SBR Latex in Construction:A Guide

SBR (Styrene Butadiene Rubber) latex is fighting against:
- polyacrylic esters (PAE) and
- styrene acrylic esters (SA)
to increase it’s market share in the polymer modified concrete industry. In this fight, we consider SBR latex the winner hands down, if we take account of both cost and performance.

In Europe we mostly use carboxylated SBRs with:

- solid contents in the region of 47-49%.

- minimum film forming temperatures round 0-3oC.

- glass transition temperatures round -5oC.


Usually they contain antifoam and antimicrobial agents.

SBR Latex modified, flexible cementitious 
coating to cover non-structural surface
 defects in new and old concrete.

MAIN ADVANTAGES OF POLYMER MODIFIED CEMENT MIXES
- Improved flexural and tensile strengths
- Better overall durability

- Reduced shrinkage

- Increased resistance to abrasion, chemicals and frost
- Improved workability for the same W/C

- Enhanced adhesion to smooth surfaces: dense concrete, steel etc.

- Suitable for potable water

- Resistant to hydrolysis.

self-leveling industrial floor materials with synthetic latex

MAIN APPLICATIONS IN EUROPE (AND GREECE)
- Amelioration of cementitious waterproofing products and tile adhesives.

- Thin, water resisting screeds, toppings, renderings, mortars etc.

- Waterproof, bonding bridges for mortars and concrete (always mixed with fresh cement and always wet on wet). Mixing proportion: 1:1,8 latex/cement by volume.

- Anticorrosion protection for reinforcements in concrete repairs (1:1 with cement by volume).

- Polymer mortars for repairs of carbonated concrete. Preventive treatments against carbonation.

SBR latex; Styrene Butadiene Latex

ACTION MECHANISMS OF SBR LATEX

1) SBR can reduce W/C for the same workability or increase workability for the same W/C. Polymer particles as well as entrained air bubbles have a ball bearing effect in the mixture. They “lubricate” the mixture particles thus reducing internal friction coefficient.

Workability improvement is further enhanced by the dispersion capabilities of the contained surfactants.

2) SBR latex due to its air entraining properties reduces bleeding considerably. This leads to an abrasion resistant surface. Though, excessive air entrainement should be avoided and most probably an antifoam agent should be used in the formula. Prolonged mixing duration entrains more air.

3) SBR latex used in cementitious waterproofing brushable products improves dramatically their water retention capability. This is a most desirable effect leading to a better hydration procedure. This water retention improvement is due to the polymer network that somehow blocks the water in the mixture.

4) SBR addition increases the water resisting properties of modified concrete and mortars.

As water evaporates, the SBR particles stick together – this is called coalescence – to form an interconnected polymer network inside the cementitious matrix. This flexible network both blocks the pores and bridges microcracks to a certain extend. Less and thinner cracks and less voids increase water impermeability.

5) SBR latex increases adhesion of aggregates to cement paste. It also enhances adhesion of cement mixes to smooth substrates: dense concrete, steel etc. This is due to the powerful bonding power of the polymer matrix.

EFFECTS OF SBR ADDITION ON PROPERTIES OF CEMENT MIXES

1. Increases tensile, flexural and impact strengths. Compressive strength remains virtually unaltered. In high dosages it could slightly decrease.

2. Overall durability increases.

3. Induced flexibility increases creep.

4. Setting times are generally reduced. Placement time also.

5. SBR addition reduces bleeding and contributes to an enhanced abrasion resistance provided that an adequate curing procedure is followed.

6. SBR latex addition increases air entrainement (despite the antifoam agent in the formula).