# Concrete with Organic Waste Materials as Aggregate Replacement
## 2 Materials and Methods  
### Organic Waste Materials  
The materials that were considered in this study to replace sand in concrete were rice husk ash, wood ash, corncob granules, and wheat straw (Figure 1), supplied, respectively, by E-Coco Products U.K., Ebay (Beech timber), The Pest Express, and Gardening Naturally.  
Figure 2 presents the particle size distribution of course and fine aggregate along with four organic waste materials. The organic waste particles have a wider and sharper shape distribution around sand particles. Particle size range was 0.25-2 mm for rice husk, 0.125-0.6 mm for wood ash, 1-0.25 mm for wheat straw (fibers), and 4-0.25 mm for corncob (spherical and cylindrical granules). Additionally, the density of the organic waste particles was slightly higher for rice husk at 1800-2100 kg/m\({}^{3}\) and lower for wood ash at 750-770 kg/m\({}^{3}\), wheat straw at 370 kg/m\({}^{3}\), and corncob at 125 kg/m\({}^{3}\), compared to that of fine aggregate at 1680-1695 kg/m\({}^{3}\). The variations of the physical properties of sand may impact the mechanical properties of concrete.  
The organic waste materials are presented in the following paragraphs.  
**Rice husk ash** is generated by the combustion of rice husk, a byproduct of rice production. When rice is milled to produce rice grains for consumption, the outer shell, known as rice husk, is separated from the grain [10]. Rice husk is usually used as a fertilizer or to produce biochar, while a small part is burned to generate electricity [18]. During combustion, the organic components of the rice husk are burned off, leaving behind the residue, which is the ash [19]. The ash produced is traditionally considered waste, which can lead to environmental concerns if it is disposed of in an open field [18; 20]. However, its  
Figure 1: Organic waste materials considered in the study as aggregate replacement.  
Figure 2: Particle size distribution of aggregates and organic waste materials: rise husk ash, wood ash, corncob, and wheat straw.  
use is currently being investigated for several applications, like soil improvement, water treatment, and as an aggregate in concrete [18; 20]. The residual carbon content in rice husk ash is approximately 5% by weight [21].  
**Wood ash** is readily available worldwide, potentially representing a viable alternative to traditional aggregates. Like rice husk ash, this organic waste is a residue from combustion processes. According to [PERSON] [16], around 70% of the wood ash generated is sent to landfills, while 20% is used as a soil supplement and the remaining 10% is used for miscellaneous applications. These applications include waste management, where it is used to control odor, and construction, where it can be used as a cement replacement in low- and medium-strength concrete [16]. The high percentage of wood ash sent to landfills makes it an ideal candidate compared to other materials. The carbon content of wood ash varies between 4 and 34% by mass [16].  
**Wheat straw** is what remains in the field when the grain is harvested, and it has several potential applications. The most-common one is leaving it in the field, serving multiple purposes: protecting the soil from erosion, conserving moisture, and facilitating the return of valuable nutrients to the soil as the straw decomposes naturally. Furthermore, wheat straw holds potential in biomass energy production, since it can be directly burned or processed into biofuels. Moreover, wheat straw can be employed as a construction material [22]. Wheat straw has a carbon content of 46.5%, meaning that 1 kg of wheat straw has taken approximately 1.7 kg of CO\({}_{2}\) from the atmosphere during its growth.  
**Corncob granules** are constituted of ground, dried corncob, which is the remaining part of the corn ear after stripping the kernels. Similar to wheat straw, it is commonly left in the field, providing the same benefits mentioned above [23]. The carbon content of this organic waste is close to 50% of its mass [24; 25].