The choice of the fine aggregate, whether produced by the crushing process or natural sand, can significantly affect the properties of concrete construction works, influencing the ease of handling, the concrete pumping capacity and the overall quality of buildings.

Natural sand has the ideal shape for application as a fine aggregate in concrete. The natural sand particles are well rounded and generally almost spherical. Spherical particles reduce the percentage of voids in concrete mixtures, so no additional product will be needed to fill these voids, which in reality will practically not exist. Well-formed natural sand, as is the case of the river sand, takes on this spherical shape due to the long course of the river flow and is therefore the ideal sand for the mixing process in concrete or mortar. Natural sand requires no more water compared to manufactured sand to improve the mixing process, so the amount of water consumed in the concrete or mortar is not increased.
The manufactured sand or the manufactured fine aggregate is produced by the process of crushing of blocks of rock of varied dimensions, going through several stages of transformation until obtaining the desired fine sand. In the specific case of Cape Verde with basalt as the dominant rock which, due to its hardness and abrasiveness makes its transformation into sand with a coefficient of shape close to that of natural sand economically unfeasible; the cost of the product would be unacceptable for the general final consumers of these products. Manufactured sand tends to be used in mixtures in places where natural sand is unavailable, as is the case in Cape Verde, where for several decades populations withdraw natural sand from seashore and stream beds, making this activity their way of life. This calls into question both the environment and agricultural activity in the most fertile areas of the country which are precisely not far from the seafront, causing contamination of agricultural plantations by the infiltration of salt water from the sea and undermines leisure spaces and seaside resorts for tourists, and Cape Verde is a country whose economy is fundamentally based on tourism.

On the other hand, the application of salt sand to the construction in Cape Verde has also had other important collateral damages in the construction industry because the salt erodes the iron structures used in the construction. This has huge economic consequences for the country.

The distance between the natural sand extraction site and its storage site for final consumption has a decisive impact on the economic sustainability of this operation. The manufactured fine aggregate tends to be more angular and scaly due to the mechanical crushing process. Being highly angular particles and sharp corners, it is necessary to add new elements to the concrete to eliminate the porosity in the constructions and consequently the infiltration of water with all its consequences for the conservation of the buildings.

In the search for alternative internal sources of natural sand for construction in Cape Verde over several decades, the populations generally engaged in the extraction of sand on the seafront as a subsistence activity, which caused the total or partial destruction of numerous tourist beaches as well as generating serious consequences for the environment and for agriculture.

GEMA MINERAL which specialises in international trade of basalt derivatives, sand and associated logistic management. We are continuously improving in order to increase customer satisfaction, productivity, and efficiency so we can better serve our valued customers and partners in the business.