Lars Wadsö

Lund University | LU · Building Materials, Lund University

Periodic dredging of harbors and other waterways is carried out to ensure sufficient depth for navigation. The Stabilization/Solidification method (S/S) is the global approach for improving the geotechnical characteristics and stabilizing pollutions in the low-compressive-strength dredged sediment (DS) for land reclamation. For this, different bind...

Nanopores are critical for the durability of cement-based materials, but the refinement of these pores by SCMs is yet to have a clear understanding. This paper studied effects of the water–binder ratio, SCMs and the drying on the distribution of nanopores using water vapour and N2 sorption isotherms. Results show that data of water vapour sorption...

Horticultural crops have a low tolerance to dehydration. In this paper, we show that the reversible electroporation (200 monopolar, rectangular pulses of 50 µs pulse duration, 760 µs between pulses and nominal field strength of 650 V/cm) of Thai basil leaves followed by 24 h resting before hot air drying at 40 °C enhanced the survivability of the t...

The purpose of this study was to investigate for how long the thermal power of hydration can be measured with isothermal calorimetry, which is a general measurement technique with stable properties that, in many cases, can detect low rates of processes. Measurements were conducted for 365 days on cement paste with Portland cement, fly ash blended P...

This study documents how the pore structure develops with time in cement-based materials with varying fly ash replacement. Heat production was measured during the first days, water vapour desorption isotherms were determined at different times up to 18 months, and moisture transport properties were measured after one year. Long-term fly ash reactio...

Progress in electrical engineering puts a greater demand on the cooling and insulating properties of liquid media, such as transformer oils. To enhance their performance, researchers develop various nanofluids based on transformer oils. In this study, we focus on novel commercial transformer oil and a magnetic nanofluid containing iron oxide nanopa...

As a novel coolant, the ethylene glycol-water (50 wt.%:50 wt.%) with graphene nanoplatelets nanofluids (GnP-EGW) were prepared at four weight concentrations (0.01, 0.1 0.5 and 1.0 wt.%), and heat transfer and pressure drop characteristics in a miniature plate heat exchanger (MPHE) were investigated. All nanofluid samples were prepared and diluted b...

Vacuum impregnation (VI) has been widely used as pre-treatment prior to, e.g., minimal processing, freezing, or drying of fruit and vegetables. Most of the investigations have focused on the applicability of VI to modify physicochemical, sensory, and nutritive characteristics. However, little attention has been paid to the metabolic consequences of...

A sorption balance is an instrument used to measure vapor uptake in a sample at controlled temperature and relative humidity. It is most commonly used to determine equilibrium values (sorption isotherms), but is also used for kinetic measurements of transport coefficients. Such measurements can be affected by the external mass transfer resistance i...

We have developed a method based on isothermal calorimetry to monitor the colonization of wood materials by decay fungi. The heat produced is a direct and continuous measure of the activity (respiration) of the fungus. This pre-study shows that wood materials treated in different ways give results that reflect the known ranking of the materials reg...

Spallation sources create a large amount of neutrons with energies up to the GeV range. To shield for these neutrons, steel and concrete are important materials. By adding different aggregates to normal concrete, one can improve the shielding effect of the concrete. Some of these aggregates can influence the rate of hydration (reaction) of the ceme...

This paper continues the discussion in a previous paper [Saeidpour and Wadsö doi:10.1016/j.cemconres.2016.02.003] where a clear effect of sorption hysteresis was seen in moisture diffusion coefficients for cement-based materials. Coefficients with vapor content as potential (Dv) had different values depending on whether the sample was in absorption...

This study investigated whether isothermal calorimetry measurements on cement paste are sufficiently accurate and precise to partially replace compressive strengths measurements on cement mortar as a quality control method at cement production. The study was also designed to provide information on mechanisms that will affect the relationship betwee...

Microbial substrate use efficiency is an important property in process-based soil organic matter models, but is often assumed to be constant in mechanistic models. However, previous studies question if a constant efficiency is appropriate, in particular when evaluating carbon (C) cycling across temperatures and various substrates. In the present st...

Water vapor diffusion coefficients have been determined with a new set-up of the cup method for mortars with three binders (OPC, OPC + 70% slag, OPC + 10% silica fume) and two water/binder-ratios (0.4, 0.5). The measurements were made as a function of relative humidity with samples on both the absorption and desorption limbs of the sorption isother...

