Independent thesis Basic level (university diploma), 15 credits / 22,5 HE credits
Moist-related damages correspond with 80 % of all damage in construction. A part of this moist-related damage occurs when the surface is applied to prematurely on concrete, such as with shallow foundations and intermediate floors. New cast concrete contains a lot of construction water, which must be allowed to dry out in order to avoid damage. In which case the level of relative humidity, RH, depends on the material combined with the concrete. The time until it reaches correct level of relative humidity is often long and is mainly dependent on the composition of the concrete and the climate. The length of drying time is a problem in today’s construction industry where prefabricated structural components and more efficient working practices have led to a reduced construction time.
Nowadays the concrete is often coated with a layer of screed before the coating is applied. Overall, there are few measuring guides for how much impact the screed has on the concrete’s dehydration. Specifically, the problems are based surrounding the measurement and calculation methods for dehydration of concrete. There is currently no reliable calculation program for determining the drying time of the concrete. Also, wrongly performed relative humidity measurements often lead to an excessively low RH value.
The goal of this work is that, through an experimental study, we can discover how the drying of concrete with three different water-cement ratios differs in comparison with the programs TorkaS 3.2 and 2.0. The aim is also to see if a layer of screed provides moisture to the concrete and thus inhibiting its drying speed. The result shows that there is a marked difference between the measured RH from borehole measurement and calculation programs TorkaS. The greatest error is detected on concrete with water-cement ratio 0, 50 and 0, 38. For 0, 50 has TorkaS 3.2 and 2.0 a margin of error around 4 % and 6 % against the measured values.
The conclusion is that the programs TorkaS 3.2 & 2.0 have underperformed with calculations in all three cases and have underestimated the drying time of the concrete. However, the results have shown a big difference between the two programs. TorkaS 3.2 with the correction factor has a significantly lower differential than TorkaS 2.0 has towards the experimental results. The conclusion is that the programs are not reliable for precise estimation in the drying process of the concrete, but should be considered more as guidance.
Furthermore, the study revealed that a layer of screed could extend the drying process of a concrete foundation with water-cement ratio of 0, 38 & 0, 50. Regarding the concrete with the water-cement ratio of 0,34, the layer of screed developed a higher level of moisture. This leads to a longer time before the concrete dries out.
2016. , 104 p.