Adhesion and durability characteristics of concrete prisms repaired by methyl methacrylate resin injection

Abstract

This work is concerned with assessing the influence of many different parameters on the adhesive joint strength of repaired concrete prisms in flexure. Test results show that the adhesive joint performance of methyl methacrylate (MMA) systems is relatively unaffected by a low testing temperature such as -20 degreesC. The increase in test temperature from 20 to 50 degreesC, however leads to a decrease in the adhesive joint strength of these systems. In spite of this fact, the MMA2 formulation (filled system) shows a much higher retention of adhesive joint strength at 50 degreesC in comparison with the MMAI (unfilled system). Therefore, this system is capable of operating up to 50 degreesC with good strength retention. Further increase in test temperature causes a more severe reduction of adhesive joint strength together with the commencement of the thermal degradation of MALA adhesives. The extent of damage caused by various chemicals varies widely depending on the type and concentration of chemicals and MMA adhesive formulation as well as adhesive thickness. Tests in an aggressive environment such as HCl reveal no corrosion at the interface between the adhesive and concrete when the adhesive thickness is 5 nun or less. The maximum reductions in adhesive joint strength are noticed under the action of distilled water The adhesive joint strengths of these samples generally reach 41 to 75% times the original strength of concrete. The same tendency is also observed for MMA systems exposed to NaOH. This study does not show clear evidence of an adverse effect of moisture on the adhesive joint performance within the moisture content range investigated. Another important finding is that the size of concrete specimen to be repaired with MMA systems limits the efficiency of adhesion process. The adhesion and durability characteristics of the MMA I system tend to decrease with increasing adhesive thickness. At 5 mm adhesive thickness, the combined effect of shrinkage and freezing and thawing can be regarded as the mechanism responsible for the damage developing at the adhesive-concrete interface with time.