25 Detection and Evaluation of Vascular Network Based …
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agent. Cyanoacrylates were selected as an effective self-healing agent which were
injected into the polyethylene based capillary tubes after damage.
25.2.1.1 Concrete Specimen Preparation
12 concrete beams of size 75 × 75 × 255 mm were cast in this study. The moulds
used for beam casting contained pre-drilled holes, 4 at either end of each specimen.
After curing for 5 days in a water bath and 1 day in the desiccator, a 6 mm rectangular
notch was sawn at the centre line of the bottom surface of each beam. Then all the
specimens were drilled at the channel openings to widen the diameter of the channel
hole to 6 mm with a depth of 10 mm to fit the capillary network tubes. Two knife
edges, which is used for the Crack Mouth Opening Displacement (CMOD) clip
gauge, were glued on both sides of the notch on the bottom surface of the specimens.
And a L-shaped deflection bracket, which is used for the measurement of central
LVDT (Linear Variable Displacement Transducer), was glued onto a side surface,
overhanging the bottom edge.
25.2.1.2 Healing Agents
More recently, researchers at Cardiff University have undertaken a substantial parametric study on adhesive-based self-healing of concrete beams. The main healing
materials that have been proposed to date are epoxy resins, cyanoacrylates, and
alkali–silica solutions, with the long-term aim of developing a material for this new
composite material [2]. In this study, cyanoacrylate of type PC20 was used as the
healing agent because of the main advantage of rapid curing due to acidity of glue
and alkalinity of concrete (pH of approximately 13).
25.2.2 Testing Methods
25.2.2.1 Experiment Setup and Instrumentation
The experiments consisted of four sets of three beams. Apart from one set of three
control beams, each set comprise three beams tested under three-point loading with
different paused time with input of self-healing agent (cyanoacrylates) between 1st
loading stage (initial loading) and 2nd loading (reloading) stage. The Test arrangement is shown below in Fig. 25.1. AE signals were recorded with a MISTRAS
EXPRESS-8 Eight-Channel system. Steel pads were bonded to the concrete and
magnetic clamps were used to hold the sensors on the surface of the specimens. Two
R15I-AST sensors (70–200 kHz) were attached on one side of the specimen with
140 mm distance between each other, as shown in Fig. 25.2.
301
agent. Cyanoacrylates were selected as an effective self-healing agent which were
injected into the polyethylene based capillary tubes after damage.
25.2.1.1 Concrete Specimen Preparation
12 concrete beams of size 75 × 75 × 255 mm were cast in this study. The moulds
used for beam casting contained pre-drilled holes, 4 at either end of each specimen.
After curing for 5 days in a water bath and 1 day in the desiccator, a 6 mm rectangular
notch was sawn at the centre line of the bottom surface of each beam. Then all the
specimens were drilled at the channel openings to widen the diameter of the channel
hole to 6 mm with a depth of 10 mm to fit the capillary network tubes. Two knife
edges, which is used for the Crack Mouth Opening Displacement (CMOD) clip
gauge, were glued on both sides of the notch on the bottom surface of the specimens.
And a L-shaped deflection bracket, which is used for the measurement of central
LVDT (Linear Variable Displacement Transducer), was glued onto a side surface,
overhanging the bottom edge.
25.2.1.2 Healing Agents
More recently, researchers at Cardiff University have undertaken a substantial parametric study on adhesive-based self-healing of concrete beams. The main healing
materials that have been proposed to date are epoxy resins, cyanoacrylates, and
alkali–silica solutions, with the long-term aim of developing a material for this new
composite material [2]. In this study, cyanoacrylate of type PC20 was used as the
healing agent because of the main advantage of rapid curing due to acidity of glue
and alkalinity of concrete (pH of approximately 13).
25.2.2 Testing Methods
25.2.2.1 Experiment Setup and Instrumentation
The experiments consisted of four sets of three beams. Apart from one set of three
control beams, each set comprise three beams tested under three-point loading with
different paused time with input of self-healing agent (cyanoacrylates) between 1st
loading stage (initial loading) and 2nd loading (reloading) stage. The Test arrangement is shown below in Fig. 25.1. AE signals were recorded with a MISTRAS
EXPRESS-8 Eight-Channel system. Steel pads were bonded to the concrete and
magnetic clamps were used to hold the sensors on the surface of the specimens. Two
R15I-AST sensors (70–200 kHz) were attached on one side of the specimen with
140 mm distance between each other, as shown in Fig. 25.2.