bluuebunny/crossref_metadata_2025 huggingface dataset:
BMP signaling induces digit regeneration in neonatal mice
Authors: Yu Ling , Han Manjong , Yan Mingquan , Lee Eun-Chee , Lee Jangwoo , Muneoka Ken
Published: January 2010

The regenerating digit tip of mice is a novel epimorphic response in mammals that is similar to fingertip regeneration in humans. Both display restricted regenerative capabilities that are amputation-level dependent. Using this endogenous regeneration model in neonatal mice, we have found that noggin treatment inhibits regeneration, thus suggesting a bone morphogenetic protein (BMP) requirement. Using non-regenerating amputation wounds, we show that BMP7 or BMP2 can induce a regenerative response. BMP-induced regeneration involves the formation of a mammalian digit blastema. Unlike the endogenous regeneration response that involves redifferentiation by direct ossification (evolved regeneration), the BMP-induced response involves endochondral ossification (redevelopment). Our evidence suggests that BMP treatment triggers a reprogramming event that re-initiates digit tip development at the amputation wound. These studies demonstrate for the first time that the postnatal mammalian digit has latent regenerative capabilities that can be induced by growth factor treatment.
Idiosyncratically tuned switching behavior of riboswitch aptamer domains revealed by comparative small-angle X-ray scattering analysis
Authors: Baird Nathan J. , Ferré-D'Amaré Adrian R.
Published: January 2010

Riboswitches are structured mRNA elements that regulate gene expression upon binding specific cellular metabolites. It is thought that the highly conserved metabolite-binding domains of riboswitches undergo conformational change upon binding their cognate ligands. To investigate the generality of such a mechanism, we employed small-angle X-ray scattering (SAXS). We probed the nature of the global metabolite-induced response of the metabolite-binding domains of four different riboswitches that bind, respectively, thiamine pyrophosphate (TPP), flavin mononucleotide (FMN), lysine, and S-adenosyl methionine (SAM). We find that each RNA is unique in its global structural response to metabolite. Whereas some RNAs exhibit distinct free and bound conformations, others are globally insensitive to the presence of metabolite. Thus, a global conformational change of the metabolite-binding domain is not a requirement for riboswitch function. It is possible that the range of behaviors observed by SAXS, rather than being a biophysical idiosyncrasy, reflects adaptation of riboswitches to the regulatory requirements of their individual genomic context.
Improving small-angle X-ray scattering data for structural analyses of the RNA world
Authors: Rambo Robert P. , Tainer John A.
Published: January 2010

Defining the shape, conformation, or assembly state of an RNA in solution often requires multiple investigative tools ranging from nucleotide analog interference mapping to X-ray crystallography. A key addition to this toolbox is small-angle X-ray scattering (SAXS). SAXS provides direct structural information regarding the size, shape, and flexibility of the particle in solution and has proven powerful for analyses of RNA structures with minimal requirements for sample concentration and volumes. In principle, SAXS can provide reliable data on small and large RNA molecules. In practice, SAXS investigations of RNA samples can show inconsistencies that suggest limitations in the SAXS experimental analyses or problems with the samples. Here, we show through investigations on the SAM-I riboswitch, the Group I intron P4-P6 domain, 30S ribosomal subunit from Sulfolobus solfataricus (30S), brome mosaic virus tRNA-like structure (BMV TLS), Thermotoga maritima asd lysine riboswitch, the recombinant tRNAval, and yeast tRNAphe that many problems with SAXS experiments on RNA samples derive from heterogeneity of the folded RNA. Furthermore, we propose and test a general approach to reducing these sample limitations for accurate SAXS analyses of RNA. Together our method and results show that SAXS with synchrotron radiation has great potential to provide accurate RNA shapes, conformations, and assembly states in solution that inform RNA biological functions in fundamental ways.
Two forms of RNA editing are required for tRNA maturation in Physarum mitochondria
Authors: Gott Jonatha M. , Somerlot Benjamin H. , Gray Michael W.
Published: January 2010

The mitochondrial genome of Physarum polycephalum encodes five tRNAs, four of which are edited by nucleotide insertion. Two of these tRNAs, tRNAmet1 and tRNAmet2, contain predicted mismatches at the beginning (proximal end) of the acceptor stem. In addition, the putative 5′ end of tRNAmet2 overlaps the 3′ end of a small, abundant, noncoding RNA, which we term ppoRNA. These anomalies led us to hypothesize that these two Physarum mitochondrial tRNAs undergo additional editing events. Here, we show that tRNAmet1 and tRNAmet2 each has a nonencoded G at its 5′ end. In contrast to the other nucleotides that are added to Physarum mitochondrial RNAs, these extra G residues are likely added post-transcriptionally based on (1) the absence of added G in precursor transcripts containing inserted C and AA residues, (2) the presence of potential intermediates characteristic of 5′ replacement editing, and (3) preferential incorporation of GTP into tRNA molecules under conditions that do not support transcription. This is the first report of both post-transcriptional nucleotide insertions and the addition of single Gs in P. polycephalum mitochondrial transcripts. We postulate that tRNAmet1 and tRNAmet2 are acted upon by an activity similar to that present in the mitochondria of certain other amoebozoons and chytrid fungi, suggesting that enzymes that repair the 5′ end of tRNAs may be widespread.
Structure of the Arabidopsis thaliana DCL4 DUF283 domain reveals a noncanonical double-stranded RNA-binding fold for protein–protein interaction
Authors: Qin Haina , Chen Fading , Huan Xuelu , Machida Satoru , Song Jianxing , Yuan Y. Adam
Published: January 2010

