixed sieve (75 μm) were introduced. Test results show that this WMP-based cement is capable of improving hardened concrete performance up to 16%, enhancing fresh concrete behaviour and can be used in architectural concrete mixtures containing white cement. CR II is an environment friendly product, cheaper and it involves small equipments with no convoluted technologies.

Assessing Mechanical Properties of Hot Mix Asphalt with Wire Wool Fibers

This paper investigates the potential application of wire wool in the modification of hot asphalt mixes (HMA). Wire wool material is widely available at local markets as a by-product of wire wool industry and as waste products from homes. For the purpose of this study, wire wool was cut into small pieces so that it can be placed in the asphalt mixes. Different percentages of wire wool were incorporated with the hot asphalt mixes (0.0%, 0.25%, and 0.5%) of the total weight of the asphalt binder. Various experimental tests were used to evaluate the modification effectiveness of combining wire wool with hot asphalt mixes, namely, the Marshall Stability, indirect tensile strength (ITS), dynamic creep, fatigue, and rutting tests. Test results proved that the addition of wire wool increased the tensile strength of the asphalt concrete mixes. However, rutting increased due to increasing percentage of wire wool. Therefore, mixes containing wire wool can be used in areas where rutting is not the expected predominant distress type.

Bias in return period of droughts estimated from tree-ring reconstructions

This article investigates the bias in return period of droughts of extreme duration evolved from trun-cating tree-ring reconstructed precipitation. 239 years of tree-ring reconstructed annual precipitation for Madaba region in Jordan, covering the period 1743–1981, was used to explore the bias. Furthermore, 100 traces of simulated annual precipitation, each of 239 years, were generated using stochastic simulation model for comparison purposes. The results show that the return period estimated from the analysis of the tree-ring reconstructed precipitation departs increasingly downward from the expected results provided by simulation or theoretical models as the drought duration increases (becomes more extreme). The bias in the estimated return period can be neglected when the drought duration is fairly short, i.e. 1–2 years for the case under study.

Innovative Application of Scrap-Tire Steel Cords in Concrete Mixes

Many researchers have investigated the use of recycled tire products in several traditional civil engineering materials. This research is exploring the use of steel cords, a by-product of the tire recycling process, in concrete mixes. Different concrete specimens were fabricated and tested in uniaxial compression and splitting tensile strength. The steel cords were substituted into the concrete mix in volumetric percentages of various ratios. Results show that mechanical properties of concrete made with steel cords are improved compared with concrete mix made with the traditional scrap-tires recycled material. Also, results show that even though the compressive strength is reduced when using steel cords, this reduction is minimal. When 2% of steel cords are used there is 18% increase in ductility. Moreover, splitting tensile tests show that concrete mixtures with any steel cords content have much greater toughness than control mixture. This mechanical property mix indicates an excellent potential application of modified concrete mix in structures that absorb large amount of energy.