Mohamed E. Abdel-Motaleb, Ahmed Mohamady

Construction Engineering Dept. Faculty of Engineering, Zagazig University, Egypt



For various reasons, mostly associated with achieving maximum density and desired voids

properties, certain desirable gradation limits are usually required of aggregates for hot

asphalt mixes, for example 4C gradation according to Roads and Bridges Authority. So,

aggregate blending to obtain the desired gradation is considered the first step in asphalt mix

design. Because it is unlikely that a single natural or quarried material will meet these

specifications, two or more aggregates of different gradations are typically blended (Bin2,

Bin1, Sand and Filler) to meet specification limits. After several trials of blending the

available aggregate sizes in Egypt (Bin2 and Bin1), Sand and Filler to meet specification

limits of 4C gradation, passing sieve No. 4 always tends to the lower limit (48%). While on

the other hand, passing sieve No. 30 always tends to the upper limit (30%). So, the objective

of this study is to investigate the effect of humpy gradation at sieves No. 4 and 30 on the

engineering properties of paving mixes in terms of Marshall properties, tensile strength, and

rutting resistance. To achieve this objective 9 different mixes with different hump ratios at

sieve No. 4 (HR4) and at sieve No. 30 (HR30) were formed and tested in Marshall, indirect

tensile test and creep test. The results of this study revealed that the HR4 which give theoptimum performance of paving mixes is 1 ± 0.5, while that for HR

30 is 2.5 ± 0.5, further

increase in HR4 or decrease in HR30 adversely affect paving mix performance.

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