Dicer or Dicer-like (DCL) protein is a catalytic component involved in microRNA (miRNA) or small interference RNA (siRNA) processing pathway, whose fragment structures have been partially solved. However, the structure and function of the unique DUF283 domain within dicer is largely unknown. Here we report the first structure of the DUF283 domain from the Arabidopsis thaliana DCL4. The DUF283 domain adopts an α-β-β-β-α topology and resembles the structural similarity to the double-stranded RNA-binding domain. Notably, the N-terminal α helix of DUF283 runs cross over the C-terminal α helix orthogonally, therefore, N- and C-termini of DUF283 are in close proximity. Biochemical analysis shows that the DUF283 domain of DCL4 displays weak dsRNA binding affinity and specifically binds to double-stranded RNA-binding domain 1 (dsRBD1) of Arabidopsis DRB4, whereas the DUF283 domain of DCL1 specifically binds to dsRBD2 of Arabidopsis HYL1. These data suggest a potential functional role of the Arabidopsis DUF283 domain in target selection in small RNA processing.
Vendor and Client Interaction for Requirements Assessment in Software Development: Implications for Feedback Process
Authors: Jayanth Rajiv , Jacob Varghese S. , Radhakrishnan Suresh
Published: January 2010

We study agency problems that arise when prototypes are used for requirements assessment. The precision with which the prototype helps a client assess his requirements depends on (a) the type of prototype provided by the vendor and (b) the client's feedback effort. The vendor can provide either a neutral or nonneutral prototype: The nonneutral prototype influences the client towards one particular set of requirements that may not be the true requirement, and the neutral prototype allows the client to assess his true requirements. This leads to the vendor's moral hazard problem. The client chooses to exert either the high or low feedback effort after the vendor provides the prototype. Because the effort is unobservable to the vendor, it can lead to the client exerting the low feedback effort: the client's commitment problem. In this paper we develop and discuss the role of the contract payment to provide the vendor with incentives to supply the neutral prototype, as well as for the client to commit to the high feedback effort. In this setting, we also examine the “anchoring” effect, wherein even a high-feedback effort can influence the client more toward a particular set of requirements with the nonneutral prototype. Our results highlight the interplay among the feedback effort, anchoring, and vendor payments.
An Analysis of Incentives for Network Infrastructure Investment Under Different Pricing Strategies
Authors: Gupta Alok , Jukic Boris , Stahl Dale O. , Whinston Andrew B.
Published: January 2010

The Internet is making a significant transition from primarily a network of desktop computers to a network variety of connected information devices such as personal digital assistants and global positioning system-based devices. On the other hand, new paradigms such as overlay networks are defining service-based logical architecture for the network services that make locating content and routing more efficient. Along with Internet2's proposed service-based routing, overlay networks will create a new set of challenges in the provision and management of content over the network. However, a lack of proper infrastructure investment incentive may lead to an environment where network growth may not keep pace with the service requirements. In this paper, we present an analysis of investment incentives for network infrastructure owners under two different pricing strategies: congestion-based negative externality pricing and the prevalent flat-rate pricing. We develop a theoretically motivated gradient-based heuristic to compute maximum capacity that a network provider will be willing to invest in under different pricing schemes. The heuristic appropriates different capacities to different network components based on demand for these components. We then use a simulation model to compare the impact of dynamic congestion-based pricing with flat-rate pricing on the choice of capacity level by the infrastructure provider. The simulation model implements the heuristic and ensures that near-optimal level of capacity is allocated to each network component by checking theoretical optimality conditions. We investigate the impact of a variety of factors, including the per unit cost of capacity of a network resource, average value of the users' requests, average level of users' tolerance for delay, and the level of exogenous demand for services on the network. Our results indicate that relationships between these factors are crucial in determining which of the two pricing schemes results in a higher level of socially optimal network capacity. The simulation results provide a possible explanation for the evolution of the Internet pricing from time-based to flat-rate pricing. The results also indicate that regardless of how these factors are related, the average stream of the net benefits realized under congestion-based pricing tends to be higher than the average net benefits realized under flat-rate pricing. These central results point to the fallacy of the arguments presented by the supporters of net neutrality that do not consider the incentives for private investment in network capacity.
Subgame Perfection in Positive Recursive Games with Perfect Information
Authors: Flesch J. , Kuipers J. , Schoenmakers G. , Vrieze K.
Published: January 2010

