Key points
- ASTM C1059 covers latex agents for bonding fresh to hardened concrete, with two types: Type I re-emulsifiable and Type II non-re-emulsifiable.
- Type I (often PVA or EVA) can be applied and left to dry, then re-wets and bonds when fresh concrete or mortar touches it.
- Type II (often acrylic) is applied wet-on-wet; if it dries before placing it may act as a bond breaker.
- Some acrylics are also used as an admixture in mortar to improve its performance.
An old concrete surface is relatively smooth and may be dusty or absorbent, so new mortar doesn't stick to it well. A bonding agent is an intermediate layer that improves adhesion and durability, used for concrete, masonry, stucco, terrazzo and cement-sand mixes on horizontal and vertical surfaces1.
1) The two types in ASTM C1059
| Type | Property | How it is used |
|---|---|---|
| Type I | Re-emulsifiable | Applied and allowed to dry fully; when fresh concrete or mortar touches it, it re-wets and bonds. Suits cases with a delay between applying and placing1. |
| Type II | Not re-emulsifiable | Placed "wet-on-wet", before it dries1. |
2) Types by chemistry
- Acrylic: typically wet-on-wet, does not re-wet once dry, and some can also be added to concrete and mortar mixes to improve performance1.
- PVA (polyvinyl acetate): good for repair work and often re-wettable, so it can be applied and left to dry before the mortar1. In practice it is preferred for dry interior work because its resistance to permanent moisture is lower; check the limits of use in the product data sheet.
- EVA (ethylene vinyl acetate): similar to PVA, and often used as a primer before levelling compounds and toppings1.
- Epoxy: epoxy bonding agents bond new to old concrete in structural work per the manufacturer's data sheet, and have a set working time within which the concrete must be placed.
3) General application steps
Common practical steps; the binding instructions are the data sheet of the product you use.
- Remove weak and crumbling parts back to sound concrete.
- Roughen and clean the surface of dust, oil and old coatings.
- Dampen the surface if the data sheet asks, without leaving standing water.
- Apply the bonding agent by brush or spray at the stated rate.
- Respect the timing: wet-on-wet for Type II, or after drying for Type I.
- Cure the new layer by keeping it moist as the mortar instructions say.
4) Pros and cons
Pros
- Better adhesion of new layers to old.
- Flexible timing with Type I.
- Some improve mortar performance as an admixture.
Cons and cautions
- They don't compensate for poor surface preparation.
- The wrong type or timing may weaken the bond.
- Some types have limits in permanently wet areas.
For structural repairs (columns, beams, exposed steel) see repair mortars under EN 1504.
Sources
The number next to a statement points to its source in this list. Sources back the general information; anything marked “practical advice” is editorial experience, not a quoted source. Anything that affects safety, structural design or electrical installations needs a licensed professional, and in Saudi Arabia the binding reference is the Saudi Building Code.
- 1Guide to Latex Bonding Agents/Additives (ASTM C1059 Type I / Type II) — Dayton Superior