## 4 Test Results and Discussion  
Figure 4 shows the flow of fresh cement mortars. The flow value of plain cement mortar was 108 mm. The flow values of all the cement mortars with borosilicate glass were slightly higher than that of plain cement mortar. However, the replacement of borosilicate glass showed no significant influence on the fluidity of the cement mortar.  
Figure 4: Flow of fresh cement mortar with borosilicate glass.  
Figure 3: Experimental setup for thermal neutron shielding performance.  
Figure 5 shows the compressive strength of cement mortar at the age of 3, 7 and 28 days. All the cement mortars with borosilicate glass showed higher compressive strength compared to the plain cement mortar, regardless of the age of cement mortar. The compressive strength of cement mortar with borosilicate glass increased as the replacement ratio of borosilicate glass increased. However, when the level of replacement ratio exceeded 75%, the compressive strength of cement mortar did not significantly increase.  
Figure 6 shows the amount of calcium hydroxide in the cement mortar at the age of 3, 7 and 28 days. The amount of calcium hydroxide in the cement mortar with borosilicate glass decreased as the replacement ratio of borosilicate glass increased up to 75%. However, when the level of replacement ration exceeded 75% (reached 100%), the amount of calcium hydroxide in the cement mortar did not decrease.  
Figure 7 shows the thermal neutron shielding rate of cement mortar at the age of 28 days. The thermal neutron shielding rates were 66%, 89%, 93%, 94% and 95% for the cement mortar with replacement ratios of 0%, 25%, 50%, 75% and 100%, respectively. All the cement mortar showed higher thermal neutron shielding rates compared to plain cement mortar. The thermal neutron shielding rate of cement mortar with borosilicate glass increased as the replacement ratio of borosilicate glass  
Figure 5: Compressive strength of cement mortar with borosilicate glass.  
Figure 6: Amount of calcium hydroxide in cement mortar with borosilicate glass.  
increased. The thermal neutron shielding rate of cement mortar with a replacement ratio of 100% showed the largest increase (approximately 43%) from that of plain cement mortar.  
It is known that borosilicate glass is a pozzolan material [8]. The pozzolans, like borosilicate glass, are silicate-based materials that consume the calcium hydroxide during the period of the hydration process of cement to produce the calcium silicate hydrates (C-S-H). The strength of cement mortar is governed by the quantity of C-S-H gel. Thus the incorporation of pozzolans in a cement mixture can increase the strength of the cement mortar because of the additional C-S-H gel produced by pozzolan reaction [9]. However, it is difficult to quantify C-S-H in cementitious materials. Since the amount of calcium hydroxide is proportional to the amount of C-S-H, it can be used to deduce the amount of C-S-H in the hydrated cement paste. From the experimental results, the cement mortar with borosilicate glass showed higher compressive strength gain in all ages. The results from TG/DSC showed that the calcium hydroxide of cement mortar with borosilicate glass decreased as the replacement ratio of borosilicate glass increased. The results of the compressive strength and the amount of calcium hydroxide tests suggest that the strength development in cement mortar with borosilicate glass is associated with the increase of C-S-H gel produced by the pozzolanic reaction.  
It is known that the thermal neutron shielding rate of concrete increases as the boron content in concrete increases [4; 5]. From the results of testing for the neutron shielding performance, the cement mortar with borosilicate glass showed higher thermal neutron shielding rates as the replacement ratio of borosilicate glass in the cement mortar increased. The increase of thermal neutron shielding rate of cement mortar with borosilicate glass is associated with the increase of boron content in the cement mortar.