@misc{9228943,
  abstract     = {{Concrete is one of the most widely used materials in the construction sector, but cement production is associated with a significant climate impact. One way to reduce this impact is to decrease the proportion of cement clinker by using alternative binders. Volcanic pozzolan from Iceland, VPI, is a supplementary material supplied by Heidelberg Materials Cement Sweden that can be used together with cement as a binder in concrete. The supplementary material is included in the product Bascement Plus Slite from Heidelberg Materials, in which approximately 20 % of the cement has been replaced with VPI. Since VPI is a relatively new material, there is a need for increased knowledge of how it affects the moisture behavior, strength development and hydration process of concrete. Relative humidity, RH, is particularly important as it is used to assess concrete drying, which in turn can affect the planning and execution of subsequent construction activities. 

The aim of this thesis was to investigate how temperature changes affect measured relative humidity in concrete with different proportions of VPI, and to compare embedded wireless RH-probes from Electrotech Kalix AB (ET) with traditional borehole measurements using Vaisala HMP40S (V) probes. The study also included self-desiccation, strength development and hydration process evaluated by calorimetry. For the RH measurements and strength testing, two concrete mixes with the same water-to-binder ratio were studied. One mix consisted of 100 % Bascement Plus Slite, while in the other mix part of the cement was replaced with additional VPI, resulting in a total VPI content of 33.3 %. After initial drying, the concrete specimens were exposed to gradual temperature changes between +20 °C and +10 °C, and between +20 °C and +30 °C. In addition, one test with an instantaneous temperature change between +20 °C and +10 °C was performed. Self-desiccation and hydration behavior were studied separately on cement mortar samples with several different VPI contents.

The results showed that RH in the concrete was affected by temperature changes, RH increased when the temperature increased and vice versa. Both the ET- and V-probes showed the same overall response, but differences were observed between the methods. The V-probes consistently measured approximately 4 percentage points higher RH than the ET-probes throughout the measurement period. The difference is significant and may affect the assessment of concrete drying time. The immediate response of the V-probes to temperature changes also deviated from the expected trend, as RH temporarily increased when the temperature was lowered and vice versa. This is likely related to the air volume in the borehole and faster temperature equalization in the measurement system. The ET probes did not show this response but instead followed the temperature changes in the concrete. 

The concrete with higher VPI content generally showed higher RH during the drying process, which may indicate a denser pore structure or slower moisture transport. However, the differences between the materials were in some cases small and should therefore be interpreted with caution in relation to the measurement uncertainty. The strength testing showed that both mixes achieved high compressive strength, but the concrete with the lower VPI content had higher strength at all testing ages. The calorimetry measurements showed that an increased VPI content resulted in a lower maximum heat flow, indicating that the reaction process is affected when the proportion of cement decreased and the VPI content increases.}},
  author       = {{Andersson, Hugo and Nilsson, Andrea}},
  language     = {{swe}},
  note         = {{Student Paper}},
  series       = {{LUTVDG/TVBM}},
  title        = {{Temperaturens inverkan på relativ fuktighet i betong - Materialkarakterisering av betong med vulkanisk puzzolan}},
  year         = {{2026}},
}