Reinforced mortar samples were exposed in humidity chambers with different relative humidity or exposed in cyclic moisture conditions. The rebars were in an “as received” condition meaning that the preexisting oxide scale were intact. The lowest chloride concentration that initiated corrosion was 1% Cl− by mass of cement, corrosion was then observe...

The AFm phase, one of the main products formed during the hydration of Portland and calcium aluminate cement based systems, belongs to the layered double hydrate (LDH) family having positively charged layers and water plus charge-balancing anions in the interlayer. It is known that these phases present different hydration states (i.e. varying water...

Physical properties of importance in drying processes have been compiled for bark, including spruce, pine, and birch in Sweden. Water vapor sorption isotherms were determined for the bark of these trees. At 95% relative humidity and 25°C, outer birch bark reached a moisture ratio (kg water/kg dry mass) of 5%, whereas inner birch bark, spruce bark,...

We used dynamic sorption balance measurements to evaluate the diffusivity for cement pastes with three different binders (OPC, OPC + 70% slag, OPC + 10% silica fume). The diffusion of water vapor in cement based materials is normally assumed to follow Fick's law of diffusion, but our results clearly show that Fick's law cannot completely describe t...

Water vapor sorption isotherms are essential data in models to predict the service life of cement based structures. This study investigates the influence of water to binder ratio (0.4, 0.5 and 0.6), and the presence of two SCMs (70% slag and 10% silica fume) on sorption isotherms, both in the hygroscopic and in the super-hygroscopic relative humidi...

The moisture content of wood is commonly determined by measuring the electrical resistance between two electrodes inserted in the wood. However, problems using this method close to wood surfaces were reported in a previous study. In the present study, the effect of the distance to a surface and the specimen size on the measured electrical resistanc...

This paper describes a novel approach to the quantitative investigation of the impact of varying relative humidity (RH) and temperature on the structure and thermodynamic properties of salts and crystalline cement hydrates in different hydration states (i.e. varying molar water contents). The multi-method approach developed here is capable of deriv...

In order to perform service life predictions of rain exposed wood structures, the moisture and temperature conditions in the structure need to be known as well as which degradation that occurs under those exposure conditions. The microclimate (the moisture conditions at the surface) is the boundary condition for moisture transport into the wood and...

Calorespirometry is the simultaneous measurement of heat and gas exchange from biological systems. Such measurements can be used to assess fundamental properties of many different types of systems from small ecosystems to isolated tissues. Techniques for calorespirometric measurements on terrestrial (non-aquatic) samples are described. Methods and...

A new vessel for simultaneous isothermal calorimetry and respirometry (calorespirometry) on terrestrial (non-aqueous) samples has been developed. All types of small (<1 g) biological samples (insects, soil, leaves, fungi, etc.) can be studied. The respirometric measurements are made by opening and closing a valve to a vial inside the sample ampoule...

In this study calorimetric measurements provided evidence of a drastic increase of spinach leaf gross metabolism as a consequence of vacuum impregnation (VI) at a minimum pressure of 150 mbar with trehalose and sucrose isotonic solutions. When applying VI extracellular air is replaced by the impregnation solution, potentially limiting tissue respir...

Milk coagulation is an important processing trait, being the basis for production of both cheese and fermented products. There is interest in including technological properties of these products in the breeding goal for dairy cattle. The aim of the present study was therefore to estimate genetic parameters for milk coagulation properties, including...

The phenomenon of water vapour sorption by anhydrous C(3)A polymorphs both in the absence and in the presence of CaSO4 center dot 0.5 H2O was studied utilising dynamic and static sorption methods. It was found that orthorhombic C(3)A starts to sorb water at 55% relative humidity (RH) and cubic C(3)A at 80% RH. Also, C(3)Ao sorbs a higher amount of...

Rot fungi are a major problem in the construction sector, and method to study under which moisture and temperature coefficients they grow are therefore of significant interest. Measurements of heat production rate have been made on wood samples with the brown rot fungus Postia placenta at different moisture contents (MCs). The results clearly show...

Activities of moulds from domestic dwellings are normally classified into three groups—primary, secondary, and tertiary colonizers—according to the minimum relative humidity they require to colonize a substrate. With the help of isothermal calorimetry it is possible to directly measure the thermal activity from moulds as a function of climatic para...