We consider a class of n-player stochastic games with the following properties: (1) in every state, the transitions are controlled by one player; (2) the payoffs are equal to zero in every nonabsorbing state; (3) the payoffs are nonnegative in every absorbing state. We propose a new iterative method to analyze these games. With respect to the expected average reward, we prove the existence of a subgame-perfect ε-equilibrium in pure strategies for every ε > 0. Moreover, if all transitions are deterministic, we obtain a subgame-perfect 0-equilibrium in pure strategies.
Flexor carpi ulnaris tendon transfer to the split brachioradialis tendon to restore supination in paralytic forearms
Authors: Anderson G. A. , Thomas B. P. , Pallapati S. C. R.
Published: February 2010

Inability to actively supinate the forearm makes common activities of daily living and certain vocational activities awkward or impossible to perform. A total of 11 patients with deficient supination of the arm underwent transfer of the tendon of flexor carpi ulnaris to the split tendon of brachioradialis with its bony insertion into the radial styloid left intact. Active supination beyond neutral rotation was a mean of 37.2° (25° to 49.5°) at a minimum follow-up of three years, representing a significant improvement (95% confidence interval 25 to 50, p < 0.001). Functional evaluation of the hand after this transfer showed excellent and good results in ten patients and fair in one.

The split tendon of brachioradialis as an insertion for transfer of the flexor carpi ulnaris appears to provide adequate supination of the forearm without altering the available pronation and avoids the domination of wrist extension sometimes associated with transfers of the flexor carpi ulnaris to the radial extensors of the wrist.
Posteromedial meniscocapsular injury associated with rupture of the anterior cruciate ligament
Authors: Bollen S. R.
Published: February 2010

While injury to the posterolateral corner is accepted as a relatively common occurrence associated with rupture of the anterior cruciate ligament, posteromedial meniscocapsular injury has not previously been recognised as such. In a prospective assessment of 183 consecutive reconstructions of the anterior cruciate ligament this injury was observed in 17 cases, giving it an incidence of 9.3%. Clinically, it was associated with a mild anteromedial rotatory subluxation and it is important not to confuse this with posterolateral rotatory subluxation. In no case was this injury identified by MRI. The possible long-term clinical relevance is discussed.
Counting the cost of surgical training: perspective from a school of surgery
Authors: Young A , Redfern N , Sher L
Published: January 2010

It has long been acknowledged that hospital doctors train their juniors with only limited extra time or support and little formal training for their role. The introduction of job planning was intended to recognise formally the additional time needed for this and other activities and the new Postgraduate Medical Education and Training Board (PMETB) standards for trainers are intended to address the need for faculty development. If these Standards for trainers are to be achieved, regulators may need to provide clearer guidance to trusts about the time required in job plans to deliver the expected standard of educational and clinical supervision and other deanery and royal college educational roles.
The leading edge: a year in the FGDP(UK)
Authors: Worker Charlotte
Published: January 2010

The Faculty of General Dental Practice (UK) has seen a number of key successes during 2009 and brought many initiatives to fruition, while several new projects have begun in earnest.
Diploma in Child Health: a surgical perspective
Authors: Grainger J
Published: January 2010

As a specialist registrar in otolaryngology a number of people have asked why I did the Diploma in Child Health (DCH) and what I gained from it. Prior to setting out on the route to the diploma my medical paediatric knowledge was essentially limited to that gleaned from four weeks of undergraduate training several years ago. I felt it would be helpful to update my limited paediatric knowledge and felt sure that the DCH would be the best way of achieving this. Through the process of taking the diploma, I certainly feel that I have gained a lot and suggest that the DCH should be considered by more surgical trainees.
Extending collaborations for knowledge translation: lessons from the community-based participatory research literature
Authors: Lencucha Raphael , Kothari Anita , Hamel Nadia
Published: January 2010

The purpose of this paper is to expand the current focus on researcher–decision maker knowledge translation (KT) partnerships to include community partners. Lessons were drawn from the community-based participatory research literature. An inductive thematic analysis was conducted, using 42 eligible articles, and resulted in the identification of four themes (principles, structure, process and relationships) and associated factors that could contribute to KT collaborations among the three groups of actors. These findings are presented in a KT Triad framework. Thus, the framework provides specific lessons to facilitate researcher– decision maker–community collaborations based on an established body of literature. Including community partners in the KT process is important for integrating community context and needs into research-to-policy deliberations.
‘What do we know? What should we do?’ Melding research validity and rhetoric in the analysis of policy making
Authors: Pearson Mark
Published: January 2010

‘Evidence-based policy and practice’ was proposed to usher in an era where explicit use was made of evidence (‘what we know’) to inform decisions made about policy and practice (‘what we should do’). Critics have focused on its allegedly technocratic nature, motivating some to develop analyses of policy making that take account of inherent social processes. One example is rhetorical analysis, which focuses on the use of discourse and argumentation in the policy-making process (Russell et al, 2008). In this paper, I welcome the insights that can be attained using rhetorical analysis, but argue that too dramatic a swing towards an interpretivist approach risks jettisoning valuable work on research validity. I argue, with reference to the work of social research methodologist Donald Campbell and colleagues, that it is both possible and desirable to meld research validity and rhetoric in furthering our understanding of the policy-making process.
Developing a guide to support the knowledge translation component of the grant application process
Authors: Goering Paula , Ross Suzanne , Jacobson Nora , Butterill Dale
Published: January 2010

