Statistical calculation of average strength for mix design and coefficient of confidence of special concretes; shotcrete, Geopolymer, FRC and conventional in-place concrete

Considering the positive attitude of special concrete, the main focus should be on statistical relationships such as acceptance control and regulations. The purpose of this paper was to statistical analysis of the special concretes, the information from previous researches, and the statistical information was collected. The collected information and results were analyzed with the software SPSS and Minitab and the histogram curves were drawn and their standard deviation were calculated. And using the formulas of the coefficients and intervals of reliability and the average compressive strength obtained from the available research and 95 and 90% confidence intervals, these results have been analyzed and compared with the proposed formulas of the design codes. The results of the analyzes showed that the use of fibers can not have a positive effect on the compressive strength of concrete, but the standard deviation and the coefficient of variation were increased and the concrete's reliability were reduced. In the case of geopolymer concrete, it can be seen that the standard deviation and the coefficient of variation were improved. Statistical analysis of the results of compressive strength of samples manufactured in ready-made concrete companies that received quality control labs showed that the deviation standard and coefficient of variation the concretes made in August and September were less than the corresponding interval from May to June, the reason for this was the increased use of concrete precision manufacturing workshops and more customer focus in the summer as well as the quality of testing.