| The investigation of the chemical characteristics of three reaction systems during early stages of hydration of Portland cement Type-I were performed using Fourier Transform Infrared Spectroscopy (FT-IR). Sequential experiments were performed at various times, ranging from 2 minutes to 24 hours of hydration, maintaining a water to cement ratio of 0.4.;One of the significant achievements of this work was the resolution of a number of hydroxyl bands between 3300--3600 cm--1. These bands have been attributed to the surface hydroxide species bound to metals. The FT-IR results indicated that atmospheric carbon dioxide greatly influenced the polymerization of the silicates. Carbonates are formed in the cement structure as a result of reactions between atmospheric CO2 and Ca(OH)2 during early stages of hydration. The results of this study have also established that the early hydration of Portland cement Type-I is retarded by the addition of Sodium Lignosulfonate Superplasticizer. The retardation is due to the adsorption of lignosulfonate anions on the calcium ion surface of C-S-H (calcium silicate hydrate). The "Charge Dispersal Model", previously proposed to explain the inhibition of cement, was successfully applied to explain the observed phenomenon in the experiment. |
