## 3 Results and Discussion
### Thermalgravimetric Analysis (TG)  
Thermalgravimetric analysis was carried out on specimens RS, C5S0, C15S2, and C45S10 to evaluate the characteristics of substances and the material transformations during the hydration process. The aim of the test was to reveal the synergic impacts of CNTs and NS on the cement hydration reaction, especially their effects as nucleation sites. According to [PERSON] and [PERSON] [54], as well as [PERSON] et al. [65], the main reasons resulting in the loss of sample weight during the increment process of temperature are the evaporation of free water in the cement matrix as well as the dehydration of bound water from hydration products and their decomposition. Figure 12 illustrates the thermogravimetric (TG) and differential thermogravimetric (DTG) curves acquired in the tests from room temperature  
Figure 10: Change in percentage of absorbed water.  
Figure 9: Results of water absorption test.  
to 1000 \({}^{\circ}\)C. Along with the increase of ambient temperature, three characteristic peaks in each curve appear at the temperature range from 50 to 230 \({}^{\circ}\)C, 400 to 500 \({}^{\circ}\)C, and 630 to 780 \({}^{\circ}\)C. The occurrence of the representative peaks of weight loss indicates the important transformation of hydration products. The mass change within the temperature scope between 50 to 230 \({}^{\circ}\)C is related to the volatilization of free water from the LWCM [54], as well as the decomposition of hydrates, especially CSH [65; 66; 67]. The second peak in the range of temperature rising from 400 to 500 \({}^{\circ}\)C can be characterized by the dehydration of hydration product CH from LWCM [54; 68], and the peak with temperature varying from 630 to 780 \({}^{\circ}\)C is ascribed to the decomposition phase of calcium carbonate (CaCO\({}_{3}\)) [54; 67].  
According to [PERSON] et al. [66] and [PERSON] et al. [68], the loss of weight in the initial two temperature extents (100-230 \({}^{\circ}\)C and 400-500 \({}^{\circ}\)C) can approximately represent the degree of hydrate dehydration (Hdh) and dihydroxylation (Hdx) during the cement hydration process, respectively. In Figure 13, the values of Hdh and Hdx were calculated and presented. Compared to the control specimen (3.05% Hdh and 0.90% Hdx), samples C5S0 and C15S2 exhibited both higher dehydration and dihydroxylation values, with increments of 22.57% and 29.51% for Hdh, as well as 128.18% and 113.97% for Hdx. This  
Figure 11: Evolution of absorbed water weight with the change of time.  
Figure 12: Results from the thermogravimetric analysis.  
confirms the existing higher hydration degree in LWCM due to the incorporation of CNTs and CNT-NS additives, resulting in an increasing amount of hydration products. This is associated with the effects of CNTs and NS acting as nucleation sites and activators, providing an auxiliary environment and promoting the process of hydration as well as the formation of hydrates. The greatest Hdh value, 3.95% was measured for sample C15S2, which demonstrates that the presence of NS led to developed synergic influence and further improved cement hydration, resulting in a higher amount of CSH generated. Sample C5S0 showed the most remarkable Hdx value of 2.06%, indicating the decreased amount of CH in the hydration with the inclusion of NS. This can be related to the silica pozzolanic reaction of NS which consumes CH and produces CSH during the hydration process [59]. Another point worth noticing is that for sample C45S10, the Hdh value showed the least increment compared to the other two modified samples, and the Hdx value was even lower than that of the control specimen, showing the limited improvement in hydration degree and fewer generated hydrates. This decline of CSH and CH can be ascribed to the great water demand for nanomaterials that compete with cement for water during the hydration process. Further, the agglomeration of CNTs and NS at high dosage is another thing that can hinder cement hydration.