Influence analysis of foamed asphalt mixture gradation based on mechanical properties
In order to determine the influence and rules of the gradation of foamed asphalt on the mechanical properties, three typical gradations of foamed asphalt including the continuous gradation AC-20, the discontinuous gradation SMA-20 and the skeleton embedded crowded structure FAC-20 were taken for dry and wet splitting strength test, besides the mechanical properties of asphalt mixture under different gradations were systematically researched. The gradation composition fluctuation of four key sieve pores consisting of 0.075 mm, 0.3 mm, 1.18 mm and 4.75 mm affecting the mechanical properties of the foamed asphalt mixture gradation were systematically researched. The experimental results showed that foamed asphalt mixture was not suited for the stable discontinuous gradation; the Wittgen stable recommended gradation of foamed asphalt had better mechanical properties; the passing rate of sieve pore size bellow 0.075mm was the key factor affecting the gradation properties of the foamed asphalt mixture, and the rate between five percent and twelve point five percent had better mechanical properties foamed asphalt mixture; the smaller sieve pore size was, the influence of the fluctuation of the passing rate on the mechanical properties of gradation was greater; among others
STRUCTURAL RESPONSE OF FOAMED-ASPHALT--SAND MIXTURES IN HOT ENVIRONMENTS
This research project was conducted to investigate the ability of foamed-asphalt to stabilize local marginal sand aggregates for use as base or subbase pavement materials. The variables measured were intended to give indications of the quality of performance of these mixtures as well as aid in the development of design procedures for the use of foamed-asphalt as a stabilizing agent under the relatively high temperature conditions in the Arabian Gulf. Quantitative information is given about the effects on mixture response of significant factors such as sand type and gradation, quality and quantity of the fine fraction, asphalt grade and its percentage, moisture content, and curing condition. Both moisture and temperature susceptibilities of foamed-asphalt mixes were found to be significantly reduced by the addition of limestone powder to modify the fine fraction of sand. Structural response of foamed-asphalt mixes was compared with that of other hot-asphalt-sand mixes commonly used as base material in Kuwait. It appears that properly designed foamed-asphalt--sand mixes have a structural thickness that corresponds to that of hot asphalt and much less susceptibility to permanent deformations under traffic loads in hot environments.
A NEW METHOD OF PREDICTING THE STIFFNESS OF ASPHALT PAVING MIXTURES
This paper deals with the study of twelve bituminous mixes selected to cover the whole range of mixes for road, airfield and hydraulic work applications. The determination of their stiffness modulus and loss angle under dynamic load, with the aid of a two-point bending machine has led to the following conclusions: (1) the stiffness modulus of the mix (ratio of the stress amplitude to the strain amplitude), at relatively low temperatures and short times of loading, is essentially dependent on: (a) the stiffness modulus of the bitumen binder contained in the mix, under the service conditions, (b) the volume percentages of the different mix components (aggregates, bitumen binder, air). (2) the loss angle (phase lag between the stress and the strain) is mainly influenced by: (a) the bitumen binder consistency, (b) the volume percentage of this binder. From these findings, a method of predicting the stiffness modulus and loss angle has been developed. This method is applicable to all asphalt paving mixtures from filler-bitumen (mastic) mixes to very open (high void) mixes for roads. The stiffness modulus and the loss angle are determined with the aid of two nomographs or a computer programme. /Author/TRRL/