Mixture proportion

At pressures to a few bars, the vapor phase is at a relatively low density, i.e., on the average, the molecules interact with one another less strongly than do the molecules in the much denser liquid phase. It is therefore a common simplification to assume that all the nonideality in vapor-liquid systems exist in the liquid phase and that the vapor phase can be treated as an ideal gas. This leads to the simple result that the fugacity of component i is given by its partial pressure, i.e. the product of y, the mole fraction of i in the vapor, and P, the total pressure. A somewhat less restrictive simplification is the Lewis fugacity rule which sets the fugacity of i in the vapor mixture proportional to its mole fraction in the vapor phase the constant of proportionality is the fugacity of pure i vapor at the temperature and pressure of the mixture. These simplifications are attractive because they make the calculation of vapor-liquid equilibria much easier the K factors = i i ... 

Among the various selection considerations are specific combustion characteristics of different fuels. One of the combustion characteristics of gaseous fuels is their flammability limit. The flammability limit refers to the mixture proportions of fuel and air that will sustain a premixed flame when there is either limited or excess air available. If there is a large amount of fuel mixed with a small amount of air, then there is a limiting ratio of fuel to air at which the mixture will no longer sustain a flame. This limit is called the rich flammability limit. If there is a small amount of fuel mixed with excess air, then there is a limiting ratio of the two at which the flame will not propagate.This limit is called the lean flammability limit. Different fuels have different flammability limits and these must be identified for each fuel. 

Table 2.5 Mixture proportions and properties of fresh and hardened concrete (water reduced)...

Mix Type of Mixture proportions and Series concrete properties of fresh concrete... 

The Hibernia offshore concrete platform on the Grand Banks off the coast of Newfoundland, Canada, is a 111 m structure and required about 165 000 m of superplaticized high-strength concrete. The typical mixture proportions and the properties of the concrete used for the skirt elements of the structure are shown in Table 7.18 [70]. The precast skirts are a series of reinforced concrete elements which were joined together to form continuous walls to support the base slab of the structure [69]. 

Table 7.18 Hibernia offshore piatform mixture proportions and strength test resuits of concrete for the precast skirt eiements (Maihotra [69])...

Silica fume when used in conjunction with superplasticizers plays an important role in improving the cohesion of the shotcrete mix, allowing for the build-up of the sprayed concrete on vertical surfaces, within a short period, without sloughing off. In addition the combination of these admixtures has provided ease of pumping, better compaction and greatly reduced the rebound, thus minimizing waste and cleaning time. Typical mixture proportions and properties for wet-mix superplasticized shotcrete are presented in references 69 and 72. 

Often it is difficult to adjust the mixture proportions to achieve desired design parameters for all properties of concrete. Consequently the properties of colloidal underwater concrete are controlled by the addition of three chemical admixtures. Minimum water-cement ratios range from 0.36 to 0.40. Cement and fine-aggregate contents are usually higher than corresponding mixes placed on land, and silica fume may be used in conjunction with a superplasticizer or conventional water reducers to reduce segregation. The key to a non-dispersible concrete with self-leveling characteristics is the successful optimization of the VEA with the superplasticizer used to increase the slump. 

A change in type or source of cement or amount of cement, or a modification of aggregate grading or mixture proportions, may be needed. 

Hover, C.K. (1998). Concrete mixture proportioning with water-reducing admixtures to enhance durability a quantitative model, CANMET/ACIInternational Workshop on Supplementary Cementing Materials, Superplasticizers and Other Chemical Admixtures, Toronto, Canada, April 6-1. 

The collective behavior corresponds to the same mixture proportions in bulk phases as at interface, so that the mixture may be treated as a pseudocomponent. This implies the same partitioning for the different species [38]. 

Larrard, F.De Concrete Mixture Proportioning. Routledge, New York. NY. 1999. Marchand. J. and J.P. Skalny Materials Science of Concrete, The American Cerantie Society. Westerville. OH, 1999. 

Admixtures Mixture proportions Properties of fresh Creep measurements on 150 > 300 mm... 

A reaction is said to be stoichiometric when the fuel and oxygen consume each other completely, forming carbon dioxide (C02) and water (H20) under ideal conditions. The equivalence ratio is the parameter relating a mixture proportion to stoichiometry. It is defined as the ratio of fuel-to-oxygen amounts times the stoichiometric ratio of oxygen-to-fuel amounts. If there is an excess of fuel, then the mixture is called fuel-rich or rich, and the equivalence ratio is greater than 1, and if there is an excess of oxygen, then it is called fuel-lean or lean and the equivalence ratio is less than 1. 

In setting down the conservation equations, we considered only fluids of uniform and homogeneous composition. Here we examine how these conservation equations change when two or more species are present and when chemical reactions may also take place. In a multicomponent mixture a transfer of mass takes place whenever there is a spatial gradient in the mixture proportions, even in the absence of body forces that act differently upon different species. In fluid flows the mass transfer will generally be accompanied by a transport of momentum and may further be combined with a transport of heat. 

A trial batch of concrete was performed, thereby producing the satisfactory mixture proportions recommended using in the construction of the left guide-wall dam section. The concrete thermal properties were tested according to the standard methods of the Chinese Test Code for Hydraulic Concrete (1982). Table 1 gives the test results. 

The mixture proportions were such that the components of the neat ERL-4221 system were present In nearly stoichiometric quantities, while the neat D.E.R.331 system had the hardener In excess. 

F. de Larrard, Concrete Mixture Proportioning - A Scientific Approach,... 

Determination of dosages for powder-type polymers was based on recommendations from the FRC technical committee in Japan. The FRC committee recommends adding 0.1% polymer for fire-resistant high-strength concrete with the strength of 60-100 MPa. Table 2 summarizes mixture proportion of the concretes. 

L.T. Phan, N.J. Carino Effects of Test Conditions and Mixture Proportions on Behavior of High-Strength Concrete Exposed to High Temperature, ACI Materials Journal, (2002), pp. 54-66... 

Mortar Mixture Proportions. Mortar mixture proportions as well as the values of consistency of fresh mortars obtained by means of flow table (according to UNI EN 1015-3) are presented in Table 1. The water to cement ratio and the cement to sand ratio were kept equal to 0.60 and 1 3 (by weight) respectively. Styrene butadiene rubber (SBR) or polyurethane (PU) waste particles were alternatively added to the mixtures at a dosage of either 10% or 30% by volume of aggregate. 

An optimization of mortar mixture proportions was carried out on mortars prepared with 10% waste particles, by adding a limestone powder as filler, at a dosage of 20% by weight of cement, replacing quartz sand, in order to improve the mortar mechanical performance. Limestone powder was added with and without an acrylic-based superplasticizing admixture, at a dosage of 1.0% by weight of cement. 

Optimized mortar mixture proportions as well as the values of consistency of fi esh mortars obtained by means of flow table (according to UNI EN 1015-3) are presented in Table 2. The water... 

Table 2 - Mixture proportions and consistency of optimized mortars.

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