عباس طالب محسن الهدابي

Hot-mix asphalt (HMA) suffers a reduction in stiffness and strength under repeated cyclic loading, such that it eventually cracks. This paper reports the measurement of asphalt fatigue degradation in terms of stiffness modulus and dissipated strain energy (DSE). Three degradation rate parameters were derived from the linear parts of the relationships against a number of cycles: normalised stiffness modulus from the traditional approach (TA), and DSE and cumulative dissipated strain energy (CDSE) from the energy concept approach. Three techniques were used to perform the fatigue test: dynamic shear rheometer, two- and four-point bending tests. Different asphalts were made from open and dense gradings of limestone and granite aggregates, and with soft and hard binders according to British standards. The tests revealed that the DSE and CDSE degradation parameters were incompatible with the TA in the strain-controlled test mode, but compatible in the stress-controlled test mode. The variation and scattering of all degradation parameters was relatively low. In conclusion, the normalised stiffness modulus degradation rate parameter looks most promising for evaluating and predicting the fatigue performance of HMA regardless of the test technique and mode.

Recently, applying of the waste materials as mineral filler in hot asphalt mixture has many advantage for economic and environmental impacts and also used to improve the hot asphalt mixtures characteristics. In this research, sugar industry waste materials has been used as mineral filler to investigate the achievable prospects to improve hot asphalt mixture properties. The aim of this study is to evaluate the effect of adding Sugar Waste (SW) materials on the properties of hot mix asphalt in comparison with the State Commission of Roads and Bridges (SCRB, R9) requirements. Two groups of hot asphalt mixtures have been prepared, the first was with the Ordinary Portland Cement (OPC) as mineral filler i.e. (control mixture) and the second was prepared with SW materials (modified mixtures). These mixtures have been assessed based on different experimental tests which were Marshall Stability and Flow, Indirect Tensile Strength (ITS), Index of Retained Strength (IRS) and Long Term Aging (LTA). The results indicate that there is an improvement in the mixture properties; slight increase in Marshall Stability, an improvement in Indirect Tensile Strength, enhanced their Marshall stability after aging when tested in accordance to LTA. Furthermore, the modified mixtures comply with (SCRB, R9).

An accurate asphalt mix design is a big issue to produce high quality pavement layer. Introduce a computer program that can be used to design different types of asphalt concrete layers i.e. base, binder and surface course will be very helpful. Therefore, the authors are introducing Asphalt Mix Design by MATLAB Program (AMDMAP) software to be used as a replacement to the manual calculations. The input data such as the characteristics of the used materials and lab work results must be available to run this program. The main output will be indicating the optimum asphalt content. Also, the relationships between Marshall Stability, Marshall flow, mixture density, Air Voids, Voids in Mineral Aggregate and Voids Filled with Asphalt vs different contents of asphalt will be produced. Mixture properties at optimum asphalt content will be indicated. Furthermore, the results will be compared with the standard specification of roads in Iraq.

Ignition of waste paper sludge at elevated temperatures to produce electricity in power generation plants utilizing fluidized bed combustion generates paper sludge ash. Due to the high concentration of lime and gelignite in paper sludge ash, it is expected that it will play a vital role as a cementitious material. This paper investigates the use of paper sludge ash to improve the mechanical properties of the granular materials, which are suitable to subbase course for road and building constructions. Also, a comparison study with the use of Portland cement as an additive to granular materials has been covered. The mechanical properties were evaluated by conducting the California bearing ratio test for the two adopted methods. Moreover, the compressive strength of the samples using paper sludge ash and cement are investigated. In accordance to the California bearing ratio test, 4% paper sludge ash was indicated as the optimum ash content at which the California bearing ratio value increased by 173% and 111% in comparison with untreated material and 6% cement, respectively. On the other hand, and by means of the compressive strength, the granular materials with 4% paper sludge ash has compressive strength higher than those with 6% cement.

One of the major problems that have plagued cold Bitumen Emulsion Mixtures (BEMs) since their introduction is high air voids. Therefore, this research will focus on this property and the attempts that have been applied to decrease the air voids of the produced new mixtures will be explained. In this connection, microwave heating has several advantages in comparison with the conventional heating method such as: it is volumetric heating, which represents an energy-saving point, and promotes rapid curing, which might enhance productivity. Therefore, a novel Half-Warm Rolled Asphalt (HWRA) has been produced by means of a pre-compaction microwave heating method. Consequently, Cold Rolled Asphalt (CRA) mixtures containing Ternary Blended Filler (TBF-2) have been mixed and then microwave heating, with 2450 MHz frequency and 300 W power, was applied in different durations in the pre-compaction method. The optimum microwave conditioning time was indicated in terms of stiffness modulus, air voids content and temperature which was 3 min microwave conditioning was chosen as the air voids decreased from 10.1% to 7.3%, the stiffness modulus decreased slightly and within an acceptable range and, finally, the temperature was in the moderate range (69 °C). The mechanical properties of HWRA have been investigated in terms of stiffness modulus, creep performance, fatigue life and fatigue fracture while water sensitivity and Long Term Oven Aging (LTOA) were conducted to investigate its durability. Generally, the performance in terms of mechanical properties and durability is promising due to high early stiffness modulus, long fatigue life and high Stiffness Modulus Ratio (SMR) in comparison with the control CRA and conventional hot asphalt mixtures.

Consuming of by-product or waste materials in highway engineering is significant in the construction of new roads and/or in renovations of the existing ones. Pulverised Fuel ash (PFA), which is a by-product material of burning coal in power stations, is one of these materials that might be incorporated instead of mineral filler in hot asphalt mixtures. Two types of surface course mixtures have been prepared one with conventional mineral filler i.e. ordinary Portland cement (OPC) while the second was with PFA. Several testings have been conducted to indicate the mechanical properties which were Marshall Stability and Indirect Tensile Strength tests. On the other hand, moisture damage and ageing have been evaluated by indicating Index of retained strength (IRS) and Long Term Aging (LTA), respectively. In accordance to the experimental investigation, the new hot asphalt mixtures i.e. with PFA mineral filler are comparable with conventional mixture and comply with the requirements which are recommended for surface course by the Standard Commission for Roads and Bridges (SCRB) in Iraq.