Mechanical behaviour evaluation of scrab tire based rubberized lightweight and normal structural concrete and response at elevated temperatures.

In recent years, the exponential increase in the world population had led to sharp increase in discarded scrap tires, creating a serious ecological problem. In addition, environmental and social damage that occur during the extraction of aggregate is one of the controversial issues of land use. The use of rubber manufactured from scrap tires in concrete production instead of natural aggregate has been considered as one of the solutions. This study investigates the comparative effects of the use of scrap tire rubber on the compressive - flexural strength, toughness of structural both normal weight and lightweight concrete produced with pumice; a lightweight aggregate on which limited research has been conducted; and also the response at elevated temperatures comparatively. The target compressive strength of 28-days cube concrete samples was determined as 30 MPa. 6 different series of rubberized lightweight and normal concrete mixtures were produced by replacing the natural aggregate. 2 types of rubber (crumb and fiber form, as fine and coarse size) with 3 different mixes and with 4 ratios of rubber content, 5%, 10%, 15% and 20% by weight, were used in the study. After the target compressive strength is achieved 72 cubes (15 × 15 × 15 cm) and 72 beams were tested. For the effect of temperature 10 × 10 × 10 cm cube specimens exposed to high temperatures (200 °C, 400 °C and 600 °C) were also tested. As a result with the use of scrap tire rubber, both bending and compressive strengths of concrete decreased. In addition to this with the increase of scrap tire rubber content, the decrease in compressive and flexural strength of rubberized lightweight concrete was less than that of rubberized normal concrete in all series. At elevated temperatures, the results show that the weight loss for all scrap tire ratios was very low (NC 0.45%, LC 1.2%) at temperatures up to 200 degrees for both normal concrete and lightweight concrete. In normal concrete, mass loss increased with increasing temperature and scrap tire ratio at 400 and 600 degrees, reaching an average of 3.00% and 9.00% respectively. Especially at 600 degrees mass loss tends to increase more rapidly with increasing temperature and tire ratio. In lightweight concrete, mass loss is more sensitive to temperature and tire ratio. The average mass loss was 7.21% at 400 degrees and 12.6% at 600 degrees, respectively. Considering the RCSI results, an increase or a slight change in strength was observed between 22 and 200 degrees, more in normal concrete. At 400 and 600 degrees, there was a decrease in strength in both concrete types and for all series. These values were determined as 0.49 ~ 0.74, 0.76 ~ 0.85 at 400 degrees and 0.31 ~ 0.50 and 0.50 ~ 0.57 at 600 degrees for lightweight concrete and normal concrete, respectively. The shape of scrap tire was effective on the strength reduction and this was the highest in the series using coarse and fine crumb scrap tire rubber. In addition, the compressive strength formula for both types of concrete depending on the waste tire ratio and temperature change was determined by multiple linear regression analysis and proposed.