Applied Journal of Physical Science

This study was carried out to evaluate the effect of chemical admixtures on the compressive strength of concretes. The concretes were produced with the concrete mix ratio of 1:2:4, while water to cement (w/c) ratios of 0.35, 0.4, 0.45, 0.5 and 0.55 were adopted. Different concrete mixtures were produced using two chemical admixtures (hydroxycarboxylic acid and MasterRheobuild 1100) applied at the rate of 1.3% (weight of the cement), during the production process. Laboratory results of the fine aggregate used for the concrete production showed that it was well graded met international standards. All the concretes were produced and tested in accordance to American Society for Testing and Materials (ASTM) standard procedures. Results indicated that the concrete produced with the chemical admixtures showed better concrete performances both in the fresh and hardened state. After 28 days of casting, concrete produced with MasterRheobuild 1100 admixture had the best compressive strength (32 MPa); compared with the compressive strength of the concrete produced with the hydroxycarboxylic acid admixture (28 MPa), and the control concrete samples that had compressive strength of 25 MPa. In addition, the fresh concrete produced with chemical admixtures gave a better slump than the fresh concrete produced without any chemical admixture. Likewise, hydroxycarboxylic acid admixture performs better among the two admixtures used, given a more linear relationship between the slump and water/cement ratio. These results showed the importance of chemical admixtures when higher compressive strength becomes a vital factor in structural constructions.