bluuebunny/crossref_metadata_2025 huggingface dataset:
Statistical Comparison of Analysis Results for Lead on Dust Wipe Samples by X-ray Fluorescence Analysis and Flame Atomic Absorption Spectrometry
Authors: Rogers John , Viet Susan , Roda Sandy , Fraser Alexa , Friedman Warren , Zhou Joey , Jacobs David
Published: July 2012

The traditional method of determining dust lead loading (mass per unit area) on surfaces is to send dust wipe samples to a laboratory for analysis, and typically it takes one or more days to obtain results. Field-portable techniques taking 10 to 15 min for dust wipe lead analysis have been developed but need to be further evaluated. Dust wipe samples (n = 878) collected from a nationally representative sample of child care centers were tested by means of x-ray fluorescence (XRF) analysis with two XRF analyzer instrument models and subsequently analyzed for lead using flame atomic absorption spectrometry (FAAS). Samples were collected from floors and interior window sills and included blank and spiked quality control samples. Weighted linear regression was used to model the relationship between XRF and FAAS measurements. The correlations between FAAS and XRF measurements exceeded 0.80 (p < 0.0001). The highly significant statistical correlation suggests that the XRF method could be used to quantify dust lead loadings to determine compliance with dust lead hazard standards as defined by the U.S. Environmental Protection Agency. Small, but significant, differences in regression parameters were found between floor or sill and quality control sample types. The use of 95 % prediction intervals could allow for rapid screening of clearance samples in the field if method standards were developed. Additional work is needed in order for researchers to understand differences among XRF instruments and the conditions under which the use of XRF testing in the field could reduce the time or cost required in order to complete clearance testing.
Educação ambiental em unidades de conservação: políticas públicas e a prática educativa
Authors: Valenti Mayla Willik , Oliveira Haydée Torres de , Dodonov Pavel , Silva Maura Machado
Published: July 2012

O objetivo deste trabalho foi realizar um estudo exploratório sobre as ações de educação ambiental desenvolvidas em unidades de conservação (UCs) brasileiras em relação a público, parcerias, linha pedagógica, objetivos, atividades, temas, avaliação e documentos de referência. Além disso, analisamos uma possível influência do Programa Nacional de Educação Ambiental (ProNEA) nessas práticas. Utilizamos dados de 56 UCs brasileiras coletados em questionário distribuído em 2007. Analisamos o total de UCs e dois grupos distintos: as que citaram e as que não citaram o ProNEA como referência. As ações educativas apresentam alguns princípios das novas tendências da educação ambiental e das políticas públicas elaboradas nos últimos anos no Brasil. Concluímos que embora uma política pública de larga escala, como o ProNEA, seja importante para orientar as mudanças desejadas, não é suficiente para que essas mudanças sejam incorporadas às práticas educativas.
Educação do campo: embate entre Movimento Camponês e Estado
Authors: Ribeiro Marlene
Published: July 2012

O artigo trata do embate entre os diferentes movimentos sociais populares do campo, identificados na unidade provisória Movimento Camponês, que demandam a educação do campo voltada aos seus modos de vida e de trabalho, e o Estado brasileiro, no que concerne aos programas governamentais oferecidos em resposta a essa demanda¹ . Visa a apontar potencialidades da educação do campo, enquanto conquista do Movimento Camponês, e os limites que esta enfrenta, no Brasil, em que o capital agrário e financeiro, relacionado ao agronegócio, disputa a propriedade da terra e exerce pressão sobre o Estado. A importância deste trabalho está em promover uma reflexão sobre os desafios colocados ao Movimento Camponês, enquanto este orienta suas ações por um projeto societário em visível confronto com o modelo neoliberal de sociedade no qual se sustentam as ações do Estado brasileiro.
Os limites da agricultura convencional e as razões de sua persistência: estudo do caso de Sumidouro, RJ
Authors: Stotz Eduardo Navarro
Published: July 2012

A predominância da agricultura convencional, caracterizada sobretudo pelo uso indiscriminado de agrotóxicos, tem levado a pesquisas acerca da percepção sobre a saúde e o ambiente implicados nas práticas agrícolas. Neste estudo, buscou-se compreender a percepção dos limites da agricultura convencional por agricultores familiares e as razões de sua persistência. Consistiu em pesquisa empírica observacional e participativa realizada em Sumidouro, RJ, entre 2006 e 2008. Verificou-se que a agricultura convencional é avaliada positivamente em termos de ganhos econômicos e sociais - dada a redução do tempo de trabalho socialmente necessário resultante do uso de agrotóxicos - e que, apesar da persistência de elementos da agricultura tradicional na memória e da percepção da dependência dos insumos e dos seus impactos, é percebida pelos agricultores como uma determinação de suas vidas. Esses elementos sugerem que, da mesma forma como o sistema agrícola convencional se impôs mediante crédito subsidiado e assistência técnica pública, alterações profundas nessa percepção e no sistema agrícola vigente devem integrar política pública ampla e de longa duração. Esta, por sua vez, deve considerar, dentre outros, a dependência do poder político local em relação aos maiores produtores e comerciantes, inclusive de agrotóxicos, e a necessidade de articulação entre pesquisa e extensão rural com a participação direta dos agricultores.
Em busca da especificidade da influência francesa na análise organizacional no Brasil
Authors: Fachin Roberto C. , Cavedon Neusa Rolita
Published: July 2012

