Is freeze-drying an alternative to solvent exchange for the hydration stop of cementitious suspensions?

In order to understand the rheological properties of cementitious suspensions at early stages, among other phases, the formation of ettringite and its time-dependent influence, whether by amount or morphology, has to be examined in detail using a suitable method to stop the hydration process. It is state-of-the-art to exchange water with isopropanol, however, the water initially remains in the system possibly leading to reduced time resolution. Our group raised the question if freeze-drying or the combination of the water-isopropanol exchange with subsequent freeze-drying might be a suitable technique to achieve an almost complete hydration stop at any time. Recently, it was shown under which circumstances low-pressure characterization techniques can be employed without destroying the samples due to loss of crystal bound water. Here, by implementing these recent results, we show under which circumstances freeze-drying indeed can be employed as fast hydration stop method. © 202

Stabilisation of sulphide rich soil: problems and solutions

The research presented in this thesis can be split into two well-defined areas. Firstly, the effects of the addition of lime (either 2%, 4%, 6% or 8%Ca(OH)2 or 1.5%, 3%, 4.5% or 6%CaO) on various engineering properties of a sulphide (pyrites) rich, naturally occurring clay - Lower Oxford Clay (LOC) - were studied. Experimental tests representing, or relating to, tests outlined in the Design and Construction of Lime Stabilised Capping Specification (DoT, 1995) were utilised and consisted of Atterberg (consistency) tests, compaction tests, unconfined compressive strength tests, linear expansion measurements and durability tests. Also, sulphate (S03) analyses, pH measurements, differential thermogravinietric (DTG) analyses and X-ray diffraction (XRD) tests were employed to confirm experimental data. Environmental conditions were chosen to reflect temperatures experienced in the UK - between 5*C, 10'C and 201C. The majority of samples were mellowed (the time delay between initial mixing and compaction) for 3 days at 201C prior to testing. The results show that small additions of lime (i. e. 2%Ca(OH)2 or 1.5%CaO) modify the engineering properties of LOC by causing flocculation, and also increase S03 levels due to increased gypsum levels via pyrites oxidation. However, strength development is poor as little cementitious bonding is formed. Mellowing further modifies the engineering properties as the increased time allows greater flocculation leading to a less dense, more porous material. Also ettringite forms during mellowing allowing expansive reactions to occur prior to compaction, consuming both calcium and sulphate in the process and leading to slightly reduced pH levels compared to similar unmellowed samples. Further additions of lime give further change to the engineering properties of the LOC, up to an addition of 6%Ca(OH)2 or 4.5%CaO. Further additions result only in supplying an excess of calcium. Strength development is improved with increasing lime additions, especially after 4 weeks of curing at higher curing temperatures (20'C); however linear expansion increases and durability worsens. However, a period of mellowing prior to compaction reduces linear expansion and improves durability. Sulphate (S03) levels are also increased with increasing additions of lime due to pyrites oxidation. In samples containing >2%Ca(OH)2 or 1.5%CaO, pH levels are maintained to a level where ettringite formation is sustained rather than gypsum formation. Secondly, the effects of a secondary stabilising agent (ground granulated blast furnace slag - GGBS - incorporated at various percentage additions (2%, 4%, 6% or 8%)) on the strength development, linear expansion and durability of mellowed, lime-modified LOC is presented. For comparative purposes, Portland cement (PC) is also used. The results show that although LOC-lime-PC samples exhibit greater strengths (especially when cured for long periods at 20"C), linear expansion is lower and durability is higher in similar LOClime- GGBS samples. As the hydration process of PC produces lime, and as lime is usually consumed during GGBS hydration, then samples containing the former stabiliser will maintain pH levels well above samples containing the latter. Therefore, on soaking disruption and expansion due to the formation of ettringite (which is unstable at pH levels <10.5) is common to LOC-lime-PC samples but not in similar GGBS samples. In conclusion, the findings from this thesis indicate that soil stabilisation with lime and GGBS is particularly effective for naturally occurring sulphide rich clay soils (such as the LOC) and is an environmentally friendly alternative to PC-stabilised soils

