The durability of concrete pavements is greatly dictated by their capacity to resist fatigue induced by flexural stresses. Known to be a critical factor in fatigue behaviour is the quality (or deterioration under loading) of the bond between the cement paste and aggregate. This paper reports on lab and large-scale trial applications of a range of modified mix charging sequences in terms of their ability to improve the flexural fatigue life of concrete pavements, and also on conventional concrete plastic and hardened properties. Flexural fatigue resistance was assessed using the ASTM C1550 round panel loading test over a range of target failure loads, eg 10² to 106 cycles. Whilst source research was initially focussed on improved distribution of SCMs, this paper demonstrates that similar techniques significantly affect rheology, setting, strength and, in some cases, fatigue capacity and bond quality – all thought to be the result of a modified transition zone (between aggregate and mortar). Importantly, each modified charging sequence was selected or adapted on the basis that such new charging techniques, if shown to be beneficial, could be readily adapted to the common dry batch concrete plants already in use in readymix batching and on-site batching or mixing plants. This study will show that, for a matched mix design, the RILEM method of batching improves the fatigue resistance (and life) of a typical Australian pavement quality concrete by 23% when compared with the conventional batching sequence presently used by premixed and typical on-site concrete batch plants.
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