*3.1. Materials*

Ordinary Portland cement (Tasek Corporation Berhad) CEM I 42.5N (Type I) which was based on MS EN 197-1 having specific gravity 3.14 and Blaine surface area 0.351 (m2/g) was used. The properties of GNP, purchased from Graphene Laboratories, Inc. USA are enlisted in Table 1. Deionized water was used for making cement based composite.


**Table 1.** The properties of GNPs used for this experiment.

#### *3.2. Preparation of Samples*

For specimen's preparation cement, GNP and deionized water were used. The details of mix proportions are given in Table 2. Here, M0 represents the control sample of cement paste while GM3, GM5 and GM10 represent samples containing 0.03%, 0.05% and 0.10% GNP by weight of cement, respectively. The GNP samples (GM3, GM5 and GM10) were used to study the influence of graphene on rheological characteristics of cement paste while for determining the strain-sensing characteristics of graphene–cement based composite, only GM3 having least percentage of GNP was considered. All measurements were repeated with identical samples for three times and averaged. For sample preparation, firstly, GNP (by weight of the cement) was added to the deionized water. To exfoliate nanoparticles, the sample was ultrasonicated (Fisher Scientific ™ Model 505 Sonic Dismembrator) for 3 min followed by magnetic stirring for 1 h to ensure uniform dispersion of GNP. Thereafter, cement was added to this aqueous solution of GNP and mixed thoroughly for 5 min in spar mixer (SP-800A). Initially, the speed of the mixer was kept low for 2 min then static for 10 s and finally high for another 2 min. Finally, rheological characteristics of cement paste were measured. The workability of cement paste was determined by ASTM C 1437-15 [24] while for determining electrical properties, prism having dimensions of 160 × 40 × 40 mm was casted. Four-stainless-steel wire meshes (11 × 11 mm cross section) with an average thickness of 1.3 mm and dimensions of 40 × 70 mm was inserted in the samples to measure the electrical properties as shown in Figure 1a. The outer two wire meshes were positioned at 10 mm from the ends of the prism while the inner two wire meshes were positioned at 40 mm from the outer wire mesh. The detailed dimensions are given in Figure 1a. The surface morphology of GNP–cement composite was investigated using Field emission scanning electron microscope (FE-SEM, AJSM-7600F with semi-in-lens) while the elemental composition was acquired using FESEM coupled with an energy dispersive X-ray spectrometer (EDS).

**Figure 1.** *Cont*.

**Figure 1.** Description of specimen and test setup (**a**) Dimensions of graphene–cement composite specimen with wire mesh details; (**b**) placement of specimen on reinforcement; (**c**) casting of reinforced concrete (RC) beam; and (**d**) overall test setup for measuring the electrical properties of graphene–cement composite specimen in the RC beam.

**Table 2.** Mix Proportions.

