The Experts below are selected from a list of 13209 Experts worldwide ranked by ideXlab platform

Gaowen Zhao - One of the best experts on this subject based on the ideXlab platform.

  • degradation mechanisms of cast in Situ Concrete subjected to internal external combined sulfate attack
    Construction and Building Materials, 2020
    Co-Authors: Gaowen Zhao, Jingpei Li
    Abstract:

    Abstract In this paper, an experimental study was conducted to reveal the degradation mechanisms of cast-in-Situ Concrete induced by internal-external combined sulfate attack. The internal sulfate attack of Concrete was conducted by adding extra sodium sulfate in Concrete mixtures. Meanwhile, the external sulfate attack of Concrete was investigated by immersing samples in the sodium sulfate solutions. The dimensions, mass, compressive strength and the sulfate concentration in the tested specimens were continuously monitored. The microstructure and mineral phases of tested Concrete were identified after the immersion. Results illustrate that chemical attack is the main cause of degradation for fully immersed Concrete in sulfate-rich environments. Cast-in-Situ Concrete suffers a fast and severe degradation when subjected to internal-external combined sulfate attack. Internal sulfate attack significantly retards the strength development of Concrete in the early corrosion stage. Development of crack system is remarkably accelerated by internal sulfate attack hence inducing a relatively faster penetration of external sulfate ions.

  • Degradation of cast-in-Situ Concrete subjected to sulphate-chloride combined attack
    Construction and Building Materials, 2020
    Co-Authors: Gaowen Zhao, Mei Shi, Jifei Cui, Feng Xie
    Abstract:

    Abstract The main aim of the present research is to determine the degradation mechanisms of cast-in-Situ Concrete subjected to sulphate-chloride combined attack. Concrete specimens were prepared and then put into sulfate or sulfate-chloride mixed solutions. The sample dimension, mass, compressive strength, and sulfate concentration of the specimens were continuously monitored. The microstructures and the complex mineral composition of the Concrete were analysed after 12 months of exposure to the corrosive environments. The results show that cast-in-Situ Concrete suffers more severe damage and greater strength loss when subjected to sulfate-chloride combined attack than when subjected to sulfate only. The diffusion and accumulation of sulfates are accelerated by the coexisting chlorides, especially in the early stages. The coexistence of chlorides in sulfate environments accelerates the degradation of cast-in-Situ Concrete induced by sulfate attack. The different performances against sulfate-chloride combined attack between cast-in-Situ and precast Concrete were mainly due to the degradation behaviour at the early stage.

  • Effect of mixed chlorides on the degradation and sulfate diffusion of cast-in-Situ Concrete due to sulfate attack
    Construction and Building Materials, 2018
    Co-Authors: Gaowen Zhao, Wei Shao
    Abstract:

    Abstract This paper reports the results of a detailed experimental study conducted to investigate the influence of mixed chlorides on sulfate-induced corrosion in cast-in-Situ Concrete. Concrete specimens with or without mixed chlorides were exposed to sulfate solutions for a period of 365 days. The concentration of sulfate solutions varied from 0% to 10%. Concrete degradation was assessed by measuring the expansion, mass loss and strength loss at regular intervals. Scanning electron microscopy (SEM), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction (XRD), thermogravimetry-derivative thermogravimetry (TG/DTG), and differential scanning calorimetry (DSC) were used to analyse the microstructural changes and the complex mineral assemblage of Concrete. The results indicate that mixed chlorides in Concrete play a positive role in inhibiting the strength formation of Concrete in the early stages and hence decreasing the strength of Concrete. The acceleration effect of mixed chlorides on the expansion and mass loss of Concrete caused by external sulfate attack is noted. Furthermore, the presence of mixed chlorides in Concrete increases the diffusivity and accumulation of sulfates. Therefore, mixed chlorides in cast-in-Situ Concrete play a significant role in accelerating the degradation process of cast-in-Situ Concrete due to sulfate attack.

Jingpei Li - One of the best experts on this subject based on the ideXlab platform.

  • degradation mechanisms of cast in Situ Concrete subjected to internal external combined sulfate attack
    Construction and Building Materials, 2020
    Co-Authors: Gaowen Zhao, Jingpei Li
    Abstract:

    Abstract In this paper, an experimental study was conducted to reveal the degradation mechanisms of cast-in-Situ Concrete induced by internal-external combined sulfate attack. The internal sulfate attack of Concrete was conducted by adding extra sodium sulfate in Concrete mixtures. Meanwhile, the external sulfate attack of Concrete was investigated by immersing samples in the sodium sulfate solutions. The dimensions, mass, compressive strength and the sulfate concentration in the tested specimens were continuously monitored. The microstructure and mineral phases of tested Concrete were identified after the immersion. Results illustrate that chemical attack is the main cause of degradation for fully immersed Concrete in sulfate-rich environments. Cast-in-Situ Concrete suffers a fast and severe degradation when subjected to internal-external combined sulfate attack. Internal sulfate attack significantly retards the strength development of Concrete in the early corrosion stage. Development of crack system is remarkably accelerated by internal sulfate attack hence inducing a relatively faster penetration of external sulfate ions.

Leonardo Chiauzzi - One of the best experts on this subject based on the ideXlab platform.

  • an experimental study on the within member variability of in Situ Concrete strength in rc building structures
    Construction and Building Materials, 2013
    Co-Authors: Angelo Masi, Leonardo Chiauzzi
    Abstract:

    Abstract Reinforced Concrete (RC) buildings can require the determination of in Situ Concrete strength during the execution of new structures to investigate low-strength results from acceptance tests and, especially, in the capacity assessment of existing structures. Most structural codes and technical recommendations indicate that in Situ Concrete strength should be estimated by means of drilled cores (Destructive Test, DT), possibly supplemented by non-destructive tests (NDTs). Besides contributing to the identification of homogenous Concrete areas and thus indicating locations where cores have to be extracted, NDTs can significantly reduce the total amount of cores needed to adequately estimate Concrete strength in an entire structure. The paper firstly reports a brief review of the most usual NDT methods (rebound number and ultrasonic pulse) and DT methods (cores) and discusses the role of the main factors influencing in Situ strength estimation. It then reports and analyses the results of a wide investigation carried out on an RC beam member extracted from an existing structure. The results show a low variability of rebound number and direct velocity values along the beam, and a high variability for surface velocity values and, especially, core strengths. The wide scatter in some test results has been seen in relationship to the micro-cracking condition arising from past applied loads. Suggestions for test location and interpretation of in Situ and laboratory test results are provided.

Yu Jing-liang - One of the best experts on this subject based on the ideXlab platform.

Sha Zhen-xin - One of the best experts on this subject based on the ideXlab platform.

  • The Construction and Application in Cast-in-Situ Concrete GBF Hollow Floor
    Shandong Building Materials, 2008
    Co-Authors: Sha Zhen-xin
    Abstract:

    The technology of the construction and application in cast-in-Situ Concrete GBF hollow floor is the priority extention item of the construction ministry.It has many advantages,such as lightening the own weights,increasing the headroom,preserving heat and insulating sound,reducing construction cost and so on.Taking the example of the hollow floor of a library building of some certain college,this paper explains construction techniques and essentials of cast-in-Situ Concrete GBF hollow floor in the following aspectsmould engineering,GBF installation,fixation,Concrete placement,etc.The study provides certain reference for the construction of homogeneous structures.