Ĭalculating the amount of bar needed can be done in a few simple steps. Using rebar as reinforcement adds considerable strength to concrete and reduces the overall slab thickness needed. The demand for new additives with special properties and tuned performance continues to increase.When installing a concrete slab or structure it is a good idea to add rebar, or reinforcing bar, to reinforce it and prevent it from cracking down the road.
Strength-retrogression prevention agents. The additives used to modify the properties of cement slurries for use in oilfield well-cementing applications fall into the following broad categories: To calculate the approximate thickening time for slurry design, add 1 to 1.5 hours to the job time. Limit the amount of trouble time to 1 to 1.5 hours. Calculate the actual job time, using the slurry volume and average displacement rate. 
When estimating job time, include the mixing time on the surface, especially if the job is going to be batch-mixed. Slurry design is affected by the following criteria:
Maintain a stable density to ensure hydrostatic controlĭo not add dispersants or retarders in excess of the amounts indicated by wellbore conditions, and provide just enough fluid-loss control to place the cement before it gels. Contain adequate retarder to help ensure proper placement. In formulating a cement slurry, the designer must consider not only the temperature but also the other downhole conditions, such as permeability and water-sensitive formations.Ī slurry should be designed for its specific application, with good properties to allow placement in a normal period. In addition to the cement, other factors, such as the correct Bottom Hole Circulating Temperature (BHCT), should be considered when designing a cement slurry to meet well requirements. For example, Class H cement with the proper additives has routinely been used at depths up to 20,000 ft. Any properly made Portland cement (consistent from batch to batch) can be used at temperatures up to 570☏. The slurry performance properties that are measured include:Ĭement manufactured to American Petroleum Institute (API) depth and temperature requirements can be purchased in most oil-producing areas of the world. What is actually known are the physical effects of these additives on the slurry performance properties. The reaction of these additives with the cement and the interaction between them is not well defined chemically. This give-and-take relationship between additives is the basis of cement-slurry design. For most downhole requirements, more than one additive is needed. The effects of the additives are reduced or enhanced by modifying the additive or by using additional additives. They will also exhibit at least one secondary characteristic that may be either beneficial or detrimental to the cement-slurry performance properties. These compounds, when used alone, will have a primary effect upon the cement slurry that is considered to be beneficial. Many chemical compounds have proved to be effective in modifying the properties of Portland-cement slurries. Table 2-Effects of Cement Admixtures on the Physical properties of Cement
0 kommentar(er)
