The concrete work for a building cannot be completed in a single operation because there is a limit to the amount of such work that can be done at a particular time. Construction joints are therefore inevitable in concrete structures. Because fresh concrete is poured on hardened concrete, a perfect blend cannot be obtained between the two. The adhesive failure that occurs at the interface between the two is called a cold joint. Such cold joints are often the sources of degradation and deterioration in concrete structures, which makes their treatment imperative. Two approaches have been used in treating such joints. Either the laitance is removed by using a retarder or reinforcement rods are placed between the two sections of concrete. However, these methods present some challenges. JOINT ACE was developed in order to meet these challenges. Its a chemical agent that is used for the surface treatment of horizontal concrete joints. Its main ingredient is an acrylic polymer emulsion that contains ultrafine particles. The durability of the construction joint is enhanced by spraying this agent on the surface after pouring fresh concrete.
JOINT ACE is a water-based treatment agent that can be stored safely. It can be easily applied with a typical sprinkling can or a manual or power sprayer. Unlike the method involving the removal of laitance with a retarder, the use of JOINT ACE does not require large equipment such as a high-pressure water jetting unit or sludge water sucker unit. It can therefore be used in response to unexpected construction needs. Moreover, since its application has no byproducts like sludge water, it can be used on sites with stringent environmental regulations.
Cylinder test pieces (φ100 mm) were prepared by core drilling into the construction joint.
Test conditions: Temp.20°C, humidity 60%, CO2 conc.5%. The test pieces were cleaved and colored with phenolphthalein.
When the treatment of a potential cold joint is insufficient, corrosive materials such as chlorides, carbon dioxide, and acids gain entry. Such materials corrode the concrete reinforcement, leading to the deterioration of the structure. Moreover, they cause efflorescence and frosting, which also result in the surface deterioration of the concrete. JOINT ACE has a chemical structure that creates an affinity for cement and facilitates bonding at a construction joint. When properly applied, it improves the durability of the construction joint.
Test pieces (600 × 150 × 150 mm) were prepared and cured for six months. The strengths of the test pieces were measured by a three-point flexural test. The strength without a Construction joint was set at “100” and each result was standardized. They are presented as an index.
Since only a prescribed and undiluted amount of JOINT ACE is required to be sprayed on the concrete surface, its performance is practically independent of the skill of the user. Moreover, it does not adversely affect the adhesion of the reinforcement to the concrete and can be applied to structures with heavy reinforcement, such as required by earthquake resistance standards. It produces stable bonding at the construction joints, even in cases where the removal of laitance would be ineffective.
Outdoor exposure for three months
Fresh concrete is poured, carefully compacted with a vibrator, and finished as usual.
Undiluted JOINT ACE is poured into a typical sprinkling can or sprayer. The equipment must be clean and free from previously contained materials.
JOINT ACE is sprayed onto the concrete surface. Spraying can commence when the concrete bleed water on the surface begins to dry. Excessive bleed water that accumulates in recesses on the surface should first be removed by absorption with a cloth or some other means. The application of the treatment agent should be uniform and approximately 300 g/m2. The spraying equipment should be thoroughly cleaned with water immediately after use, since the agent is difficult to remove once dried.
Since freshly applied JOINT ACE can be washed out by rainwater, preventive measures such as covering with a sheet should be taken. An interval of above 24 h after the surface treatment is recommended before the next section of fresh concrete is poured.
The treated surface should be checked before the next section of fresh concrete is poured. Sufficient compaction of the fresh concrete should be done to avoid the usual problem of formation of honeycombs.
|Specific Gravity (at 25°C)||0.9-1.1|
|Flash Point||Not given|
|pH (undiluted solution at 25°C)||6-8|
|Viscosity (undiluted solution at 25°C)||<100 mPa·s|
JOINT ACE comes in 18-kg cans, each of which is sufficient for treating about 60 m2 of concrete.
Direct exposure of JOINT ACE to sunlight should be avoided. It should be stored in a well-ventilated room at about 5-35°C with the tin can tightly closed.
Disclaimer: The information herein is subject to change without notice. The information presented herein is true and accurate to the best of our knowledge, but without any guarantee unless explicitly given. Since the condition of use is beyond our control, we disclaim any liability, including for patent infringement, incurred in connection with use of these products, data or suggestions. Buyers must determine for himself, by preliminary tests, or the suitability of these products for his purposes. Careful precautions are required in handling all chemical products. Please refer to our MSDS.