Title: Use of a Superplasticizer in the Manufacture of Extra-High-Strength Block
Author(s): Lucas E. Pfeiffenberger and Thomas B. Ray
Publication: Symposium Paper
Appears on pages(s): 21-40
Keywords: absorption;admixtures; compressive strength; concrete
blocks; high-strength concretes; impact strength; manufacturing;
melamine resins; mix proportioning; plasticizers.
The purpose of this study was to examine the effect of adding various dosages of a melamine-based superplasticizer in the manufacture of extra-high strength block. Seven batches of block were cast as follows: a) reference mixtures in which no admixture was added; b) reference mixtures using a conventional block plasticizer; c) four mixtures using various dosages of su-perplasticizer: 1% by weight cement, 2%, 3%, and 2% with additional water. Halfway through each batch, the feed finish times were increased. The block were steam-cured at low pressure. The testing program consisted of a) impact-resistance and compressive strength at 24 hours; b) absorption and unit weight; and c) compressive strengths at 7, 14, and 28 days. All block exceeded the 5000 psi (34.5 MPa) net compressive strength requirement of extra-high strength block. The effect of the superplasticizer increased as the dosage increased. The superplasticizer also allowed for shorter feed times to achieve the same finish times. The encouraging results of this preliminary study indicate more work needs to be done to investigate the possibility of leaner cement mixes, lower temperature curing conditions, and possibly shorter feed finish times to achieve the economic advantages inherent with the use of superplasticizers.