Taisir S. Khedaywi

Effect of Segregation on Fatigue Performance of Asphalt Paving Mixtures

The main objective of this research was to investigate the effect of segregation on fatigue performance of asphalt paving mixtures. Segregation in asphalt concrete pavements occurs when coarse material is concentrated in some areas of the pavement and fine materials in others. Segregation has been one problem that has resulted in poor performance in many pavements. Materials used in the study included gravel, natural sand, and an AC-20 asphalt cement. Aggregates were selected to meet the Indiana Department of Transportation specification for a No. 8 binder with a maximum aggregate size of 1 in. (25 mm). To simulate various levels of coarse and fine segregation, four artificially segregated mixtures were prepared in addition to the control asphalt mixture. Slabs were compacted for the five mixtures using the Purdue linear compactor. These slabs were cut into beams that were used to test for the fatigue properties of the five segregated asphalt concrete mixtures. Limits of fatigue were examined when flexural stiffness was one-third and one-half of the initial stiffness at 200 load applications. Results of the investigation indicated that the fatigue life of segregated asphalt concrete mixtures was significantly affected.

Pozzolanic activity of Jordanian oil shale ash

Abstract The ash of the retort residue of the oil shale from central Jordan has been further tested to evaluate its pozzolanic activity. According to the preliminary experiments the ash had cementive properties. Thermogravimetric analyses were performed on ash, cement, ash blended cement and ash-lime pastes. In the blended pastes, addition of ash seemed to decrease the amount of lime generated. In the ash-lime paste the lime consumption by ash with time followed a similar trend to the reactions of trass and silica fume with lime. The ash-lime reaction was mainly a diffusion controlled process obeying the Ginstling-Brounshtein equation. The pozzolanic activity of the ash, as indicated by its lime activity and rate constant, was not as high as the other pozzolans compared, mainly due to its lower fineness. Tests on compressive strengths of cement and lime mortars blended with ash confirmed the findings, indicating that up to 20% of cement could be replaced by ash used as an admixture. Ash-lime mortars could gain moderate strengths under accelerated curing, suitable for some building units.

Laboratory Study for Comparing Rutting Performance of Limestone and Basalt Superpave Asphalt Mixtures

The primary objective of this research effort was to conduct a rutting performance-based comparison between limestone and basalt Superpave asphalt mixtures using dynamic creep rutting tests. Two sets of mixtures were prepared using limestone and basalt ag- gregate, mixed with one asphalt binder having a Superpave performance grade of PG 64-10. To overcome the stripping potential of the Superpave basalt asphalt mixtures, 1% by total weight of the basalt aggregate was replaced by hydrated lime for the filler portion of the aggregate. Rutting was evaluated at four different temperatures (40, 50, 60, and 65°C) and one loading frequency of 8 Hz. Rutting test results indicated that the basalt Superpave asphalt mixtures exhibited superior performance relative to the limestone Superpave asphalt mixtures. The difference in the rut depth at 19,200 loading cycles between the limestone and basalt asphalt mixtures was statistically sig- nificant at levels of α ¼ 1, 5, 1, and 0.5% for the temperatures 40, 50, 60, and 65°C, respectively. The difference in the rut depth at 200,000 loading cycles between the two asphalt mixtures was statistically significant at levels of α ¼ 1, 5, 0.1, and 0.1% for the temperatures 40, 50, 60, and 65°C, respectively. In addition, the difference in the number of loading cycles to rutting failure between limestone and basalt asphalt mixtures was also statistically significant at a level of α ¼ 0.1% for all temperatures. DOI: 10.1061/(ASCE)MT.1943-5533.0000519.

AGGREGATE RUGOSITY AND SIZE EFFECT ON BITUMINOUS MIXES

Higher costs and possible restricted availability of asphalt have stimulated research and discussion on how to reduce the amount of asphalt in bituminous mixes without sacrificing service. A hypothesis was proposed suggesting that for each coarse aggregate type with different surface characteristics there is a specific fine aggregate size that contributes to developing an interlocking mechanism between the surfaces of coarse aggregates when they are combined in a bituminous mix. To test this hypothesis, two types of coarse aggregates having different surface characteristics or rugosity, limestone and rounded gravel, were used. For each aggregate, two one-size fractions were tested—19 mm to 25 mm and 6.4 mm to 4.75 mm. One type of fine aggregate (limestone) with five one-size fractions was used. Four flow binder film thicknesses were chosen. The packing volume and rugosity concepts were the theoretical basis. Asphalt and aggregate mixes were tested in compression. The results were evaluated by the use of regression equations. Graphical presentations and illustrations were used as necessary. Unconfined compression test results showed that for one-size limestone coarse aggregate, the highest strength values were associated with No. 60 to No. 80 fines in the mix and for one-size rounded gravel coarse aggregate, the highest strength occurred when No. 200 to No. 270 fines were added to the mix. The highest strength was associated with 50 μm flow binder film thickness for all mixes.

