## 4 Conclusions  
In this experimental study, a sustainable green LWCM was developed and can be used for further production of LWC. The engineering application of the cement mortar includes, but is not limited to, cold-bridge materials, the manufacture of cement blocks for exterior and interior finishing, and structural materials for building components that  
Figure 15: XRD patterns of LWCM. require comparatively less load-bearing capacity, such as intells of windows and doors. The cement mortar was designed to be prefabricated in factory conditions; nevertheless, onsite production can be also achieved with the preparation of nanosuspension in advance. Based on the obtained results, primary conclusions can be drawn as follows:  
* In contrast with the reference sample, specimens with nano additives presented development in flexural strength at various extents, but the binary effects of CNTs and NS cannot always guarantee greater flexural behaviour than that of specimens with only CNTs. The most remarkable flexural strength was measured for specimen C15S2, with an 89.02% increment observed, whereas specimen C45S10 exhibited the lowest improvement in flexural strength with only an increase of 7.53%;
* In comparison to the control specimen, enhancement and reduction in compressive strength were both measured. Regardless of the NS content, the presence of 0.45% CNTs always accounted for a decline of strength, owing to the increasing difficulty of dispersion and agglomeration of CNTs. Similarly, despite the changes in CNT content, samples with 1.0% NS presented decreases in compressive strength. The most impressive improvement was measured for the sample C5S0, with a growth of 17.35% to 21.09 MPa;
* Compared to the compressive strength of samples with only CNTs, the synergic addition of NS cannot further improve the strength. The greatest value of LWCM under the synergic use of CNTs and NS was measured for specimen C5S2, with the value increasing by 12.60%. Overall, the binary usage of NS and CNTs was more effective to improve flexural behaviour than compression. This can be attributed to the bridging effect of CNTs, which is more dominant than the filling and nucleation effects of CNTs and NS on the enhancement of mechanical characteristics;
* The incorporation of nano additives accounted for the reduction of absorbed water of modified specimens. Sample C5S2 showed the greatest decrease in the percentage of absorbed water, viz., 11.40%. This can be related to the increasingly dense and homogeneous microstructure. Sample C45S10 showed the lowest reduction of absorbed water, with only a decrease of 0.30%. For all the samples, the capacity of absorbing water reached saturation at an early stage within 24 h, after which the increment of water absorbed was very limited;
* Three morphologies of FAC were observed in the micrographs via microscope: intact spherical FAC, broken FAC, and partially reacted FAC. The existence of FAC led to the loose and highly porous microstructure. The agglomeration of FAC promoted the propagation of large voids and cracks. The filler effects of NS and CNTs were observed for the modified samples, which effectively filled up the voids in LWCM, forming a denser microstructure. The bridging and pull-out effects of CNTs were identified in the micrographs, which effectively restrained the propagation of microcracks, benefiting the development of flexural strength. * TG analysis demonstrated that CNTs can effectively improve the hydration degree in LWCM, and the synergic use of NS further enhanced this positive effect, owing to the nucleation effects of nano additives. Sample C15S2 showed the highest amount of CSH formed during hydration process, and specimen C5S0 had the greatest amount of CH. This is associated with the influence of NS which participates in the reaction, consuming CH and producing CSH. * XRD analysis proved the positive effects of CNTs and NS on promoting cement hydration, but the degree was limited.