Natural carbonation was in an air-conditioned room (T = 20[degrees]C, RH = 65%), for one year on mortars mixtures of CPA, CRS, CZ30%, and CL30%.
During air conservation of samples, the superficial part dries quickly, which slows the hydration and leads to a greater depth of carbonation. CL30% mortar affected by a high carbonation depth, insufficient wet cure, clinker substitution by slag, and the amount of Ca[(OH).sub.2] will be reduced in part by the low amount of Portland cement and on the other hand by the pozzolanic reaction (consumption of the portlandite).
The dosage of the clinker decreases and makes higher kinetics of carbonation. This is directly attributed to the role played by the porosity of cementitious matrix.
More lime in cement induced lower carbonation. Slug and pozzolan cement contain less of portlandite than CPA and CRS ones.
The formation of calcite during CPA cement carbonation results in the formation of a protective layer on the skin of material which slows down the diffusion of carbon dioxide, so carbonation can be stopped.
According to the curves, the calcium hydroxide Ca[(OH).sub.2] content of calcium hydroxide for cement stored in the wet conditions is higher than that of air and the CaC[O.sub.3] content of the cement preserved in the air is more important due to the natural carbonation, highlighting the 65% drying effect especially on cement with a high additive contents, minus the quantity of portandite produced.
(iii) A reduced amount of hydrated cement consequently decreasing the compressive strength with a greater carbonation depth especially, for cement with a higher addition content preserved in air causing a negative effect on the chemically bound water contained in the CSH hydrates [4, 58].
The objective is, on the one hand, the monitoring of the quantity of portlandite and, on the other, the study of the effect of the quantity of portlandite as one of the indicators of durability on the kinetics of natural carbonation.
The method of assaying portlandite and calcium carbonates by TGA is based on the molar masses (atomic); the objective was the control of portlandite quantity and the study of its effect as one of durability indicators on the natural carbonation kinetics.
From portlandite's dosage of cement pastes, the profile of the portlandite Ca[(OH).sub.2] content of the carbonation mechanism is analyzed.
It highlights the impact that the initial mineralogical composition has on the behavior of cementitious materials in the face of carbonation as for the portandite content.
Correlation between Portlandite and Carbonation. As can be seen from Figure 14, for the two curing media, the correlation is acceptable for that in air ([R.sup.2] = 0.7343), that it is not too strong for that preserved in water ([R.sup.2] = 0.3512), although this tendency is coherent.
Correlation between Natural Carbonation and Compressive Strength.