Carbonation model for concretes with fly ash, slag, and limestone calcined clay - using accelerated and five - year natural exposure data

Author(s):  
Sundar Rathnarajan ◽  
B.S. Dhanya ◽  
Radhakrishna G. Pillai ◽  
Ravindra Gettu ◽  
Manu Santhanam
2021 ◽  
Vol 25 (6) ◽  
pp. 87-96
Author(s):  
Cuong Manh Phung ◽  
Krittiya Kaewmanee ◽  
Somnuk Tangtermsirikul

2022 ◽  
Vol 320 ◽  
pp. 126306
Author(s):  
Jun Liu ◽  
Zhen Liang ◽  
Hesong Jin ◽  
Gediminas Kastiukas ◽  
Luping Tang ◽  
...  

CORROSION ◽  
10.5006/3705 ◽  
2021 ◽  
Author(s):  
Sripriya Rengaraju ◽  
Radhakrishna Pillai ◽  
Ravindra Gettu ◽  
Lakshman Neelakantan

Fly ash and limestone calcined clay cement (LC3) are being used/introduced in concrete to enhance chloride resistance. In this study, sixty specimens (with steel in three concrete systems, namely OPC, fly ash, and LC3 with surface resistivity of ≈10, ≈25, and ≈200 kΩ.cm, respectively) were subjected to impressed corrosion and the results were compared with 15 lollipop steel-mortar specimens subjected to natural corrosion under wet-dry/chloride conditions. It was found that the traditional way of impressed corrosion tests can induce microstructural changes in highly resistive concrete cover and at steel-concrete interface; hence, are not suitable for evaluating corrosion resistance (say, corrosion rate and corrosion-induced cracking) in highly resistive concrete systems. Further, the Raman spectra from the corroded steel surfaces indicated that the impressed corrosion and natural corrosion tests led to different forms of corrosion (i.e., uniform and pitting, respectively) and different compositions of corrosion products (i.e., ‑Fe2O3 and FeOOH phases). This led to different expansive stresses making the lab-to-field correlations inappropriate in case of highly resistive concrete systems. This paper recommends natural corrosion tests exposed to wet-dry conditions and not the impressed corrosion tests for assessing corrosion phenomena of steel in highly resistive concrete systems.


Author(s):  
Anjaneya Dixit ◽  
Hongjian Du ◽  
Juntao Dang ◽  
Sze Dai Pang

2021 ◽  
Vol 5 (10) ◽  
pp. 271
Author(s):  
Priyanka Gupta ◽  
Nakul Gupta ◽  
Kuldeep K. Saxena ◽  
Sudhir Goyal

Geopolymer is an eco-friendly material used in civil engineering works. For geopolymer concrete (GPC) preparation, waste fly ash (FA) and calcined clay (CC) together were used with percentage variation from 5, 10, and 15. In the mix design for geopolymers, there is no systematic methodology developed. In this study, the random forest regression method was used to forecast compressive strength and split tensile strength. The input content involved were caustic soda with 12 M, 14 M, and 16 M; sodium silicate; coarse aggregate passing 20 mm and 10 mm sieve; crushed stone dust; superplasticizer; curing temperature; curing time; added water; and retention time. The standard age of 28 days was used, and a total of 35 samples with a target-specified compressive strength of 30 MPa were prepared. In all, 20% of total data were trained, and 80% of data testing was performed. Efficacy in terms of mean absolute error (MAE), root mean square error (RMSE), coefficient of determination (R2), and MSE (mean squared error) is suggested in the model. The results demonstrated that the RFR model is likely to predict GPC compressive strength (MAE = 1.85 MPa, MSE = 0.05 MPa, RMSE = 2.61 MPa, and R2 = 0.93) and split tensile strength (MAE = 0.20 MPa, MSE = 6.83 MPa, RMSE = 0.24 MPa, and R2 = 0.90) during training.


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