Damage behavior of the multiple ITZs in recycled aggregate concrete subjected to aggressive ion environment

Yue, Gongbing; Ma, Zhiming; Liu, Miao; Liang, Chaofeng; Ba, Guangzhong

doi:10.1016/j.conbuildmat.2020.118419

Cited by 80 publications

(14 citation statements)

References 52 publications

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“…After the process of soaking, the compressive strength of RC prepared by S-RCA, C-RCA, and Si-RCA has decreased by 21%, 19.5%, and 12.1%, respectively. Compared with the former, the compressive strength of RC increases slightly after 30 d of SO 4 2− erosion, which may be due to SO 4 2− reacts with CH and C-S-H in concrete to generate a small amount of AFt, which can fill the pores in concrete [ 26 , 27 ] and thus increase the compressive strength. The above results also reveal that nano-SiO 2 modified RC exhibits a higher compressive strength than CO 2 cured one.…”

Section: Resultsmentioning

confidence: 99%

A Comparative Study of the Properties of Recycled Concrete Prepared with Nano-SiO2 and CO2 Cured Recycled Coarse Aggregates Subjected to Aggressive Ions Environment

Gao

Gong

et al. 2021

Materials

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This research focused on the modification effects on recycled concrete (RC) prepared with nano-SiO2 and CO2 cured recycled coarse aggregates (RCA) subjected to an aggressive ions environment. For this purpose, RCA was first simply crushed and modified by nano-SiO2 and CO2, respectively, and the compressive strength, ions permeability as well as the macro properties and features of the interface transition zone (ITZ) of RC were investigated after soaking in 3.5% NaCl solution and 5% Na2SO4 solution for 30 days, respectively. The results show that nano-SiO2 modified RC displays higher compressive strength and ions penetration resistance than that treated by carbonation. Besides, we find that ions attack has a significant influence on the microcracks width and micro-hardness of the ITZ between old aggregate and old mortar. The surface topography, elemental distribution and micro-hardness demonstrate that nano-SiO2 curing can significantly decrease the microcracks width as well as Cl− and SO42− penetration in ITZ, thus increasing the micro-hardness, compared with CO2 treatment.

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Section: Resultsmentioning

confidence: 99%

A Comparative Study of the Properties of Recycled Concrete Prepared with Nano-SiO2 and CO2 Cured Recycled Coarse Aggregates Subjected to Aggressive Ions Environment

Gao

Gong

et al. 2021

Materials

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“…With the increase in the calcination temperature, the removal rate of the recycled aggregate gradually increased. This was mainly due to the difference in thermal expansion between the aggregate and mortar under the action of the high temperature of recycled coarse aggregate, which produced an obvious thermal stress concentration at the interface transition zone and produced a large number of microcracks and damage at the interface transition zone and the mortar matrix, which weakened the interface structure performance of the recycled aggregate [ 39 ]. Under the action of mechanical external force and self-collision, the separation and recycling of recycled aggregate and old mortar were realized, and the grain shape of the treated recycled aggregate was relatively round.…”

Section: Resultsmentioning

confidence: 99%

Quantitative Analysis of Surface Attached Mortar for Recycled Coarse Aggregate

Song³

et al. 2021

Materials

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Due to the large amount of old hardened cement mortar attached to the surface of aggregate and the internal micro-cracks formed by the crushing process, the water absorption, apparent density, and crushing index of recycled coarse aggregate are still far behind those of natural coarse aggregate. Based on the performance requirements of different qualities of recycled coarse aggregate, the performance differences of recycled coarse aggregate before and after physical strengthening were observed. The results showed that the physical strengthening technique can remove old hardened mortar and micro powder attached to the surface of recycled coarse aggregate by mechanical action, which can effectively improve the quality of recycled coarse aggregate. The optimum calcination temperature of the recycled coarse aggregate was 400 °C and the grinding time was 20 min. The contents of the attached mortar in recycled coarse aggregates of Class I, II, and III were 7.9%, 22.8%, and 39.7%, respectively. The quality of recycled coarse aggregate was closely related to the amount of mortar attached to the surface. The higher the mortar content, the higher the water absorption, lower apparent density, and higher crushing index of the recycled coarse aggregate.

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“…Bond behaviour of corroded reinforcement has been experimentally studied by many researchers in the past [15,16]. However, it must be considered that many factors contribute to the degradation of reinforced concrete, including the neglect of designers, builders, and companies that can lead to the production of material of not excellent quality; but the greatest danger is the exposure of concrete to aggressive environments [17,18].…”

Section: Introductionmentioning

confidence: 99%

Case study on the mineralogical and petrophysical analysis of reinforced concrete slabs of a highway viaduct of the S.G.C. Orte-Ravenna

et al. 2021

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For the maintenance of the safety and security of people traveling on the road, renovation of the reinforced concrete is necessary, especially for bridge or viaduct slabs. Being able to quantify the degradation of slabs and propose methodologies for its retrofit or maintenance is crucial not only in the mineralogical-engineering field but also for socio-economic implications. In this study, samples of deck slabs of a viaduct from the highway E45 near the locality of Bagno di Romagna (Emilia Romagna, north of Italy) were subjected to a testing program to evaluate mechanical and mineralogical parameters through thermographic analyses, compression, and Ultrasonic Pulse Velocity tests and morphological observation. The analyses allow to better recognize the damage of the reinforced concrete samples and they have shown that the cause of the detachment of the asphalt has mainly a natural origin, due to temperature variations and precipitation, with a secondary cause in the anthropogenic impact. The work aims to understand the relationships between the structure of the aggregates and the characteristics of concrete to understand the development of degradation. This knowledge could be used to prevent future damages to the highways. Article Highlights• Concrete slabs analysed provided information about the relation between damage level, mechanical behaviour, size and distribution of aggregates.• Thermographic analyses were useful to understand how deep the damage was in the slabs and to detect any detachment of the asphalt. • Compressive tests, through the failure load value, shown that the ultimate strength level decreased due to formation of microcracks.

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Damage behavior of the multiple ITZs in recycled aggregate concrete subjected to aggressive ion environment

Cited by 80 publications

References 52 publications

A Comparative Study of the Properties of Recycled Concrete Prepared with Nano-SiO2 and CO2 Cured Recycled Coarse Aggregates Subjected to Aggressive Ions Environment

A Comparative Study of the Properties of Recycled Concrete Prepared with Nano-SiO2 and CO2 Cured Recycled Coarse Aggregates Subjected to Aggressive Ions Environment

Quantitative Analysis of Surface Attached Mortar for Recycled Coarse Aggregate

Case study on the mineralogical and petrophysical analysis of reinforced concrete slabs of a highway viaduct of the S.G.C. Orte-Ravenna

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