جستجوی مقالات مرتبط با کلیدواژه « recycled aggregates concrete » در نشریات گروه « عمران »

AbstractIn this study, the toughness and durability of concrete with recycled aggregates and magnetic water against melting and freezing cycles and mechanical properties such as compressive and tensile strengths are investigated. Variables include the number of different cycles of water in the magnetic field, different amounts of super-plasticizer, steel fibers and micro-silica. A total of 242 samples were made in 11 different mix designs. It should be noted that half of the samples mentioned contains steel fibers. The results of most experiments have shown that magnetic water, although having a very high effect on the mechanical properties of concrete, should not be used alone as a compensating agent for defects caused by recycled aggregates. Using microsilica as a mineral admixture with magnetic water improves the concrete properties, significantly. The toughness indices were determined by ASTM C1018, JSCE and PCS method and concrete durability test by BS EN 140: 2003. Among the recycled aggregate concrete mixes, the best toughness results were for the samples containing microsilica and steel fibers. Also, ten round magnetic water resulted in an increase in the durability of recycled aggregate concrete by approximately 25% compared to one round of magnetization.

Around 25 billion tons of concrete is used each year globally that means over 3.8 tons per person in the world each year. Occupying about 60% to 70% of the volume, aggregate is a main ingredient of concrete. Nowadays, there is an increasing trend toward using sustainable concrete and reusing of aggregates from demolished concrete is one way to achieve this aim. Although using recycled concrete aggregate (RCA) does not lead to significant reduction of CO2 emission, but it reduces using natural resources (natural aggregate) as well as helping to reduce dumping construction and demolition wastes in landfills. More than 900 million tons of construction and demolition waste is produced each year only in Europe, the U.S., and Japan. A comprehensive literature review on mechanical properties of recycled aggregate concrete (RAC) including compressive strength, splitting tensile strength, modulus of elasticity and modulus of rupture is presented. In addition, databases are created for mechanical properties of RAC in order to lead to changes or acceptance in design codes and standards’ provisions. These data were compared with the American, European, Australian, Japanese, Canadian standards provisions. Results of this study show that existing code provisions are not always conservative for mechanical properties of RAC.