Noboru Saeki

OPTIMIZATION OF CLSM MIX PROPORTION WITH COMBINATION OF CLINKER ASH AND FLY ASH

This research evaluated, from the ecological and economical points of view, the potential use of off-specification fly ash plus non-standard clinker ash (bottom ash or coal ash) in Controlled Low Strength Materials (CLSM). The effect of mixture proportions on the short-term as well as long-term compressive strength of CLSM is mainly investigated. A wide range of fly ash/clinker ash ratio was evaluated in order to provide a cost effective mixture design for various material costs. Two different sources of fly ash including off specification fly ash and three different sources of clinker ash were used with three levels of mixture combinations. A total of 20 mixtures was tested for the flowability, bleeding and short-term and long-term compressive strengths. (Strength developments up to 91 days were reported in this study). Test results showed that there is an optimum combination of fly ash to clinker ash ratio on the physical properties of CLSM. Compressive strength improved with increasing the rate of replacement of clinker ash up to 50% in the case. It is found that there was no disadvantage of using off-specification fly ash and non-standard clinker ash in the physical properties of CLSM. CLSM with off-specification fly ash plus non-standard clinker ash showed excellent performance on the physical properties indicating the ecological and economical applicability to CLSM.

STEEL FIBERS MADE FROM STEEL CANS IN CONCRETE ENGINEERING

Recycling steel cans instead of making new products uses so much less energy, pollution, water and water pollution. In Japan in 1994 about 472,000 tons of steel cans could not be recycled. It meant a huge amount of steel plates could be reused as steel fibers to reinforce plain concrete by considering many advantages of fibrous concrete. Reusing of waste steel cans as a construction material in plain concrete can improve concrete properties and also protect corrosion of reinforced concrete. In this matter behaviour of steel fibers made from steel cans in a transparent gel and concrete specimens were studied. Results of experiments showed that such fibers with average thickness of 0.25 mm increase flexural strength of plain concrete about 150%. Durability of these fibers under an accelerated and artificial aggressive environment showed that more than 75% of fibers in the concrete matrix were sound. However, such fibers in contact with steel bars could cathodically protect corrosion of steel bars. (A) For the covering abstract see ITRD E121685.

CORROSION PROTECTION SHIELD OF STEEL BARS, DUE TO STEEL FIBERS IN CONCRETE

Severe deterioration caused by corroding reinforcing steel in concrete structures is a major concern in the maintenance of safe and reliable infrastructure. The corrosion behavior of steel fibers and steel bars under two different aggressive conditions of modified ferroxyl gel reagent and wet-dry salt spray are described. In general, the results in the aggressive gel environment indicate that when steel fibers and steel bars were contacting each other, the initiation of corrosion in the steel fibers became considerable. When the steel fibers were electrically connected to the steel bars, the steel fibers tend to become the anode while the steel bars tend to become the cathode. The corrosion initiation, its propagation and the growth of the corrosion zones occurred in the steel fibers. The steel bars, set in the cathode zone, were protected by the surrounding steel fibers which formed a corrosion protective shield. This galvanic protection behavior by steel fibers was clearly observed in ferroxyl transparent gel.