A literatura em administração produzida no Brasil apresenta forte influência da literatura americana, segundo estudos anteriores de acadêmicos brasileiros. Não foram identificados estudos sobre a influência dos países francófonos, particularmente França e Canadá (Québec), na academia brasileira. O trabalho pretende suprir a lacuna quanto à influência desses países, analisada a partir de publicações feitas em periódicos e nos encontros nacionais de administração (Enanpads) dos períodos 1995-99 e 2000-01. Especula-se também quanto à especificidade dessa influência, ou seja, em que áreas ela se manifesta mais detidamente, a julgar pelos autores mais citados. Procede-se também uma comparação da influência dos países francófonos na área de Administração e em outros campos do conhecimento (literatura, filosofia, moda, religião), tentando estabelecer ligações com a maneira' francesa' de ver o mundo.
Evidence of contamination by oil and oil products in the Santos-São Vicente estuary, São Paulo, Brazil
Authors: Azevedo Juliana Souza , Lopes Belisandra , Katsumiti Alberto , Braga Elisabete Santis , Roche Helené , Ribeiro Ciro Alberto Oliveira , Bebianno Maria João
Published: July 2012

Different components of the mixed function oxidase (MFO) system and the levels of fluorescent aromatic compounds in bile (FACs) were measured in Cathorops spixii in order to assess the impact of polycyclic aromatic hydrocarbons (PAHs). Fish were sampled in an estuary (Santos/São Vicente) with a history of contamination by PAHs, mainly due to the presence of the industrial complex of Cubatão city and of another of low anthropogenic influence (Cananéia) on the Brazilian coast. FACs were higher in fish from the polluted site, and the PAH 5 and 6-ring metabolites were the most frequent - with 14% and 15%, respectively. Levels of the different components of the MFO system showed the same variation profile as the FACs for both estuaries. Therefore, the values found for somatic indexes and biomarkers with data of bile PAH metabolites indicate the presence of organic contaminants, especially in the area subject to the influence of the industrial complex on the Santos/São Vicente estuary.
Pattern of distribution and environmental influences on the Scienidae community of the Southeastern Brazilian coast
Authors: Schmidt Thassya Christina dos Santos , Dias June Ferraz
Published: July 2012

The Sciaenids have among the highest species richness, numerical abundance and biomass of any family of fishes along the Brazilian coast. The aim of this study was to analyze the composition and spatial and temporal distribution of as well as the influence of temperature, salinity and depth on the sciaenid assemblage of Santos Bay. A total of 29,306 individuals belonging to 13 genera and 21 species were captured, between November 2004 and December 2005, with Stellifer rastrifer representing 70.4% of the total composition. Highest abundance and biomass occurred on the east side of the bay, and the highest species richness occurred near the mouth of the Santos Channel, which was also the site with least similarity to the other sites. Highest abundances occurred in April 2005 and lowest in September 2005. Key environmental factors influencing distribution of sciaenids were depth and temperature.
Comparação de métodos de mensuração de área foliar para a cultura da melancia
Authors: Souza Marcelo Sobreira de , Alves Samara Sibelle Vieira , Dombroski Jeferson Luiz Dollabona , Freitas José Dijalma Batista de , Aroucha Edna Maria Mendes
Published: July 2012

A determinação da área foliar é de grande importância em estudos agronômicos e fisiológicos, por fornecer informações sobre o metabolismo vegetal, e as técnicas utilizadas devem ser simples, rápidas e precisas. O presente estudo objetivou comparar métodos de mensuração de área foliar, para a cultura da melancia. Para isto, foi avaliada a precisão de quatro métodos de mensuração (experimento 1) e comparada a área foliar, pelo método de integração obtido no equipamento LI-COR® modelo LI 3100, aos 0, 30, 60, 90 e 120 minutos, após determinada com o auxílio de um scanner (experimento 2). O delineamento utilizado no experimento 1 foi o inteiramente casualizado, com quatro tratamentos e 19 repetições. Os tratamentos corresponderam aos métodos Integrador de área foliar AM 300, Integrador de área foliar LI-COR® modelo LI 3100, Discos foliares e Análise de imagem digital (scanner), sendo, estes, comparados com o método referência (scanner), conforme o coeficiente de correlação linear (r). Para o experimento 2, o delineamento utilizado foi o de blocos casualizados com seis tratamentos e dez repetições (folhas), sendo cada folha considerada um bloco, com suas médias comparadas pelo teste Tukey, a 5%. Houve diferença na estimação da área foliar, conforme o método empregado. O método dos discos foliares foi considerado o mais preciso, para a cultura da melancia, e a utilização do LI-COR® modelo 3100 não é recomendada para esta cultura, principalmente quando as leituras são realizadas em maior intervalo de tempo.
Risk factors relating to helminth infections in cows during the peripartum
Authors: Silva Jenevaldo Barbosa da , Rangel Charles Passos , Baêta Bruna de Azevedo , Fonseca Adivaldo Henrique da
Published: July 2012

