Gray Cement Research Articles

Round robin on Rietveld quantitative phase analysis of Portland cements

Interlaboratory studies on the precision and accuracy of Rietveld quantitative phase analysis (R-QPA) of mixtures of crystalline phases have already been carried out. However, cement-related materials are samples of variable complexity, ranging from three phases in white Portland clinkers to more than eight phases in grey cements, that need to be specifically investigated. Here, the results are reported from a round robin on the R-QPA of cement-related materials from laboratories with experience in this type of analysis. The aim of the work was to evaluate the levels of precision and accuracy associated with Portland clinkers and cements. Two sets of samples have been investigated, artificial mixtures and commercial samples. Artificial mixtures were prepared by mixing (weighing) synthesized single-crystalline phases in the appropriate proportions: (i) white clinker (Ca3SiO5, Ca2SiO4and Ca3Al2O6) and (ii) grey cement (Ca3SiO5, Ca2SiO4, Ca3Al2O6, Ca4Al2Fe2O10, CaCO3and CaSO4·2H2O). These two samples were used to assess the accuracy and uncertainty of the procedure, as an expected mineralogical phase fraction, the `true mineralogical percentage', is available under the assumption of negligible non-diffracting contents. In order to assess the validity and limitations of the Rietveld-based approach for cement materials, three commercial samples were measured: (i) white Portland clinker, (ii) grey Portland clinker and (iii) a type-I grey Portland cement. The samples studied have been chosen in order to cover most of the different typologies of binders. Reproducibilities and general uncertainty values, with a level of confidence of 95%, are reported and discussed.

Natural radioactivity measurements in building materials in Southern Lebanon

Using γ-spectroscopy and CR-39 detector, concentration C of naturally occurring radioactive nuclides 226Ra, 222Rn, 214Bi, 228Ac, 212Pb, 212Bi and 40K, has been measured in sand, cement, gravel, gypsum, and paint, which are used as building materials in Lebanon. Sand samples were collected from 10 different sandbank locations in the southern part of the country. Gravel samples of different types and forms were collected from several quarries. White and gray cement fabricated by Shaka Co. were obtained. γ-Spectroscopy measurements in sand gave Ra concentration ranging from 4.2 ± 0.4 to 60.8 ± 2.2 Bq kg −1 and Ra concentration equivalents from 8.8 ± 1.0 to 74.3 ± 9.2 Bq kg −1. The highest Ra concentration was in gray and white cement having the values 73.2 ± 3.0 and 76.3 ± 3.0 Bq kg −1, respectively. Gravel results showed Ra concentration between 20.2 ± 1.0 and 31.7 ± 1.4 Bq kg −1 with an average of 27.5 ± 1.3 Bq kg −1. Radon concentration in paint was determined by CR-39 detector. In sand, the average 222Rn concentration ranged between 291 ± 69 and 1774 ± 339 Bq m −3 among the sandbanks with a total average value of 704 ± 139 Bq m −3. For gravel, the range was found to be from 52 ± 9 to 3077 ± 370 Bq m −3 with an average value of 608 ± 85 Bq m −3. Aerial and mass exhalation rates of 222Rn were also calculated and found to be between 44 ± 7 and 2226 ± 267 mBq m −2 h −1, and between 0.40 ± 0.07 and 20.0 ± 0.3 mBq kg −1 h −1, respectively.

