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.

This paper describes the results of experimental testing of glass fiber reinforced plastic (GFRP) composite beam strengthened reinforced concrete (RC) slabs with two symmetrical openings. Specimens, one-half scale, have been designed and fabricated to reflect the most common RC bathroom slab used in school buildings. The specimen had dimensions of 2000 mm (width) × 150 mm (thickness) × 3000 mm (length) were used with the two openings of 300 mm × 400 mm. The aim of this study is to investigate the most effective strengthening method using GFRP composite beams in slabs with openings for enhancing the load-carrying capacity and stiffness. Test results showed that the strengthened slabs seems to increase the load-carrying capacity by 29%, 21% and 12% over that of the control specimen for diagonal, parallel and surround strengthening respectively. Furthermore, test results showed that the diagonal-strengthened system is one of the most effective methods for strengthening an RC slab with openings in terms of load-carrying capacity, stiffness and crack patterns.

The ordinary Portland cement is a main binding material in normal concrete or high-performance fiber cementitious composites. However, the carbon dioxide (CO₂) emission during the ordinary Portland cement manufacturing process is up to about 7.0% of global manmade CO₂. The ordinary Portland cement is also known to have toxic substances. The purpose of current research is to develop a near-environmental and strain-hardening fiber low cementitious composite in which the binder is mixed by replacing 60% of the amount of cement with ground granulated blast-furnace slag with or without using alkali activators, or replacing with fly ash. Five mixture proportions with proper fluidity and viscosity of the composites in order to easily mix fibers and to uniformly disperse fibers were determined according to reducing the amount of cement and replacing it with ground granulated blast-furnace slag with or without alkali activators, or replacing with fly ash. The mechanical characteristics of the strain-hardening fiber low cementitious composite were evaluated experimentally by the slump flow, compression, and direct tension tests. The strain-hardening fiber low cementitious composite exhibited the slump flow of 520–670 mm and the tensile strain capacity of 2.3%−4.8% with multiple micro-cracks.

The longevity of drainage pipes is dependent on the material properties of the pipe, the surrounding load, the abrasive characteristics of the effluent, and the frequency, velocity, and quantity of the effluent that flows through the pipe. Each of these parameters has impacts on the age-related abrasive decrease in the wall thickness of the drainage pipe. Traditionally, the rotating pipe test is used to assess the vulnerability of drainage pipes to abrasion. To simulate more realistically the natural environment of drainage pipes, we designed an abrasion test that keeps the drainage pipe at variable slope with respect to the horizontal and continuously pumps abrasive slurry through the pipe for $30\text{days}$ . The time dependent change in wall thickness of a cellulose fiber reinforced cement pipe was simultaneously compared to the change in wall thickness of a steel-reinforced concrete pipe. The wall thickness of the fiber reinforced cement pipe decreased approximately 5 times faster than the thickness of the steel-reinforced cement pipe.

This paper describes the results of long-term tests on reinforced concrete (RC) beams strengthened with hybrid composite beam (HCB) under two different sustained loads. Test specimens were fabricated to reflect the most common RC beam size used in school buildings in South Korea. The specimens had dimensions of 400 mm (width) × 600 mm (depth) × 6000 mm (length), and were tested with or without external strengthening by a hybrid composite beam (HCB). Test results showed that strengthening the RC beams with HCB not only reduced the instantaneous deflection but was also effective in decreasing long-term deflection. In this study, time-dependent factors were investigated using a modified version of the American Concrete Institute (ACI) equation. Time-dependent factors of HCB-strengthened RC beams found in the present work differed from those of other investigations due to various experimental conditions. In the present study, we found that the ACI equation may not provide a reasonable estimation of the long-term behavior of HCB-strengthened RC beams.