Effect of superplasticizer type on performance of high-volume fly ash concrete

Superplasticized high-volume fly ash concretes with 50% of portland cement replacement were made by incorporating 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 mrn. 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, 150xl50 mrn in size, 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 compressive strength, was obtained at early and later ages independently of the curing temperature (5 and 20°C), and the fineness of the portland cement and fly ash. Due to the lower w/cm of concrete with the AP admixture with respect to those with the SN superplasticizer, the durability of high-volume fly ash concrete can be improved in terms of lower penetration rate of C02 or chloride ions.