Setting of concrete

Clock-type induction periods occur in the spontaneous ignition of hydrocarbon-oxygen mixtures [2], in the setting of concrete and the curing of polymers [3]. A related phenomenon is the induction period exhibited... 

The setting of concrete is an exothermic reaction, and large masses of concrete in building foundations, bridges and dams will heat up, causing expansion cracks if not checked. To counteract this heating, the materials are cooled before and as they are mixed, so that the concrete is laid some 15 K colder than ambient, and warms to ambient on setting. In practice, the final mix temperature can be held down to 10°C. 

Time of setting of concrete mixtures by penetration resistance Compressive strength of cylindrical concrete specimens Flexural strength of concrete (using simple beam with third-point loading)... 

It is important to ensure that when using corrosion inhibitors with other conventional admixtures, they are added separately, at different times of the mix cycle. Corrosion-inhibiting admixtures which also accelerate the set of concrete may require the combination of a retarding admixture when ambient and mix temperatures exceed 35°C. In like manner, set-retarding corrosion inhibitors may require the addition of an accelerator to offset the retardation of early strength development (e.g. use of sodium nitrite in conjunction with sodium benzoate). 

Table 7.22 Effect of temperature on the time of setting of concrete (Ref 108 with permission)...

Once a Lie algebra has been defined in the abstract sense via the defining commutation relations Eq. (3), it is of practical interest to find physical realizations of the generators in terms of position and momentum operators, which also satisfy these defining commutation relations. We shall call such a set of concrete operators a realization of the Lie algebra. In practice, as we shall see, we often work backwards by starting with a set of concrete operators... 

Bicarbonate ion is usually the chief anion in freshwaters. In and on silicate rocks, the HCOj concentration is usually 50 to 200 mg/L, whereas in groundwaters that contact a few percent carbonate materials up to pure limestone and dolomite, bicarbonate levels are usually in the range of 200 to 400 ppm. Seawater contains 140 mg/L HCOj. Carbonate alkalinity (CO3 ) rarely exceeds 10 mg/L. Why The presence of caustic alkalinity (free OH ) at pH s above 10 usually indicates artificial contamination of a water by, for example, Ca(OH)2 (portlandite) from the setting of concrete at newly completed wells. Cg concentrations can reach 1000 ppm as HCO3 in sodium carbonate-bicarbonate brines found in evaporative, closed basin lakes. 

However, each DPM is specific to a particular project, and the information relevant for a new project may be scattered among several models. Therefore, knowledge from completed projects which is considered to be important for other design projects can be collected, generalized, and finally represented by work process and decision templates which provide for simpler retrieval than a set of concrete DPMs. As the relevant parts of a decision template can directly be incorporated into the new DPM, the effort for documenting decision rationale in a new project is considerably reduced. 

The setting of concrete as defined by the stiffening times in BS 5075 Part 1 for concrete containing these admixtures must be within 1 hour of the equivalent plain concrete mix. In practical terms normal water-reducing admixtures can be regarded as not affecting the setting characteristics of the concrete. 

Fig. 4.32 Initial set of concrete mixture as a function of temperature and setting retarder addition (according to [84]) (admixture contents in % by mass given on the plots)...

Note that Astr6e computes an abstract semantics and provides local abstract invariants attached to program points. Thus, in case of a potential runtime error users can access the alarm message along with its context and the invariants. But it does not provide a concrete execution trace for the alarm, since each abstract trace represents a set of concrete execution traces. 

Anodising layers do not resist alkaline media they are dissolved during the setting of concrete and therefore do not improve the resistance of aluminium in contact with concrete [4]. 

---