Natural aggregates can be materials classified as natural or mechanically ground from mineral soils or rock mass. Mineral soils consist mainly of inorganic stone types, which over the years, under the influence of water, weather and pressure, have lost their size and formed. Say no to plagiarism. Get a tailor-made essay on “Why violent video games should not be banned”?Get the original essayIn Finland, repeated ice ages significantly affected the development of soils, and different types of soils separated and formed layers. Thanks to this, aggregate fractions suitable for concrete production are readily available. The most common type of soil in Finland is moraine. The consumption of aggregates in concrete production is very high, which means that sources must be readily available. When aggregates must be transported from another country, costs will increase and options may be limited. Particularly in southern Finland, it is difficult to find naturally suitable fine aggregates. (Suomen Betoniyhdistys, 2005a, p.32) Good sources of suitable natural aggregates are diminishing since the removal of aggregates began to endanger groundwater sources; it is for this reason that the possibility of underwater sources of aggregates has been studied since the 1980s. (Uudenmaan ympäristökeskus, 2006)In Finland, mainly granite-based aggregates are used and they are increasingly often crushed mechanically. In Finland, rock masses are mostly hard enough for concrete production, but weathering of rock masses can be a problem in some areas. Naturally graded and crushed aggregates have slightly different properties, primarily due to different grain shapes and surface textures. By using crushed aggregates, the void content and combined friction of the aggregates are higher than those obtained with naturally graded aggregates with the same particle size distribution. To achieve the same consistency with crushed aggregates, a higher percentage of the finer part of the combined aggregates and an increase in the amount of water are generally required. Increasing water results in increasing the amount of cement to achieve the same water-cement ratio. On the other hand, the bond between cement stone and crushed aggregates is stronger than that between cement stone and naturally calibrated aggregates; the impact resistance of crushed rock is also greater. At least in theory, this allows higher water-cement ratios to achieve some strength with crushed aggregates. Keep in mind: this is just a sample. Get a personalized paper now from our expert writers. Get a personalized test However, it should be noted that the shrinkage and creep of hardened concrete depends on the volume percentage of cement stone and the water-cement ratio; these deformations increase with higher water-cement ratios. (Suomen Betoniyhdistys, 2005a, 46.)