Since the early 1990s, many studies were conducted to utilize waste tires as a replacement for natural coarse and fine aggregates in concrete, known as rubberized concrete or rubber-concrete. In this paper, an experimental study was performed on the strength properties of concrete containing fine-rubber particles as a replacement of fine aggregate, using destructive and non-destructive tests. Ultrasonic pulse velocity (UPV) tests were used to evaluate the strength property of rubber-concrete as a non-destructive test. Compressive and splitting tensile strengths were determined for four different volume contents of fine-rubber particles and exponential equations were proposed for the relationship between compressive, splitting tensile strength and the UPV of rubber-concrete, respectively. With the limited conditions in this paper, it found that UPV tests could also be used to estimate the compressive and tensile strengths of rubber-concrete, that are used in other types of concrete.

The mechanical properties of alkali-activated slag fiber composites (ASFC) were investigated with varying volume fractions of PVA (Polyvinyl alcohol) fibers. Ground granulated blast furnace slag (GGBS) and alkali-activators were used as the main binders instead of cement, which emits a large amount of carbon dioxide during the manufacturing process. The measured slump flow of ASFC showed a high fluidity at a fiber content of 1.5 vol.% or less. The tensile, flexural, and shear strength of ASFC showed higher values as the amount of fiber increased. Compared to the existing high ductility fiber composites showing strain hardening behaviors with a fiber content of 2.0 vol.%, ASFC proved that it could exhibit high ductility characteristics due to multi-microcracks even at low fiber mixing rates of 1.0% and 1.25%. ASFC could be expected to lower the manufacturing cost with a low fiber content and provide improved workability with high fluidity. In addition, when manufacturing structural components using the developed ASFC, it is expected that the amount of fiber could be selected and used according to the required performance.

Bed mattresses are rated as products to cause a fire hazard because of their very high heat release rate among indoor combustibles. In this study, fire growth rate and flame height were measured through a series of combustion experiments on a full scale in order to provide information regarding mattress fire characteristics. The experiments were conducted in an open space, and bed mattresses as the test samples were installed at different installation heights (0~515 mm). The experiment results revealed that the higher the bed mattress was installed, the higher the fire growth rate, the heat release rate, and the flame height. Additionally, the time of the mattress to reach 1 MW was evaluated as the category “medium” in the NFPA 72 standards. The flame heights showed a good coincidence compared to the existing flame height model equations, proving the applicability of the model to the mattress combustion.