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Experimental Research on the Durable Properties of Ultra High Toughness Cementitious Composites(UHTCC)

Author: CaiXinHua
Tutor: XuShi
School: Dalian University of Technology
Course: Structural Engineering
Keywords: Ultra high toughness cementitious composites Durability Steel corrosion Bond Performance Protective layer cracks due to corrosion
CLC: TU528
Type: PhD thesis
Year: 2010
Downloads: 508
Quote: 4
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Abstract


Ultra high toughness cementitious composite (Ultra High Toughness Cementitious Composites, referred to as UHTCC) under tensile loading strain hardening characteristics and excellent crack control ability, ultimate tensile strain tensile loads stable to reach more than 3% can form a multi-seam cracking form and reach the ultimate tensile strain corresponding crack width is less than 0.1mm. The new high-performance fiber-reinforced cement-based composite materials to improve the durability of reinforced concrete structures, seismic performance, maintenance and refurbishment of the old structure has broad application prospects, the last decade has been the research at home and abroad hot spots. Basic mechanical performance of UHTCC material, with steel and concrete composite component more, but less for its durability characteristics reported. Therefore, in the early a lot of work on the basis of the research group on UHTCC basic mechanical properties and UHTCC reinforced concrete composite component research, its frost resistance and carbonation resistance, permeability and basic durability characteristics of the experimental study and analysis, and the UHTCC and bonding properties of corroded reinforced, UHTCC replace the protective layer of concrete beams to resist the reinforcement corrosion performance testing and analysis. Thesis, reads as follows: (1) by rapid thawing test laboratory method to study the different number of freeze-thaw cycles UHTCC mass loss, change of the dynamic elastic modulus UHTCC trabecular bending the performance, UHTCC sheet bending performance, and under the same test conditions for ordinary concrete, steel fiber concrete and air-entrained concrete test results were compared. The results show that, UHTCC not mixed with air-entraining agent has good frost resistance after 300 freeze-thaw cycles to maintain high bending tensile strength and flexural toughness. Based on the test results given the UHTCC use in cold regions. (2) by rapid laboratory test methods carbide UHTCC carbonation resistance test. Including the state no cracks UHTCC carbonation properties, UHTCC trabecular presplit with the carbonation performance and UHTCC sheet cracks state carbonized bending performance, and comparison with ordinary concrete test results under the same conditions. The results showed that the anti-carbonation properties with UHTCC age growth gradually increased, and the cracking mode has a number of fine cracks under load, carbonation resistance in the fractured state better than ordinary concrete specimens; carbonation can slightly improve compressive strength and UHTCC sheet the initial cracking bending stress, its flexural toughness basically no impact, and given reference recommendations how the evaluation UHTCC carbonation resistance based on the test results and analysis. (3) through to the impermeability test of the test chamber, the rapid chloride permeability test and the free chlorine ion content measurement test studied UHTCC penetration properties, and compared with ordinary concrete under the same conditions. The results showed that, UHTCC impermeability much better than ordinary concrete, low chloride ion diffusion coefficient, and with the gradual increase in the age, UHTCC impermeability increased as compared with ordinary concrete obviously, chloride ion diffusion coefficient with age period of growth gradually reduce. (4) Accelerated Corrosion Methods and direct pullout tests by the electrochemical bonding properties of corroded reinforced UHTCC and different corrosion rate were pilot studies and analysis, and compared with ordinary concrete specimens. Different corrosion rate UHTCC reinforced average bond stress - slip curve, the bond - slip the continuous curve model describes the average UHTCC reinforced bond stress - slip relationship; analysis UHTCC reinforced average The bond strength with the variation of corrosion rate found UHTCC can delay the adhesive force between the UHTCC reinforced steel corrosion is reduced, and played the role of class stirrups. (5) replace the reinforced concrete beams, UHTCC protection layer of concrete ideas produced four different types of beams, including UHTCC thickness of 15mm and 50mm, and rebar reinforced concrete beams and the Reinforcement UHTCC beam, accelerated corrosion test methods the main reinforcement corrosion, and failure mode of each beam experienced different corrosion time bending bearing capacity, bending fracture characteristics and other properties. The results showed that, UHTCC has superior resistance to the protective layer of rust cracking function in the lower level of corrosion rate UHTCC thickness of layer to the the 50mm beam Reinforcement UHTCC beam ultimate bearing capacity reduction is smaller, and the bending crack width of the beam load close to yield remained below 100 μm, still played an excellent crack control ability. (6) using the method of the the elastoplastic mechanical and cavity expansion analysis, consider the ultimate tensile strain UHTCC drawn the formula reinforced the critical corrosion rate corrosion cracking occurs UHTCC as a reinforced protective layer failure, and an illustrative example is the effectiveness of the UHTCC resistance corroded expansion force, and by the parameters analyzed and discussed the impact factors reinforced the critical corrosion rate UHTCC protection layer corrosion cracking failure.

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