The aim of this study was to investigate whether season, lactation number, breed standard and milk production were risk factors relating to occurrences of gastrointestinal nematodes in dairy cows during the peripartum period. Eighty-four cows were randomly selected through proportional stratified sampling. In order to analyze the fecal egg per gram (EPG) count, the data were subjected to the Spearman test, Kruskal-Wallis test at 5% significance and linear regression. At the time of calving, the cows showed high EPG counts in relation to all variables analyzed. Among the animals studied, we observed that purebred Holstein cows at their first lactation and with high milk production showed high EPG counts (600) and comprised the group most at risk within the herd studied. In this group, the animals showed moderate EPG during the prepartum period (300) and a significant increase (p < 0.01) in EPG count from the time of calving (900), i.e. an increase of the order of 300%. Selection of animals for milk production in tropical countries should be based not only on productive potential, but also on adaptive features.
Dog parasite incidence and risk factors, from sampling after one-year interval, in Pinhais, Brazil
Authors: Martins Camila Marinelli , Barros Cristiane da Conceição de , Bier Daniele , Marinho Ana Paula , Figueiredo Jaqueline Maria Gonçalves , Hoffmann Juliano Leônidas , Molento Marcelo Beltrão , Biondo Alexander Welker
Published: July 2012

Domestic animals in urban areas may serve as reservoirs for parasitic zoonoses. The aim of this study was to monitor the parasitic status of household dogs in an urban area of Pinhais, in the metropolitan region of Curitiba, Paraná State, Brazil, after a one-year period. In May 2009, fecal samples, skin scrapings and ticks were collected from 171 dogs. Questionnaires were applied to the owners (sex, age, environment and anthelmintic use). In May 2010, 26.3% (45/171) of the dogs were fecal samples reanalysed. From the fecal samples, 33.3% (57/171) in 2009 and 64.4% (29/45) in 2010 were positive. The parasite species most observed were, respectively in 2009 and 2010, Ancylostoma sp., 66.7 and 44.8%, and Strongyloidesstercoralis, 26.3 and 3.4%. All the skin scrapings were negative, and no ticks or protozoa were found. There was no statistical association (p > 0.05) between positive fecal tests and age, sex or environment. In 2009 alone, dogs with a history of antiparasitic drug administration were 2.3 times more likely to be negative. A great number of replacement dogs was noticed one year later. Therefore, isolated antiparasitic treatment strategies may have no impact on parasite control, given the risk of introduction of new agents, thereby limiting the prevention strategies.
Movimentos sociais e análise organizacional: explorando possibilidades a partir da teoria de frames e a de oportunidades políticas
Authors: Rosa Alexandre Reis , Mendonça Patrícia
Published: July 2012

O objetivo deste trabalho consiste em recuperar o debate sobre movimentos sociais e explorar possibilidades de análise organizacional a partir da teoria de frames e a de oportunidades políticas. Para isso, discutimos como os debates sobre movimentos sociais produziram diversas possibilidades de análise, as quais tentaram dar conta de uma dicotomia fundamental no campo, qual seja, a escolha entre "estratégia" ou "identidade" como ênfase da ação coletiva. Entre as alternativas formuladas para superar a respectiva dicotomia, estão as teorias de frames e das oportunidades políticas que, em conjunto, buscam resgatar a dimensão cultural e política dos movimentos sociais. Para discutir a contribuição dessas teorias nas áreas de administração pública, políticas públicas e gestão social, buscou-se trazer exemplos de análises empíricas que fizeram uso de tal literatura recentemente no Brasil. Embora desenvolvida em outro contexto sociopolítico, acreditamos que esta abordagem teórica tem grande potencial analítico e pode ser testada em outras análises que busquem compreender tais dimensões da ação coletiva nos movimentos sociais em contexto brasileiro.
Perceived dysphonia by the clinician's and patient's viewpoint
Authors: Ugulino Ana Celiane , Oliveira Gisele , Behlau Mara
Published: July 2012

PURPOSE: To verify the relationship between the clinician's vocal evaluation and vocal self-assessment and voice-related quality of life. METHODS: Participants were 96 individuals: 48 with vocal complaints and voice deviation (VCG), mean age of 51 years, with diagnosis and indication of voice therapy; and 48 with no vocal complaints and healthy voices (NVCG), mean age of 46 years. All participants answered the Voice-Related Quality of Life (V-RQOL) questionnaire, performed a vocal self-assessment and were submitted to auditory-perceptual analysis of voice. RESULTS: Mean V-RQOL scores were different between groups for all domains. Self-assessment results also showed differences between groups, which was not the case in the auditory-perceptual analysis of sustained vowel and connected speech, showing that the patient's perception was worse than the clinician's. There was correlation between the V-RQOL domains (Socio-emotional and Physical: 76.8%; Socio-emotional and Total: 90.8%; Physical and Total: 95.8%), as well as between the Socio-emotional (-52.9%), Physical (-43.1%) and Total (-52.2%) domains and the self-assessment. However, no correlation was found between auditory-perceptual analysis and self-assessment measures, except for a weak correlation between vocal self-assessment and auditory-perceptual analysis of the sustained vowel (33.3%). CONCLUSION: The clinician's perception does correspond to the individual's self-perception of his/her vocal quality and the impact of a voice deviation on his/her quality of life, but not directly. The individual's perception about his/her vocal quality and voice-related quality of life complements the clinician's perception regarding the overall degree of the voice deviation.
Laboratory method for determining the air content of fresh concrete
Authors: McIntosh J. D. , Preston A. G.
Published: July 2012

