Influence Of Wet Conditions Research Articles

Influence of Wetting Conditions and Concrete Strength of Both Substrate and Repair Material on the Bond Capacity of Repaired Joints

Ultra-high performance concrete (UHPC) is an appropriate material to repair and rehabilitate aged structures due to its excellent properties, such as high compressive strength and durability. Several studies have demonstrated the effectiveness of applying UHPC in old buildings as a rehabilitation or repair material, but the bond between concretes needs more investigation. In this sense, the bond between normal-strength concrete (NSC) and UHPC is currently being studied. Three main parameters are responsible for ensuring a good bond: the surface treatment of the substrate (roughness), the wetting conditions, and the mechanical strength of the substrate. Thus, the present study investigated the bond between concretes experimentally. The concrete of the substrate was carried out in three grades: C25, C45, and C60. The repair concretes were C25, C45, C60, and UHPC. The following parameters were evaluated: wetting conditions, air surface dry (ASD), saturated surface dry (SSD), substrate strength, and repair concrete strength. All models received surface treatment by wire brushing. Slant shear and splitting tensile tests were performed to evaluate the mechanical behavior and the failure modes of the bond between concretes. The bond strength was classified and compared to existing predicting models. The results showed that most expressive strength gains occurred in SSD models with lower strength substrates and UHPC. Furthermore, the influence of surface wetting conditions becomes smaller as the strength of the substrate is reduced.

Coexisting sub-zero temperature and relative humidity influences on sensors and composite material

The paper is focused on coexisting influence of sub-zero temperature and different relative humidity levels on fibre Bragg grating (FBG) sensors and glass composite. The analyses were performed at different environmental (dry/wet) and sensors boundary (‘free’, woven, glued, embedded) conditions. Strain values determined for sub-zero temperatures differ among sensors, even these embedded into the material. The influence of wet conditions on the measured strain values was stronger for −50 °C than −20 °C. The influence of phase change of water (in the container)/moisture (inside the material) from liquid to the solid state was taken into consideration. Additionally, the application of THz spectroscopy allowed to observe the internal composite structure changes due to the coexisting influence of temperature (from sub-zero to room temperature) and different humidity levels. A theoretical model based on the theory of laminates was presented and discussed.

Influence of wet conditions on snow temperature diurnal variations: An East Antarctic sea–ice case study

A one-dimensional snow–sea–ice model is used to simulate the evolution of temperature profiles in dry and wet snow over a diurnal cycle, at locations where associated observations collected during the Sea Ice Physics and Ecosystem eXperiment (SIPEX-II) are available. The model is used at two sites, corresponding to two of the field campaign׳s sea–ice stations (2 and 6), and under two configurations: dry and wet snow conditions. In the wet snow model setups, liquid water may refreeze internally into the snow. At station 6, this releases latent heat to the snow and results in temperature changes at the base of the snow pack of a magnitude comparing to the model-observation difference (1–2°C). As the temperature gradient across the snow is in turn weakened, the associated conductive heat flux through snow decreases. At station 2, internal refreezing also occurs but colder air temperatures and the competing process of strengthened heat conduction in snow concurrent to snow densification maintain a steady temperature profile. However, both situations share a common feature and show that the conductive heat flux through the snow may significantly be affected (by 10–20% in our simulations) as a result of the liquid water refreezing in snow, either through thermal conductivity enhancement or direct temperature gradient alteration. This ultimately gives motivation for further investigating the impacts of these processes on the sea–ice mass balance in the framework of global scale model simulations.

Some effects of low oxygen partial pressures on the development of Calliphora vomitoria

The influence of wet conditions and low pO 2 on the survival and development of non-feeding final instar larvae and puparia of Calliphora vomitoria has been investigated. The larvae delay the formation of the puparium in wet conditions in air and in dry or wet conditions in 10 and 5% oxygen. This may be related to the susceptibility of the newly formed puparia to oxygen shortage. The pupal respiratory horns play an important part in maintaining O 2 uptake when the puparia are surrounded by particles covered with a film of water but are not involved in aiding survival in low pO 2. Zero age puparia are killed by a 2 day exposure to 10% O 2 but later stages can continue to develop in this gas. Fifty per cent of the 0, 1 and 9 day old puparia are killed by about a 12 hr exposure to 1% O 2 whereas 50 per cent of the 2 to 8 day old puparia can survive over 1·5 days exposure to this gas. Development, as measured by respiration rates and the timing of the emergence of the adults, is delayed by 1% O 2 by the amount of time that the insects spend in that gas. However, the first phase of elongation of the pharate adult longitudinal flight muscle, occurring between the third and fourth day of puparial life, is only slightly slowed down in 1% O 2. The variations in susceptibility to 1% O 2 and the growth of the muscles are discussed in relation to published accounts of protein synthesis in the puparium.