Research funding agencies often expect that grant applications include a knowledge translation (KT) plan but many applicants and reviewers are without any clear idea of how to develop or assess such a plan. This paper arises from the development of a guide to support the KT component of the research grant application process. The authors reflect on some of the controversial issues related to KT definitions and scope that they struggled with as they developed the guide. Recommendations regarding implementation include training for reviewers and applicants as well as building broad infrastructure supports. The paper will be of interest to both practitioners and funders of research.
Clinical application of a lectin-antibody ELISA to measure fucosylated haptoglobin in sera of patients with pancreatic cancer
Authors: Matsumoto Hitoshi , Shinzaki Shinichiro , Narisada Megumi , Kawamoto Sayuri , Kuwamoto Kana , Moriwaki Kenta , Kanke Futoshi , Satomura Shinji , Kumada Takashi , Miyoshi Eiji
Published: February 2010

Background: Recent advanced techniques in glycobiology have produced a number of tumor marker candidates. As a result from the glycomic approach, we found that fucosylated haptoglobin in sera was a possible tumor marker for pancreatic cancer (PC). Although Aleuria aurantia lectin (AAL) blotting can detect fucosylated haptoglobin, it is difficult to quantify fucosylated haptoglobin precisely. To overcome this problem, we developed a fucosylated haptoglobin detection kit as a sandwich enzyme-linked immune sorbent assay (ELISA) using AAL and the Fab portion of anti-haptoglobin antibody. In the present study, we investigated the clinical application of this lectin-antibody ELISA kit to measure fucosylated haptoglobin in PC.

Methods: We measured fucosylated haptoglobin in patients with PC with a lectin-antibody ELISA kit. The fucosylated haptoglobin measured with this assay was compared with lectin blotting data, and the discrepancy was analyzed by immunoprecipitation methods. The concentration of fucosylated haptoglobin was investigated with respect to the clinical stage of PC. We also measured fucosylated haptoglobin, using 397 cases of several types of cancers including PC, benign diseases, and normal controls.

Results: The sensitivity and specificity for the differential diagnosis of PC from normal controls was 50% and 91%, respectively. The results from lectin-antibody ELISA were significantly correlated with data from previous AAL blotting studies. Positive rates of fucosylated haptoglobin with this method in patients with PC were significantly higher in cases of stage IV compared with other clinical stages. Fucosylated haptoglobin was increased in several types of cancers, in which fucosylated haptoglobin was reported to increase.

Conclusions: While certain cases showed a discrepancy in fucosylated haptoglobin concentrations between the lectin-antibody ELISA and conventional lectin blotting, this novel type of lectin-antibody ELISA might be useful for a tumor marker for PC.

Clin Chem Lab Med 2010;48:505–12.
A Procedure for Testing Concrete Masonry Unit (CMU) Mixes
Authors: Berg ER , Neal JA
Published: January 2010

A laboratory method for the evaluation of concrete masonry unit (CMU) mix designs is proposed. The zero slump requirement and the unique method of molding CMU using simultaneous vibration and compression on an automated assembly line basis make CMU mix design a unique subset of concrete mix design. The compression and vibration of a block machine is simulated by the use of a drop hammer to compact the test specimens. The different compaction methods are equated by modifying the height of the hammer drop or the number of drops to obtain the same density as that obtained from the production block machine. The volumetric fill method of a production machine is replaced with weighing the mix placed in each mold prior to compaction to provide a uniform amount of material. Numerous batches can be made quickly in a laboratory using small amounts of material on a cost-effective basis. Two-inch (50-mm) cubes for strength testing based upon modified ASTM C 109 (Test Method for Compressive Strength of Hydraulic Cement Mortars (Using 2-in. or 50-mm Cube Specimens)) procedures, and 1-in. (25-mm) square bars for change of length testing based upon modified ASTM C 157 (Test Method for Length Change of Hardened Hydraulic-Cement Mortars and Concrete) procedures can both be made using standard molds and testing equipment.
Expandability of Solid-Volume-Reducing Reactions of Alkali-Magnesite and Alkali-Dolomite
Authors: Tong L , Tang M
Published: January 2010

The work presented in this paper concerns two solid-volume-reducing reactions between alkali-dolomite (ADR) and alkalimagnesite (AMR). It was found that the two reactions can cause considerable expansion of compacts made from dolomite or magnesite powder and 20% Portland cement when cured at 150 and 60°C in 10% KOH solution. The results confirmed an earlier suggestion that the formation and growth of crystalline products in a confined space may be expandable.

The expandability of the alkali-magnesite reaction was first recognized by the authors using newly developed test methods—150°C autoclaving of concrete microbars and miniature rock prism tests. Although magnesite itself is rarely used as a concrete aggregate, it is reasonable to investigate the reaction since concrete aggregates may contain a certain amount of magnesite.
Limestone Additions to Portland Cement—An Old Controversy Revisited
Authors: Mayfield LL
Published: January 2010

A current proposal in ASTM Committee C-1 on Cement would allow up to 5% limestone to be interground with clinker into portland cement under the provisions of ASTM Specification for Portland Cement (C 150), the basic standard covering portland cement. This important and far-reaching proposal would change the definition of portland cement and has resulted in considerable controversy within the Committee. There are strong arguments on both sides of the question. The proponents claim a significant savings of energy during production without a degradation in quality and even cite improvements in some cement and concrete characteristics. The opponents charge that limestone acts merely as an adulterant, that strengths are reduced, and that the proposal should be abandoned on ethical grounds.