Summary:

A method for determining the amount of air entrained in fresh concrete, based on the variation of air volume with pressure, is described and illustrated. It is intended for laboratory use, and from the point of view of convenience in making the test is particularly suitable for this purpose. One form of apparatus can be readily assembled from standard chemical equipment and other common materials. The reproducibility and accuracy of results appear to be good.
Continuous reinforcement in concrete pavement
Authors: Cashell Harry D. , Benham Sanford W.
Published: July 2012

Summary:

Concrete pavements, unless constructed with closely spaced transverse joints, generally crack transversely at frequent intervals. These cracks tend to open appreciably with time unless the pavement is reinforced. For some years there has been a continued interest on the part of highway engineers regarding the practicability of concrete pavements constructed without transverse joints and reinforced longitudinally with continuous bonded steel in sufficient amount to hold all cracks closed.

In the autumn of 1938 a considerable number of continuously reinforced sections, ranging from 20 to 1,310 ft in length, were constructed near Stilesville, Indiana, on US 40 as a co-operative research project to study the effects of varying amounts of longitudinal steel in sections of various lengths.

The behaviour of the sections during the first ten years of service life shows conclusively that continuous reinforcement can be depended upon to prevent the opening of transverse cracks in concrete pavements. In the long, heavily reinforced sections many fine cracks have developed in the central region. These cracks have not opened and have ravelled only slightly with traffic and exposure, a condition that has required no maintenance and may be considered superficial. The sections have remained strong, durable structural units.

The presence of even the heaviest longitudinal bar reinforcement has apparently not affected adversely the condition of the concrete in the pavement. The concrete appears to be sound throughout, there has been no spalling, and there is a complete absence of longitudinal cracking above the bars. Infact, the manner in which the steel has held closed all cracks, especially those in the more heavily reinforced sections, is believed to have been conducive to distributed interfacial pressure at the cracks which should tend to minimize damage to the concrete from concentrations of presswe such as sometimes develop at cracks in plain concrete pavements.

Pumping has developed at many of the transverse joints, but, wth two exceptions, has not been observed at any of the vast number of transverse cracks. This indicates that a concrete pavement without transverse joints and containing adequate longitudinal reinforcement is not nearly so susceptible to pumping as pavements of other designs.

In spite of the many transverse cracks that have developed in the long sections, the riding quality of the pavement has remained excellent and the pavement itself has been protected from damaging impact forces such as tend to develop where the surface alinement is not maintained.
The use of unstressed wires in pre-tensioned concrete members
Authors: Lazarides T. O.
Published: July 2012

Summary:

In the serial fabrication of pre-tensioned concrete members the odd lengths of wire left over are often considered as waste. At the very slight cost of straightening them, these odd lengths of wire could be put to very efficient use. Used as a tensile reinforcement, unstressed wires make it possible to reduce or prevent the formation of cracks and so to increase the ultimate safety factor or to reduce the section or the prestress of a member designed for a given load and span. Used as a shear reinforcement in I-shaped members, unstressed wires are very efficacious in preventing failure by differential shear and so make possible the use of a thinner web; quite short lengths of wire may be used in this fashion.
The deformation of concrete
Authors: Freyssinet E.
Published: July 2012

Summary:

Attention is drawn to our lack of knowledge of the laws of the deformation of concrete, and examples are given of slabs prestressed in two directions which have carried loads four or five times greater than those predicted by classical computation, without cracks being formed.

To explain these and similar cases, the author develops his theory of the constitution of concrete; that it is a complex “solid-liquid” to which the laws of thermodynamics may be applied. This enables general laws to be formulated which explain known experimental results and allow new ones to be predicted. In this way shrinkage, creep, and—in general terms—everything concerning the elastic, plastic, instantaneous and time-dependent deformation of concrete is explained, as well as the well known autogenous healing property of cracked concrete. The paper ends with a discussion of the deformation of concrete in shear.
The compaction of concrete slabs by surface vibration: first series of experiments
Authors: Kirkham R. H. H. , Whiffin A. C.
Published: July 2012

Summary:

An experimental vibrator, operating on the top surface, has been used to compact freshly placed concrete (mix 1:2½:5; water-cement ratio 0·60) of low to very low workability. A study has been made of the effects on the compaction of slabs 18 in. thick of varying the frequency of vibration within the range 1,500-6,000 v.p.m., the acceleration within the range up to 12g, the amplitude within the range 0·004 to 0·064 in., and forward speeds of travel within the range 1-8ft per min. The density of the concrete was measured after test, while measurements were made during the experiments of the vibration occurring at various depths in the concrete.