Corrosion of steel structures in the marine environment is a major problem. The deterioration of this kind of structures is costly and difficult to predict both when designing new structures and when estimating the remaining service life time for existing structures. The aim of this investigation was to find indicative values for the corrosion rate...

The exposure of bacterial cells to pulsed electric fields (PEF) leads to the reversible formation of pores in the cell membrane if an applied energy is below the critical level. Therefore, the effect of electric field pulses with amplitudes below 14 kV/cm and the applied energy up to 12.2 J/cm3 on the growth of Lactobacillus plantarum 564 cells was...

If water stays on wood surfaces or is trapped in gaps, the wood is supplied with water for a long period of time and high local moisture contents are reached. This can lead to decay by rot fungi, and it is therefore important to avoid such water traps in order to limit the decay rate. This paper presents two methods: one for determination of durati...

Aluminum-based sacrificial anodes were installed to reinforced concrete to stop ongoing corrosion in cooling water tunnels in a Swedish nuclear power plant. The steel rebars were also unintentionally connected to stainless steel water pumps. Therefore, the consumption rate of the sacrificial anodes was higher than predicted. An experimental and a f...

The wood moisture content influences the service life of wood structures since wood is susceptible to decay by rot fungi if it is exposed to high moisture contents during long periods of time. In rain exposed structures, the moisture content close to end grain surfaces and joints can be significantly higher than the average moisture content, but mo...

The water interactions of polymer electrolyte membranes are of significant interest when these materials are used in for example fuel cells. We have therefore studied the sorption thermodynamics of Nafion 117 with a sorption calorimeter that simultaneously measures the sorption isotherm and the mixing (sorption) enthalpy. This unique method is suit...

The energy use for maintaining comfortable indoor temperatures are to a certain extent dependent on the thermal storage capacity of materials in contact with the indoor air. This article describes a conceptual model for investigating the effects of increasing the thermal storage capacity of building materials. A building is modeled as an exterior w...

This paper concerns thermometric and direct and indirect investigations of the heat produced by the thermogenic dragon lily (Dracunculus vulgaris) and its main pollinating beetle Protaetia (formerly named Potosia) cretica. The experiments were performed on scented and scentless populations at Panormo, Therisos and Lassithi on the North coast of Cre...

a b s t r a c t This study explores metabolic responses of germinating barley seeds upon the application of pulsed electric fields (PEF). Malting barley seeds were steeped in aerated water for 24 h and PEF-treated at varying voltages (0 (control), 110, 160, 240, 320, 400 and 480 V). The seeds were then allowed to finish germination in saturated air...

Glycerol and urea are examples of small, water-soluble molecules with low vapor pressure that can protect lipid membranes upon dehydration. Both are a part of the Natural Moisturizing Factor in human skin, and are also present in other organisms, where they prevent drying due to osmotic stress. This study was conducted in order to understand the me...

The behavior of the surviving population of Lactobacillus plantarum 564 growing in MRS broth after pulsed electric field (PEF) treatments of different intensities was monitored by isothermal calorimetry, optical density and plate counts. Bacterial cells were treated with monopolar square pulses at varying nominal electric field strengths and number...

The phenomenon of water vapour sorption by powdered cement constituents exposed to different relative humidities and temperatures was studied. The individual clinker phases C3S, C2S, C3A, C4AF, calcium sulfates and CaO were tested. Using a water sorption balance, the amount of chemically and physically sorbed water per unit of surface area of the p...

A calorimetric method to determine water activity covering the full range of the water activity scale is presented. A dry stream of nitrogen gas is passed either over the solution whose activity should be determined or left dry before it is saturated by bubbling through water in an isothermal calorimeter. The unknown activity is in principle determ...

Es ist bekannt, dass Trockenmörtel während längerer Lagerung in feuchter Atmosphäre veränderte Eigenschaften bei der Anwendung (z. B. verzögertes Abbinden oder geringere Fließfähigkeit) zeigen können. Es wird allgemein angenommen, dass diese Effekte auf eine geringe, an der Zementkornoberfläche stattfindende Hydratation zurückzuführen sind. In di...

