This report presents a computer program for the computation of required average strength, f'cr, based on the field strength test data. Based on the recent Code (ACI 318-83), four different cases--available data more than or equal to 30, available data for two consecutive sets more than or equal to 30, available data more than or equal to 15 but less than 30, and no field data available for comparable concrete--are identified and solved. The necessary equations and flow chart are presented so the reader more clearly understands the sequence of operations. Input/output data are explained using sample problems that illustrate the capability of the program to handle the different cases. The steps presented are written for one particular brand of computer, but the specialized commands are kept to a minimum so that the user can easily modify the program to other types of similar widely used computers.

This paper is intended to show the application of ACI 214-77 and the use of computer-generated data in evaluating concrete data. A computer program written in FORTRAN 77 and utilizing a CALCOMP plotter is used to analyze concrete strength results in accordance with ACI 214-77. To facilitate interpretation of the results, the following information is plotted: average of individual tests, five-test moving average, average strength, and required strength; test range, ten-test moving average range, and average range; and a five- and ten-test moving coefficient of variation and the overall coefficient of variation. Besides providing the information required by ACI 214-77, other concrete data is provided. For instance, histograms of the strength test results are plotted. Slump and entrained air content are plotted if this information is available. The slump and air data may prove to be beneficial when interpreting individual strength tests. A case study is examined to determine the usefulness of the FORTRAN program and the benefits provided by computer plotting of concrete data.

The cover meter, commonly known as the pachometer, is a useful instrument in locating steel reinforcing bars within concrete members. The instrument works on the principle that steel bars present in the developed magnetic flux field will cause a meter deflection. The larger the steel bar or the closer it is to the probe, the larger the meter deflection. Many times the cover meter is used to locate steel to minimize the chances of cutting the reinforcing during coring operations. At other times, it is desirable to learn the placement of the bars for structural reasons, such as times when the loading of a structure is being changed and the reinforcing placement is not known, for rehabilitation of older structures, or in times of controversy when the quality of construction is questioned. The paper analyzes data for a project in which the placement of reinforcement was questioned. A correlation was established for the cover meter for the meter reading and the measured cover. Statistical analysis of the data was used to 1) establish a regression model, 2) learn the expected accuracy of a reading, and 3) establish a meter reading that would have a specified confidence for a desired cover. Since the cover data included a range of values for reinforcing bars relatively close to the surface to three inches or more below the surface, a statistical analysis of the instrument's variability for differing bar depths was made.

SP-101 As a designer or engineer you need reliable test data when determining the strength of concrete. Computer Use for Statistical Analysis of Concrete Test Data will explore new ways in which the computer can help you achieve statistically more accurate results from your testing procedures. In addition, this important new volume presents various tools to help you interpret test results, and reports on the measures of reliability which can be used in establishing specifications and design criteria for the strength of concrete. This state-of-the-art publication, offers insight into the use of computers, including micro and mini computers, in concrete quality control and quality evaluation. With topics such as: analysis of in-place test data with spreadsheet software, computer analysis and plotting of computer data, analysis of cover meter data, and development of prediction relations from compression test data using regression analysis, Computer Use for Statistical Analysis of Concrete Test Data will be an indispensable source of information.

Using linear regression to analyze concrete strength data, the Corps of Engineers has developed two computer programs that help predict 90-day strengths from one-day accelerated cured-cylinder strengths. These programs use equations from ACI 214-77 and provide the user with standard deviations, predicted strengths, and graphs of the data for concrete that can be used for any design age.