A small variation in the workability of the concrete was found to have a considerable efIect on the surcharge required and the depth of compaction achieved. Consequently the effect of the method of compaction has only been studied so far for concrete of one workability, only those tests where the compacting factor was within a narrow range around 0·80 being considered.

When the vibrator operated at constant acceleration and constant number of vibrations per foot of travel, increase of amplitude of the beam increased the depth of compaction. At constant acceleration and amplitude of the beam, slower speeds of travel gave increased depth of compaction. When both the amplitude of the beam and number of vibrations per foot run were constant, the depth of compaction was unaffected by change of acceleration.

The total work done on a particle at a given depth was found to be related to the density attained at that depth. A connexion has been found between equivalent depth of compaction and the product of the amplitude of the beam and the number of vibrations per foot run. The depth of compaction increases with this factor but attains a limiting value, probably dependent on the concrete mix and the characteristics of the vibrator. It seems desirable, with vibrators designed to operate at constant acceleration, to operate them with a large amplitude and low frequency.
Tests on concrete beams reinforced with 12 gauge wires of an ultimate strength of 120 tons per sq.in.
Authors: Hajnal-Kónyi K.
Published: July 2012

Summary:

Two beams of 8 × 18 in. cross-section, 12 ft long, reinforced with twenty-eight 12 gauge wires of an ultimate strength of 120 tons per sq.in. were rested to failure on a span of 11 ft. The concrete cube strength was 3,990 and 5,400 lb per sq.in. respectively. In both cases failure occurred by fracture of the reinforcement although the wires were not prestressed. Strain measurements taken at various stages of loading show a linear distribution.

The actual steel stress at failure was much higher than the stress obtained from the stress-strain diagram of the steel on the basis of the average strain measured at 97 per cent of the maximum load.
Crystallographic research on the hydration of Portland cement. A first report on investigations in progress
Authors: Bernal J. D. , Jeffery J. W. , Taylor H. F. W.
Published: July 2012

Summary

The results of investigations carried out at Birkbeck College since 1948 are described.

(a) Anhydrous cement compounds. The crystal structure of tricalcium silicate (C3S) has been determined. The crystal is built from Ca++, (SiO.)4-, and O-- ions; co-ordination of the Ca ions by oxygen is unsymmetrical. In atite, the form present in cement, some Si is replaced by AI, and Mg ions are present in otherwise vacant sites. Possible relationships between structure and cementing properties are discussed.

(b) Hydration Products. At room temperature, action of water on C3S can yield, under appropriate conditions, either of two compounds, calcium silicate hydrates (I) and (II). These differ in composition but are closely related in structure. The first has been detected in a sandtime block, and one of them, probably the second, is present in set C3S pastes. Direct detection of the hydrated compounds in set cement has so far been hindered by experimental difficulties, but it is probable that one or other of these substances is present. Hydrothermal reactions in the CaO-SiO2H2O system have been studied; it is probable that steam curing of cement at 100°C does not yield silicate hydration products very different from those formed at room temperature, but that at 180°, basically different compounds may be produced.

Calcium silicate hydrate (I) has a layer structure, in which entry or removal of water molecules, due to changes in temperature and/or humidity alters the inter-layer spacing. The layers themselves are elongated in one direction, giving rise to a fibrous structure. These facts may explain the cementing power of the substance, and may also account for the volume changes observed in set cement.
Tests of properties of fresh concrete
Authors: Bergström Sven G.
Published: July 2012

Summary

A description is given of a deformability meter for studying the properties of fresh concrete which has been evolved at the Swedish Cement and Concrete Research Institute. Examples are adduced to demonstrate the effects produced by varying mixes and by the admixture of resins. The test results afford information on the tendency to segregation and the workability of the concrete. This information permits certain qualitative forecasts regarding the properties of hardened concrete.
The design of reinforced concrete beams of large initial curvature
Authors: Wright W.
Published: July 2012

Summary

When the initial curvature of a reinforced concrete section is large in comparison with its depth, the stress can no longer be assumed to increase linearly outwards from the “gravity”* axis and, as a result, the neutral axis is displaced towards the centre of curvature. In this paper the appropriate equations for balanced design are derived and design charts for pure bending are given for one set of values of the permissible stresses and modular ratio.
The design and use of a demountable mechanical strain gauge for concrete structures
Authors: Morice P. B. , Base G. D
Published: July 2012

Summary

This paper describes the principle, design and use of a form of demountable mechanical strain gauge which has been found particularly useful for determining strains in concrete structures. The instrument which uses a lever and dial gauge is cheap to make and use, and is located on 8 in. gauge lengths which are formed by pairs of punched and drilled steel discs glued to the concrete surface.

With practice, 200 strains per hour may be measured with an accuracy of about ±5 × 10−6 under most laboratory test conditions. Even greater accuracy has been obtained using the gauge in its ideal horizontal position and with the readings lying within a small range on the dial. In development tests of this kind 90 per cent of measured strains were within ±3 × 10−6 of the mean.