Fungal colony size development, often measured as the increase in colony diameter, is used frequently as a parameter for presenting and modelling fungi's biomass growth. Another measure of fungal growth is the heat production rate (thermal power), which represents the metabolic activities of the fungi. In this study, the colony size and the heat pr...

Isothermal calorimetry is a powerful technique for the study of kinetics of physical, chemical, and biological processes, for example, of their temperature dependence. A new heat conduction calorimeter that simultaneously makes measurements on four samples at four different temperatures is presented in this article. Results from tests with four bio...

Isothermal titration calorimetry (ITC) is the measurement of the heat produced by the stepwise addition of one substance to another. It is a common experimental technique, for example, in pharmaceutical science, to measure equilibrium constants and reaction enthalpies. We describe a stirring device and an injection pump that can be used with a prev...

Isothermal calorimetry and diffuse reflectance infrared DR–FTIR spectroscopy are combined to correlate evolutions of spectroscopic signatures with rates of chemical reactions as reflected in the rate of heat emitted during the first 38 h of cement hydration. Portland limestone cement mortar is employed and the analysis is repeated for two different...

The moisture sorption and swelling of spruce specimens impregnated with linseed oil and unimpregnated controls were studied in two sorption experiments: from 0 to 55% relative humidity (RH) and from 55% RH to water saturation. Sorption isotherms were also determined using a sorption balance. The impregnated specimens had lower rates of both moistur...

Isothermal (heat conduction) calorimetry is a general technique to study processes through the thermal power they produce. This paper deals with operational issues concerning isothermal calorimeters. In this paper it is shown that steady-state and pulse calibrations give the same result; that the use of mobile heaters (placed in the reaction ampoul...

Cement hydration needs water to proceed and if water is lost by drying, the hydration rate will decrease. This can be of importance in cases when concrete surfaces are exposed to drying so that their strength development will be retarded. We describe a method based on isothermal calorimetry to assess how the rate of cement hydration is influenced b...

Many façades made with thin rendering on thermal insulation have problems with biological growth. In this study, surface temperature and surface relative humidity were monitored over a 20-month period on test house façades with different constructions (thermal inertia), surface colour and compass directions. This data were used to test three theore...

All physical, chemical and biological processes produce heat and isothermal calorimetry is a general measurement technique to study all kinds of processes by the heat they produce. This paper gives several examples of studies of biological processes in the food area using isothermal calorimetry. It is for example shown how different unit operations...

Discontinuous gas exchange cycles (DGCs) are frequently observed with insects, i.e. oxygen take up and carbon dioxide release occur interrupted by periods of a few minutes up to many hours. The paper presents direct and indirect calorimetric experiments on DGCs of the scarabid rhinoceros beetle Oryctes nasicornis. A direct/indirect calorimetric ex...

The influence of temperature on the growth of the mould Penicillium roqueforti growing on malt extract agar was studied by correlating the produced heat (measured by isothermal calorimetry), ergosterol content (quantified by GC-MS/MS) and biomass of the mould at 10, 15, 20, 25 and 30 degrees C. The results were analysed with a simple metabolic mode...

We investigate how small polar molecules, urea and glycerol, can act to protect a phospholipid bilayer system against osmotic stress. The osmotic stress can be caused by a dry environment, freezing, or through exposure to aqueous systems with high osmotic pressure due to solutes like in saline water. A large number of organisms regularly experience...

In this study, we investigated the metabolic responses of potato tissue induced by pulsed electric field (PEF). Potato tissue was subjected to field strengths ranging from 30 to 500V/cm, with a single rectangular pulse of 10μs, 100μs, or 1ms. Metabolic responses were monitored using isothermal calorimetry, changes on electrical resistance during th...

Sorption balances are instruments in which samples are weighed as they are exposed to a programmed relative humidity (RH). Such instruments are used to measure sorption isotherms and to study solid-vapour interaction. There are different methods to validate the performance of the RH generation in such instruments by charging them with saturated sal...

Floor adhesives on cement-based substrates may degrade if the pH is high enough and this has in many cases led to emissions of odorous substances and deteriorated indoor air quality. We have used isothermal calorimetry to assess the degradation rate of two floor adhesives as a function of pH. The rate of heat production measured by the calorimeter...

