Yes, it is possible to make a concrete countertop without using aggregate by using a mix of general-purpose cement and fine-grade sand. This type of mix is commonly referred to as a "mortar mix" and is often used for applications like countertops, tiling, and masonry work where a smoother finish is desired.
The ratio of water, sand, and cement you use will depend on the specific requirements of your project and the consistency you desire for the concrete. However, a typical ratio for a mortar mix used in countertop applications is as follows:
Cement: Use a general-purpose cement (such as Portland cement) without added aggregates. The typical ratio for cement in a mortar mix is 1 part cement.
Sand: Use fine-grade sand that is free of large particles. The typical ratio for sand in a mortar mix is 2 to 3 parts sand.
Water: The amount of water needed can vary depending on factors like humidity, temperature, and the specific cement and sand used. Start by adding water gradually and mix until you achieve a workable consistency. The typical ratio for water in a mortar mix is around 0.4 to 0.6 parts water, but this can be adjusted as needed.
Keep in mind that mixing concrete can be a delicate process, and getting the right consistency is crucial for the strength and appearance of the final countertop. Too much water can weaken the concrete, while too little water can make it difficult to work with and result in a rough finish.
When mixing the mortar, you can do it by hand or use a concrete mixer. Mix the dry ingredients (cement and sand) thoroughly before adding water. Gradually add water while mixing until you reach the desired consistency. The goal is to achieve a mix that holds its shape when molded, but is not too wet or too dry.
After the countertop is molded, it needs to be cured properly to develop its full strength and durability. Curing involves keeping the concrete moist and covered for a specific period (usually several days) to prevent cracking and ensure proper hydration.
For larger or more complex countertop projects, it's always a good idea to consult with a professional or do thorough research to ensure you get the mix proportions and curing process right for your specific application.