**2. Materials and Mix Design**

A series of cement mortars (CM) were prepared to study the effect of the proportion of silica sand in laser scabbling. The materials involved in this study were Ordinary Portland Cement (OPC), silica sand containing about 93% SiO2 weight with a median size range of 0.15~0.53 mm. Mineral admixtures consist of cement and silica sand whose chemical compositions are shown in Table 1. In addition, Table 2 shows the proportions of the mortar samples. The label of the samples was given the same as the silica sand to cement ratio. The specimens were fabricated by mixing cement and silica sand in a laboratory mixer for 60 s before adding water and mixing for 3 min. After mixing, the mixtures were then poured into a cylindrical shape with a diameter and thickness of 53 ± 0.5 mm and 12 ± 0.35 mm, respectively. To improve hydration, the cast samples were enclosed in a plastic sheet. The specimens were removed from the mold after 24 h of storage at room temperature and immersed in a water tank for 28 days of curing. After that, the samples were then taken out and dried to eliminate the remaining water.

**Table 1.** Chemical compositions of cement and silica sand measured by XRF analysis.



**Table 2.** Mix compositions of the mortar specimens (proportions by weight).