A method for simultaneous determination of the diffusion and sorption properties of cement-based materials is presented. It is a gravimetric method where one small specimen is exposed to stepwise changes in relative humidity while its mass is being measured. As sorption in cement-based materials is slow, the change in relative humidity to the next...

An increasing interest in the moisture buffering of indoor surface materials and new tools for calculation of energy demands and indoor climate calls for relevant material properties of all materials exposed to the indoor air. Textile fabric represents a large portion of the surface materials present in dwellings and offices and is therefore of spe...

Most processes (whether physical, chemical, or biological) produce or consume heat: measuring thermal power (the heat production rate) is therefore a typical method of studying processes. Here we describe the design of a simple isothermal heat conduction calorimeter built for use in teaching; we also provide an example of its use in simultaneously...

Film formation from latex dispersions with varying concentrations of sodium dodecylsulfate (SDS) and sodium persulfate (NaPS) was studied with a sorption balance. The drying rate decreased significantly at a critical volume fraction of polymer (phi pc). Under constant drying conditions the phi pc varied due to differences in particle stabilization....

Water in building materials not only influences important physical properties and chemical processes but is also related to the well-being of the occupants of a building. The drying of cementitious materials is complex, involving several different drying processes. The conditions for each drying process change as the material changes its properties...

The initial drying of dispersion samples with varying geometries and surface areas was continuously recorded in a sorption balance at different temperatures and relative humidities. The samples were applied as small (5–20mg) droplets on glass. We were able to show a linear dependence of the evaporation rate on the exposed surface area of the sample...

The effect of postharvest long-term storage and pre-treatments on the mass transfer rates during osmotic dehydration of carrots was investigated. Four blanching times were used and the carrots were sampled during 12 weeks of storage. Cell vitality was measured by isothermal calorimetry on cores taken from blanched slices. During the storage period,...

Two methods of quantifying fungal activity have been compared and correlated: isothermal calorimetry for measuring heat production and gas chromatography–tandem mass spectrometry (GC–MS/MS) for measuring ergosterol, a proxy for biomass. The measurements were made on four different fungi: Penicillium roqueforti, Cladosporium cladosporioides, Neopetr...

Biofuels are commonly stored in large stacks that may heat up and self-ignite from microbiological and chemical heat production. This paper shows how isothermal (heat conduction) calorimetry can be used to measure heat production rates of biofuels at relatively low temperatures close to where self-heating starts to become a problem. Measurements ca...

We investigated possible physiological effects of the application of anti-browning substances on metabolically active potato tissues. The use of citric acid, ascorbic acid and l-cysteine for browning prevention of fresh-cut potatoes increased their metabolic heat production as measured by isothermal calorimetry. This effect was particularly high af...

This article focuses on experimental studies of self-heating characteristics of wood pellets. Controlled experiments have been conducted in physical scales from 1 dm3 to 4 m3 with wood pellets. Basket tests have been conducted according to the "crossing-point method" to derive kinetic data on the exothermic reactions responsible for self-heating an...

We investigate how a small polar molecule, urea, can act to protect a phospholipid bilayer system against osmotic stress. Osmotic stress can be caused by a dry environment, by freezing, or by exposure to aqueous systems with high osmotic pressure due to solutes like in saline water. A large number of organisms regularly experience osmotic stress, a...

Summary Vezetknv

Isothermal calorimetry has high potentiality in order to provide an integrated view of the effect of different unit operations on the quality maintenance of minimally processed fruits and vegetables (MPFV). In this paper a study of the effects of slicing and anti-browning treatments on metabolic response and respiration of MP vegetables studied by...

We review the potential of isothermal calorimetry as an analytical tool to provide an integrated view of the effect of different processing steps on the quality and shelf life of minimally processed fruits and vegetables. Variations in processing operations involved in product development in the food industry are studied through a factory scenario...

The anti-browning effects of acidificant and antioxidant substances in potatoes have been broadly studied in the literature. However, to our knowledge there is no information about their effects on the metabolism of the wounded tissue. We here have studied the influence of anti-browning substances on the metabolism of fresh-cut potatoes. Cylinders...

When plant tissue is wounded a number of protective processes start. We have made a study by isothermal calorimetry of the heat production response of root and tuber tissue to wounding. Samples with different surface to volume ratios were prepared from carrots, potatoes and swedes (rutabaga) and the thermal power was measured in closed glass ampoul...

