Evaluation of Recycled Latex Paint for Use in Concrete

Latex in Concrete History Virgin latex has been used for decades in high end projects (bridge deckings) Benefits - increased resistance to chlorides - protects from rapid moisture loss - durability in cyclical freezing & thawing

Latex in Concrete History Disadvantages –High cost of virgin latex –Cost of increasing amounts of air entraining and water reducing agents

Project Objectives Determine the effects of substituting recycled latex paint for water in concrete. Determine the extent in which properties are enhanced, particularly with respect to durability.

Phase 1: Characterization of Latex in Concrete Mixtures Mixtures were prepared in a CSA certified lab using: –Local stone, sand and water –Portland cement –Air entraining and water-reducing agents –Recycled latex paint (50 % water)

Phase 1: Characterization of Latex in Concrete Mixtures Most latex additives entrap inordinate amounts of air in concrete, which adversely affect compressive strengths and durability Air entraining agents are added to achieve proper air void parameters

Phase 1: Characterization of Latex in Concrete Mixtures Results of recycled latex paint in concrete - did not entrap inordinate amounts of air - did not affect set time - did not reduce flexural strength - only slightly reduced compressive strength

Phase 2: Advanced Concrete Durability Studies Air Voids on Hardened Concrete (ASTM C457) Hardened concrete must meet proper air void spacing to be durable in cyclical freeze-thaw environments.

Phase 2: Advanced Concrete Durability Studies Freeze-Thaw Testing (ASTM C666) To indicate if concrete has resistance to freeze- thaw cycles and a propensity to scale on the surface.

Phase 2: Advanced Concrete Durability Studies Chloride Diffusion Testing (ASTM 1556) Used to model the long term performance or service life prediction of concrete structures.

Phase 2: Advanced Concrete Durability Studies Results -Data indicates that mixtures do not behave differently than normal concrete -A mixture of 15 % latex for water resulted in excellent resistance to cyclical freeze-thaw with a durability factor of 93 (70 is minimum standard)

Phase 2: Advanced Concrete Durability Studies Results: -The 15 % latex mixture showed a chloride diffusion rate 20 % less than concrete without latex. -This translates into an approximate increase of 20 % in the service life of reinforced concrete structures in a chloride environment such as bridge decks, median barriers, wharfs, etc..

Phase 3: Field Demonstration A large reinforced pad containing latex paint (1000 sq ft) is being placed in actual environmental conditions Performance and durability will be analysed over the next year

Conclusions Substituting recycled latex paint for water in concrete: –did not trap excess air –did not affect flexural strength –did not affect set time –may decrease compressive strength slightly –provides normal air void parameters –provides excellent resistance to freeze-thaw cycles –provides excellent chloride resistance

Recycled Latex Paint vs Virgin Latex Similar benefits as virgin latex have been observed at lower costs Opens new markets for recycled latex paint, reducing costs to manage it Potential for international reuse model

Next Steps Market Analysis –Cost advantages of using paint over virgin latex –Volumes of paint that could be used for structural concrete