A very interesting adjunct to the carbonate additions proposal—the name used in committee work—has been the sense of history that this proposal has inspired. Regardless of individual viewpoints, many Committee C-1 members have turned to the past in an effort to gain insight into the ramifications of this proposal. This paper is a historical review of portland cement and cement specifications.
Economical Binder Proportioning with Cement-Replacement Materials
Authors: Butler WB
Published: January 2010

A method is presented for establishing the most economical binder proportions over an appropriate range of strengths based upon a matrix of trial mixes in which the amounts of cement and other binder component are varied.
Evaluation of the Frost Resistance of Concrete Using Critical Dilation
Authors: Buck AD
Published: January 2010

A new definition of critical dilation is proposed for use in ASTM Test Method for Critical Dilation of Concrete Specimens Subjected to Freezing (C 671). Using this new definition, only a single cycle of freezing is needed to determine whether or not a specimen is frost resistant.
Cementitious Properties of Nonferrous Slags from Canadian Sources
Authors: Douglas E , Malhotra VM , Emery JJ
Published: January 2010

This report presents data on the characterization of nine Canadian nonferrous slags. The characterization includes the determination of grinding energy, fineness, chemical composition, estimates of glass content, pozzolanic activity, and strength development. Grinding the slags to 4000 cm2/g seems to be economically feasible. The chemical analysis indicates that calcium oxide contents for all samples are low with the exception of a lead slag. It is concluded that for research purposes, glass content should be measured with a scanning electron microscope image analyzer. Slag activity should be estimated using the ASTM Specification for Ground Iron Blast-Furnace Slag for Use in Concrete and Mortars (C 989) test. The 28-day index indicates a direct relationship between strength and glass content when determined at 23°C in specimens cured in the moist room. Tests carried out at 38°C fail to confirm that strength development is directly related to vitrification.
Influence of Air Temperature on the Setting of Concrete Containing Set Retarding Admixtures
Authors: Fattuhi NI
Published: January 2010

Concrete mixes containing set retarding (R) or water reducing and set retarding (WRR) admixtures of different compositions were prepared and then tested by the Proctor penetrometer apparatus to determine the penetration resistance-time relationships. The initial temperature of the different mortar mixes after sieving was 22 ± 1°C. The influence of admixture composition and air temperature (30, 40, and 50°C) on the initial and final times of setting for the different concretes were examined. Admixture dosages used were within the limits recommended by the manufacturers. The results showed that the longest retardation in the times of setting was that achieved by using a phosphate based admixture, followed by that based on lignosulfonate. However, the retardation influence was reduced with an increase in temperature. Linear and nonlinear relationships were found between air temperature and initial and final times of setting for the reference and admixture concretes, respectively.
Variations in the Chemical Composition, Specific Surface Area, Fineness, and Pozzolanic Activity of a Condensed Silica Fume
Authors: Nebesar B , Carette GG
Published: January 2010

The production of condensed silica fume (CSF) from the silicon and ferrosilicon furnaces of a Canadian plant was sampled at regular intervals over a period of 180 days in 1982. For each type of furnace the variability in composition, specific surface area, fineness, and pozzolanic activity of the material were determined. The results indicate that only a few samples are responsible for the majority of outliers in chemical composition and fineness by a 45-µm sieve, and these generally also account for some deviations in pozzolanic activity. The type of furnace affects the composition, specific surface area, and fineness of condensed silica fume; however, the pozzolanic activities of the two types of material are, with minor exceptions, comparable.
Determining the Static and Dynamic Properties of Hardened Normal Weight and Heavy Weight Concrete
Authors: Graham DE
Published: January 2010

This paper describes a method for determining the material constants of normal weight and heavy weight concrete under static and dynamic loading at 7, 28, and 90 days. The tests were conducted at the University of California, Structures and Materials Laboratory, Berkeley, CA, for comparing the compressive strength, modulus of elasticity, Poisson's ratio, and static tensile strength of normal weight and heavy weight concrete for a nuclear power plant.
Freeze-Thaw Durability of Concrete With and Without Silica Fume in ASTM C 666 (Procedure A) Test Method: Internal Cracking Versus Scaling
Authors: Pigeon M , Pleau R , Aitcin P-C
Published: January 2010

