# Experimental Study on the Strength and Durability for Slag Cement Mortar with Bentonite
## 3 Proposed Experimental Tests  
The basic properties, especially the consistency of the fresh mixture for the slag cement with bentonite, are important because of the better absorption capacity of bentonite. Therefore a flow-table test (ASTM C230) for the fresh mortar and the setting time (ASTM 191 and 266) were both examined for fresh mixtures of slag cement mortar [27]. Figure 1 shows the testing result for the flow-value corresponding to the replacement ratio of bentonite. It was found that the flow-value drops with respect to the increment of the substitution ratio of bentonite. However, the flow-values for all of the test specimens were still high. The results of tests showed that both the readings of the flow table test and setting time [27] complied with the ASTM standard. For the properties of hardened specimens, the capacity of moisture absorption based on ASTM C642-90 was performed to test specimens that were cured in the lime water for 28 days. A series of standard compressive strength tests (ASTM C109) were also carried out for the slag cement mortar with various substitution ratios of bentonite for the binding material. The water/binder ratios were also taken into account during the compressive strength tests. The tests of \begin{table}
\begin{tabular}{c c} \hline
**Physical Appearance** & **Light Tan/Gray-Green Powder** \\ \hline Specific gravity & 2.3–2.6 \\ Bulk density & 48–52 (lb/ft3), 769–833 (kg/cm3) \\ \hline Viscometer dial reading at 600 rpm & Min: 30 \\ Yield point/plastic viscosity ratio & Max: 3 \\ Filtrate volume & Max: 15 cm3 \\ Residue \textgreater{}75 micron (wet screen) & Max: 4\% wt \\ Moisture & Max: 10\% wt \\ \hline \end{tabular}
\begin{tabular}{c} \hline
**Suspension of 22.5 grams into 350 cm3 water** \\ \end{tabular}
\end{table} 
Table 2: Material properties of bentonite. \begin{table}
\begin{tabular}{c c c c c c} \hline
**Specimen Code** & **Cement (kg)** & **Slag (kg)** & **Bentonite (kg)** & **Water (kg)** & **Sand (kg)** \\ \hline
0 BT445 & 0.2500 & 0.2500 & 0 & \\
25 BT445 & 0.2498 & 0.2498 & 0.00125 & \\
50 BT445 & 0.2493 & 0.2493 & 0.00250 & 0.223 & 1.375 \\
75 BT445 & 0.2483 & 0.2483 & 0.00375 & & \\ \hline
0 BT485 & 0.2500 & 0.2500 & 0 & \\
25 BT485 & 0.2498 & 0.2498 & 0.00125 & \\
50 BT485 & 0.2493 & 0.2493 & 0.00250 & 0.243 & 1.375 \\
75 BT485 & 0.2483 & 0.2483 & 0.00375 & & \\ \hline
0 BT550 & 0.2500 & 0.2500 & 0 & \\
25 BT550 & 0.2498 & 0.2498 & 0.00125 & & \\
50 BT550 & 0.2493 & 0.2493 & 0.00250 & 0.275 & 1.375 \\
75 BT550 & 0.2483 & 0.2483 & 0.00375 & & \\ \hline \end{tabular} Note for coding: XXBTXX; The first set of numbers is for the percentage of bentonite: 50 BT—0.50% bentonite. The second set of numbers is for the ratio of the water/binder (w/b): 50 BT445=0.445 w/b.  
\end{table} 
Table 3: Proportional design for the materials applied. compressive strength were performed on the specimens cured for both 7 days and 28 days to examine the early strength. The micro-morphological characters of each concrete specimen were determined using scanning electron microscopy (SEM, S-3000N, Hitachi, Tokyo, Japan), a powerful analytical technique for material characterizations. Before the observation, each sample was dried in a conventional oven over 24 h until the weight was stable to avoid residual water existing in the voids. To provide an electronic conductive surface for higher quality SEM images, fine gold particles were sputtered on the specimen surface using a sputter coater (E-1010, Hitachi, Tokyo, Japan). All preparations were based on the guidelines of ASTM C1723-16 [28]. SEM images captured using an accelerated voltage of 15 kV and were characterized by the secondary electron mode, which benefited the inspection of the topography of the surface.