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Introduction
Published in M. Pigeon, R. Pleau, Durability of Concrete in Cold Climates, 2014
The influence of cement on the size distribution of capillary pores is related to the fineness of the cement. Cements with a higher fineness have a larger number of particles per unit mass, which results in the formation of a larger number of smaller capillary pores. Furthermore, the finer cement particles tend to subdivide the space between the larger particles into smaller pores. This purely physical phenomenon leads to a finer pore-size distribution, although the total pore volume is not significantly affected. A finer distribution yields a lower amount of freezable water, since the amount of ice that can form at a given temperature decreases with the size of the pores (Chapter 2). The permeability of the paste is also reduced, and this reduction has both a positive effect (since the ingress of moisture into the concrete from outside is more difficult), and a negative one (since the higher resistance to the internal flow of water increases the internal disruptive pressures caused by the forced movement of water from the capillaries to the air voids during the freezing process).
Alkali-activated lime-pozzolan cements
Published in Caijun Shi, Pavel V. Krivenko, Della Roy, Alkali-Activated Cements and Concretes, 2003
Caijun Shi, Pavel V. Krivenko, Della Roy
Costa and Massazza (1974) studied 6 commercial Italian pozzolans with different surface areas. They observed that the correlation between combined lime and surface area was valid only before seven days, and the activity of the pozzolans depended on the reactive content SiO2+Al2O3. But no correlation was found between the fixed Ca(OH)2 and the surface areas for different pozzolans in another research (Mortureux, B. et al. 1980). Rossi and Forchielli (1976) also did not find any proportionality between surface areas and reactivity with lime for the same material. A strength test on 22 pozzolans (Chatterjee and Lahiri 1967) indicated that there was no general correlation between the compressive strength at 28 or 60 days and surface area (either by Blaine or BET method) of different materials. However, the strength increased as fineness increased for a single material.
Physical Characteristics and Product Variation
Published in V. M. Malhotra, V. S. Ramachandran, R. F. Feldman, Pierre-Claude Aïtcin, Condensed Silica Fume in Concrete, 1987
V. M. Malhotra, V. S. Ramachandran, R. F. Feldman, Pierre-Claude Aïtcin
The fineness of condensed silica fume can be evaluated by three different methods: The residue by sieving on a 45-μm sieve.2-4The direct measurement of the diameter of about 200 condensed silica fume particles.6The measurement of the specific area, which is an indirect measurement of the fineness. This is the most common method used.
Synthesis, characterizations and application of polyaniline-paint as anticorrosion agent
Published in Inorganic and Nano-Metal Chemistry, 2021
Fatima Assassi, Nassira Benharrats
To obtain 100 g of paint, all the raw materials necessary for the formulation are weighed, then the anticorrosion agent (phosphate zinc or conductive polymer) is introduced gradually and with moderate stirring. Then, the epoxy resin, the pigments, the fillers, the additives and the solvent mixture are added progressively underlow stirring. After that, 50% by weight of glass beads are added to the mixture. These are used as a grinding element under high-speed grinding in aim to obtain paint with fineness grain size. The fineness of grinding is determined by standardized control called gauge fineness. When a good fineness is obtained, the paints are filtered to remove the glass beads, and then a hardener (amine type with a ratio of paint/hardener 86/14) is added.
Machinability of Inconel 718: A critical review on the impact of cutting temperatures
Published in Materials and Manufacturing Processes, 2021
Kore Mahesh, Jibin T Philip, S N Joshi, Basil Kuriachen
The quality of any machined component in basic terms can be graded by the surface roughness/fineness of the product. A high value of fineness indicates a reduction in the micro cracks, stress concentration, fatigue cracks initiated at the boundaries of the grains. Kaminski et al.[102] studied the surface roughness (of the final/finished product) and the rise in temperature of nickel alloy (Inconel 718) during machining under HPJ cooling conditions. The maximum pressure of the coolant was considered up to 300 MPa. Built-up-edge (BUE) and surface roughness were significantly reduced through HPJ cooled cutting in contrast to dry machining. The lowest cutting temperature and flow rates identified are 70 MPa and 71 ml/min, respectively. Ezugwu and Bonney[111] measured the variation in surface roughness values (of the final/finished product) ensuing machining of hard to cut material (Inconel 718) through conventional and HPJ cooled machining processes. The cutting fluid was supplied at the cutting region in the incremental order of pressure values (11, 15, and 20.3 MPa). The surface finish values in HPJ cooling exhibited lower values than the conventional machining process. It has resulted due to the reduction in cutting forces at the interface zone. Courbon et al.[75,112] performed machining tests on Inconel 718, considering the effects of variation in fluid pressure, nozzle diameter, and cutting speed under the HPJ cooling environment. The high-pressure fluid supplied through a fixed diameter nozzle and at high cutting speeds aided in achieving better surface roughness values. Nevertheless, the surface quality degrades at lower cutting speeds.
A dry separation technique for improving the quality of coking coal middlings
Published in International Journal of Coal Preparation and Utilization, 2020
Zhen Li, Yanhong Fu, Chao Yang, Anning Zhou, Wei Yu, Lijun Liu, Jinzhou Qu, Wei Zhao
In this study, the feasibility of dry quality improvement technology for scarce coking coal middlings was studied using coking coal middlings obtained from the Xiqu Coal Preparation Plant of the Shanxi Coking Coal Group. The results indicated that quality improvement can be achieved using a jet milling–fineness classification system. The ash contents of the four classified products obtained through jet milling–fineness classification decreased with classification. The maximum ash gradient was found to be between the classifier-I and bag filter products. The classifier-I and cyclone products comprised the majority of the total products.The particle size, total mineral content, and pyrite content of the classified products decreased with classification. Hence, a certain degree of separation can be achieved by fineness classification. The higher the classification accuracy, the better the separation effect.Cyclone products can be used as high-yielding quality improvement products. The influence of the rotation speed of classifier-II and the crushing pressure on the ash content of the cyclone products was significant, and the influence of the rotation speed of classifier-II was greater than that of the crushing pressure. The influence of the process parameters on the yield of the cyclone products was not significant.Classified products were obtained whose ash content, sulfur content, particle size, and separation accuracy varied with classification. Moreover, quality improvement and quality classification can be realized using the jet milling–fineness classification system detailed in this paper.