Performance Analysis of a Recycled Concrete Interfacial Transition Zone in a Rapid Carbonization Environment

Abstract

Based on the characteristics of recycled concrete interface structures, a multi-interface reconstruction model was established. To study the microstructure evolution of the interfacial transition zone (ITZ) during the carbonization process of recycled concrete, the microstructure characteristics of the ITZ of C30, C40, and C50 grade recycled concrete and the mortar matrix before and after carbonization were studied through the microhardness tester and SEM. e results show that the microhardness values of the ITZ and the mortar matrix are obviously increased and that the width of the ITZ decreases, while the ITZ performance of the C50 grade recycled concrete is not significantly changed. e ITZ exhibits a large amount of granular CaCO 3 after carbonization, the pores are refined, and microcracks are generated. Overall, there are significant differences in the microstructures between the ITZ and the mortar matrix before and after carbonization.

Effect of Metallic Inclusions on the Compressive Strength of Cement‐Based Materials

“…If all these considerations and derivations are correct, then the fit of the exponential pattern (11) to the cement mortar data should result in the same values of f o and f 1 as in equation (6), and the parameter M o should be equal to 0.49 as in equation (10). e results of the fitting procedure are presented in Figure 9.…”

“…In concrete research, there is a continuous interest in mechanical processes acting in the transition zones between hydrated cement matrices and aggregates [1][2][3][4][5][6]. e aggregates (sand grains and gravels) in the cement matrix (sometimes called the cement stone) play the role of fillers that do not usually increase the compressive strength of the cement-based materials, although high-quality aggregates (e.g., granite, basalt, and gneiss) very often show higher compressive strength than the cement stone itself.…”

Influence of Graphene Oxide on the Mechanical Properties, Fracture Toughness, and Microhardness of Recycled Concrete

“…After surface polishing to GONM or GORM half-split block following flexural strength testing with 240, 320, 600, and 1200 mesh sand papers, polishing cloth, and polishing agent in sequence, the microhardness values ( H v s) of GONM and GORM within a 4 × 5 lattice box were measured by a Vickers microhardness tester (HX-1000T type, Laizhou, China) under 0.05 kgf load with a 10 s compression duration in accordance with standard ASTM E384-08 (Philadelphia, PA, USA) [52]. It is worth noting that in order to reflect the indentation gradient of H v in the interface region, the height difference between each adjacent two points within the 4 × 5 lattice box was set to 10 μm, as demonstrated in Figure 4 [4]. The corresponding H v of the GONM and GORM specimen could be derived by Equations (4) and (5):F=trued22sinθ Hv=P/F=trueP×2sinθd2=1.8544P/d2 where F , d , θ , and P is the notch area (μm 2 ), the diagonal length (μm) of the rectangular pyramid indentation, the angle between the notch head and the specimen surface (°), and the applied load (N) of the specimen, respectively.…”

“…Construction waste shows a fast-increasing trend with urbanization and industrialization, and the annual output of construction waste has climbed up to 3.5 billion tons, causing a non-negligible threat to the environment [1,2,3]. Recycling research and technology on construction waste not only conserves many natural aggregate resources but also reduces construction waste pollution, which effectively conforms to the requirements for the sustainable development of the construction industry [4]. Extensive and intensive research on the performance of recycled concrete by incorporating this waste after crushing as a recycled aggregate and/or admixture has been explored all around the world, and its workability, mechanical properties, and durability are found to be generally inferior to those of normal concrete [3,4,5,6,7].…”

“…Recycling research and technology on construction waste not only conserves many natural aggregate resources but also reduces construction waste pollution, which effectively conforms to the requirements for the sustainable development of the construction industry [4]. Extensive and intensive research on the performance of recycled concrete by incorporating this waste after crushing as a recycled aggregate and/or admixture has been explored all around the world, and its workability, mechanical properties, and durability are found to be generally inferior to those of normal concrete [3,4,5,6,7]. Indeed, owing to recycled concrete being a type of heterogeneous material with multi-phases and multi-interfaces, its microstructure is more complicated than that of normal concrete, and the existence of multiple but weak interfaces is the main reason for the low compressive strength and long-term property of recycled concrete [5,8,9,10].…”