Rethinking Interest Representation in the European Union

In 2004, the European Economic and Social Committee moved out of the grey cement building it had occupied in the old centre of Brussels, a building far removed from the European Union's other institutions. It moved into a modern glass and steel construction, right next to the European Parliament, the Council of Ministers, and the Commission. Did this change of abode represent anything more than the need for more office space after enlargement towards the East? The answer, judging from Stijn Smismans' recent book, is 'yes'. The Economic and Social Committee, constituted of representatives of national employer federations, trade unions, and such other economic groups as farmers and the professions, gives opinions on proposed European legislation. It is one of the original institutions of the European Union, established in 1958, as was the Council of Ministers, the Commission, the Court of Justice, and the Parliament. Since then, a number of similar committees and agency boards have been created.' They resemble the Economic and Social Committee in that they give representatives of national (or pan-European) interest organizations the opportunity to advise on European policy. These committees and agency boards differ from the Economic and Social Committee in that their mandate is far

The application of Raman spectrometry to investigate and characterize cement, Part I: A review

Raman spectrometry has received attention for the past 3 decades in its application to the characterisation of pure cement phases, white and grey cements. Various configurations of instrumentation and laser excitation sources have been used, as reported in a limited number of papers. The first demonstrated investigation in 1976 by Bensted, illustrated the characterisation of various pure mineral cement phases with the use of a visible excitation source and a standard dispersive configuration. This was soon followed by an investigation of pure phases, as well as white and grey cements in 1980 by Conjeaud and co-workers using a microprobe configuration and visible excitation. Considerable difficulties with excessive fluorescence phenomena, especially with grey cements, have however been reported from the initial to the most recent publication. This review aimed to report on Raman studies of pure synthesized cement phases, cement phases as found in white and grey cements, various forms of gypsum and related compounds as found in cement and concrete, hydration of pure cement phases, as well as those of white and grey cement and lastly carbonation effects. Results reported are discussed and tables of summarized observed Raman shifts are given.

Investigations of chemical and physical properties of white cement concrete

Abstract To address questions concerning the behavior and performance of white cement concrete, a research program was designed to conduct comparative studies of type I gray and white portland cements. Different properties of cement paste and cement mortar, made with the two different cements, were measured and compared. Test results indicated shorter setting time of white cement paste and greater ultimate tensile and compressive strength for its mortars than the corresponding values for the gray cement. Results of tests on samples of fresh concrete indicated greater slump and shorter times of initial and final set of mixes prepared with the white cement. Tests conducted on samples of hardened concrete indicated greater ultimate compressive strength of the white cement cylinders. Finally, full-scale companion reinforced concrete beams, identical except for the type of cement, were designed to fail in shear or in flexure. Test results indicated no difference that could be attributed to the type of cement used. Advanced Cement Based Materials 1995, 2, 161–167

Investigations of Chemical and Physical Properties of White Cement Concrete

To address questions concerning the behavior and performance of white cement concrete, a research program was designed to conduct comparative studies of type I gray and white portland cements. Different properties of cement paste and cement mortar, made with the two different cements, were measured and compared. Test results indicated shorter setting time of white cement paste and greater ultimate tensile and compressive strength for its mortars than the corresponding values for the gray cement. Results of tests on samples of fresh concrete indicated greater slump and shorter times of initial and final set of mixes prepared with the white cement. Tests conducted on samples of hardened concrete indicated greater ultimate compressive strength of the white cement cylinders. Finally, full-scale companion reinforced concrete beams, identical except for the type of cement, were designed to fail in shear or in flexure. Test results indicated no difference that could be attributed to the type of cement used. Advanced Cement Based Materials 1995, 2, 161–167

The properties and performance of polymer modified GRC

Recently, there has been increasing interest in the potential advantages of adding a polymer to the matrix of GRC formulations, especially for use in cladding. This paper describes some experiments, carried out in order to provide specific information on the moisture movement and mechanical properties of GRC materials reinforced with 5% weight of cem-fil fibre and modified by forton polymer. Three mix formulations were tested: (1) a high polymer content mix, with 10% of polymer by weight; (2) a low polymer grey cement mix, with about 5% of polymer; (3) a polymer-free mix, used as a control. After adding the cem-fil fibre, the test boards were produced by a normal hand spray/rolling process. Tests were carried out on: (1) cure shrinkage and moisture movement; (2) accelerated ageing and laboratory durability; (3) effects of wet and dry testing and different curing conditions. The conclusions reached included the following: (1) drying shrinkage and moisture movement on subsequent exposure can be reduced significantly by adding appropriate polymers to GRC mixes; (2) for GRC containing a polymer, the mechanical properties of samples tested in 'wet' and 'dry' conditions are significantly different; (3) relatively crude covering or wrapping of polymer GRC materials (e.g. polythene sheet) is effective in creating a damp cure environment. (TRRL)

The face of death: case history, literary histories.

