Takashi Horiguchi

Applicability of Controlled Low-Strength Materials with Incinerated Sewage Sludge Ash and Crushed-Stone Powder

This paper discusses the applicability of new controlled low-strength materials (CLSM) that include incinerated sewage sludge ash. The incinerated sewage sludge ash was used as a replacement for fly ash, which is the main component of CLSM. A dust powder made during crushed-stone production was used as a fine aggregate. This new type of green CLSM is a promising sustainable cementitious material with the capability to reduce CO 2 emissions. The test results show that adequate strength development and reasonable flowability can be achieved if the mixture proportion is carefully designed. The leachate characteristics of the new CLSM are evaluated in this paper, and the test results show acceptable leachate levels. The test results also confirm that a wide range of municipal solid wastes could be used as materials in the new green CLSM. Finally, backfill construction was conducted with this new CLSM, and the excellent performance was confirmed.

Effect of Elevated Temperatures on Flexural Behaviour of Hybrid Fibre Reinforced High Strength Concrete

The structural properties of concrete have been studied most widely as a function of compressive strength at elevated temperature. However, only a limited number of studies have been conducted on the flexural behaviour of High Strength Concrete (HSC) at elevated temperature.In this paper, an investigation of the flexural behaviour (bending strength and fracture energy) of HSC and Hybrid-Fibre-Reinforced High Strength Concrete (HFRHSC) was carried out. Physical properties and fracture energy were evaluated during heat exposure (hot test) and after heat exposure (residual test).The results show maximum load decreased suddenly at 200 °C under the hot test environment. For specimens containing steel fibres, the maximum load did not drop suddenly in the hot test condition. It was verified from the Load-Crack Mouth Opening Displacement (CMOD) curve.In the hot tests, the HFRHSC mixture was very effective in preventing brittle fracture.

Recovery Behavior of Hybrid Fiber Reinforced High Strength Concrete After Fire Exposure

High-strength concrete shows particular characteristic behavior at elevated temperatures, such as explosive spalling, that is rarely observed in normal-strength concrete. This behavior has been attributed to the very dense concrete matrix usually associated with high-strength concrete. Recently the addition of polypropylene fibres into high-strength concrete was reported to be very effective against the explosive spalling. However, it is hopeless to maintain the residual strength and the fracture toughness when the fibres melt. Steel fibre reinforcement can help to maintain the residual strength and fracture toughness after heated. In this paper, hybrid fibre reinforcement with the combination of polypropylene and steel fibres is proposed for improving the strength as well as the fracture characteristics after heating. This paper investigates the recovery possibility, up to 6 months observation, of heated hybrid fibre reinforced high-strength concrete. Tests results of hybrid fibre reinforced concrete sho...

Fiber-reinforced High-strength Concrete under Elevated Temperature―Effect of Fibers on Residual Properties

Addition of polypropylene fibers was known to be an effective way in mitigating the explosive spalling failure mechanism, which occasionally happened during heat exposure of high-strength concrete. This paper presents the experimental results on residual properties of fiber-reinforced high-strength concrete under elevated temperature. Some variables being focused on, concerning the effect of fiber on high-strength concrete residual properties, included fiber volume fraction (Vf), fiber length (lf), and fiber material. Meanwhile, residual properties being observed included compressive strength (fc), splitting tensile strength (ft), modulus of elasticity (E), and water permeability coefficient (k). Results from the tests showed that residual properties of polypropylene fiberreinforced high-strength concrete was significantly reduced compared with steel fiberreinforced high-strength concrete, especially in the terms of permeability performance, even though polypropylene fiber was found to be more effective in mitigating explosive spalling.

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.