Effect of Air Entraining Admixture on Corrosion of Reinforced Concrete

2017

CivileJournal

In recent years, the use of nano-particles to improve the properties of concrete has created a new perspective on concrete technology. Studies in this field indicate improved concrete properties and higher strength by adding nano and micro silica particles to concrete mixes. In this regard, 12 mixing designs with different amounts of these admixtures with three types of cement strength classes (525,425,325) and 36 cubic samples (10 × 10 × 10) were designed and tested to measure compressive strength, of which we have only used 6 mixing plans in this research. The purpose of this research is to present a new method for concrete mix design by optimizing principles. Therefore, in this paper, the Taguchi statistical methods and the factorial design of the optimal mixing plan for this type of concrete are used to reduce the number of experiments to predict the optimal composition of the materials. The results obtained from the MINITAB software show that the effect of combined micro-silica and nano-silica on the compressive strength is in one direction and the effect of these two factors is more than cement strength grade of the cement and also the optimal value for micro-silica and nano-silica are estimated to have an optimum amount of micro-silica and nano-silica of 95 and 38 grams, respectively.

Section: Introductionmentioning

confidence: 83%

Optimizing Compressive Strength of Micro- and Nano-silica Concrete by Statistical Method

Zarehparvar-Shoja

2017

CivileJournal

“…It is also indicated that the fracture energy of concrete after number of cycles is lower than original value before cycling . However, entry of allowable air can improve concrete strength under freezing and thawing condition …”

Section: Introductionmentioning

confidence: 99%

“…23 However, entry of allowable air can improve concrete strength under freezing and thawing condition. 24,25 Discussion on this paper must be submitted within two months of the print publication. The discussion will then be published in print, along with the authors' closure, if any, approximately nine months after the print publication.…”

Section: Introductionmentioning

confidence: 99%

Genetic prediction of cement mortar mechanical properties with different cement strength class after freezing and thawing cycles

Ghaemi‐Fard

Ebrahimi

2018

Structural Concrete

This study predicts the mechanical properties of cement mortars. It focuses specifically on cement strength classes of 32.5, 42.5, and 52.5 MPa, respectively. To this end, a total of 270 specimens using 54 mix designs were constructed and subjected to freezing and thawing cycles (FTCs) at −18 and 18 °C. Then, mechanical properties such as compressive and flexural strength and porosity of the specimens after 0, 50, 100, 150, and 200 cycles were obtained. Afterward, genetic expression programming (GEP) was used to predict the obtained results and to represent nonlinear relationships between the mechanical properties, freezing and thawing cycle, and cement strength class. The experimental data was used for training and testing of two GEP approach models. The results show that the strength of mortar reduces with increase in FTC. On other hand, a close correlation was observed between the predicted and experimental values when cement strength class and number of cycle were considered as independent input parameters. This fact indicates the significance of the aforementioned parameters along with the other parameters such as water to cement ratio, sand to cement ratio, and weight of cement on the accuracy of the prediction.

“…Therefore, research on reduction of the concrete permeability which can lead to a reduced corrosion, has been of great interest . One of the factors that can increase RC life time against freeze‐thawing cycles and permeability is air‐entraining agent (AEA). The accurate content of AEA that can effectively improve or negatively affect the permeability properties of RC has not yet been determined.…”

Section: Introductionmentioning

confidence: 99%

Corrosion behavior and optimization of air‐entrained reinforced concrete, incorporating microsilica

Ghanei

Davoodi

2018

Structural Concrete

Self Cite

Nowadays, corrosion evaluation of steel embedded in reinforced concrete (RC) plays an important role in repair, protection and maintenance of RC structures. Air‐entraining agent (AEA) and microsilica (MS) are among the most important admixtures, which affect the corrosion rate (CR) of RC. Specifically, 12 mix designs incorporating different contents of AEA (ie, 0, 0.7, 1.4, 2.1, 2.9, and 3.6% by weight), half with 10% MS, were constructed. The corrosion behavior of RC specimens after exposure to 3.5% NaCl environment was investigated using half‐cell potential (HCP) and electrical resistance (ER) as conventional tests and Tafel polarization as a more powerful corrosion test. Moreover, an optimization process was conducted on the mix design parameters using Taguchi and Factorial methods to analyze the effective factors and sensitivity of CR to each factor. The results of Tafel test indicate that they are noticeably more reliable and reasonable as compared to HCP and ER tests. Moreover, the results show that incorporating a low content of AEA (up to 0.7%) effectively improves the corrosion behavior of RC specimens, while the mix design containing 0.7% AEA together with 10% MS is the optimal design in terms of a decreased CR. The results also show that Factorial is a more applicable method in the field of corrosion evaluation of RC, due to the yield of more accurate findings as compared to Taguchi.