Tests on various locating discs show that normal, drilled mild steel discs give the best results.
Curing temperature, age and strength of concrete
Authors: Bergström Sven G.
Published: July 2012

Summary

The effects of curing temperature and age on the strength of concrete can be expressed in terms of a single parameter given by the product of age and temperature, as has been suggested by Nurse.(1)*· and Saul.(2) In this parameter, the temperature is reckoned from — l0°C, which seems to be a reasonable value of the lowest temperature at which any appreciable increase in strength can take place. In the present paper, the correctness of this assumption is verified by means of check calculations made on previously known test series and on some new Swedish tests. It is to be noted, however, that special precautions must be taken to protect the concrete from freezing during the initial period after placing, and that the humidity of the ambient air must be taken into account. Moreover, the deterioration of concrete subjected to repeated freezing and thawing must be studied as a separate problem.
Creep tests on prestressing steel
Authors: Gifford F. W.
Published: July 2012

Summary

Details are given of tests on 0·2 in. diameter prestressing steel maintained under approximately constant strain, in order to determine the relaxation of stress at various initial loads, including the effect of initial overstressing.

A special testing technique was developed facilitating a simple but sensitive method of measuring the force in the wires, which were of a sufficient length to give a good average value of the effect of creep.
Effect of various factors on the flexural strength of concrete test beams
Authors: Nielsen Knud E. C.
Published: July 2012

Summary

The paper describes bend tests on plain concrete beams carried out by the author at the Swedish Cement and Concrete Research Institute, Stockholm (the CBI), as part of their research programme. The test results are here used as a basis for an analysis of the effect of various factors on the flexural strength of concrete test beams.

The reported results of previous workers in this field are summarized and discussed. These are so presented as to provide additional data for an analysis of the applicability of various theories of the effect of dimensions of the test specimen.

The paper closes with some practical considerations which should be taken into account when determining the flexural strength of plain concrete beams.
The workability of vibrated concrete
Authors: Plowman J. M.
Published: July 2012

Summary

The paper describes a method of comparing the workability of mixes of low water content by measuring the power required to vibrate them under standard conditions. A relationship between the number of gaps in a grading and the average power demand is obtained from energy-time curves for various mixes and types of grading. An example illustrates the use of this relationship in calculating the weight of concrete which can be vibrated on a table under given conditions.
Statistical methods in concrete research
Authors: Wright P. J. F.
Published: July 2012

Summary

The application of statistical methods has helped greatly in planning and interpreting concrete research at the Road Research Laboratory and, as no statistical text-book deals specifically with the problems of concrete technology, this paper aims to bring such methods to the attention of research workers elsewhere.

The assessment of variation in test results is discussed and some useful statistical processes are introduced. These include a test for the difference between two sets of results, the method of analysing the causes of variation in test data and the fitting of equations to experimentally determined relationships between two variables. An appendix gives a method for fitting a Gaussian distribution to a series of test results.

A subsequent paper will deal with the design of experiments in concrete research.
Heat of hydration in concrete
Authors: Rastrup Erik
Published: July 2012

Summary

The paper traces the development of a function between time and temperature, which makes it possible to refer the process of hardening of concrete at varying temperature to hardening at constant temperature.

It is further shown that it is possible to predetermine the temperature of concrete during hardening when properties of concrete, sizes and shape of the specimen, insulation and external temperature are known. The time temperature function can also be applied to the development of strength. The validity of the theory is demonstrated by the results of tests upon 27 American and 3 Danish cements.
An investigation of the erosive effect on concrete of soft water of low pH value
Authors: Halstead P. E.
Published: July 2012

Summary

An investigation is described in which the effect of soft moorland water on concrete has been studied by tests on 4 in. concrete cubes. Cubes were immersed in moorland water or tap water for periods of up to four years and were then weighed and crushed to determine their compressive strength. After immersion in soft water, all types of concrete lost strength and weight to an extent which increased as the immersion was prolonged. Cubes made of Portland cement concrete of very high strength or high alumina cement concrete lost about one-third of their strength after four years' immersion. Cubes of concrete of all other types, irrespectire of strength or kind of cement used, lost about half their strength after four years' immersion. Concrete containing entrained air behaved similarly, but concrete painted with bitumen maintained its strength whilst the coating was intact.
An investigation into methods of carrying out accelerated freezing and thawing tests on concrete
Authors: Wright P. J. F. , Gregory J. M.
Published: July 2012

Summary

It was noted in earlier investigations that accelerated freezing and thawing tests on concrete carried out using a continuously refrigerated room produced results more rapidly than similar tests using a cabinet-type refrigerator, although in each case the specimens reached the same limiting temperatures of about 5° and 60°F. Attempts have therefore been made to modify the technique so that results can be obtained more rapidly in the refrigerator.

The tests show that damage occurs more rapidly when specimens are frozen immersed in water than when frozen in air, although the rate offreezing is lower. This suggests that evaporation of water from the surface of the specimens before freezing may mitigate the damage by reducing the stresses developed near the surface when the water freezes. Little was gained by the use of a brine bath surrounding the water-immersed specimens.

