C-S-H gel is the main product in the Portland cement (PC) hydration. Of their structure and composition depends the cement properties (strength, durability¿). The mixes of others materials with PC provides new cementitious materials with different properties. Understand the changes produces in the hydration products in these blends improves their use. This work studies the changes produced in the C-S-H gel by means Fourier Transform Infrared Spectroscopy (FTIR). Several samples were studied, PC (as reference system), a system formed by PC and calcium aluminate cement (CAC) with a 75/25 ratio, and two system formed by PC, CAC and calcium sulfate (C¿) with an 85/15 ratio of PC/CAC with 3 and 5% of C¿. All samples were cured in two environmental; at the air and under water, in order to observe the influence of curing. The samples were studied at the 6 hours, 7 days, 12 and 32 months of age. Results show in the PC, it changes to lower wavenumbers in the Q2 units positions over time. This fact indicates a little transformation of structure like-tobermorite to structure like-jennite providing a C-S-H less compact. Addition of CAC in PC hydration decreases the migration of Q2 units to lower wavenumbers indicating that C-S-H structure is more compact in this case. When C¿ is included in the system, this migration of Q2 units is lower and the bands are sharper indicating the structure like tobermorite presence. Other effect visible in the spectra is the decrease of bands due to Q1 units with the addition of CAC. The greater presence of aluminates in the system provides substitutions of Si4+ by Al3+ in the C-S-H structure. This fact produces longer chains reducing the units Q1. Different behaviors are observed in the cured conditions showing higher transformation towards structures like-jennite in the samples cured under water. Several conclusions can be drawn of this work. First, it use of infrared spectroscopy as powerful tool in the cement chemistry field. Not only as characterization technique but also it can be used for obtain structural information about cement phases, both hydrated as anhydrous. Regarding addition of other hydraulic materials at PC, the study shows formation of C-S-H more compact that will provide better mechanical properties. Also the cured conditions have influenced about hydrated products structure.

ICCC 2015, Beijing, China, 13~16 October 2015; http://iccc2015.csp.escience.cn/dct/page/1

Peer Reviewed