The paper presents the effect of fiber length on the mechanical properties and water absorption of bamboo fiber/polystyrene-modified unsaturated polyester composites. The fiber length varied from 2.5 mm to 15 mm at the fiber volume fraction of 0.2, 0.25 and 0.3. For water absorption, the specimens were immersed in distilled water at temperature of 40°C. The results showed that for all volume fractions, the tensile, flexural, and the impact properties tended to increase with the increase of fiber length; however, there was an optimum fiber length for the tensile and flexural properties. The water uptake increased with the increase of both fiber length and volume fraction. In wet condition, for all volume fractions, the flexural properties degraded, whereas, the impact strength did not indicate degradation, even; it significantly increased for all fiber lengths.

An ultrasonic pulse velocity (UPV) test is often applied to determine the quality of concrete structures. It is well known that there are several factors which can influence the reading of ultrasonic velocity in concrete. One of the factors is the presence of steel reinforcement. Therefore, this paper is intended to evaluate the ultrasonic pulse velocity propagation either in plain or reinforced damaged concrete. A study on sound concrete is also provided as a comparison. Three mixes of concrete were provided, with 25 MPa, 35 MPa, and 45 MPa target compressive strengths. The specimens were 200x200x200 mm cube concrete specimens and 100x150x1100 mm reinforced concrete beam specimens. Each specimen was examined for velocity readings in sound and damaged concrete (25% and 50% of maximum load). In all concrete grades of both plain and reinforced concrete, the ultrasonic velocity decreases as the damage level increases. During intact conditions, the velocity of reinforced concrete is around 4.5% higher than that of plain concrete. However, damaged reinforced concrete has a lower velocity than plain damaged concrete. Furthermore, a new equation for predicting ultrasonic pulse velocity in reinforced concrete is proposed.