Measurements of the temperatures of the specimens during freezing and thawing suggest that two cycles per day could be carried out successfully in the refrigerator in place of the one cycle per day formerly used.
An energy approximation to the solution of a corner-supported rectangular slab
Authors: Morice P. B.
Published: July 2012

Summary

The Rayleigh-Ritz method is used to obtain an approximate solution to the problem of the de flexion of a rectangular flat slab supported only at its four corners and loaded with either an arbitrarily positioned point load or uniformly distributed load. The assumed functional approximation does not completely satisfy the stress-free boundary condition, yet despite this experimental results show reasonable agreement with the predicted values in the case of single concentrated loads on two steel plates.
A vibration method for measuring the thickness of concrete road slabs in situ
Authors: Jones R.
Published: July 2012

Summary

A method has been devised for determining the thickness of concrete road slabs by measuring, at the surface of the slab, the velocity of propagation of vibrations at audio and ultrasonic frequencies.

A vibration generator acting vertically on the surface of the slab produces vibrations of known frequency which are detected by a pick-up. The pick-up is moved progressively away from the generator and positions are noted at which the vibrations at the generator and pick-up are in phase. The distance between successive positions gives the wavelength (λ) of the vibrations; the velocity of propagation is determined from the product of the wavelength and frequency.

In the frequency range from 1,000 c/s to 4,000 c/s, the vibrations are identified asffexural waves and their velocity (V) depends upon the frequency, the thickness (T), and the elastic constants of the concrete slab. At frequencies above 50 kc/s, the velocity is constant, and the propagation becomes sensibly independent of the frequency and the thickness of the slab, i.e. it is then the Rayleigh wave velocity (VR) of surface waves in the concrete. From the theoretical analysis, a graph is prepared giving the variation of V/VR with the quantity πT/λ, and this enables the thickness of the slab to be calculated from the experimental results.

Tests have been made on slabs of thicknesses varying from 4 to 9 in., some slabs being laid directly on the subgrade and some on prepared bases of soil cement and hoggin. The results have generally been satisfactory and, in many cases, the dimensions of cores drilled from the slabs have agreed with the calculated values of thickness to within ±10 per cent.
Some tests on the effect of time on transmission length in pre-tensioned concrete
Authors: Base G. D.
Published: July 2012

Summary

A certain amount of work already published has indicated that the transmission length in pre-tensioned concrete increases very considerably with time. Evans reports a transmission length increase for 0·08 in. diameter high-tensile steel wire from 58 diameters to 125 diameters in two and a half years, with most of the increase taking place in the first month after transfer. A Swiss report also quotes figures showing an eventual doubling of the transmission length at transfer for wire of 2 and 3 mm diameter.

Recent work by the Cement and Concrete Association on 0·2 in. diameter smooth wire indicates no such increase in transmission length, there being little movement, over several months, of the point at which maximum concrete strains were reached in the units tested.
The sleeve pump for semi-solids
Authors: Ede A. N.
Published: July 2012

Summary

A pumping cycle has been designed for unsaturated fragmentary materials which makes use of the pumped material jammed in a tubular sleeve as a piston for forcing forward further material in an outlet barrel. The return stroke of the sleeve is made at rapid acceleration, releasing the material in the forward position and resetting the sleeve for a further cycle. Preliminary performance figures are given, and the means of application to pumping concrete is indicated.
The investigation of the quality of thick concrete by ultrasonic pulse propagation
Authors: Cawkell A. E.
Published: July 2012

Summary

The velocity of ultrasonic pulses through concrete is measured by an oscillograph timing technique. The relation between velocity and concrete quality has been described els ewhere. To increase the rangge—about 8 ft through good quality concrete with the standard instrument (type UCT)—higher power, and low frequency sharply directional magnetostriction tranducers were used.

Practical details of the tests are described, and it is considered that 20 ft is the maximum path length possible with this method.

Further developments are discussed.
Some relaxation tests on prestressing wire
Authors: Kajfasz Stanislaw
Published: July 2012

Summary

The paper describes relaxation tests performed on single and twin-twisted prestressing wire, and the results are compared with published results of other investigations. A general equation relating relaxation, stress and time is developed, and the results are shown to be in good agreement with this.
The effects of age and water/cement ratio upon the relation between ultrasonic pulse velocity and compressive strength of concrete
Authors: Kaplan M. F.
Published: July 2012

Summary

Experiments have been made on concretes with varying aggregate/cement and water/cement ratios, with the main object of ascertaining the effects of changes in age and water/cement ratio upon the relation between ultrasonic pulse velocity and the compressive strength of concrete. It was found that the ratio of changes in pulse velocity and compressive strength due to a change in water/cement ratio is not generally the same as that due to a change in age. Because of this, the relation between pulse velocity and compressive strength cannot be expected to be independent of age and water/cement ratio. It appears, however, that, for compressive strengths up to about 4,000 lb/in2, the relation may for practical purposes be regarded as being so. For concrete of the same aggregate)cement ratio, it was found that low pulse velocity at an early age predicts low strength at later ages.
Synthetic compounds related to tobermorite: an electron-microscope, X-ray, and dehydration study
Authors: Gard J. A. , Howison J. W. , Taylor H. F. W.
Published: July 2012