The hydrothermal precipitation of arsenical solids in the Ca-Fe-AsO4-SO4 system at elevated temperatures

Hydrothermal precipitation experiments were carried out in sealed test tubes to investigate the characteristics of solids precipitated from Ca-Fe-As04-S04 solutions at temperatures up to 225°C. The solids precipitated from solutions were examined by studying the individual Fe-AsC>4, Ca-AsCTj and Fe-Ca- As04 systems at low (3). Precipitation of solids in the Fe-AsC>4-SC)4 system at pH1:1. The family of Type-2 compounds show close similarities and are usually produced from starting solutions with Fe:As >1:1 at temperatures >175°C. These compounds are light brown in colour and are composed of crystals up to 50(j.m, they easily accommodate sulphate into their lattice and have compositions which approximate to:- Fe3(As04)2(0H)x(S04)y (where x and y = 0 to 1). The formation of the Type-1 compound is common in the temperature range 150 - 225°C from solutions with ratios of Fe:As of 95% of the contained arsenic from solution. High temperatures are preferable (>175°C) as this promotes the growth of crystalline arsenical compounds. For optimum conditions the Fe:As ratio in the solution must be around 1:1 to satisfy the Fe:As requirements of the precipitated compound (scorodite or the Type-2 compound, 1:1 or ~1.5:1 respectively) and most of the arsenic is removed within 30 minutes. When higher Fe:As ratios are used, the rate at which the compounds are precipitated is reduced. In the Fe-AsC>4 system at pH5 using an Fe:As ratio of ~1:1, a crystalline compound; designated Type-3 (approximating to Fe2(FIAs04)x(As04)y), is precipitated from arsenical-ferrihydrite sludges at temperatures above 125°C. Only at elevated pHs (>3) do calcium arsenate compounds begin to precipitate, and during neutralisation of iron-rich solutions arsenic preferentially combines with iron rather than calcium. In sulphate-rich solutions calcium will precipitate as gypsum rather than combine with arsenate to produce calcium arsenate compounds. From precipitation work carried out in the calcium-arsenate system, it was found that at temperatures below 100°C, the solids are partly hydrated and are usually composed of one of the following:- pharmacolite, haidingerite, or guerinite (CaHAsC>4.2H20, CaHAs04.H20 and CasH2(As04)4.9H20, respectively). In the temperature range 100 - 200°C at pH's4). Solids precipitated at pH's above 8 and at temperatures above 100°C precipitated johnbaumite (Cas(As04)30H). Above 200°C, the predominant solid approaches a Ca3(AsC>4)2 composition which contains only minor amounts of constitutional water. This work has examined a wide range of solution compositions and it has been found that all the hydrothermally prepared calcium arsenate-type compounds have very high apparent solubilities (>1000mg/L). Through experimental observation and consideration of some theoretical concepts a preliminary assessment of the long term behaviour of crystalline arsenic bearing metallurgical wastes in the environment has been made. Through empirical solubility testing and comparison with natural analogues it can be predicted that crystalline scorodite should have a low solubility for prolonged periods of time. Since scorodite is commonly found in many weathering zones and in most climatic regions of the world it is considered to be the most stable arsenate compound formed in nature and may be suitable for arsenic disposal purposes

Salt weathering in the coastal environment: the deterioration of wall paintings at Delos, Greece.

