How to Glue Cement to Cement: Step-by-Step Guide?

A concrete bonding adhesive like QUIKRETE No. 9902 bonds new cement to old concrete — after the surface is cleaned down to sound material.

Fresh cement won’t grip old concrete alone: the old surface is dense and often sealed with curing compounds or dust, and new material shrinks as it cures and peels away. Getting it right comes down to one product choice and one cleaning job.

What Bonds New Cement to Old Concrete?

A concrete bonding adhesive is the correct product. Household glue, caulk-tube construction adhesive, and thin-set mortar lack the chemistry to grab a cement substrate.

QUIKRETE Concrete Bonding Adhesive, No. 9902, bonds new concrete, plaster, and stucco to existing concrete, plaster, and stucco, indoors or out. It eliminates the need to roughen the surface — but the surface must still be clean, sound, and free of anything that blocks a bond. To compare brands and sizes, see our roundup of the best glue for cement.

Preparing the Surface

Adhesive only holds as well as the concrete beneath it. Loose, crumbly, or deteriorated material must come off first; the manufacturer names shotblasting as the preferred abrasive method. Then clean out dust, dirt, oil, grease, wax, paint, curing compounds, coatings, and laitance — the weak, chalky layer on cured concrete. Rigorously clean and dust-free is the standard.

Damp is fine; wet is not. Apply to a dry or damp surface, never a contaminated one or one visibly holding water. Don’t apply over painted concrete unless the paint is completely gone and the substrate properly prepared.

Three Application Methods and Their Timing

• Paint-on adhesive: shake or stir, then brush, roll, or spray undiluted to roughly paint-coat thickness. Let it dry — typically 2–3 hours, though temperature, humidity, and substrate vary that — then place the new concrete, topping, or plaster. Exception: apply gypsum and finish plaster while the adhesive is still tacky.
• Slurry coat: mix roughly 2 parts Portland cement to 1 part bonding adhesive until lump-free, then trowel, brush, or squeegee a thin coat and rub it in. Place the topping before the slurry dries. A dried slurry coat is a dead bond.
• Self-leveling resurfacer primer: dilute 1 part adhesive with 2 parts clean potable water, stir, and saturate the surface with a broom, roller, or garden sprayer. Low-porosity concrete usually needs one coat; porous concrete needs two. Let it dry to the touch before the resurfacer goes down.

Clean tools right after with warm soapy water — hot water handles drips. Cure the repair per the topping’s own instructions; the adhesive doesn’t replace proper placement, reinforcement, joint design, or curing.

Limits, Mistakes, and Conditions That Kill the Bond

The adhesive is not a fix for structural problems — movement, cracks, settlement, or an unsound substrate must be solved first.

For exterior toppings under that, the manufacturer’s FAQ points to Sand/Topping Mix with QUIKRETE Concrete Acrylic Fortifier instead, and says not to use Concrete Bonding Adhesive in continuously wet environments.

Two hard rules from the data sheet: don’t apply below 50°F (10°C), and don’t mix with QUIKRETE Concrete Acrylic Fortifier, No. 8610. Store below 100°F (38°C) and keep from freezing.

Product variants differ, so your package’s data sheet controls.

Safety: protective gloves, eye protection, and adequate ventilation. Don’t eat, drink, or smoke while handling it, keep the container tightly closed, wash thoroughly afterward, and dispose of contents and container per local regulations. Absorb spills and keep them out of surface-water drains. No verified current retail price appears in the manufacturer’s documentation — expect it to vary by retailer, package size, and location.