Summary

Tobermorite-like preparations with Ca/Si ratios in the range 0·8–1·4 have been synthesized at room temperature and hydrothermally, and a systematic study has been made using the methods indicated in the title. The results are compatible with the existence of three phases: tobermorite (5CaO.6SiO2.5H2O), CSH(I) (0·8–1·33 CaO.SiO2.aq.), and CSH(II) (1·5–2·0 CaO.SiO2.aq.). CSH(II) may have a layer structure in which one surface of each layer is composed of hydroxyl groups, analogous in some respects to the hydrated form of the clay mineral, halloysite. The evidence of the electron microscope gives some clues to possible mechanisms of conversion of CSH(I) and CSH(II) into tobermorite.
The use of models of reinforced concrete structures
Authors: Fumagalli Emanuele
Published: July 2012

Summary

This paper discusses the use of models to determine the behaviour of full-scale structures in reinforced concrete, with particular reference to recent work done at the ISMES laboratories in Bergamo, Italy.
A co-ordinated approach to the shrinkage testing of concretes and mortars
Authors: Fulton F. S.
Published: July 2012

Summary

Investigations into the shrinkage of concretes and mortars are seldom sufficiently comprehensive. In consequence, the results are often related to one particular factor which is regarded as having a major influence on shrinkage.

In this paper a theory is developed which correlates fairly well with observed results, and which draws attention to the various factors which should be studied in any fundamental investigation into shrinkage.

An empirical formula is also put forward which correlates well with accepted shrinkage values. It is suggested that, for any aggregate or combination of aggregates, a shrinkage index may be determined empirically which permits an evaluation of the shrinkage potentialities of mixes made with such aggregates, and which may be used to predict the shrinkages of comparable mixes.

Finally it is pointed out that the interpretation of shrinkage test results presents considerable difficulty.
Relation between the change of water content and the consistence of fresh concrete
Authors: Popovics Sándor
Published: July 2012

Summary

The assumption that a change of consistence in a concrete mix that is due solely to a change of water content is independent of the composition of the mix (type of cement, cement content, original water content, original water/cement ratio, air content, grading and maximum size of aggregate) is tested and shown to be valid within wide limits. This assumption is called “assumption of independence” and its use in the prediction of consistence is called “k procedure”.

In the appraisal of this assumption, it is first proven mathematically that the assumption of independence is identical with the assumption that the consistence of concrete is a parabolic function of the water content, and the degree of the parabola is independent of the composition. Then it is shown that for six methods of measuring consistence the experimental results substantiate the existence of such a parabolic relation within wide limits.

A parabolic formula for the k thinning factor is derived, and its numerical forms for six methods of measuring consistence are presented. It is shown for various cases that the use of the k factor in the prediction of consistence is simple and the calculated results are in accordance with experimental data.
A simple technique for recording load-strain curves for concrete beams loaded in flexure
Authors: Trott J. J.
Published: July 2012

Summary

A method is described for automatically recording load versus strain using a commercial X-Y plotter. Typical curves are given showing the results obtained with pavement-quality concrete and with lean concrete. The modulus of elasticity of the lean concrete was derived from the tangent to the load-strain curve at the origin and was found to be less than that obtained by resonance tests. A reasonable correlation was found between the elastic modulus and the strains at which micro-cracking was assumed to begin.
The distribution of pressure in a model silo containing cement
Authors: Lenczner D.
Published: July 2012

Summary

This paper, which is an extract from a wider field of investigation of the pressure distribution in a model silo containing different materials, at rest and during flow, describes tests with cement at rest. The results are compared with some of the better-known theories on silos. The main conclusions are that the pressure distribution on the silo base with cement at rest is not uniform hut decreases from the centre outwards, that Janssen's fundamental assumptions when applied to cement are wrong, and that laky's theory over-estimates the load carried by the silo walls whereas, for silos of proportions commonly met in practice, Airy's theory gives quite satisfactory results.
A new hypothesis of sulphate expansion
Authors: Chatterji S. , Jeffery J. W.
Published: July 2012

Summary

On the basis of published data and their own observations, the authors suggest that sulphate expansion is caused by the solid state conversion of C4AH13 to calcium aluminate monosulphate and that this expansion mayor may not be accommodated depending on the concentration of lime in the liquid phase.
Relation between phase composition, over-all porosity and strength of hardened lime-pozzolana pastes
Authors: Jambor Jaromir
Published: July 2012

Summary

By means of X-ray analysis, differential and gravimetric thermal analysis, electron microscopy, and chemical analysis, the main hydration products of 22 pastes made from lime and various pozzolanic materials and hardened in water for 400 days were found to be calcium hydro-silicates of the tobermorite group (approximate formula C0·8-1·1.S.H0·9-1·5) and Strätling's compound, C2ASH11. A formula is developed giving the compressive strength of the pastes in terms of the volume of the hydration products produced.
A concrete jetty with frost damage
Authors: Idorn G. M.
Published: July 2012

Summary

A mass-concrete jetty by the Baltic Sea was inspected because its surface had deteriorated. The observations suggest freezing and thawing as the obvious cause of damage. As an introduction and for comparison, some examples of frost damage to concrete in Denmark are described.