Abstract
This paper presents the compression failure process of basalt fiber concrete with recycled aggregate and analyzes the main factors of basalt fiber and recycled aggregate affecting the compressive strength of recycled concrete. The damage mechanism of recycled aggregate concrete is analyzed by the acoustic emission technique. With the method of acoustic emission (AE) b-value analysis, the evolution and failure process of recycled concrete from the initial defect microcrack formation to the macroscopic crack is studied. Based on the AE clustering analysis method, the damage state of recycled concrete under load grade is investigated. Finally, the failure mode of recycled concrete is explored according to the RA-AF correlation method. The results show that when the concrete reaches the curing age, the strength grade of basalt fiber regenerated coarse aggregate concrete is the highest. The basalt fiber increases the strength of regenerated fine concrete by 4.5% and the strength of coarse concrete by 5%, and reduces the strength of fully recycled aggregate concrete by 6.7%. The b-value divides concrete into three stages: initial damage, stable development of internal damage, and internal damage. The variation of AE energy, count, and event number is related to AE activity and crack growth rate. Matrix cracking is the main damage state of concrete, which is greatly affected by the strength of cement mortar. The load grade of fiber cracking in fully recycled aggregate, recycled fine aggregate, and recycled coarse aggregate concrete is 65, 90, and 85%, respectively. Basalt fiber increases the tensile failure event point of recycled concrete and delays the cracking of recycled concrete under compression. When the load grades of fully recycled fiber, recycled fine aggregate fiber, and recycled coarse aggregate fiber concrete are 65–95, 90–100, and 85–100%, respectively, the tensile failure activity increases.
Highlights
Since the reform and opening up, China has made remarkable achievements in infrastructure construction
The results showed that recycled aggregates and the existence of the steel fiber reinforced concrete increased the water-absorbing capacity by 49% over the natural concrete, and the tensile splitting strength of steel fiber recycled concrete was higher than ordinary concrete [16]
The factors influencing the compressive strength of concrete at 3, 7, and 28 days are discussed in
Summary
Since the reform and opening up, China has made remarkable achievements in infrastructure construction. About 600 million tons of construction waste is generated in China every year, of which concrete waste accounts for 30–35% [1]. How to effectively reuse waste concrete has become an important issue. With the development of modern concrete technology, recycled concrete technology has been proposed and is gradually being applied to actual projects, which can effectively solve the problem of waste concrete treatment. The failure mechanism of recycled aggregate is similar to that of natural aggregate, there are great differences in their physical properties. The density of recycled aggregate is low, and old Materials 2020, 13, 4009; doi:10.3390/ma13184009 www.mdpi.com/journal/materials
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