Portland cement

... In the case of cement paste containing up to 20% replacement of bentonite together with 4% CW ... 3. YM Zhang, W. Sun and HD Yan, Hydration of high-volume fly ash cement pastes. ... 4. M. Cheriaf, JC Rocha and J. Pera, Pozzolanic properties of pulverized combustion bottom ash. ...

The main aim of the environmental protection agencies and the government are to seek ways and means to minimize the problems of disposal and health hazards of by-products. Some of the industrial by-products have been successfully used in the construction industry for the production of cement and concrete. Copper slag is one of the materials that is considered as a waste material which could have a promising future in construction industry as partial substitute of either cement or aggregates. Many researchers have already found it possible to use copper slag as a concrete aggregate. But not much research has been carried out concerning durability and corrosion studies of copper slag admixed concrete. This paper presents the results of an experimental study on various corrosion and durability tests on concrete containing copper slag as partial replacement of sand and cement. For this research work, M20 grade concrete was used and the tests were conducted for various proportions of cop...

Concrete in farm buildings is subjected to severe corrosion if manure is stored below slatted floors. Many chemicals associated with manure are identified as having a detrimental effect on concrete and the reinforcing steel embedded in the concrete. Of these, hydrogen sulfide is the most corrosive agent that leads to the rapid deterioration of concrete in barns. As well, manure has high concentrations of sulfates. In the present study, 48 concrete cylinders, 100 mm diameter and 100 mm high, were made with Portland cement, and various combinations of slag, fly ash and silica fume. Each has a reinforcing steel bar embedded in it. 24 cylinders are half immersed in sodium sulfate (20,000 ppm SO4 2- ) and also subjected to hydrogen sulfide gas (1,000 ppm H2S). The second set of 24 is subjected only to hydrogen sulfide gas. In each set, there are 8 different treatments. The specimens results indicate that after 16 cycles (each cycle is about five weeks long) of testing over 28 months, spe...

... In addition, waste glass seemed to positively contribute to the mortar micro-structural properties resulting in an evident improvement of its mechanical performance [Corinaldesi et al. 2005a]. Mixed colored glass can be utilized in flowable self-compacting slurry or concrete [Naik ...

Rice husk ash (RHA) has been used as a highly reactive pozzolanic material to improve the microstructure of the interfacial transition zone (ITZ) between the cement paste and the aggregate in high-performance concrete. Mechanical experiments of RHA blended Portland cement concretes revealed that in addition to the pozzolanic reactivity of RHA (chemical aspect), the particle grading (physical aspect) of cement and RHA mixtures also exerted significant influences on the blending efficiency. The relative strength increase (relative to the concrete made with plain cement, expressed in %) is higher for coarser cement. The gap-grading phenomenon is expected to be the underlying mechanism. This issue is also approached by computer simulation. A stereological spacing parameter (i.e., mean free spacing between mixture particles) is associated with the global strength of the blended model cement concretes. This paper presents results of a combined mechanical and computer simulation study on t...

In this study, the strength development and lechability aspects of metal-contaminated soil treated with ordinary portland cement (OPC) were investigated. The soil was collected from a scrap metal yard within the outskirts of Kuala Lumpur, Malaysia. Metal composition analysis indicated that the predominant metals present in the soil were iron (42,194 mg/kg), aluminium (8874 mg/kg), zinc (690 mg/kg), lead (428 mg/kg), copper (107 mg/kg) and chromium (52 mg/kg). The contaminated soil was treated with OPC using cement-to-dry soil (C/Sd) ratios of 0.5, 1 and 2. The effectiveness of the treatment was evaluated by performing unconfined compressive strength (UCS) as well as crushed and whole block leaching (WBL) tests on the treated soil. The treatment results were compared to the solidified waste acceptance criteria which were compiled based on the regulatory waste disposal limit at a disposal site in the United Kingdom and the maximum concentration of contaminants for toxicity characteristic of solid wastes from United States Environmental Protection Agency. Results indicated that chemical stabilization of metal-contaminated soils using OPC was effective for prevention of metal leaching from both disintegrated samples subsequent to years of weathering (crushed block) and intact samples (whole block) into the environment. © 2005 Elsevier Ltd. All rights reserved.

www.sciencedirect.com/science/article/pii/S0360132305003987

This contribution investigates the effects of seawater and colloidal silica (NS) in the amounts of 1, 3 and 5 wt%, respectively, on the hydration, strength development and microstructural properties of Portland cement pastes. The data reveal that seawater has an accelerating effect on cement hydration and thus a significant contribution to early strength development was observed. The beneficial effect of seawater was reflected in an improvement in compressive strength for up to 14 days of hydration, while in the 28 days compressive strength values were comparable to that of cement pastes produced with demineralized water. The combination of seawater and NS significantly promotes cement hydration kinetics due to a synergistic effect, resulting in higher calcium hydroxide (CH) production. NS can thus react with the available CH through the pozzolanic reaction and produce more calcium silicate hydrate (C-S-H) gel. A noticeable improvement of strength development, as the result of the s...

