Students in the materials class prepared three mortar míxes with water to cement ratios of 0.50, 0.55, and 0.60. Three 50-mm mortar cubes were pre- pared for each mix. The cubes were cured for 7 days and then tested for com- pressive strength. The test results were as shown in Table P6.16. ТАBLE P6.16 Mix w/c Мaximum Compressive Average Compressive Strength (MPa) No. Ratio Cube No. Load (kN) Strength (MPa) 1 79.4 1 0.50 80.1 81.9 1. 74.7 2 0.55 2 74.5 3 72.5 1. 65.8 2 69.3 3 0.60 71.2 Determine the following: a. The compressive strength of each cube. b. The average compressive strength for each mix. c. Plot the average compressive strength versus w/c ratios for all mixes. d. Comment on the effect of increasing w/c ratio on the compressive strength of the cubes.

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8 In a ready-mix plant, cylindrical samples are prepared and tested periodi- cally to detect any mix problem and to ensure that the compressive strength is higher than the lower specification limit. The minimum target value was set at 27.6 MPa. The compressive strength data showm in Table P7.48 were col- lected. Use one system of units only as specified by the instructor. TABLE P7.48 Sample No. Compressive Strength, MPа Sample Compressive Strength, No. MPa 1 33.9 14 39.8 2 32.6 15 29.4 39.1 16 35.1 4 29.7 17 32.2 42.1 18 35.7 6 29.8 19 37.5 7 36.1 20 25.5 8 34.1 21 31.1 9. 36.1 22 25.4 10 28.9 23 28.3 11 39.8 24 25.4 12 31.2 25 27.0 13 28.0 a. Calculate the mean, standard deviation, and the coefficient of variation of the data. b. Using a spreadsheet program, create a control chart for these data showing the target value and the lower specification limit. Is the plant production meeting the specification requirement? If not, comment on possible reasons. Comment on the data scatter.

Design the concrete mix according to the following conditions:Design Environment• Concrete slabo Subjected to freeze and thaw.o Required design strength = 21 MPao Slab thickness = 300 mm.o Statistical data indicate a standard deviation of compressive strengthof 1.7 MPa is expected (more than 30 samples).• Only air entrainer is allowed.• Available Materials:o Air entrainer:▪ Manufacture specification is 9.5 mL/1% air/100 kg cement.o Coarse aggregate:▪ 25 mm nominal maximum size▪ Crushed stone▪ Bulk oven-dry specific gravity = 2.573▪ Absorption = 2.8▪ Oven-dry rodded density = 1922 kg/m3▪ Moisture content = 1o Fine aggregate:▪ Natural sand▪ Bulk oven-dry specific gravity = 2.540▪ Absorption = 3.4▪ Moisture content = 4.5▪ Fineness modulus = 2.60o Cement:▪ Type I Cement▪ Specific gravity = 3.15Find the required quantities of cement, water, coarse aggregate, fine aggregate, aircontent, and admixture per 1 m3 of concrete. Summarize the findings in a table.Based on this information, find the…