Effect of polymer modification of the paste–aggregate interface on the mechanical properties of concretes

We investigated the effect of thin viscoelastic polymer coatings around aggregate particles on the mechanical properties of “micro-concretes” with a maximum aggregate diameter of 10 mm. Aggregate particles > 5 mm were pre-treated with a latex at dosages of up to 2% by mass and dried prior to using the treated aggregate in the micro-concrete mix. Cured prisms were tested in flexion. The results show that thin polymer coatings on aggregates have a significant effect on micro-concrete cracking behaviour at much lower polymer dosages than are commonly used in polymer-modified mortars. We observed a significant improvement in post-peak energy absorption relative to the use of the same amount of polymer dispersed in the bulk paste. But, under the conditions tested here, reductions in the strengths and moduli of the composites due to the polymer additions appear to have more than outweighed the observed positive effects of increases in fracture energy and characteristic length.