# Development of Fiber Reinforced Sustainable Dredge Bricks
## 3 Results and Discussion
### Rainfall Simulation Tests  
The rainfall simulation test consisted in spraying a quantity of water on the material's surface and measuring the amount of wear. Figure 4 illustrates the erosion testing using a custom designed rig. To simulate erosion from rainfall, the erosion testing time was determined by estimating the kinetic energy produced by the annual rainfall in the Beaumont, Texas, USA area and generating the same kinetic energy using water exiting the nozzle on the erosion rig. The National Oceanic and Atmospheric Administration (NOAA) estimated  
Figure 3: Water absorption tests of uncoated and coated bricks. Figure 2: SEM images of four types of CSEB: without fibers (**A**), with PVA (**B**), with polyester (**C**) and with kenaf fibers (**D**). that the average annual rainfall of Beaumont, TX was 60 inches [30]. The kinetic energy of annual rainfall was calculated using the equation: \(\mathrm{Ek}=\mathrm{K}\times\mathrm{Pa}\), with \(\mathrm{K}=24\,\mathrm{J}/\mathrm{m}^{2}/\mathrm{mm}\). The equivalent kinetic energy of annual rainfall was found to be \(36.6\,\mathrm{k}\mathrm{J}/\mathrm{m}^{2}\). Based on industrial recommendations regarding external surface wear, a 15-year life span was chosen that included a 150% safety factor. The [PERSON]'s equation was used to determine the velocity of the water leaving the nozzle and using this value and that of the calculated kinetic energy, the mass of water needed was calculated using the equation: \(\mathrm{Ek}=\frac{1}{2}\,\mathrm{mv}^{2}\). The solved mass was divided by the unit weight to find a total volume, and this was divided by the measured flow rate to time of spraying. The flow from the nozzle was adjusted and the previous steps were repeated until the required spray time was 3 h.  
After spraying, the deepest indentations in the bricks were measured and a dry post-erosion weight was measured to evaluate material loss. This erosion test was performed at three-hour intervals on three bricks for CSEB without the inclusion of fibers, uncoated, and coated. Following the erosion test, each brick was oven dried for 36 h at 200 \({}^{\circ}\)C and air dried for another 48 h to bring each brick to its pre-test moisture level. We note that since Enviro-Crete coated brick were uncoated on one side, the moisture did not evaporate at the same rate as it did with others. The erosion testing was then repeated on uncoated bricks that contained fibers. Figure 5 shows images of the bricks following the erosion test. The control represents uncoated bricks before and after the test. Numerous indentations can be observed. When uncoated bricks were mixed with fibers, some indentations are also clearly visible. In particular the samples containing PVA eroded more which is probably the result of larger voids/gaps between PVA and the stabilized DM that were observed in Figure 2B and associated with lower USC strength as reported in Table 1. The bricks containing either polyester or kenaf fibers seem to have experienced smaller but more numerous indentations which is expected and consistent with the USC strength as shown in Table 1. To quantify the effect, the average size of the indentations and of the change of mass following the test were measured and are reported in Table 2.  
Figure 4: Modified Water Erosion setup. A specific flow of water impacts the brick for three hours simulating 15 years of rainfall erosion. The data for the lime-sand mortar coating is not reported because the coating failed. The lime-sand mortar coating failed within 15 min of the spray test most likely because of a lack of bonding between the coating and the brick surface as discussed earlier for higher-than-expected water absorption. For optimal application this coating requires a greater sand and cement ratio as opposed to the more clayy soil of the dredge material.