دانلود رایگان مقاله انگلیسی اثر امولسیون آسفالت کاتیونی به عنوان یک افزودنی در خواص انتقال بتن متراکم شده با غلتک - نشریه الزویر

abstract

This study aims to investigate the effect of cationic asphalt emulsion (CAE) as an admixture on durability characteristics of roller compacted concrete (RCC). To this aim, the CAE was added to the RCC mixture at 0%, 2%, 4%, 6%, 8%, and 10% of the cement mass; these mixtures were designed by the maximum density method according to ASTM D1557. The cubic and cylindrical specimens were fabricated using vibrating hammer; water absorption, sorptivity, water penetration depth, and electrical resistivity tests were conducted to evaluate the durability of the mixtures. The water penetration test was carried out on cubic specimens in accordance with BS EN 12,390-8: 2009; moreover, by cutting each cylindrical specimen, two 100 50 mm discs for conducting sorptivity and one 100 100 mm cylinder for conducting the water absorption and electrical resistivity tests were prepared. The results indicated that the decrease in the water absorption, penetration and sorptivity, and the increase in the electrical resistivity of the mixtures can be obtained by increasing the CAE content. Also, the analysis of variance (ANOVA) at 95% confidence level based on Dunnett comparison procedure denoted a significant improvement in the RCC transport properties by adding CAE. Scanning electron microscope (SEM) images were studied and it was revealed that filling the capillary pores and coating the inner surface of larger pores with asphalt exhibited a change in the structure of cement paste pores and demonstrated an improvement in the transport properties of the RCC. Performing electrical resistivity test is of great importance for evaluating the durability of concrete due to its non-destructive and rapid properties. Therefore, intrinsically linear regression models were estimated between its results and other durability indicators, which show proper fits based on their coefficient of determination (minR2 > 0.83). The findings revealed that electrical resistivity test can be employed to estimate the various transport properties of the RCC.

4. Conclusions

In the present study, various percentages of CAE (2% to 10%) were used as an admixture in the manufacturing process of the RCC mixture, and the transport properties of these mixtures were investigated. The transport properties of concrete can control its durability in a variety of environmentally harsh conditions. Therefore, due to the large surface of the RCCP and its high probability of being exposed to destructive conditions, the characteristics of the RCC are of great importance. In conclusion, the following findings are worthy of note:

The results indicate that the transport properties of the RCC mixtures are improved if asphalt is added. Analysis of variance confirms this significant positive effect at 95% confidence level, and also, SEM images justify how the results of the transport properties are changed by modifying the RCC with CAE.

Considering the importance of non-destructive tests, for the evaluation of RCC transport properties, proper models were developed based on non-destructive electrical resistivity test. Using these models, it is possible to obtain the estimations of water absorption, sorptivity and water penetration depth of the RCC mixtures.

According to the transport properties and SEM images of the RCC mixtures, it is determined that using asphalt has a positive effect on the structure of hardened cement paste pores and reduces the amount of capillary pores. The CAE can be an appropriate admixture for using in the RCCP in areas where the possibility of base layer saturation is high, since the amount of destructive solutions being absorbed by the RCC concrete surface from this layer could be directly reduced because of filling the capillary pores with asphalt.

Significant improvement in the penetration property of the RCC concrete against water pressure indicates the proper performance of this admixture under high hydrostatic pressure. The RCC used in the construction of the dam is an application of this type of concrete under high pressure hydrostatic pressure. Of course, the mixture design for this type of RCC using its given method should be repeated.

Results of ANOVA show that if equal or more than 4% CAE is used in RCC, it can be expected to improve all the transport properties of this mixture and accordingly its durability.