RESISTANCE OF CONCRETE WITH LIMESTONE SAND OR POLYMER ADDITIONS TO FEED ACIDS

摘要

By using limestone sand or polymer additions in the concrete mix, it was attempted to reduce the deterioration of concrete floors in pig houses by lactic and acetic acid. To simulate in a standardized and automated way chemical attack by those acids and abrasion caused by animals and cleaning, a testing apparatus for accelerated degradation tests was developed. Concrete cylinders mounted on rotating axles were turning through containers with simulation liquid. After each attack cycle the concrete was brushed with rotary brushes. Concrete degradation was measured with laser sensors connected to a computer and the average attack depth and the Ra-value, which is a measure of surface roughness, were calculated. Results of previous experiments, showing that concrete with blast furnace slag cement was much more resistant than the reference concrete with ordinary portland cement, were confirmed. The use of limestone sand and possibly limestone aggregates led to a quicker neutralization of the aggressive liquid, but was insufficient to reduce the average attack depth. When limestone sand and limestone aggregates were used, the increase in concrete roughness was smaller than for concrete with limestone sand and gravel aggregates. Addition of 10% polymers to the concrete mix increased the resistance significantly, when care was taken that the polymer cement concrete (PCC) didn’t contain too much air voids. The most resistant PCC, containing a styrol acrylic acid ester showed after six cycles an average attack depth 12 times smaller than the reference concrete. Furthermore the potential benefit of the polymers was probably underestimated, as an investigation with the scanning electron microscope showed that the emulsified polymer had not completely formed a film.