The freeze-thaw durability of concrete with and without silica fume was investigated in accordance with the requirements of ASTM Test Method for Resistance of Concrete to Rapid Freezing and Thawing (C 666 Procedure A). The water-cement ratio of all mixes was 0.5, and the silica-cement ratio of the silica fume mixes 0.1. The test results show that the critical value of the air-void spacing factor in these ASTM C 666 tests is significantly lower for the silica fume concretes. These concretes are therefore more susceptible to internal cracking caused by rapid freeze-thaw cycles in water, even though the use of silica fume decreased the surface scaling of the test specimens. This confirms that scaling and internal cracking are two different forms of frost damage caused by rapid freeze-thaw cycles in water. The use of silica fume also decreased the internal cracking of the nonair-entrained mixes damaged during the tests.
Chloride Concentrations in Concrete Pore Solutions Resulting from Calcium and Sodium Chloride Admixtures
Authors: Diamond S
Published: January 2010

Cement pastes prepared from a “typical” ASTM Type I portland cement at a water/cement ratio of 0.50 were mixed with various calcium chloride (CaCl2) admixture treatment levels, hydrated for various periods, and then subjected to pore solution expression. The expressed pore solutions were then analyzed for chloride and hydroxide ion concentrations. It was found that the concentration of chloride ions drops rapidly but reaches an equilibrium level by about ten days. The equilibrium concentrations attained varied between 20 and 50% of the original concentration in the mix water, the latter value being for the highest CaCl2 treatment level, 2% by weight of the cement. Substituting sodium chloride (NaCl) for CaCl2 as the admixture produced only minor differences in equilibrium concentration. The equilibrium Cl−/OH− ratios for treatments of 0.5% CaCl2 and above were found to be beyond that considered to be the boundary for depassivation, slightly above 0.3. X-ray diffraction results were ambiguous but differential thermal analysis (DTA) trials provided some evidence for the formation of Friedel's salt in these pastes. However, it was considered likely that at least some of the chloride not retained in solution is associated with calcium-silicate-hydrate (C-S-H) gel.
The Application of Neutron Radiography to the Study of Microcracking in Concrete
Authors: Najjar WS , Aderhold HC , Hover KC
Published: January 2010

Radiography of concrete specimens using a neutron flux as the penetrating radiation has been used to identify and study microcracking. The key to the technique is the partial impregnation of the microcracks with a medium with a high neutron attenuation capacity, so as to result in a sharp contrast between the cracks and the surrounding solid mass. Gadolinium has been used as the neutron-attenuating contrast agent, which is applied in the form of an aqueous solution of gadolinium nitrate.

The resulting radiographs are compared with more conventional X-ray studies of the same specimens. Neutron radiography appears to be more effective than X-radiography for the identification of cracking.
Mechanical Properties and Freezing and Thawing Resistance of High-Strength Concrete Incorporating Silica Fume
Authors: Malhotra VM , Painter KA , Bilodeau A
Published: January 2010

This report presents results of an investigation dealing with the mechanical properties and freezing and thawing resistance of high-strength, silica fume concrete using ASTM Test Method for Resistance of Concrete to Rapid Freezing and Thawing (C 666-84, Procedure A). Eighteen nonair-entrained and six air-entrained concrete mixtures, 0.06 m3 in size, were made. The water-to-(cement + silica fume) ratio (W/C + S) of the mixtures ranged from 0.25 to 0.36, and the percentages of cement replacement by silica fume were 0, 10, and 20% on a weight basis. Any loss in slump due to the use of silica fume was compensated for by the use of a superplasticizer.

A number of test cylinders were made for testing in compression at various ages, and test prisms were cast for determining their resistance to repeated cycles of freezing and thawing in accordance with ASTM C 666, Procedure A. Sawn sections of some of the prisms were used for determining the air void parameters of the hardened concrete.

Nonair-entrained, high-strength concrete with a compressive strength of up to 87 MPa at 28 days, regardless of the W/C + S and irrespective of the silica fume content used, had durability factors less than 12 when tested in accordance with ASTM C 666, Procedure A.

Also, air-entrained concrete prisms incorporating 10 and 20% silica fume as replacement for cement failed to complete 300 cycles of freezing and thawing.
High-Strength Semi-Lightweight Concrete with Up to 50% Fly Ash by Weight of Cement
Authors: Johnston CD , Malhotra VM
Published: January 2010

This paper discusses the effects of including a Western Canadian subbituminous fly ash in superplasticized, air-entrained, semi-lightweight concrete. Mixtures were proportioned with 100 ± 20mm slump and 5 ± 1% air content. Cement contents ranged from 250 to 500 kg/m3 with additions of fly ash up to 50% by weight of cement.

In the freshly mixed state, the effects of the fly ash are to reduce the initial water demand, increase the dosage of air-entraining admixture required for the specified air content, and reduce the rate of slump loss after addition of superplasticizer. The dosage of superplasticizer required remains essentially constant when expressed as a percentage of the total weight of binder (cement + fly ash).

