Research on Improvement of Process Performance of Carbon Fiber Sheet Reinforced Adhesive

   Abstract: Carbon fiber sheet-reinforced adhesives have been widely used in the field of reinforcement and reformation of concrete structures, but their research on the improvement of process performance has not received enough attention. This paper studied the effect of modified amine curing agents on the pot life of epoxy resin-based carbon fiber sheet-reinforced adhesives. At the same time, it also discussed the thixotropic agents and put forward a method to determine the adhesive infiltration properties. The self-made curing agent has been used to formulate winter and summer formulations suitable for different seasons, and the process performance is good.

    【Key words】 Carbon fiber sheet   Reinforcement   adhesive   Process performance   Epoxy resin

0. Preface

    Carbon fiber sheet reinforced concrete structure has many outstanding features, such as: high strength, light weight; construction is simple; the beginning of the structure can be freely cut; easy to design and so on. Therefore, although this technology was introduced into China in less than ten years, it has been widely used in the field of reinforcement and reconstruction of concrete structures, and the corresponding specifications (or standards) ( CECS 146 : 2003 Technical Specification for Reinforced Concrete Structures of Carbon Fiber Sheets) Has been introduced. At present, with the exception of carbon fiber sheet (carbon fiber cloth and carbon fiber board) still need to be imported, the adhesive used with it has been made domestically. There are many brands of domestic carbon fiber sheet reinforcement adhesives, but there is still a big gap between product quality and foreign ones. The main performance of adhesives is in terms of process performance, such as : poor thixotropy, easy-flowing construction of vertical surfaces and upward viewing surfaces; no consideration was given to construction. At ambient temperature, there are no winter or summer formulations, resulting in a very short service life of the adhesive in the summer and slow curing of the adhesive in winter; poor wettability of the carbon fiber and unsatisfactory construction quality.

   Carbon fiber sheet-reinforced adhesives generally include three types of adhesives (by application): 1. Primer (also known as base resin); 2. Repair adhesive (also known as leveling material or putty); 3. Adhesive (also called adhesive) Impregnating resin). Their respective roles are as follows: 1. Primer: The brush is applied on the concrete base layer to strengthen the surface strength of the concrete, so that the adhesion between the concrete and the carbon fiber is improved. 2 , repair glue: leveling concrete surface, easy to paste carbon fiber sheet. 3 , impregnated resin: the carbon fiber sheet together to make it a slate hardened; at the same time the carbon fiber and concrete bonded together, also form a composite whole, a total resistance to external forces. Among the three adhesives, impregnating resin is the most important, and its performance directly determines whether the carbon fiber sheet can effectively reinforce the reinforced concrete structure. According to the characteristics of the two-component modified epoxy resin adhesives, the process performance improvement of the impregnating resin (adhesive) is systematically studied. The obtained adhesive has excellent process performance.

1. Experiment

1.1 The main raw materials and instruments

   Liquid Bisphenol A Epoxy Resin, Industrial Products; Modified Amine Curing Agents, Industrial Products; Self-made Curing Agents, Industrial Products; Thixotropic Agents, Industrial Products; Additives, Industrial Products; NDJ-4 Rotating Viscometer; Roll grinding machine; universal material testing machine

1.2 Experimental Methods

   ( 1 ) Preparation of adhesive component A: Epoxy resin and additives are fully mixed to obtain a component.

   ( 2 ) Preparation of Adhesive B component: The B component is obtained by thoroughly mixing all types of hardeners (or several mixed hardeners) and auxiliaries.

   ( 3 ) Determination of the applicable period

   According to GB/T 12954-91, the adhesive A and B components are mixed in a certain weight ratio, and the pot life is tested in a constant temperature water bath of 23 ±value=".5" unitname="°C"> 0.5 °C.

   ( 4 ) Determination of tensile shear strength

   After the components of A and B were uniformly mixed in a certain weight ratio, the tensile sheared carbon steel test piece was bonded according to GB/T 7124-1986 , cured at room temperature for a certain period of time, and then tested for tensile shear strength.

   ( 5 ) Determination of thixotropy

   The thixotropic agent is added to the nail of the adhesive component and mixed uniformly. According to GB/T 2794-1995, the second gear rotor speed (rotor speed is 0.6r/min and 6r/min ) is used to test the viscosity, and the low speed is measured. The ratio of the viscosity to the measured viscosity at high speed is the thixotropic index TI ( TI ≥ 1 ).