Mechanical Characteristics of Rubberized Concrete Subjected to Cycles of Severe Low Temperature

摘要

Old tires build up has been a major problem for many years. These heaps of tires constitute a fertile ground for insects and mosquito, which threaten the health of humans. They could also be a dangerous fire hazard. Disposal of these tires in landfill space consumes great volume since they do not decompose. This necessitated finding new venues and applications where these old tires can be put to a good use. One of these venues is to shred the tires or granulate them for incorporation into concrete mixture. The presence of granulated rubber in concrete can improve the concrete's ability to resist excessive deformation when subjected to cycles of severe low temperature. This kind of concrete mix has applications in building facades in areas with harsh weather conditions. In this experimental study, 144 concrete cubes were made with varying percentages of water-cement ratio and rubber content. Three water-cement ratios were used, 0.47, 0.54, and 0.61. In addition to non-rubberized concrete cubes, three rubber contents were used, 5, 10, and 15% by volume of fine aggregate used in the concrete mix. To simulate a variety of exposure conditions, the cubes were tested under the following conditions: room temperature; freeze once in air for 28 days; ten freeze-thaw cycles in water, 24 hours each; and twenty freeze-thaw cycles in water, 24 hours each. Concrete specimens were frozen to -20 degrees centigrade. It was concluded that the addition of rubber in concrete reduces the workability of the fresh mix and its 28-day strength. Rubberized concrete loses strength with the increase of rubber content and/or the water-cement ratio. Freezing the specimens once in air results in little or no effect on the strength of the concrete as compared with that of the specimens tested without freezing. Freezing the specimens once in water results in a slight reduction in the strength of concrete. Subjecting the concrete specimens to ten or twenty freeze-thaw cycles in water results in a small loss of strength. Freezing and thawing did not seem to affect the rubberized concrete's ability to deform in a ductile manner under the application of compressive forces. The added rubber lowered the potential for crack development.