Study of the bond strength of reinforcing steel embedded in concrete column using the drilling method combined with epoxy glue

Abstract

Drilling and inserting reinforcing bars into existing reinforced concrete columns to cast additional concrete beams is a common practice in the expansion of small-scale residential buildings. In general, most contractors used the method of drilling and inserting reinforcing bars and fastening them with epoxy glue in concrete columns. This research studies the bond of reinforcing bars embedded in concrete with epoxy glue, whereby the pullout behavior of reinforcing bars embedded in reinforced concrete columns was studied. The concrete column samples used in the pullout test had a cross-sectional area of 0.2 x 0.2 meters and a length of 0.6 meters, with a compressive strength of 28 MPa. The main variables used in the comparative study were: 2 types of main rebars in reinforced concrete columns, i.e. 4-DB12 and 4-DB16; 2 sizes of rebars embedded in the concrete columns, i.e. DB12 and DB16; 2 levels of embedded length of rebar in concrete columns, i.e. 120 mm and 160 mm; and 2 different numbers of embedded rebars for the withdrawal test, 1 and 2 bars. All rebars were SD40 standard. The study's results showed that an increase in the embedded length of rebar, the size of rebars, and the number of embedded rebars resulted to a significant increase in the pullout force. However, if the embedment length of the rebar was small and two rebars were used for embedment, the pullout behavior of the rebar using the drilling method combined with epoxy glue would be reduced rapidly due to the concrete breakout failure.