Experimental Fracture Toughness Study for some Modified Asphalt Mixtures

Abstract

The use of modifiers or additives in the asphalt mixtures is a suitable and common method for improving their mechanical properties especially under high temperature service conditions. However, for cold climates which the pavement of roads usually experience subzero temperatures, the overall failure mechanism of asphalt layers may be occurred mainly due to elastic brittle fracture and growth of initiated cracks inside the pavements. Fracture toughness is the most important parameter for characterizing the crack growth and failure of cracked materials and structures such as the asphalt pavements. Hence, the main aim of this research is to study the effect of different additives including Poly phosphoric acid (PPA), Styrene butadiene styrene (SBS), Anti striping agent (ANTI), Crumb rubber (CR) and FT-paraffin wax (Sasobit) on the low temperature mode I fracture resistance of asphalt mixtures. A series of asphalt samples with different percentages of the mentioned additives were manufactured in the shape of semi circular specimens containing vertical edge cracks. The test samples were then loaded monotonically using a symmetric three-point bend fixture at a constant subzero temperature of-15°C. The value of mode I fracture toughness (KIc) were determined by recording the critical fracture loads of tested specimens. It is shown that all the investigated additives increase the low temperature fracture toughness of the asphalt mixture and the maximum increase in the value of KIc occurs when the sasobit and CR additives are used.

Investigation of fatigue and fracture properties of asphalt mixtures modified with carbon nanotubes

“…On the other hand, six replicates can be produced from each superpave gyratory compactor cylindrical sample leading to reduction of discrepancies in asphalt mixture properties due to inherent heterogeneous nature of these randomly distributed composite materials. The SCB testing configuration has been applied in estimating the fracture properties of many brittle and quasi‐brittle materials and also asphalt concretes . The behaviour of asphalt mixtures at intermediate ambient temperatures does not follow the framework of linear elastic fracture mechanics, and it should be described by nonlinear fracture mechanics approach.…”

“…The SCB testing configuration has been applied in estimating the fracture properties of many brittle and quasi-brittle materials [26][27][28][29][30][31][32] and also asphalt concretes. [33][34][35][36][37][38][39][40][41] The behaviour of asphalt mixtures at intermediate ambient temperatures does not follow the framework of linear elastic fracture mechanics, and it should be described by nonlinear fracture mechanics approach. In the current research study, the J-integral concept was incorporated to investigate the fracture properties of asphalt mixtures.…”

Effect of temperature and air void on mixed mode fracture toughness of modified asphalt mixtures

“…Because of the huge amount of costs that are spent annually for the maintenance and rehabilitation of cracked roads and pavements, it is necessary to study the affecting parameters on cracking behavior of asphalt mixtures at low temperatures. The use of linear elastic fracture mechanics (LEFM) is a suitable discipline for evaluating the fracture toughness of asphalt pavements based on the crack tip stress field [1][2][3][4][5][6][7]. In this framework, the stress intensity factor (SIF) is known as the main parameter for describing the crack growth resistance.…”

“…Since 1970, a large number of research works have been performed to study the fracture resistance of different asphalt mixtures using the concept of fracture energy or the stress intensity factor by employing numerical analyses, simulation techniques and experimental methods [1][2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18]. The influence of asphalt characteristic specifications including the binder type, aggregate type, size of aggregates, air void contents, temperature, and loading condition have been investigated in the past for different asphalt mixtures.…”

The effect of loading rate on fracture energy of asphalt mixture at intermediate temperatures and under different loading modes

“…At low temperature conditions, the probability of brittle crack initiation and propagation in the AC layer becomes more due to the relative brittleness of pavements at these temperatures. Thus, many researchers have studied low temperature fracture behavior of asphalt mixtures using the principles of linear elastic fracture mechanic (LEFM) [7][8][9][10][11][12]. Various fracture models have been considered for different characteristics of asphalt mixtures, but such models are generally suitable for low temperature testing conditions, in which the type of fracture is dominantly linear and elastic.…”