In the hardened state, the emphasis is on establishing how the proportion of fly ash to cement affects strength, unit weight, and cost. Each mixture is evaluated in terms of strength-weight ratio and cost in terms of cement equivalent in kg/m3, using the relationship between the costs of cement and fly ash locally to convert the cost of the fly ash into an equivalent cement cost. The bar chart used for this purpose readily facilitates the identification of optimal mixture proportions from the point of view of strength-weight ratio and cost. In addition, the development of strength is examined at various ages to show how the fly ash progressively asserts its effect on relationships between strength and effective W-C ratio. Finally, resistance to freezing and thawing is reported in terms of Procedure A of ASTM Test Method for Resistance of Concrete to Rapid Freezing and Thawing (C 666-84), and performance is shown to be unsatisfactory when using presaturated lightweight aggregate with the specified 14-day moist curing regime. Performance improves substantially after drying followed by further soaking simulative of the curing of lightweight concrete in structures following construction.
Creep of Lightweight Aggregate Concrete Under Variable Stresses
Authors: Tasdemir MA , Akyüz S , Uzunhasanolu N
Published: January 2010

In this work, the creep of lightweight aggregate concrete under constant stress is described by a logarithmic function of time, and the variations of the coefficients with age are experimentally determined. Using the relation thus obtained, an attempt is made to predict the creep of lightweight concrete specimens with the same composition under stepwise varying stresses, assuming a linear viscoelastic behavior. It was established that there is good agreement between the predicted and experimental values.
Production and Evaluation of a New Source of Granulated Blast Furnace Slag
Authors: Douglas E , Wilson H , Malhotra VM
Published: January 2010

A granulation pilot plant was installed at Algoma Steel Corp., Sault Ste. Marie, Ontario, for the production of about 40 metric tons of granulated blast furnace slag to be tested for concrete and mine backfill applications. The granulated slag was obtained by quenching the molten slag by jets of high-pressure water. Heat loss was maintained at the level expected when the full-size plant is in operation so as to generate a representative slag sample. The granulated slag was allowed to drain in the slag pit before being transported to the grinding facilities, where it was dried in a converted kiln, reducing the moisture content from 8 to 0.3%. The unit power consumption for grinding the granulated slag was similar to typical figures for grinding portland cement clinker in the lower Blaine range.

Quantitative X-ray diffraction analysis showed that the granulated slag was about 90% glass. The magnesium oxide content was about 18% and was likely in the form of a calcium magnesium alumino silicate glass.

Mortar tests performed according to ASTM Specification for Ground Iron Blast-Furnace Slag for Use in Concrete and Mortars (C 989) showed that the slag ground to 4600 and 6080 cm2/g met the requirements for Grades 100 and 120, respectively.

The slag investigated has considerable potential for partial replacement of portland cement in concrete. At comparable fineness, the strength characteristics of the concrete incorporating the Canadian granulated slag are comparable with those of the concrete made with the other Canadian slag (pelletized) used in the investigation.
Freeze-Thaw Durability of Wet-Mix and Dry-Mix Shotcretes with Silica Fume and Steel Fibres
Authors: Morgan DR , Kirkness AJ , McAskill N , Duke N
Published: January 2010

This investigation was undertaken to study the freeze-thaw durability of wet-mix and dry-mix shotcretes when tested according to ASTM Test Method for Resistance of Concrete to Rapid Freezing and Thawing (C 666) Procedure A. Parameters of the air voids system were determined using ASTM Recommended Practice for Microscopical Determination of Air-Void Content and Parameters of the Air-Void System in Hardened Concrete (C 457-82).

The effect of substitution of condensed silica fume for part of the cement was studied for plain shotcrete mixes as well as for mixes containing steel fibres. It was concluded that excellent durability was achieved in nonfibre and steel fibre shotcrete mixes manufactured by both the wet-mix and dry-mix shotcrete processes when approximately 13% of the cement was replaced with silica fume. After 300 cycles of freeze-thaw, excellent durability factors exceeding 95% were achieved in both wet-mix and dry-mix shotcretes having total air contents in the range of 4.5 to 6.5% and spacing factors in the range of 0.27 to 0.31 mm. Substantial increases in compressive strength were also realized during the period of freeze-thaw testing. Flexural strength and toughness of the samples were also not significantly affected by the freeze-thaw cycling.
New Approach for a Concrete Scaling Test Based on Field Conditions
Authors: Moukwa M , Adkins D
Published: January 2010

The microenvironment existing at the surface of a concrete element which has shown rapid deterioration in the form of scaling has been established. Field measurements of the microclimatic elements within the concrete surface layer throughout the winter give new insight into the understanding of the surface scaling. It was found that solar effects have a pronounced effect on the scaling of the concrete surface. Basis for a new scaling test which simulates the deterioration of concrete in the field under severe freeze-thaw conditions has been developed. It consists of partial thawing and complete refreezing of the surface. Erratum to this paper appears in 11(1).
Evaluation of Test Methods for Measuring the Bond Strength of Portland Cement Based Repair Materials to Concrete
Authors: Knab LI , Spring CB
Published: January 2010

Three bond strength test methods were evaluated for screening and selecting repair materials used in overlaying and patching portland cement concrete. Bond strengths of three repair materials to base concrete were investigated using two uniaxial tension bond strength test methods and a slant shear bond strength test method. The differing strengths of the repair materials caused different failure patterns, which had to be considered in the analyses of the failure stresses.

Substantial differences in the failure stresses of the uniaxial tension and slant shear test methods were attributed to their different geometries and loading conditions. These differences emphasized the need to select test method(s) with geometry, loading conditions, and stress states that are anticipated for the in-service repair material.