Studying rutting performance of Superpave asphalt mixtures using unconfined dynamic creep and simple performance tests

This study aimed at evaluating asphalt mixtures for rutting using two test procedures. The first procedure was the dynamic creep test, which was performed using the 5-kN Pneumatic Universal Testing Machine (UTM-5P). The second procedure was the flow number test which was performed by the Superpave Simple Performance Tester (SPT), currently known as the Asphalt Mixture Performance Tester (AMPT). Test specimens were prepared using crushed limestone aggregate and 60/70-penetration-grade asphalt binder having a performance grade (PG) of 64-10. Two aggregate gradations were used and compared in this study: a gradation passing above the restricted zone (ARZ) representing a fine gradation, and another gradation passing below the restricted zone (BRZ) representing a coarse gradation. Asphalt mixtures were compacted using the Superpave Gyratory Compactor (SGC). The SGC samples were then cored and sawed to produce fabricated test specimens of the desired height (150 mm) and diameter (100 mm). Specimens were tested at four temperature levels: 40°C, 50°C, 55°C, and 60°C. For comparison purposes, identical test parameters were used for both tests including: specimen dimensions, load frequency, load and rest periods, contact stress, and deviator stress. Test results were analysed to investigate the permanent deformation behaviour of the asphalt mixture with the temperature. The results for fine-graded mixtures and coarse-graded mixtures were analysed and compared. A comparison between the two test procedures was made based on the test results. The analysis and comparison were made based on the number of cycles at failure, the strain at failure, the number of cycles to reach 1.5% strain, and the strain at 1000 cycles. Both one-way ANOVA and two-way ANOVA procedures were used in the comparison. Results showed that a significant difference between ARZ asphalt mixtures and BRZ asphalt mixtures in the measured properties existed. The significance level was found to be strongly related to the test temperature. Results also showed that the flow number test and the dynamic creep test results had different behaviour with test temperature and sometimes opposite behaviour. The significance of the difference was also found to have an interaction with the test temperature. Based on the results and the comparison, it was clear that the SPT flow number test showed better accuracy and reproducibility of test results. The flow number test results also showed better fitting and no departures from the expected trend, unlike the dynamic creep test results.

Assessment of the potential for using EAFD in cement paste in Jordan

This paper presents an experimental investigation on the effect of electrical arc furnace dust (EAFD) on normal consistency, setting time, soundness, dry bulk density and compressive strength of hardened cement pastes. EAFD dusts were used to partially replace cement at 0, 1, 3, 5, 10, 15 and 20% by weight. Test results showed that the cement paste with EAFD produced paste with lower normal consistency than original cement paste (0% of EAFD). The rate of decrease in normal consistency is observed to be more for percentage replacement (10–20%). In addition, the result found that EAFD prolonged the setting time of cement paste. The dry bulk density of paste was strongly affected by the replacement of EAFD. EAFD decreased the dry bulk density and therefore increased the porosity.

Mechanical Behavior of Asphalt Mastics Produced Using Waste Stone Sawdust

This study intended to evaluate the use of waste stone sawdust filler with asphalt binders and compare the mechanical properties of the waste filler-asphalt mastic with those of the asphalt mastic produced using the typical limestone filler. The mastics were prepared at four filler-to-asphalt ratios by volume of asphalt binder: 0.05, 0.10, 0.20, and 0.30. A dynamic shear rheometer (DSR) strain-controlled frequency sweep test was used to evaluate the properties of the control asphalt binder and the mastics. The test used a constant strain of 10% and loading frequencies of 10, 5.6, 3.1, 1.78, 1.0, 0.56, 0.31, 0.178, and 0.1 Hz and was conducted at wide range of temperatures: 10, 20, 30, 40, 50, 60, and 70°C. The test measured the complex shear modulus ( ) value and the phase angle for the binder and the mastics. The findings of this study showed that the stone sawdust filler demonstrated higher resistance to fatigue and rutting behavior than the limestone filler. However, the elastic behavior of the two asphalt mastics was nearly similar and increased with the increase in volume ratio. It was also found that the best-fit model described the relationship between the volume ratio and each of and , and the mastic-to-binder modulus ratio was the exponential model with high coefficient of determination ( ). The differences in the value between the limestone filler and the stone sawdust filler were relatively insignificant particularly at low loading frequencies and high temperatures. Finally, the mastic-to-binder modulus ratio decreased with the increase in loading frequency.