Concrete carbon fibers

Table 1 shows the specifications of the concrete, carbon fiber sheet and adhesive resin investigated in the present work. The concrete blocks of 30 x 20 x 90 mm were made of normal grade Portland cement and cured in water for 4 weeks. The carbon fiber sheet (UT70-30, Toray) was a unidirectional cloth bound with a few lateral fibers. The adhesive resin (DK-530, Denka) was a modified acrylic resin of two component system. 

Chen P.and Chung, D.D.L, Dispersants for carbon fibers in concrete. Extended... 

T. Sugama, L. E. Kukacka, N. Carciello, and B. Galen. Oxidation of carbon fiber surfaces for improvement in fiber-cement interfacial bond at a hydrothermal temperature of 300° C. Cement Concrete Res, 18(2) 290-300, March 1988. 

Chen P.and Chung, D.D.L., Carbon fiber reinforced concrete as an intrinsically smart concrete for damage assessment during dynamic loading, pp. 168-9, Extended Abstracts, 22st Biennial Conference on Carbon, 1995, pp 168 169. 

Carbon fiber introduction into commercial markets happened in the mid-1960s and since then their application has increased substantially. Some of these applications include airplanes, spacecraft parts, compressed gas tanks, automotive parts, bridges, reinforced concrete, structural reinforcement, recreational sports equipment, and electrochemical systems [6,7]. 

Pitch-Based General Performance Carbon Fiber (GPCF). As described in the introduction, continuous-strand GPCF has been produced commercially only by the Kureha Chemical Industries Company. Public attention has recently been attracted to this type of carbon fiber by the success in using carbon-fiber-reinforced concrete in the construction of the Arsasheed Monument in Iraq (24) by the Kashima Construction (Kashima Kensetsu) Co. Future construction projects in Japan plan to utilize further this type of fiber-reinforced concrete. Such applications may lead to mass consumption of fiber if its price can be brought below 9/kg ( 4/lb). The authors believe that some substantial reductions in the price of the general-performance fiber, perhaps to 6.5/kg ( 3/lb), may occur in the near future. 

Figure 10. Flexural performance of carbon-fiber-reinforced concrete. is the volume fraction of carbon fiber.

Our study applies an adsorption process using chemically activated carbon fibers (CACF) to effect NOx> a prevalent atmospheric pollutant difficult to control. A concrete understanding of adsorption and desorption behavior and surface chemistry on was progressed. 

EXPERIMENTAL CHARACTERIZATION OF CARBON-FIBER/CONCRETE ADHESIVE INTERFACE FOR RETROFITTING OF CONCRETE BRIDGE STRUCTURES... 

Concrete structure. Retrofitting, Carbon fiber sheet. Adhesive interface, Mixed mode. Fracture toughness. Fracture criterion... 

Fig. i. Schematic drawing of retrofitting method for concrete beams with tensioned carbon fiber sheets. 

Fig. 2. Experimental results of 4-point bending test for concrete beams with and without bonding of carbon fiber sheets.

In the present work, a novel experimental method was proposed to evaluate the modes I-fll fracture toughness of the adhesive interface between concrete and carbon fiber sheets. The validity of the evaluation formula was studied on the basis of the results of finite element analysis. The mixed mode fracture toughness and fracture criterion of the adhesive interface were also studied on the basis of the results of fracture toughness test using the proposed method. 

The MMD (Mixed Mode Disk) specimen was proposed to investigate the modes I+II fracture behavior of the adhesive interface between concrete and carbon fiber sheets. This specimen, which consists of two concrete blocks inserted carbon fiber sheets and steel jigs, is basically similar to the Arcan specimen, as shown in Fig. 3 [12]. However, the evaluation formula for the Arcan specimen can not be directly applied to the MMD specimen owing to the difference of geometries and the existence of carbon fiber sheets. For the present specimen, the adhesive region was set to be smaller than the face of... 

Two concrete blocks were carefully bonded by inserting a carbon fiber sheet with the adhesive resin and cured at room temperature for 48 hours as the manufacturer s recommendation. A thin releasing film was inserted between the concrete blocks and carbon fiber sheet to introduce an artificial crack and to make an adhesive region of 20 x 10 mm The blocks were then bonded to the steel jigs with the same adhesive resin, as shown in Fig. 11. A liquid type primer was used to gain the adhesiveness of the interface between the concrete and carbon fiber sheet. 

As shown in Fig. 14, a thin concrete layer always remained on the adhesive region the crack path was inside the concrete blocks. Hence, the experimental results did not strictly indicate the properties of the adhesive interface. However, this behavior totally agreed with the actual fracture behavior of the RC beam reinforced with carbon fiber sheets [6]. This behavior was also consistent with the finite element results, where the principal stress in the concrete blocks partially exceeded their tensile strength. 

Fig. 15. Mixed mode fracture toughness of the adhesive interface between concrete and carbon fiber sheets each plot is the average value of 5-10 test data.

In order to apply the characterization and structural design of the concrete bridge structures retrofitted with tensioned carbon fiber sheets, the mixed mode disk specimen was proposed and applied to the mixed mode fracture toughness tests. The following conclusions were derived from the results and discussions ... 

It is of note that during the 1989 San Francisco earthquake, certain overhead road supports that were retroactively strengthened by cladding with a relatively thin layer of carbon fiber-reinforced concrete allowed them to survive while conventional concrete pillars failed [20]. Similarly, in Japan, which experiences several hundreds of earthquakes each year of widely ranging intensity, carbon fibers have been extensively adopted for concrete reinforcement. More carbon fiber is employed in the Japanese construction industry than anywhere else [21]. 

With few exceptions weight reduction of parts in mobile applications is good. However, the carbon-fiber example shows the situation can only be judged for the concrete case and application. 

One can see that epoxy polymer concrete exhibits higher compressive strength, with values ranging from 3.8-4.3 times higher than commercial concrete. Compressive strength of this PC shows an increase of 1.5 times when glass fibers are added to the epoxy resin matrix and 2.0 times with the use of carbon fibers [8],... 

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