Sewage sludge ash-based mortar as construction material: Mechanical studies, macrofouling, and marine toxicity

Incinerated sewage sludge ash is tested here as a cement and aggregate substitute in mortar blocks. It can be used at various percentages to reduce the overall cost of production and promote ash recycling. The compressive strength of the cast blocks was tested at 28 days to determine the optimal combination of ball milled ash (replacing cement) and sewage sludge ash (replacing sand). This was compared with a control block made of cement and sand only. The cast blocks with the optimal ash formulation were tested for their flexural strength and other properties such as surface functional groups, constituent phases and porosity. The control and ash mortars exhibited similar properties. A potential application of these blocks is to use them as part of seawalls. These blocks were thus suspended in the sea for 6 months. Marine organism attachment was observed over time in both control and ash mortar blocks. There was no significant difference between the mortars after 6 months. The mortar blocks were also subjected to leaching tests (NEN-7345). The leachates did not exhibit toxicity to microalgae. In contrast, mild toxicity was observed in the sea urchin embryo development assay. Overall, the study suggests that sewage sludge ash is a potential material to be used for seawall construction as it has the desirable mechanical properties. However, there remain some residual marine toxicity concerns that need to be further addressed.

5S Multifunctional Intelligent Coating with Superdurable, Superhydrophobic, Self-Monitoring, Self-Heating, and Self-Healing Properties for Existing Construction Application

There is a constant drive to develop ultra-high-performance multifunctional coatings for existing construction used in modern engineering technologies. For these materials to be used in unsound infrastructure protections, they are required to present enhanced robustness while bearing functionalities to meet multiple uses. Single-function coating is not smart enough to provide satisfactory protection, and the preparation process of multifunctional materials is complex, costly, and provides poor durability. Thus, existing coatings are not suitable to generate an intelligent closed-loop protection system. Herein, we report an innovative 5S multifunctional intelligent coating (5SC) for existing construction materials with superdurable, superhydrophobic, self-monitoring, self-heating, and self-healing properties. The 5SC material showed highly durable superhydrophobic properties as revealed by the main failure tests of building materials including physical friction (abrasion, scratching), 100% tensile strain, photoaging (3000 h of ultraviolet (UV) aging), acid corrosion (concentrated hydrochloric acid and sulfuric acid), and freeze-thaw aging (salty solution). The coated surface was highly sensitive to pressure, with monitoring thresholds from 1 to 30 000 N per 0.01 m². It showed an early heating rate as high as 6 °C/min while maintaining very good self-monitoring and ice-melting drainage performance to protect the existing structures. This novel composite material is suitable for constructions in extreme areas where corrosion and freeze-thaw damage can occur. This multifunctional material presents a very broad range of applications and development potential in the construction field.