I. After Every Use: Thorough Cleaning Comes First

Don't put the mold aside immediately after demolding. While the concrete residue has not fully hardened, remove any remaining mortar, especially from joints, internal corners, bolt holes, and around locating pins. If hardened material accumulates in these areas, the mold may not close properly during the next assembly, resulting in grout leakage through the joints. This can leave the finished concrete components with excessive flash and burrs, requiring additional manual grinding.

Use soft tools such as a rubber mallet, plastic scraper, or copper brush for cleaning. Avoid striking the mold with a heavy steel hammer or using an angle grinder aggressively, as this can dent the mold panels or scratch the sealing surfaces. For stubborn concrete buildup, wet the residue first and allow it to soften before carefully scraping it away.

After cleaning, wipe the mold completely dry. This is especially important because storing the mold while it is still wet can accelerate rust and corrosion.

II. Release Agent: Never Use Used Engine Oil

Using used engine oil as a mold release agent is a common cost-cutting practice in small workshops. Although it may appear to work in the short term, used oil contains impurities and acidic contaminants and has inconsistent viscosity. Over time, it can leave a sticky layer of oil residue on the mold surface, making it easier for dust and cement slurry to adhere.

It can also contaminate the concrete surface, causing yellowing or uneven discoloration and, in severe cases, affecting subsequent plastering, finishing, or waterproofing work.

Always use a professional concrete form release agent. Both water-based and oil-based products can be used, provided they are suitable for the mold and applied according to the manufacturer's instructions. Apply a thin, even coating. Excessive release agent can cause surface defects such as bubbling or dark discoloration on the finished concrete. Allow the release agent to form a proper film before placing concrete.

III. Mold Joints and Sealing Strips: Areas That Need Special Attention

The sealing strip at the mold joints is one of the components most susceptible to aging and wear. After each use, check whether the strip is compressed, cracked, detached, or damaged. A worn or damaged sealing strip can allow grout to escape during casting, causing the edges and corners of the finished concrete culvert to become rough or damaged.

Do not allow hardened cement slurry to build up on the sealing strip. Clean it gently with a soft brush rather than scraping it with hard tools. If the sealing strip has lost its elasticity or no longer provides adequate sealing, replace it promptly. It is a relatively inexpensive component, and timely replacement can prevent more serious casting defects.

Locating pins, pin holes, and locking bolts should also be cleaned after every use and lightly lubricated with grease. If debris accumulates inside the pin holes, the locating pins may not seat correctly, causing the mold to be misaligned and ultimately affecting the dimensional accuracy of the finished square culvert.