We describe a simple, yet practical and precise, way of measuring sorption isotherms with each sample in its own glass jar with a saturated salt solution. The measurements are done with below-balance weighing and with the sample kept inside the closed jar during the whole measurement period, providing constant relative humidity (RH) conditions. The...

Heat conduction calorimetry is a convenient method to detect cement-admixture incompatibility. However, such instruments tend to be used mainly in chemical laboratories. This paper presents the design of a simple unthermostated heat conduction calorimeter that can simultaneously monitor the heat production rate in 14 samples of cement paste or mort...

When plant tissue is wounded a number of protective processes start. We have made a study by isothermal calorimetry of the heat production response of root and tuber tissue to wounding. Samples with different surface to volume ratios were prepared from carrots, potatoes and swedes (rutabaga) and the thermal power was measured in closed glass ampoul...

The purpose of this investigation was to test calorimetry as a means of quantifying cell damage occurring at various stages of mild blanching treatments. Calorimetric measurements were carried out on cores taken from carrot slices blanched at 100 °C for 5–45 s. The calorimetric data were corrected for the influence of wounding stress due to slicing...

This paper presents results from dynamic calorespirometric measurements on the two mould fungi Penicillium roqueforti and P. camemberti growing on agar. The measurements were made with two isothermal heat conduction calorimeters connected by a tube. In one of the calorimeters, the sample was placed and the other contained a carbon dioxide absorbent...

The possibility of predicting the shelf-life of pasteurized carrot juice by isothermal microcalorimetry or change in pH was investigated and compared with traditional plate count results. A small increase in thermal power (2 µW), maximal increase of and acceleration of thermal power all gave rapid, well-correlated results for the shelf-life, as did...

The effects of de-aeration and modification of the headspace atmosphere on carrot juice shelf-life were investigated. The shelf-life was defined by microbial growth, determined by isothermal calorimetry and plate counts. Compared with storage under air, de-aeration of carrot juice by helium or nitrogen bubbling, followed by flush packaging had no e...

This paper presents a microcalorimetric technique to simultaneously measure water activity and enthalpy of mixing (differential heat of sorption) as functions of composition at high water activities. The instrument consists of a sorption vessel in a double twin microcalorimeter. A sample at high water activity is placed in one chamber of the vessel...

The design and some properties of a new general-purpose isothermal microcalorimeter are reported. The instrument is a twin thermopile heat conduction calorimeter, which is designed for use up to 200 °C. The calorimetric units and surrounding heat sink are suspended inside a hollow aluminium construction, which is thermostated. Above that unit a sec...

Sorption of vapors of water, ethanol, and other liquids on solids like pharmaceuticals, textiles and food stuffs are of both practical and theoretical importance. In this article we present a technique to simultaneously measure sorption isotherms and sorption enthalpies. The sample is contained in one end of a sorption vessel. In the other end a va...

In this work, we describe the application of a sorption calorimeter to study the binary system n-octyl β-d-glucoside/water at 25, 40, and 60 °C. At 25 °C we also carried out experiments with heavy water which showed similar results to those with normal water. The method used allows one to simultaneously obtain information about the activity of wate...

An approach to teaching calorimetry is offered through practical, versatile undergraduate experiments using an isothermal heat conduction calorimeter, which measures a variety of heat changes--enthalpies of phase changes, hydration, dissolution, adsorption and desorption, and reaction--as well as the metabolic rate of living organisms. Isothermal h...

A wide scope of application of a novel isothermal sorption microcalorimeter is presented. With the technique, it is possible to simultaneously and independently in one experiment obtain the sorption isotherm of a sample along with the corresponding differential enthalpies of sorption. The method is suited for measurements with water vapor as well a...

The formation of a stochiometric salt hydrate takes place at a well defined vapor activity. We have compared three methods to measure this vapor activity. In two of the methods we used a sorption balance in step mode and in ramp mode, respectively, and in one method we used a newly developed sorption microcalorimeter. The tests were made with the f...

So-called isothermal calorimeters are often built on the heat conduction principle. This may sound as a contradiction, as heat conduction is a result of non-isothermal conditions, but most measurements with microcalorimeters and other such instruments are essentially isothermal as the temperature differences within the instruments are in the order...