Salt weathering, apart from being an important geomorphologic agent, comprises a major hazard for both modern and heritage structures. Although its action is witnessed globally, it is particularly aggressive in coastal environments. The coastline attracted in antiquity a considerable part of human activity that has left valuable built traces. Conservation research is frequently called upon to define sustainability in this aggressive context. Wall paintings comprise an integral part of the built heritage. The particular importance of wall paintings and finishing layers derives from their unique aesthetic function in the building's integrity as well as the plethora of information that they carry. Whereas wall paintings are more susceptible than masonry materials, the tolerance against loss is much smaller due to their descriptive nature and scale. It is not until recently that international heritage organisations recognised the technical particularities of wall paintings suggesting that they must be investigated independently and treated in situ. This project aims to identify the particularities of wall paintings' susceptibility to salt weathering in the coastal environment. The methodology is composed of both in situ and ex situ experiments. The in situ investigation follows a comparative approach, guided by specific variables, in a number of monuments at the archaeological site of Delos island. The goal of the in situ investigation is to determine the optimal conditions for preservation, by modeling the salts interactions, in an effort to define sustainability against salt weathering in this aggressive environment. The ex situ approach comprises laboratory simulation of the weathering mechanism and aims to describe the particularities of the substrate that lead to the distinct loss of the external finishing layer, which carries the principal information. The results of the project underline the importance of kinetic deviations deriving from the solution and the substrate properties. Despite the limitations of determining the optimal conditions for preservation, the variables that directed the comparative approach permitted the generation of a periodic model in agreement with the phenomenological observations. The model suggests that the potential of salt damage in real conditions of various contamination pathways and sources cannot be restricted to a single resultant. Although the model follows a certain periodicity in response to the annual climatic cycle, random events and fractionated accumulation lead to the production of mixtures with variable composition. Additionally the results stress the role of solar radiation and air movement as evaporation accelerators. Consequently environmental control against salt weathering should be directed towards multiple components which in the case of coastal environments, mainly due to the presence of marine aerosols, cannot be achieved simply by hygrothermal management. On the other hand we traced specific deviations from the theoretical model of salts interactions, concerning mixtures commonly found in coastal regions that should also be taken into account. Besides we tested the hypothesis of salts accumulation at the interface of rendering layers, caused by hydraulic discontinuity, with a weathering simulation. The aim of this investigation was to provide evidence descriptive of damage. It has been shown that the external layer of wall paintings is particularly susceptible to marine aerosols and it can be damaged independently and in advance of the bulk mortar. The salts crystallise selectively under the lime wash layer causing gradually its detachment from the mortar. The results of the weathering simulation raise serious implications for remedial and preventive conservation practice and suggest that research must focus as well on the kinetics of particular cases

