Question

. In order to evaluate the suitability of non-potable (non-drinkable) water at the job site for mixing concrete, six standard mortar cubes (2" x 2" x 2") were made using that non-potable water and six others using potable water. The cubes were tested for compressive strength after 7 days and the following load failure results were obtained (in lb) Cubes made with potable water 17,800 16,530 16,820 15,690 18,820 16,700 Cubes made with non-potable water 16,200 14,530 (Missin 16,100 15,870 14,380 Assume that the non-potable water satisfies the ASTM requirements (in terms of both the strength and cement setting time using the Vicat test) and it will be used at the job site, calculate the minimum load of the missing observation

Answer 1

Let5 seven days avg 100 pressure strength of the both portable & non portable water the value of avg compressive strength for the non portable water should not be cos than 90% of compressive strength of potable H_2O result E_avg = C_1 + c_2 + c_3 + c_5 + c_6 + c_7/n where there are n is the no of samples Avg compressive strength of non potable H_2O is C_NP avg = 16200 + 14530 + 15820 + 14160 + 16100 + 15870 + 45380/7 = 107060/7 = 15294.286 ps C_p avg = 17800 + 16530 + 16820 + 17920 + 15690 + 188920 + 10720/7 = 120300/7 = 17185.714 ps 90% of compressive strength of potable H_2O sample 90/100 C_p avg = 90/100 * 17185.714 = 15467.143 psi > 15294.286 psi avg of compressive strength of non potable H_2O is 90% avg compressive strength due to portable H_2O samples \r\n 5) alk to ASTM c191 the selting time test is also used to calculate the accessibility of non potable H_2O