Polymer cement concrete is a composite concrete that consist of synthetic polymer within the binding material. Polymer concrete has advantages of higher properties, low energy requirements and low labor costs. It is also called as Polymer Portland cement concrete (PPCC) or latex-modified concrete (LMC).
The composition, properties and applications of polymer cement concrete are explained below.
- Composition of Polymer Cement Concrete (PCC)
- Properties of Polymer Cement Concrete
- Considerations in Polymer Cement Concrete Construction
- Applications of Polymer Cement Concrete
Composition of Polymer Cement Concrete (PCC)
To the Portland cement a prepolymer (monomer) of a dispersed polymer is incorporated to make PCC. This combination creates a polymer network in situ during the curing process of the concrete.
The use of typical vinyl monomers can interfere with the hydration process or can get degraded. So the use of prepolymers are found more effective as perform the function required. In order to improve the mechanical properties of the PCC, these prepolymers can be added in higher proportions.
As this concrete property is based on the incorporation of a polymer, special care and attention is taken while adding the latex. The emulsion employed increases the lubrication properties of the mix. Hence, only less amount of water is required for workability of the mix.
Requirements of Polymers used in PCC
- The latex under ambient conditions must be able to form a film so that it properly coats the cement and the aggregate particles. This helps to create a strong bond between the aggregate and the cement matrix.
- A growing micro rack must be intercepted by the polymer network formed. This is done by dissipating energy through the formation of a micro fibril.
Polymer Latex used in PCC
- Poly ( Vinyl esters)
- Poly Epoxies ( Vinylidene – chloride)
- Styrene Utadiene
Properties of Polymer Cement Concrete
1. Highly Impermeable
The polymer phase in the concrete will help reduce the porosity and microcraks that are formed in cement matrix. This acts as an additional binding material other than the Portland cement used.
2. High Durability
A dense and water tight concrete is obtained by the use of PCC. This prevents chemical attacks, water penetration and hence no chance of corrosion. The internal micro cracks in cement matrix too is prevented. This increases the life of the structure.
3. Resistance to weathering Conditions
The PCC structure being impermeable they are less affected by the changing weather conditions.
Considerations in Polymer Cement Concrete Construction
- PCC overlays have excellent long-term performance.
- Mixing of PCC must be done in a concrete mobile mixer.
- Handling, placing, and finishing of PCC is to be completed in less than 30 min.
- PCC requires one to two days of moist curing followed by air drying.
- Styrene-butadine PCC has excellent durability for exterior exposures or environments where moisture is present.
- Surface discoloration occurs when the concrete is exposed to UV light, except for acrylic polymers.
- It is used as overlay of bridge decks, floors, and patching of any concrete surfaces ranging in thickness from 4 to 100 mm for concretes.
- Acrylic latexes are used for floor repair and patching and in cases where color retention is important.
- These overlays produce high-strength wearing surface that is very durable against weathering.
- PCC must be placed and cured at 7 to 30 °C.
- Mobile, continuous mixers, fitted with an additional storage tank for the latex must be used for large applications of polymer modified concrete.
- The mixing time is limited to 3 min for small batches or for mortar mixers.
- PMC has a tendency for plastic shrinkage cracking during placement and special precautions are necessary when the evaporation rate exceeds 0.5 kg/m2/h.
- The modulus of elasticity is generally lower compared to conventional concrete and hence its use in axially loaded members must be evaluated accordingly.
- Polyvinyl acetate mixtures must not be exposed to moisture.
- Epoxy emulsions are more expensive.
Applications of Polymer Cement Concrete
1. Bridge deck coverings
The use of PCC helps to provide highly impermeable and water tight surface that will prevent the ingress of moisture and chlorides thus avoiding reinforcement corrosion, spalling and microcracks.
2. Floor construction
Increased chemical resistance properties, high physical and mechanical properties make it best choice for industrial floor construction. These are also used in pavement construction where the area is subjected to heavy traffic.
3. Precast construction
Good workability and heat curing characteristics demand it for precast operations. PCC units with a less water cement ratio can be obtained.
4. Used as patching compounds
PCC can be used for patching and repair works of ordinary Portland cement concrete. This increases the strength and life of existing structure. PCC must be applied only after the removal of old material.