DETERMINATION OF CLIFF-LORIMER k FACTORS FOR A HITACHI H700H 200 kV SCANNING TRANSMISSION ELECTRON MICROSCOPE

La technique proposée par Cliff-Lorimer pour la microanalyse X des lames minces demande la connaissance des coefficients k qui relient le rapport des intensités mesurées au rapport des concentrations. Dans cette contribution on détermine ces facteurs pour un microscope électronique en transmission, en employant des témoins minéralogiques et des alliages homogènes. On compare les valeurs expérimentales et les valeurs théoriques obtenues par application des facteurs k.The Cliff-Lorimer ratio technique for thin film X-ray microanalysis requires knowledge of the k factors which relate the measured X-ray intensities to the composition of the specimen. This paper reports the determination of k factors at 200 kV for an analytical transmission electron microscope (Hitachi H700H with a LINK 860 system) using mineral standards and homogeneous alloys. The experimental data are compared with calculations of theoretical k factors

Experience and recent innovations in cathodic protection of steel in concrete

This paper reviews 25 years of experience with cathodic protection of steel in concrete in The Netherlands. Three phases have passed from the late 1980s until present: pioneering, development and maturity. In the first period CP was mainly applied to precast elements corroding due to mixed in chlorides. The parties involved worked together to draw up a Technical Guideline. In the second period, application to bridges was developed, including post-tensioned structures, which was then innovative. Furthermore, galvanic anode systems were introduced. In the third period, CP became a fully accepted method of securing safety and serviceability. The annual number of projects increases considerably and increased competition has reduced prices. Renewed collaboration led to a database that allowed analysis of various aspects of CP system working life; and to new developments in modelling. Major successes and lessons learned will be presented. Technical and non-technical developments are highlighted and some recent findings on long term behaviour are discusse

Nomenclatural and taxonomic notes on Alcmeone robusta (Butler) comb.n. (Hemiptera, Auchenorrhyncha, Membracidae)

Ceresa robusta Butler, 1877 is transferred to the genus Alcmeone Stål, 1867 and A. sinuata Fonseca & Diringshofen, 1974 is considered its new synonym

Investigations into the cause and consequence of incipient anodes in repaired reinforced concrete structures

The incipient anode (or halo) effect often occurs on repaired reinforced concrete structures. The diagnosis of this problem is widely reported in literature to be macrocell activity. It is deemed that the cause of incipient anodes is the loss of the natural cathodic protection provided by the corroding steel to the steel in the parent concrete adjacent to the patch repair. This diagnosis however, is based on very limited data. Indeed recent potential measurements on field structures repaired with cementitious proprietary materials have provided data that suggests that macrocell activity is not a cause of incipient anode formation but is instead a consequence. Alternative mechanisms that may cause incipient anode activity include repair/parent material interface effects, residual chloride contamination within the parent concrete, and/or vibration damage to the steel/parent concrete interface during repair area preparation. The aim of the work presented here was to assess the impact of macrocell activity on the formation of incipient anodes around the perimeter of repairs in patch-repaired reinforced concrete structures. Data was collected from a major multi-storey car park and a bridge structure both located in the UK. The analysis challenges the widespread view that macrocell activity is a cause of incipient anode formation. Indeed this work illustrates that the data supporting the existing diagnosis is not convincing and suggests that macrocell activity is primarily a consequence of incipient anode formation and the cause is more likely to be a result of other factors

Longitudinal guided waves for monitoring chloride corrosion in reinforcing bars in concrete

Corrosion of reinforcing steel in concrete is one of the major durability problems faced by civil engineers as they maintain an aging infrastructure. The problem accelerates since steel is embedded inside concrete. If it remains unnoticed inside concrete, it further accelerates and can cause loss of life and property. This article discusses a nonintrusive corrosion monitoring technique for early detection of damages in steel embedded in concrete. Corrosion manifests itself in debond and pitting steel bars. Guided ultrasonic waves offer a potentially attractive solution for this problem. But it is imperative to excite the right mode for detection of a particular type of corrosion. In the present work, longitudinal guided ultrasonic waves have been utilized to monitor notch and debond defects in steel bars in concrete simulating pitting and delamination phenomena caused by corrosion. Two ultrasonic techniques of pulse transmission and pulse echo were used to monitor the healthy and damaged specimens. The developed methodology is successfully applied for real time monitoring of RC beam specimens undergoing accelerated chloride corrosion. The ultrasonic signals effectively relate to the state of reinforcing bars