Bonding behaviour between old and new foamed concrete with different substrate surface

摘要

Recent years, method of concrete strengthening has been a rising issue. In structureudof concrete or concrete repairing works, the most Important element is that the bondinguditself. The surface preparation of concrete substrate will give differ results in term of udbonding behavior. Performance of a structural system such beams and slabs are relies onudbehavior of the bonding between the old and new concrete. The research intended atudstudying the bonding strength between the old and new foamed concrete due to surfaceudpreparations. Factors such as roughness of surface, compaction, and concrete curing affect udthe bond. In this study, the surface of the old concrete were partially chipped using a lightudjackhammers and differed in terms of its numbers. The research was also to observe failure udmode pattern due to different number of chippings. Samples were tested for two differentudmethods namely Splitting Test and Slant Shear Test. The slant shear tests were conducted udto investigate the bonding strength in term of shear. For slant shear test, 12 blocks sizingud100 mm x 100 mm x 400 mm were prepared. Meanwhile, the slant shear test wasudconducted to measure the axial tensile strength of a concrete submitted to compressionudalong its length. For this test, 12 cube specimens ofize 150 mm x 150 mm x 150 mm were udprepared. These tests were conducted on 28 days after standard air curing because at day 28udthe concrete had fully achieved its true strength. Foamed concrete was used to reduce theudself-weight of the structural element compared to the conventional concrete. For each udtesting method, three samples were prepared and differed in term of surface roughness of 0,ud10, 20 and 30 number of drill holes. From the results, S30 for Splitting test and SR30 Slant udshear test showed the highest in terms of bonding strength compared to lower surfaceudroughness with values of 2.17 N/mni2 and 21.73 N/mrn2 respectively. However, udalludtypesudof surface roughness are failed intermof bonding.