Structure and properties of poly(vinyl alcohol)-modified mortar and concrete: Fid-Bau Portal

Structure and properties of poly(vinyl alcohol)-modified mortar and concrete

Kim, Jae-Ho / Robertson, R.E. / Naaman, A.E.

The structure and properties of mortars and concretes containing up to 2 wt% (based on cement) of poly(vinyl alcohol) (PVA) were examined and compared with those without PVA. Among changes occurring with the addition of PVA were increases in air void content and apparent fluidity and a reduction in the bleeding of fresh mortar and concrete. The increased fluidity caused increased slump for fresh concrete. The microstructure was examined by polarizing optical microscopy and scanning electron microscopy in backscattered mode of cut surfaces after hardening. The porous interfacial transition zones around sand grains and coarse aggregate were significantly reduced, and the cement particles were uniformly distributed without significant depletion near aggregate surfaces. For mortars, using a prewetting mixing technique, the compressive strength was decreased moderately, but the flexural strength was unchanged. For concretes, with the same mixing technique, the compressive strengths after 28 days of hydration were relatively unchanged, but the postpeak area of the compression stress-strain curve was reduced, accompanying a change in fracture behavior from debonding to cohesive failure of the coarse aggregate. When concrete having the same air void content with PVA as without was made, the compressive strength was moderately increased.