High Strength High Performance Concrete-Using Fly Ash and Superplasticizer Admixture

This paper gives some results of flowing and high strength concretes using type F fly ash (FA) and naphthalene based superplasticizer (SP). In series S, SP was used only to produce flowing concrete and in series H it was used to reduce W/C and to cause the concrete to flow. In each studied series the portland cement content was maintained fixed at 250 kg/(meter cubed). Fly ash was added as a percentage of the normal portland cement from 10% up to 150%. For reference series a 0.8 W/C was used, and for series S, 200 liters of water was used to attain a nominal consistency of 60.0 cm DIN. For reference series H a reduction of 35% of mixing water of series S was used (70 L). To find the maximum amount of FA and SP dosage in series S, SP admixture was used to obtain the reference consistency of 60.0 DIN. In series H where the admixture was used as high-range water-reducing-retarder admixture (HRWRRA) in large dosages, the concrete became very cohesive and significant slump loss was noted. When superplasticizer-retardant admixture (SPRA) was used as HRWRRA to produce flowing concrete under established conditions, it was possible to obtain a very significant compressive strength gain at 56 days, which was the upper limit of the age covered in this study. An increment of 160% (from 25 to 65 MPa) at 56 days was attained for series H in relation to the reference mixture without FA and SP. To obtain high strength concretes using high volumes of fly ash it is essential to use SP admixture.