مقاله انگلیسی رایگان در مورد اثر امولسیون آسفالت کاتیونی به عنوان یک افزودنی در خواص انتقال بتن متراکم شده با غلتک (الزویر)

Roller compacted concrete (RCC) is defined as a type of concrete that, in its unhardened state, is able to support a roller while being compacted. The amount of cement paste required in this concrete is just as much as filling the voids between the aggregates and the water content is designed for having enough workability [1]. The first implementation of roller-compacted concrete pavement (RCCP) dates back to 1930 in Sweden [2]. In North America, the first experience with the construction of RCCP occurred in 1942 during the construction of an airport runway in Washington. However, in Canada, the RCC was first used as a surface layer in 1976 in the construction of a log sorting yard. The initial design was a layer of stabilized aggregates with a thickness of 14 in. as the base layer and 2 in. of asphalt concrete surface. However, a pavement with a thickness of 14 in. consisting of an 8 in. stabilized base with 8% cement and 6 in. aggregates with 13% cement was built upon the request of the owners. This positive experience in the construction of RCCP increased the application of this type of pavement in Canada in the following years. The main difference between the RCC and conventional concrete is the amount and gradation of the aggregates, amount of cement, and water; so that the aggregates used in the construction of the RCC are dense- or well-graded and make up 75% to 85% of the total volume of the materials. Also, the amount of fine aggregates is higher than those of conventional concrete. These factors cause high stiffness of the fresh RCC and zero (or less) value of the slump, so that it cannot be compacted using traditional concrete paving machines [3]. Due to the large surface of RCCP and its potential exposure to a variety of harsh conditions (e.g. freeze–thaw cycles), durability of this type of concrete and its proper performance under these conditions is very important. Although concrete is damaged due to various factors, water transport properties have a direct influence on concrete durability against non-mechanical damages [4,5]. Water transport in concrete is carried out by various mechanisms, including diffusion (displacement of mass or ion due to concentration difference), sorption (water displacement due to capillary action), permeability (movement of water under pressure), migration (displacement of ions due to force of electrical field) and adsorption (fixation of water molecules on the surface of materials) as the main cases among others [6–۱۰]. The surface contact of unsaturated concrete with water leads to the absorption of moisture due to the porosity of concrete and its capillary action. This is the most important measurable property in porous solids and can be used as a suitable indicator for the evaluation of various building materials, considering the ease of testing and the reproducibility of its results [11].