Abstract
To understand the complex deformation features and failure mechanisms of expanded polystyrene (EPS) concrete and reveal the composite effect of expanded polystyrene beads and polypropylene fibers, a series of experiments were conducted on the poured EPS concrete specimens. Meanwhile, a cloud computing system for 3D realistic failure process analysis (RFPA3D) was established to model the fine failure process of a real concrete structure. The micromorphology of the EPS concrete specimens was obtained via CT scanning and further processed using digital image processing technology. The Otsu algorithm was applied to automatically recognize the segmentation thresholds of each partition image and a procedure for CT image processing was designed to automatically realize digital image segmentation and merging. Then, the numerical models reflecting the microstructures of the EPS concrete specimens were built using the processed digital images and a series of 3D numerical simulations were performed using cloud-computing-based RFPA3D. The results show that for concrete with low EPS volume fracture, the non-smooth convex-step-shaped failure morphology, which is a typical brittle fracture characteristic, appears. In contrast, ductile fracture occurs for concrete with a high EPS volume fracture. Simultaneously, the addition of polypropylene fibers of a certain length can effectively prevent the formation and expansion of new cracks in the cement matrix. In addition, the peak strength of concrete increases with an increase in homogeneity while the residual strength generally decreases with an increase in homogeneity. Moreover, a more heterogeneous material presented more acoustic emission precursors before macro fracture. All these achievements greatly improve our knowledge of the design, construction, and maintenance of EPS concrete in civil engineering.
Highlights
In recent decades, the digital image processing (DIP) technology has been developed as an electronic method for manipulating digital images, generating visual signals, storing them as an array of pixel points, and extracting image information from them
Only a few small cracks can be found on the surface of the specimen and the initial stress–strain curve is nearly linearly elastic; in the collapsed stage, many new cracks occur at the existing microcracks, pores, bonding surfaces between polystyrene particles and cement, and other defects because of the high-stress con centration and low strength at these positions; in the strain-softening stage, the concrete specimen loses its maximum bearing capacity quickly, maintains the residual strength, and the axial strain continues to grow, indicating that the deformation modulus maintains a continuous decline
The experiments indicate that when PP-expanded polystyrene (EPS) concrete is in the curing process, many microcracks are produced during the shrinkage hardening process and the addition of polypropylene fibers of a certain length can effectively prevent the formation and expansion of new cracks in the cement matrix
Summary
The digital image processing (DIP) technology has been developed as an electronic method for manipulating digital images, generating visual signals, storing them as an array of pixel points, and extracting image information from them. Sun and Wang (2015) [4] studied the pull-out failure process of reinforced concrete (RC) specimens, using an image-based modeling approach by considering random meso-structures within a material. The CT-scanned results can provide accurate material structure data, which can be addressed by DIP to generate a series of interrelated images for numerical model establishment. Achieving real structure modeling and fine failure process simulation of EPS concrete using high computational efficiency and convenient resource allocation of cloud computing has. To reveal the failure mechanisms and strength characteristics of EPS concrete, the 3D realistic failure process analysis (RFPA3D) method [32,33] was applied to model progressive concrete fracture. The cloud computing system of RFPA3D was established to realize a fine simulation of the failure process of real concrete structures. The fracture mechanisms and diverse failure modes of EPS concrete were further studied
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