Abstract
This research aims at analysing the mechanical performance of concrete with recycled aggregates from concrete pavements. First, the characteristics of various natural and recycled aggregates used in the concrete were thoroughly analysed. The composition of the recycled aggregates was determined and several physical and chemical tests of the aggregates were performed. In order to evaluate the mechanical performance of recycled concrete, cube compressive strength and flexural tensile strength tests were performed. The effect of recycled aggregates on the strength of recycled concrete is related to the strength of recycled aggregates, the strength of natural aggregates, and the strength of old concrete. The strength of recycled concrete decreases with increasing water‐cement ratio. However, due to the water absorption of the recycled aggregate, it has a certain inhibitory effect on the strength reduction. As the replacement rate of recycled aggregates increases, the optimal sand ratio decreases. The sand ratio is controlled between 32% and 38%, which is ideal for recycled concrete. With the increase of fly ash content, the 7 d strength of recycled concrete has decreased to some extent, but the 28 d strength has been slightly improved. In addition, for compressive strength and flexural tensile strength, the optimal content of fly ash is different.
Highlights
In several developed countries such as Europe and the United States, the use of recycled aggregates for concrete has been for many years [1]
According to De Vries, the application of recycled aggregate in construction engineering has become a priority in many places around the world [2]. 78000 tons of recycled aggregates were used in the Netherlands in 1994
E test methods of mechanical properties such as compressive strength and flexural tensile strength of recycled aggregate concrete were carried out according to the specification JTG E30-2005
Summary
In several developed countries such as Europe and the United States, the use of recycled aggregates for concrete has been for many years [1]. Many Chinese investigators have engaged in the studying of recycled aggregates and most aspects of mechanical property and structural performance have been covered. E difference between the elastic modulus of recycled aggregate and cement mortar is small, and the interface between the two is strengthened. Many microcracks on the surface of the recycled aggregates will suck in new cement particles, making the hydration of the contact area more complete and forming a dense interface structure. Based on the previous research, this study replaces coarse and fine aggregate at the same time and compares the effects of recycled aggregate replacement rate, water-cement ratio, sand ratio, and fly ash content on the mechanical properties of recycled aggregate concrete, such as cube compressive strength and flexural tensile strength
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