Kohonneen lämpötilan vaikutukset sementtipastan vanhenemiselle

Long-term effects of elevated temperatures (65 °C - 345 °C) on the ageing of concrete and cement paste were studied. According to the literature review, harmful effects on ageing are porosity increase resulting from drying and dehydration of cement minerals, movement of moisture due to the uneven temperature, drying shrinkage, spalling, and carbonation. Delayed ettringite formation was found not to be significant when the exposure of cement paste or concrete to elevated temperatures lasts more than 2 days and there is no water storage after the exposure. The laboratory tests were carried out for studying the effects of elevated temperatures on cement paste. The cement paste specimens made of ordinary or sulphate resisting portland cement were exposed to temperatures of 95 °C, 175 °C and 345 °C for 124 days and also to cooling cycles in water and relative humidity 45%. The specimens were studied with thermal analysis and x-ray diffraction. Compressive strength and porosity tests were also performed. Decreasing of portlandite and increasing of calcite was observed when the exposure temperature was risen. Porosity increased as the exposure temperature increased and compression strength after 124 days in 345 °C was 70-80% of original. Ordinary portland cement behaved better than sulphate resistant cement at elevated temperatures, in respect of porosity and compressive strength. In the study, the ageing was also simulated numerically. The numerical model was implemented in geochemical Crunchflow software. The simulations were compared to the values received from laboratory experiments and the same agreements were observed but also clear deviations indicating needs for further research. The simulations were performed for predicting the phenomena after one and two years of exposure. Simulations showed that even after 124 d in 175 °C not all calcium-silicate-hydrate has disappeared, it did decompose after two years of exposure. According to the calculations at the temperature of 345 °C almost all cement hydrates are decomposed and only dicalciumsilicate is left. Calculations and experimental results suggest that temperature of 95 °C cannot be considered detrimental for cement paste. Temperature of 175 °C is not harmful for short periods, but after 1 year, almost all C-S-H is decomposed. 345 °C is harmful for cement paste also for short periods. In the simulations no differences were observed between the behaviour of different cements at the elevated temperatures.Työssä tutkittiin kohonneen lämpötilan (65 °C - 345 °C) vaikutuksia betoniin ja sementtipastaan. Kohonneesta lämpötilasta aiheutuva huokoisuuden kasvaminen dehydrataation ja kuivumisen takia, epätasaisesta lämpötilasta johtuva kosteuden siirtyminen, kuivumiskutistuminen, hajoaminen ja karbonatisoituminen ovat kirjallisuustutkimuksen mukaan haitallisia vaikutuksia betonille tai sementtipastalle. Myöhästyneen ettringiitin muodostuminen ei ole mahdollista, jos lämpötilarasitus kestää yli 2 päivää ja sitä ei seuraa vesisäilytys. Kohoneen lämpötilan vaikutuksia sementtipastaan tutkittiin kokeellisesti. Kokeissa käytettiin tavallisesta ja sulfaatinkestävästä sementistä valettuja kappaleita, jotka sijoitettiin lämpötiloihin 95 °C, 175 °C ja 345 °C 124 päivän ajaksi. Osa kappaleista pidettiin myös välillä huoneenlämpötilassa, vesisäilytyksessä tai 45% suhteellisessa kosteudessa. Kappaleille tehtiin huokoisuus- ja puristuslujuuskokeet sekä termovaaka- ja röntgendiffraktioanalyysi. Portlandiitin väheneminen ja kalsiitin lisääntyminen havaittiin analyyseista altistuslämpötilan kasvaessa. Myös huokoisuus kasvoi lämpötilan mukana. Altistuminen 345 °C lämpötilaan laski sementtipastojen puristuslujuutta 20-30%. Huokoisuus- ja puristuslujuuskokeiden vertailu osoitti, että tavallinen portland sementti kesti paremmin lämpötilarasitusta kuin sulfaatinkestävä sementti. Ikääntymistä simuloitiin numeerisella mallilla, joka implementoitiin Crunchflow-ohjelmaan. Simuloinnin tuloksia verrattiin kokeellisesti määritettyihin arvoihin. Yhtäläisyyksien lisäksi arvoissa havaittiin myös eroavaisuuksia, joten lisätutkimukselle on tarvetta. Simulaatioita tehtiin myös yhden ja kahden vuoden aikavälille. Laskentojen mukaan lämpötilassa 345 °C melkein kaikki sementtihydraatit ovat hajonneet ja vain dikalsiumsilikaattia on jäljellä. Laskentojen ja kokeellisten tulosten mukaan 95 °C ei ole haitallinen sementtipastalle. 175 °C lämpötila ei ole haitallinen lyhyellä altistuksella, mutta esimerkiksi vuoden jälkeen melkein kaikki kalsium-silikaatti-hydraatti on hajonnut. 345 °C lämpötila on vaarallinen lyhyilläkin altistusajoilla. Laskennoissa ei huomattu eroja tavallisen ja sulfaatinkestävän sementin välillä

Freshwater biology and water supply in Britain

This paper is designed to give a general account of freshwater biology as it bears on waterworks practice. Most water that is used for consumption will commonly go through a storage reservoir. Here special reference is given to the biological relations in standing waters, the biological control of water supplies, methods of plankton estimation, the biology of slow sand filtration and the use of algicides

