#question and answer
In a project, part of the foundation section has been concreted, and the other part, which is supposed to be connected to the previous concrete, has been postponed for 2 years, and new concrete is supposed to be poured on top of the old concrete after two years. Now the question is, in order to achieve the necessary adhesion between the new concrete and the old concrete, what measures should be taken? (At the same time, he notes that the issue of sealing is also important for the employer in this matter). Are solutions such as chipping old concrete or using concrete glue sufficient for this purpose?
1⃣ The connection between the old and new concrete generally includes roughing up the old concrete and creating ghosts with a dry surface on the surface of the old concrete and pouring new concrete on top of the old concrete or next to it. In valid regulations, there is no requirement to use latex materials (concrete glue).
2⃣ If the new concrete has a low slump or the maximum diameter is larger than 25 mm. In horizontal seams, it is better to use a fine-grained mortar called connecting mortar, but in vertical seams, such a measure cannot be adopted. Fine-grained mortar should have a maximum size of about 4 mm with equal to or less than the main concrete and be smooth (with a slump of more than 15 cm) in order to penetrate the exposed sands due to compaction. Due to the high sensitivity of this mortar, 10 to 20% of the cement weight can be used from latex.
3⃣ In vertical seams (which is probably related to your question), such a joint mortar cannot be used, and if there are specific sensitivities such as the desired project, such as sealing or corrosion of rebars, it can be made of latex (concrete glue) or He used latex grout (mixture of latex and cement) on the vertical surface. Latex with a thickness of about 1 mm and latex grout with a thickness of about 2 mm can be used.
4 ⃣ However, it is better to use a smoother concrete in vertical joints like horizontal joints, so that the concrete mortar fits in the height and height of the old concrete.
5⃣ New concreting should be poured before the latex or latex grout hardens to help the connection at the joint location. Also, it is necessary to keep the place of the vertical seam (depending on its thickness) unsaturated for 2 to 7 days so that the latex polymerization can be done properly.
Source: Iranian Concrete Association
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This post is written by Oralyol1392