Four-point bending test on prismatic-shaped specimens

7 Four-point bending test on prismatic-shaped specimens 

This test method determines the asphalt s behaviour under repetitive fatigue loading in a four-point bending test equipment in which the inner and outer clamps are symmetrically placed and a slender rectangular-shaped specimen (prismatic beam) is used. The prismatic beam is subjected to four-point periodic sinusoidal bending with free rotation and translation at all load and reaction points. 

The height, H, and width, B, of the specimens depend on the maximum aggregate size, D, and should be at least 3 x D (or 2.5 x D in the case of large values of D). The difference between the maximum and minimum measured value of the width and height is not greater than 1.0 mm. 

The effective length, L (from clamp to clamp), should be at least six times the highest value of width, B, or height, H. The total specimen length (L d should not be higher than 1.1 X L. Hence, for asphalts with D = 20, the specimen dimensions could be 60 mm x 60 mm X 380 mm. 

The specimens are produced and prepared as in the three-point bending test and the minimum number is 18, 6 specimens for each of the three levels of chosen loading mode (constant deflection or constant force). 

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