Mix stability

Petroleum and Goal. The alkanolarnines have found wide use in the petroleum industry. The ethanolamines are used as lubricants and stabilizers in drilling muds. Reaction products of the ethan olamines and fatty acids are used as emulsion stabilizers, chemical washes, and bore cleaners (168). Oil recovery has been enhanced through the use of ethan olamine petroleum sulfonates (169—174). OH—water emulsions pumped from wells have been demulsifted through the addition of triethanolarnine derivatives. Alkanolarnines have been used in recovering coal in aqueous slurries and as coal—oil mix stabilizers (175—177). 

Prior to study initiation, stability of the test chemical in the diet must be determined over a test period at least equivalent to the time period during which animals are to be exposed to a specific diet mix. Stability of test samples under the conditions of the proposed study is preferable. Labor and expense can be saved when long-term stability data permit mixing of several weeks (or a month) of test diet in a single mixing interval. 

The stability of the concrete mix can be considered in terms of its cohesion , which is a subjective term used to describe its ability to maintain a homogeneous appearance when subjected to applied stress. Lack of cohesion leads to segregation of the mix components into layers relevant to their densities. A further term associated with mix stability is that of bleeding , which is the movement of water to the surface of the fresh concrete. This phenomenon can occur either in isolation or as a manifestation of segregation. Bleeding in excess is normally considered to be undesirable because of the dangers of water runs at the shutter/concrete interface and cracking due to plastic settlements, and there is also the possibility of adverse effect on the concrete-reinforcement bond due to the collection of water beneath the steel. 

Concrete which is produced using fine aggregates deficient at the fine end of grading, e.g. sea dredged aggregates, exhibit a tendency to bleed and segregate. The presence of a small amount of entrained air (2-4% by volume) leads to an improvement in cohesion, or mix stability. Alternatively, with mixes which are adequate in this respect, a reduction in sand content can be made when air is entrained without loss of cohesion. The amount that can be removed is approximately equal on a volume basis and leads to a reduction in water-cement ratio to minimize the effect of entrained air on compressive strength. 

Accelerating admixtures based on calcium chloride, formate, nitrate, and thiocyanate have no significant effect on the workability, air content, mix stability, or water-cement ratio of concretes into which they are incorporated. The only properties of plastic concrete which are affected are the heat evolution and setting time. 

The most recent enhancement of bromine biocide chemistry is the development of a stabilized single liquid bromine, under the brand Stabrex , from Nalco (now owned by Degremont/Suez Lyonnaise Des Eaux). The product is most likely a sodium hypochlorite/sodium bromide mix, stabilized with sulfamic acid. It contains 14% available halogen as Br (6% as Cl), and is stable for several months. Stabrex probably has some benefits over other bromine chemistries, but is also a premium priced product. 

It emanates from Eq. (5) that as mentioned before the combinatorial entropy of mixing stabilizes the mixture and that X < 0 favors miscibility of the components, especially, in the case of high-molar-mass polymers (each r large) when the combinatorial entropy of mixing tends to very small values. 

The unfoamed mixture should be as concentrated as possible, consistent with mix stability, In order to minimize wet add-on and to maximize energy savings. 

The remaining 10.8 wt % of sulfur performs as a mix filler. These large agglomerations of sulfur do not perform in the same way as conventional mineral fillers which are dispersed in asphalt hot-mix. The latter, at the concentrations typically used, generally improve the void filling capacity of the asphalt binder (or reduce the VMA) without effecting such dramatic changes to mix stability as does sulfur. 

It is therefore recommended that the sulfur concentration in the binder be maintained at a low level, sufficiently high to meet mix stability requirements but without lowering the standard of mix flexibility i.e., 20-30 wt %. Flexibility should not be confused with fatigue resistance, which... 

The allowable sulfur concentration in the binder depends on the properties of the asphalt. For example, asphalts A and B (Appendix, Table A-I) exhibit significantly different viscosities at the Marshall test temperature of 60°C. This difference is reflected by differences in mix stability at similar asphalt contents, shown in the Appendix and in Figure 6, i.e., 11120 N and 5960 N for asphalt A and B, respectively, at a content of 6 wt %. Asphalt B yields high-stability mixes and is not as prone to softening by low sulfur concentrations in the binder, whereas asphalt A exhibits the reverse behavior. 

Thermopave mixes use substantially higher sulfur contents. Microscopic examination of mixes prepared in the laboratory and in a commercial Cedarapids hot-mix plant verified that some of the sulfur is finely dispersed, therefore contributing to the dilution of the asphalt, but most of the sulfur agglomerates readily to perform as a mix stabilizer. 

Starting with the basic concept of the electrokinetic potential of colloidal particles, the so-called zeta potential, i.e., the electrokinetic potential at the shear plane, the most important well-established methods of zeta potential determination are discussed separately. Taking into account the peculiarities of kaolin particles, the relevance of these methods for characterizing kaolin particles in the absence and the presence of polyelectrolytes are outlined here. Thereby a mixed stabilization by oppositely charged polyelectrolytes is discussed in more detail. 

Marshall Stability. A factorial study was made to determine the Marshall stability for mix compositions with asphalt contents of 2-10% and sulfur contents of 0-20 wt % of mix. The mix stability of the two-... 

The sand-asphalt-sulfur mix stability increased to a peak value with increasing sulfur content for all asphalt levels. 

The mix stability decreased with increasing asphalt content for all sulfur levels. 

Extremely high mix stabilities were attained by using sulfur compared with mix stabilities for dense graded asphalt concrete mixes which seldom exceed 2000 lb (8900N). 

Sand-asphalt-sulfur mix stabilities were adequate even with excessively high asphalt contents, e.g., 10% asphalt. 

On the basis of these observations, we concluded that using sulfur in an asphalt mix permits design for a predetermined mix stability value. This approach is unique in the realm of asphalt mix design because the stability level of conventional asphalt mixes is governed within narrow bounds by aggregate grading. Because the use of sulfur in mixes provides more freedom in the use of materials, it allows the designer to select the most appropriate stability level to optimize mix performance for a specific use. 

Flexibility and Fatigue Resistance. The data presented in Figure 4 indicate that a given mix stability level may be attained using a variety of bitumen contents with the corresponding sulfur contents. For example, 1000-lb stability mixes may be made with asphalt contents of 2-10%. The major component influencing mix flexibility is the asphalt content. Thus, a lean mix composition, with only 2% asphalt, would be very brittle whereas the mix with 10% asphalt would be quite flexible and able to conform to roadway deformations without cracking. 

Other forms of stability constant can be derived from the fundamental definition given in Eq. 2. For example, if one of the reagents is the hydrogen ion activity can be measured with a suitable electrode, and this will give rise to a mixed stability constant when the other species are represented by concentrations. 

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