EFFECT OF HUMPY GRADATION ON PAVING MIXES PROPERTIES

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