Abstract
The effect of the coarse aggregate type on the fatigue flexural behavior of concrete was investigated in this work. Three types of the coarse aggregates were selected from three different careers (CA1, CA2 and CA3). The mechanical parameters of these aggregates were determined (Los Anglos and Micro Deval). Prismatic specimens (70×70×280 mm) for each concrete mixture were made with aggregates of each source. The flexural fatigue tests were conducted on these concrete samples with varying levels of loading of 55 to 80% and the ultimate flexural strength. The test frequency is around 80 Hz and it is automatically determined by pulsing the fatigue machine for a resonance situation (the phase shift is δ=0) between the mass-spring-specimen system. The obtained results show that the aggregates which have the similar parameters (Micro Deval and LA), provide better adhesion with cement paste, and therefore a greater bending strength. The strength evolution at short-term age is typical for specimens based on aggregates with low wear resistance by triturate (a high Micro Deval coefficient). Regarding the fatigue flexural behavior, the concrete specimens based on CA1, which have similar coefficients of Los Angeles and Micro Deval (respectively 18 and 16) present the behavior (load/cycle numbers) close to that of the model prototype of the Wohler curve. This can be explained by a high homogeneity of the charge distribution during fatigue test compared to other concrete mixtures. Also, it was noted that the relationship between the endurance limit and the coefficient of Los Angeles is inversely proportional: The aggregates which have good strength to fragmentation (low coefficient of LA), as aggregates CA2 case give an endurance limit at around 70% max bending load. Key words: Coarse aggregate, Los Angeles, Micro Deval, bending test, fatigue testing, endurance limit.
Highlights
The concrete as a material is considered to be a composite material wherein the aggregates forming the backbone solid and playing the role of reinforcement ensuring the mechanical performance in relation to the various stresses
Observation at test end Rupture and the main characteristics of aggregates such as (Micro-Deval and L.A), the fatigue flexural behavior of concrete with CA1 aggregates appears much better than other concretes (Figure 7)
The obtained results show that the aggregates which have parameters and the Los Angeles and micro Deval similar as the case of coarse aggregates 3 (CA3), provide better adhesion with the cement paste, and a greater mechanical strength to bending
Summary
The concrete as a material is considered to be a composite material wherein the aggregates forming the backbone solid and playing the role of reinforcement ensuring the mechanical performance in relation to the various stresses. These changes are mainly related with the progressive growth of internal micro cracks, which result in an increase of irrecoverable strain which manifest at the level changes in the material’s mechanical properties (Sun et al, 1999; Shang and Song, 2006; Hasan et al., 2008; Li et al, 2011; Shi et al, 1993; Lee and Barr, 2004; ACI 215R-74, 1997) It was noted by Mudock and Kesler that fatigue failure in concrete is due to progressive deterioration of the bond between the coarse aggregate and the matrix cementitious. The present study focuses on the parameters effect of coarse aggregates on the flexural fatigue behavior of concrete
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