Nowadays, it is a rather frequent phenomenon on construction sites that the workability of fresh concrete is increased by adding water. But how does this practice affect the quality of concrete? Water additions will result in a change of the water/cement ratio and subsequently lead to dramatic changes in the concrete’s strength and durability properties. The ultimate outcome will be a concrete exhibiting other characteristics than those initially intended, meaning that the stability of construction components upon and after installation can no longer be guaranteed. It is for these reasons that the currently applicable European Standard for concrete, EN 206-1, does not allow any addition of water on truck mixers upon arrival at the construction site. However, several national standards, for example Germany’s DIN 1045-2 as a supplement to the European Standard EN 206-1, do allow the production of concrete with lower amounts of water and the subsequent addition of water on construction sites into truck mixers. In such cases, it is mandatory to mix the concrete for unequivocally prescribed time spans thereafter (1 min per m³, minimum of 5 min). These standards aim at ensuring a superior concrete quality after production during transportation and its processing at the construction site. To further ensure a compliance with current standards and hence the quality of the concrete delivered, it is necessary to monitor the addition of water directly on trucks mixers.
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