Like most other building processes, mixing concrete was also a manual job during the ancient times. However, it was also a job that required the workmen to be extremely skilled at calculating the right proportions so as to make the perfect mix. Even a slight miscalculation could result in the mix becoming weak and hence losing the properties of strength and durability. Also it was essential to mix only that much amount which could be consumed within a specific time period as otherwise the mix would harden and become useless. This often proved to be tedious job for the concrete mixer as it involved both physical and mental alertness. Moreover, it also meant that a greater number of workmen with these specific skills were required for extensive construction projects.
However, with the invention of the concrete mixer, by Gebhardt Jaeger, a Colombus Industrialist, significant changes in the construction industry. For one, it fastened the pace of work as the creation of the mix required the use of only one skilled workman even for a major construction leaving the others free to look after the other aspects of building. Secondly, the use of hydraulic concrete mixers made it possible for people to significantly reduce the number of days for completing work. Thirdly it was extremely cost effective as it required could be operated by much less skilled labors, whose wages were significantly low.
Since the invention of the first hydraulic concrete mixer, various advances have been made to its design and features. Consequently, today there are three main categories of these mixers. The first of these are the twin shaft mixers, which are known for their intense mixing capabilities within a short period of time. They are generally used for mixing high strength concrete, RCC and SCC. The second type of mixers are the vertical axis mixers, which are mostly used for mixing precast and prestressed colored concrete, usually in small batches. The final category is of drum mixers which are used for mixing huge amounts of concrete remand are mostly found at sites where high production speed is a priority.
It is largely believed that construction of high rises and multistory buildings received a great boast after the invention of concrete mixers. While this statement cannot be considered to be exactly true, it definitely shows the importance of hydraulic concrete mixers in modern day construction industry.