The effect of various additives (Ca(OH)2, K2SO4, Na2SO4, Al2(SO4)3) was evaluated on the hydraulic character and stability of pastes of 50–75% Fluorgypsum, 15–30% Portland cement and 10–20% Blast furnace slag. Characterization included length changes, compressive strength, SEM, DTA and XRD. The combination of Na2SO4 and Al2(SO4)3 favored early strength but caused detrimental expansion and strength losses after 90 days; whereas the use of only K2SO4 was favorable for strength and dimensional stability. The type of additive had a more important effect on stability and strength than the amounts of cement and slag. XRD indicated the presence of anhydrite, gypsum, ettringite, CaCO3 and an unidentified phase, the interaction of these is proposed to explain the behavior of the cements investigated. SEM showed that cement and slag reacted forming C–S–H that enhanced the hydraulic character by engulfing the gypsum crystals.

Aim  To compare the major constituents present in ProRoot mineral trioxide aggregate (MTA), ProRoot MTA (tooth coloured formula), ordinary Portland cement and white Portland cement using powder X-ray diffractometery.Methodology  X-ray diffractometery of the four materials was carried out with the divergence and scatter slits set at 1° and the receiving slit at 0.10 mm. The scan range was set at 5–70° and continuous scans for the θ–2θ range were run with a scan speed of 2° min−1. The patterns obtained were then compared with the Powder Diffraction Files (PDF) found in the International Centre for Diffraction Data database. The three strongest peaks were used for the identification of the constituents. The relative intensities were plotted against the angle 2θ and compared with the plots in the PDF.Results  The main constituents were found to be tricalcium silicate, tricalcium aluminate, calcium silicate, and tetracalcium aluminoferrite in all the four cements with the additional presence of Bi2O3 in ProRoot MTA and ProRoot MTA (tooth coloured formula).Conclusions  The four cements had similar major constituents. Data on Portland cement may be used for the further development or modification of ProRoot MTA in order to improve its physical characteristics and expand its scope of clinical applications.

A mathematical model is presented for estimating compressive strength of high-strength concrete incorporating pozzolanic materials, based on the strength of a control ordinary Portland cement (OPC) concrete made with similar mixture characteristics and curing history. In this study, metakaolin (MK) and silica fume (SF) were used as cement replacement materials at 5%, 10%, and 15% by mass. Water/cementitious materials (w/cm) ratios varied from 0.27 to 0.33, and strength testing was conducted up to an age of 180 days. It was found that the strength of a pozzolanic mixture could be related to the strength of its equivalent control by a linear function. Key parameters involved in the model are the pozzolanic and dilution factors, which can be correlated to the pozzolan content in the mixture. The study concludes that the accuracy of the model increases with concrete age. At ages 28 days and above, 97% of the estimated strengths are within ±5% of the actual value.

Berisi tentang :
A. Definisi, Sejarah Semen, Konsep Dasar mengenai Semen

I. Bahan Dasar
II. Proses Pembuatan Semen
III. Senyawa Kimia
IV. Reaksi Hidrasi
V. Panas Hidrasi
VI. Pengikatan dan Perkerasan
VII. Jenis Semen Portland
VIII. Perbedaan Produk Semen
IX. Cara Penyimpanan Semen

B. Penelitian-penelitian Semen

This research aims to study the problems of the rotary kiln of al Kufa cement plant. The heating process of the furnace starts by burning a certain amount of wood near the fuel outlet inside the rotary kiln to provide the initial combustion process of the heating oil at (80-100°C). Then the front fan of the furnace is operated while the heating process is continuing for 24 hours. The most important problems that appear during the use of the rotary kiln were: mechanical wear, thermal wear and chemical wear. These problems have been diagnosed and taking the necessary treatments to reduce them, whereas the operational limits must e observed during the operation. When mechanical, thermal or chemical problems occur they will result high torque furnace that causes the risk of the main vehicles of the rotary kiln.