Statistical quality control of concrete. Chapter 4. Quality Control 2019-01-17

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Quality Control Issues

statistical quality control of concrete

This category verifies if a process is functioning properly or not. Soft, porous aggregate can result in weak concrete with low wear resistance. The table belowshows the number of defective tires in each sample of 20tires. The key function of the acceptance-sampling method is to guide the decision between accepting or rejecting the quality of the products. If the second sample met the specifications, and as a result the first sample was disregarded and its value not recorded, then the historical data will tend to underestimate the actual variability associated with the process being measured.

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Statistical Control

statistical quality control of concrete

In this case, all data must be recorded and used in the analysis as to whether the product was truly in or out of control. Infact it is an integral part of any manufacturing process. As soon as you see the advantages of this tool you will never want to use a spreadsheet again! These situations can be very depressing and disappointing. In this study, only the database of precast prestressed piles will be used. One way of ensuring quality control is integrating quality into the process. Trabalho da disciplina de Confiabilidade em Engenharia Oce√Ęnica. It applies statistics to specify the requirements of 1 how many measurements are needed; and 2 how to make an acceptance or rejection decision based on measured data.


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What is Statistical Quality Control?

statistical quality control of concrete

Introduction The seaport located in Rio Grande, in Rio Grande do Sul state, is one of the busiest ports in Brazil. This seaport has eight privately managed terminals that operate with containers, bulk grain commodities mainly soybean and wheat , oil, petrochemicals and fertilizers. The samples consist of two 02 cylinders and the highest of both values obtained by the compressive test is considered the strength of the sample. This shift of the process mean is called the off-centering of theprocess. One of the keys to achieving a balance in testing frequency is to relate the testing frequency to the rate and consistency of production.

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Chapter 4. Quality Control

statistical quality control of concrete

The compressive strength of the concrete is considered as a random variable that must be controlled by standardized sampling and testing in order to ensure the structural safety. Its base is situated 13. The advantages and disadvantages of using different sampling methods are compared. Concreto - Ensaios de compressão de corpos de prova cilíndricos. The contractor should be in the best position to know what tests are the best indicators of control and what frequency is necessary for control. Control charts Based on : P. Due to the simplicity of its implementation, this type of control chart can be used not only to control many processes but also to help find changes in product characteristics and verify non-conformities.

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Statistical Quality Control.

statistical quality control of concrete

Size of concrete cylinder is 150mm dia 300mm long. This probability distribution has been studied as an alternative to the model proposed by Gauss when it does not provide adequate fitness to the results. This system ensures consistent quality for the contractor's clients. Estudo probabil√≠stico da resist√™ncia √† compress√£o de concretos utilizados em funda√ß√Ķes. It also will be a disadvantage to the agency when encountering a contractor that needs more frequent sampling and testing to maintain control.


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Quality Control Issues

statistical quality control of concrete

According to Azevedo and Diniz 2008 , it is a well-known fact that the compressive strength of concrete depends on the level of quality control exerted in all stages of concrete production. Regarding the acceptance criterion of Brazilian, North American and European norms, data showed that, for the bottom slab, two of the lots would not comply. The analysis should involve the statistical properties that will be used to establish action limits. So, in order to achieve a quality and a durable building structure, maintaining the quality and standard of concrete is paramount. If this approach is taken, the limits will not be as useful since they will not have been developed for each specific plant or operation. Lot 5 did not have values above or below the limits, while the others had different characteristics; lot 4 surpassed the lower control limit and lot 2 surpassed the higher control limit. The analysis also reveals a few unusual events that were not apparent from visual interpretation of the data, including a possible precursor to the aforementioned event.


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Chapter 4. Quality Control

statistical quality control of concrete

For example, some operations may require sampling from different locations than others. As such, they may be of little actual benefit in establishing useful control limits for a specific plant operation. Shewhart atBell Laboratories in the early 1920s. Lot 10 was the only set of samples that did not exceed any limit. If approval is required, then does this mean that once approval is obtained the contractor has no further restrictions? Acceptance sampling determines if a whole lot of products is acceptable based on the results of random inspection. Concrete - Part 1: Specification, performance, production and conformity. However, when the agency decides to initially develop a generic plan, the data should come from several typical operations.

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Quality control of concrete

statistical quality control of concrete

According to Devore 2006 , the mathematical equation for the probability distribution of the normal variable depends on two parameters, mean and standard deviation. The water needs to be pure in order to prevent side reaction from occurring which may weaken the concrete or otherwise interfere with hydration process. The pier structures were made of reinforced concrete, mostly precast, divided into precast prestressed piles and precast structural elements. The data had a few lots that did not fit satisfactorily into any of the distributions, but, when the probability distribution failed in the goodness-of-fit test, the other got the same result. To be valid, the historical data must have been obtained using a random sampling procedure. Edwards Deming invited Shewhart to speak at theGraduate School of the U.

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Statistical Control

statistical quality control of concrete

If the contractor's process variability does not allow control limits that are completely within the specification limits, then this indicates that the contractor cannot consistently meet the specification requirements. The reasons for this are discussed above and again in chapter 5. Compression test of concrete Cylinder b Tensile Strength Test Split Cylinder Test When the cylinder split the tensile strength of concrete is determined. However, in reality it is difficult to impose product inspection along every process- so much more if the production is quite large. When this is done, all test results should be reported and the retest should be noted as such. However, more often than not, the failure is a result of negligence and lack of attention to quality on the jobsite during construction.

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