Studies in the Heterocyclic and Carbocyclic Series

PART I. Catalytic hydrogenation of 2-9'-fluorenyloyclohexanone, prepared by the reaction of 9-bromofluorene and the sodio-derivative of ethyl cyclohexanone carhoxylate and decarbeth-oxylation of the product, has resulted in the isolation of two stereoisomeric alcohols, cis- and trans-2-9' -fluorenyl-cyclohexanol, and a hexahydride of one of these. Both carbinols yield the same product on dehydration with phosphoric acid. The structure of this product is established as 9-cyclo-Delta1-enylfluorene by the following series of steps microhydrogenation and double bond estimation with perphth-alic acid indicate the presence of one double bond, as does the isolation of an epoxide from the perphthalic acid oxidation and a dihydroxy-derivative via the osmium tetroxide-pyridine complex; the position of the double bond is established by the formation of the same product by the dehydration of 1-9'-fluorenylcyclohexanol; The possible alternative structure of cyclohexylidenefluorene (formed by double-bond migration) is excluded by the fact that this compound, prepared by the dehydration of 9-cyclohexylfluoren-9-ol, is distinct from the product. The absorption spectra of these various dehydration products and their hydrogenation product 9-cyclohexylfluorene, have been recorded and shown to be in accord with the structures variously assigned to them. This work extends and corrects that of Hurd and Mold who isolated one alcohol from the hydrogenation of 2-9'-fluorenylcyelohexanone and regarded its dehydration product as 1:9-cyclohexylenefluorene. PART II. The maleic anhydride adduct with 9:10-diphenyianthracene has been prepared (a) according to the procedure of Bachmann and Kloetzel by refluxing the hydrocarbon in xylene with a thirty mole excess of maleic anhydride, and (b) according to the procedure of Dufraisse, Velluz and Velluz by fusing equal weights of the same two reactants. The adducts are shown to be identical by comparison of their melting points and absorption spectra, and by comparison of three derivatives, their diethyl esters, their dimethyl esters and the trans-dimethyl esters obtained by isomerisation. The suggestion of Dufraisse, Velluz and Velluz that the widely different melting points recorded for the adduct prepared by the two methods are due merely to the different procedures adopted in taking the melting points has been experimentally confirmed. The absorption spectra are in agreement with that recorded for the Dufraisse adduct by Gillet who demonstrated that its similarity to the absorption spectrum of 1:4-diphenyl-naphthalene indicated that 1:4-addition of maleic anhydride had taken place instead of the 9:10-addition, normal with other anthracene derivatives. Chemical confirmation of Glllet's structure for the adduct has now been obtained by an estimation with perphthal-ic acid which showed the presence of an ethylenic double bond and by the characterisation of the epoxides prepared by per-phthalie acid oxidation of the diethyl and dimethyl esters of the adduct. No pure products could be isolated when permanganate oxidation and ozonisation were used similarly to attack the isolated double bond. PART III. The structure of the product of the reaction of o-nitro-aniline with 1-naphthylamine, first prepared by Wohl and Lange and described by them as an "amino-naphthophenazine" without assigning it any definite structure, has been established as 5-amino-ang-benzophenazine and not 7-amino-5:12-diazanaphthacene as suggested by Allen and Webster. Deamination to ang-benzophenazine shows the compound to possess that ring system and not the ring system of lin-benzopnen-azine (i. e. 5:12-diazanaphthacene). Comparison (absorption spectrum and melting point) with an authentic sample of 5-amino-ang-benzophenazine shows that the two compounds are identical. PART IV. The Friedel-Crafts reaction of quinolinic anhydride with naphthalene has been thoroughly investigated and found to give poor results under all the experimental conditions which were tried. Two products were isolated; beta-naphthoyl-picolinic acid, so designated because it has a melting point in agreement with that recorded by Jephcott for the compound which he proved to have this structure and which he prepared by a similar Friedel-Crafts reaction, and alpha-naphthoylpicolinic acid whose structure was proved by potassium hydroxide fusion and by a positive Skraup test for a picolinic acid. Numerous attempts to cyclise this alpha-naphthoylpieolinic acid or its zinc dust and ammonia reduction product, beta-naphthylmethylpicolinie acid, using a wide variety of cyclising agents have all proved unsuccessful. From the few examples present in the literature of cyclisations in which the carboxyl group is attached to the nitrogen ring, evidence is adduced in support of the claim that compounds containing a carboxyl group in the alpha-position to the ring nitrogen atom are peculiarly difficult to cyclise and a possible explanation for this phenomenon is suggested