A study on effect of silica fume and surface penetrant on bonding strength for overlaying

Abstract

Currently, concrete structures are at risk of deteriorating conditions due to their exposure to various severe environments. Repairing and strengthening these structures is a better solution than replacing them by new constructions. As a retrofitting method, the top/bottom surface overlaying or jacketing method is commonly used around the world. In this method, polymer cement mortar (PCM) is sprayed/troweled onto the surfaces of concrete, and PCM adhesive strengthens the concrete structures. However, the concrete-PCM interface is considered to be the weakest part of a structure, and it may cause brittle fracture. This study focused on how this interface can be strengthened more effectively to prevent brittle fractures and investigated the effects of applying surface penetrant and silica fume from the perspective of chemical reactions. In addition, the reaction time relationship between PCM hydration and surface penetrant application time is also investigated based on a preliminary experiment. Mixing silica fume into PCM was conclusively found to strengthen the interface bonding strength in some conditions. Applying surface penetrant to an interface could decrease the interface strength if the application time was inappropriate. However, the results of an application time experiment indicated that it is possible to strengthen the interface via the surface penetrant.

Durability Enhancement Effect of Silica Fume on the Bond Behavior of Concrete–PCM Composites under Environmental Conditions

“…A small amount of silica fume results in less C-S-H at the interface, whereas material stagnation is caused by using a large amount of silica fume [60]. Based on the findings of previous studies [28], a 5% silica fume of PCM mass was used in this study. Since silica fume powder is not liquid and is difficult to spread in the interface, it was used by mixing into PCM powder right before overlaying and hydrating together.…”

“…Since silica fume powder is not liquid and is difficult to spread in the interface, it was used by mixing into PCM powder right before overlaying and hydrating together. Superplasticizer of 1.0% of the PCM mass was mixed in preparing modified PCM repair material to prevent the formation of silica fume lumps, whereas it was not used to prepare normal PCM repair material (without silica fume) following the outcome of trial flow test by the author and previous group research in our team [28][29][30]. The use of superplasticizer has no impact on the mechanical performance of the composites as observed in the trial test by the author.…”

“…In technical literature, many studies revealed that a supplementary cementitious material such as silica fume can be used as a filler, pozzolan, or admixture to improve the performance of mortar and concrete [22][23][24][25]. In the previous study [26][27][28][29][30], it has also been shown that silica fume modified PCM as a repair material significantly improves the concrete-PCM interfacial bond, thus offering a broad prospect for the application of the PCM overlaying method for the strengthening of deteriorated reinforced concrete (RC) structures.…”