Abstract:
One of the most common difficulties in the execution of concrete structures is cold
joint because of delay in concrete casting due to several circumstances as well as
improper casting sequence. The discontinuity in concrete element leads to structural
weakness, increasing the permeability, corrosion of the reinforcement, reducing the
durability and bad appearance of concrete. In this research, the aim to eliminate the
cold joint by applying the bonding agent.
In order to evaluate the effect of the bonding agent on cold joint, 76 number of cubes
were cast using grade 30 concrete. Out of them, 36 specimens contain cold joint with
20° degree of inclination to the horizontal plane for compressive strength with and
without applying bonding agent other 36 specimens had cold joint in the horizontal
plane for splitting tensile strength with and without applying bonding agent and
considered delay time of one hour interval up to 5 hours.
After 28 days of curing, all specimens were tested as per standard method. The
experimental result of compressive strength shows that cold joint with applying
bonding agent give 6% improvement as compare to without applying bonding agent.
But, the experimental result of splitting tensile strength shows that no considerable
influence on cold joint as applying bonding agent compare to without applying
bonding agent. However, there is considerable reduction in the compressive strength
(30.50%) and tensile strength (33.14%) compare with initial specimens with applying
bonding agent.
Further, observation based on failure surface of tested specimens clearly indicated that,
there are no aggregate inter logged in between two layers when delay time past the
initial setting time of the first layer. So, the reduction in strength due to the cold joint
purely depends on aggregate interlocking.
The better options are to avoid the cold joint by using admixtures (retarders) to increase
the initial setting time, adopt proper casting sequences and vibrate the layers together
even within the initial setting time.
Citation:
Pushparuban, P. (2021). Investigation of effects of bonding agent on performance of cold joint in concrete member [Master's theses, University of Moratuwa]. Institutional Repository University of Moratuwa. http://dl.lib.uom.lk/handle/123/18779