3.5.2. Weakness

While other agricultural wastes such as rice husk ash, bagasse ash, palm oil fuel ash, etc., have been widely used to replace OPC in cementitious materials, there is little knowledge and availability on the properties of biochar made from date palm fronds and cementitious materials from it in most regions of the world. As a result of this lack of understanding, date palm fronds biochar application is very limited in the construction industry due to the lack of high confidence in the material. Furthermore, the effect of biochar on composite cement performance still requires various experiments to be completed to draw a more accurate conclusion. It is imperative to conduct an imminent study that examines the properties of date palm fronds biochar and its impact on cementitious materials' long-term performance to promote the practical application of date palm fronds.

The use of date palm fronds biochar in cementitious materials also has a weakness: its lower strength at high volume percentages. However, higher date palm fronds biochar content (1.5%) in the cementitious mix reduces its engineering performance, limiting its application as a binder component in cementitious materials [51,52]. Conversely, other agricultural wastes, such as rice husk ash, wheat straw ash, palm oil fuel ash, etc., are effective even at high dosages (up to 20%) in cementitious materials [53,54]. Combining date palm fronds biochar with high-reactive materials such as nano- and micro-silica makes it possible to use high dosages of date palm fronds biochar without affecting its engineering properties [55,56]. However, the date palm fronds biochar amount in the cementitious matrix must be carefully controlled since it can reduce free water and, consequently, the fluidity of concrete, increasing the demand for superplasticisers.

Similarly, cementitious materials that contain date palm fronds biochar have a longer setting time, making them less suitable for applications requiring shorter setting times. A chemical additive such as an accelerator can be added to cementitious materials incorporating DPFA as a replacement for OPC to shorten their initial and final set times [57].