For the two higher strength repair materials investigated, the relative precision (repeatability) of the slant shear and one of the uniaxial tension test methods (pipe nipple grips) were comparable and relatively good (coefficient of variation values were about 5%). It was concluded that both the slant shear test method and the pipe nipple grips uniaxial tension test method are promising methods for screening and selecting repair materials of the type investigated (portland cement concrete or latex-modified concrete) for overlaying or patching portland cement concrete.
Behavior of Cement-Reduced and “Flowing” Fresh Concretes Containing Conventional Water-Reducing and “Second-Generation” High-Range Water-Reducing Admixtures
Authors: Whiting D , Dziedzic W
Published: January 2010

Fresh concretes were prepared using cements of high and moderate C3A contents and having a cement content of 323 kg/m3 (545 lb/yd3) and a water-to-cement ratio of 0.50. Conventional water-reducing agents based on lignosulfonates and carboxylic acids were used to reduce water and cement contents by 8 to 9%. Second generation high-range water-reducing admixtures (HRWR) were used to reduce cement and water contents by 15 to 16%. Testing included slump loss, air loss with time, setting time, and bleeding. Similar tests were carried out on flowing concretes, where cement and water contents were maintained constant and HRWR was added to increase initial slump levels to 200 to 300 mm (8 to 9 in.). In this series, testing was carried out at both 23°C (73°C) and 32°C (90°F).

Use of chemical admixtures to reduce both water and cement contents resulted in accelerated rates of slump loss and shorter working times compared to controls. When used to produce flowing concretes, working times were equivalent to those for mixes not containing the admixtures. In general, setting times were increased from 1 to 2 h at 23°C (73°F) and by lesser amounts at 32°C (90°F). Bleeding of flowing concretes was greater than that of control mixtures, especially when a copolymer-type HRWR was used. Rate of air loss was significantly greater in cement-reduced mixtures containing HRWR compared with controls; however, air loss rates in flowing concretes were roughly equivalent for all mixtures tested.
Durability of Concrete under Simulated Arctic Conditions
Authors: Moukwa M , Aitcin P-C , Regourd M
Published: January 2010

The durability of 0.44 W/C concrete under simulated Arctic conditions was studied. The length change of concrete specimens was monitored throughout the test. Samples taken from the concrete specimens before and after the test were analyzed to determine the effects of simulated Arctic conditions on the microstructure of the concrete. The results showed that the alternating conditions of immersion in seawater and exposure to cold air mostly affect the surface layer of the concrete and facilitate a deep migration of aggressive ions like magnesium and sulfate.
Another Look at the Portland Cement/Chemical Admixture Incompatibility Problem
Authors: Dodson VH , Hayden TD
Published: January 2010

Reports of incompatibility between portland cement and chemical admixtures have increased over the past ten years. Specifications written by architects and engineers calling for the use of admixtures in concrete often result in strange occurrences, that is, rapid set, accelerated stiffening, increase in time of set, lack of water reduction. This paper addresses the effect of the composition of the cement and that of the chemical admixtures on incompatibility with respect to the problems of rapid set and accelerated slump loss.

The use of natural anhydrite (CaSO4) as a substitute or partial replacement for gypsum (CaSO4 · 2H2O) in the manufacture of portland cement is gaining in popularity. Admittedly, portland cement containing large amounts of natural anhydrite will perform normally, but not necessarily so in concrete containing the common chemical admixtures.

The data presented in this paper attempt to show why large amounts of natural anhydrite in portland cement can cause incompatibility problems in the presence of chemical admixtures. The rate of solution of natural anhydrite, which is much slower than that of gypsum or calcium sulfate hemihydrate, is further retarded in the presence of chemical admixtures, which leads to a “sulfate-starved” system in the concrete, often producing rapid set and an increase in rate of concrete slump loss.
Na2SO4 Soundness Test Evaluation
Authors: Sheftick W
Published: January 2010

The Illinois Department of Transportation (IDOT) uses the sodium sulfate (Na2SO4) soundness test as one of its main aggregate acceptance tests. Unfortunately, many accusations concerning the lack of reproducibility and validity of the soundness test are continually voiced by aggregate producers and specifying agencies.

In order to better understand the sodium sulfate soundness test, IDOT conducted an evaluation program to identify the major problem areas in the test method. The evaluation program consisted of eight separate evaluations. Samples from a number of different Illinois aggregate sources were tested for each evaluation. The evaluations looked at (1) temperature control, (2) different Na2SO4 materials, (3) repeatability, (4) validity, (5) increased cycles, (6) cooling of samples, (7) pan versus basket soaking, and (8) the method used to interrupt the test.

Several general conclusions were drawn from the evaluations on the sodium sulfate soundness test. These conclusions identify areas of the test procedure which could produce erratic and erroneous results. One area was that temperature must be accurately controlled, both during soaking and during cool down of the samples. Another was that the specified method of interrupting the test produces results that do not correlate with running the test straight through to completion. There are also several other items that indicate potential problems and that should have additional research run on them.

The overall summary concluded that when tighter control, especially temperature, is maintained, the sodium sulfate soundness test seems to provide valid test results.