THE FACE OF DEATH: CASE HISTORY, UTERARY HISTORIES RICHARD E. PESCHEL* and ENID RHODES PESCHELi The Tunnel Our hospital is divided, basically, into two buildings: die antiquated one, still in use, was constructed about 1900; and the odier, more modern , was built in die 1950s. Some of the integral parts of the hospital— for example, the Emergency Room (the ER) and die morgue—are located in die old building; whereas other essential sections—including die Intensive Care Unit (the ICU) and the Coronary Care Unit (the CCU)—are situated in the new building. The buildings are linked by an underground tunnel. Because of diis haphazard arrangement, patients often have to be transported through the tunnel from die old building to die new one: diat is, many patients brought in on an emergency basis—someone widi a suspected heart attack, for instance—must be admitted dirough die ER in die old building and then conveyed on a stretcher to the new building, via the tunnel. This tunnel is like no odier. It is long (approximately one-and-a-half city blocks from end to end) and narrow: about two stretchers wide. Its gray cement floor looks worn, as though scarred widi die weight of all the feet and wheels diat have hurried over its sunless surface. Yellowish, rectangular tiles line the walls. Their jaundiced appearance recalls die pollution-tainted tiles of tunnels that wend dieir ways beneath rivers. But here there are no cars or honking horns or smiling faces in vehicles; no policemen standing guard along die walls; no toll-takers, eidier. No visible toll-takers, at any rate. Yeteither before or after diis tunnel, a toll is certainly taken, of that you can be sure. The traffic through this subterranean passageway, you have surmised correcdy, is exceedingly strange. Though it is assuredly physical, a com- * Assistant professor of therapeutic radiology, Yale University School of Medicine, New Haven, Connecticut. t Editor, Medicine and Literature. Address: 1 1 Manor Drive, North Haven, Connecticut 06473.© 1983 by die authors. 0031-5982/83/2603-0390$01.00 394 I Richard E. Peschel andEnidRhodes Peschel · The Face ofDeath bination of bodies and equipment, it is also almost eerily ethereal. One might expect to see ghosts or phantoms curling through die corridor. The ambience in this roadway underneath die ground, this lower roadway—this via inferna, as the ancients might say—is heavy, congested, and oppressive. You have a hard time breadiing, even if you are healdiy and not in distress, like the patient on die stretcher. The only sound you hear is the droning of die ventilation fan. You wonder if it is really working, the air of this place is so stale. There are no windows, but it is bright. Fluorescent filaments fling down light from above and make you squint. Except for one curve, the tunnel is straight. Ifyou stare directly ahead, you think that you are caught in an almost endless tube. The interns in our hospital hate this tunnel, curse it, dread it, and must travel through it time and time again. They loathe it for good reason. When an intern "on call" in the new building is assigned a new patient who is considered critically ill (e.g., someone being sent to the ICU or die CCU), diat intern has to go through die tunnel, pick up his patient in the ER, and accompany him to the new building—through die tunnel. Thus, the intern has to make this terrible trip twice: once widiout his patient, and once with him. Because the patient is probably gravely ill, he is hooked up to all sorts of life-sustaining and life-monitoring equipment: a cardiac monitor and intravenous poles, for example, and perhaps some other emergency gear. There is also a defibrillator, in case the patient has a cardiac arrest. The incessant nightmare of every intern in our hospital is diat his patient's heart will stop or that his patient will stop breathing in that tunnel. For die intern knows that when he is in there, he himself is the only medical person on whom he can call for help. In that tunnel, an intern is so isolated, in fact...