Effect of Superplasticizer Type on the Performance of High-Volume Fly Ash

Superplasticized high-volume fly ash concretes with 50 % of portland cement replacement were manufactured by using two different chemical admixtures based on sulfonated naphthalene (SN) or acrylic polymer (AP). Portland cement with a Blaine fineness of about 400 or 500 m2/Kg was replaced by 50 % of ground or un-ground fly ash. The content of the cementitious material (portland cement + fly ash) was about 470 kg/m3. The concretes with SN were manufactured with a slump in the range of 190-200 mm, whereas the slump of the concretes with AP was in the range of 220-230 mm. Due to the different effect of the superplasticizers, the water-cementitious material ratio (w/cm) was 0.32 or 0.29 for the SN or AP admixture respectively, although the dosage was slightly lower for the latter. Cube specimens were cured at 5°C or 20°C and compressive strength was measured at 1 to 90 days. Due to the lower w/cm, the strength of the concretes with the acrylic polymer was significantly higher with respect to those with SN. The better performance of the AP superplasticizer, in terms of compressiv