Quality control methods for cementitious gravel

The cemented sand-gravel dam is a new type of dam between the granular dam and the rigid dam.The two main aspects of controlling the quality of the cemented sand-gravel are compressive strength and density.In terms of strength,the maximum particle size of the cemented sand gravel material aggregate is 150 mm.According to the existing concrete test regulations,the full-graded test piece of this material should be a cube with a side length of 450 mm,but the production of the test piece is laborious and time-consuming,the cost is high;in terms of density control,the traditional irrigation method test takes a long time and affects the progress of the project,so it is necessary to find a simpler alternative method to simplify the test and reduce various cost inputs. Strength:150 mm cube specimens with a side length of 150 mm (eliminate particles above 40 mm) and 450 mm cube specimens with a side length of 450 mm (fullgraded test specimens) were prepared.The 150 mm cube specimens were cured for 14 days and 28 days,with a side length of 450 mm.The compressive strength test was carried out after reaching the corresponding prescribed age of cured cubes for 180 days.For the obtained compressive strength test data,linear fitting was performed by the least square method,and the linear relationship between the 14-day age of the 150 mm cube specimen and the 180day age of the 450 mm cube specimen was obtained.In terms of density,the rolling test site for the density test is arranged on the left bank platform between the upstream of the dam and the downstream of the cofferdam,with an area of 2,400 m2 (40 m×60 m).Twenty-eight measuring points were evenly distributed in the test site.First,the density was checked by a nuclear densitometer,and then a pit was dug at the same location for density parallel inspection by irrigation method.The diameter of the test pit was 450 mm and the depth was 450 mm.Similarly,the least square method is used to linearly fit the measured data,and the linear relationship fitting formula of the density result is obtained.To further verify the effectiveness of the nuclear densitometer test method,a verification analysis was performed at the initial stage of the dam filling in 2015,and the number of samples was increased to 30,and the linear formula fitted by the two methods was also obtained. The fitting result of the 14-day small specimens and the 180-day large specimen shows that the fitting curve is R180=1.542 7R14-4.951 93,and the correlation coefficient r=0.97.The fitting result of the 28 day small specimens and the 180 day large specimen shows that the fitting curve is R180=1.607 8R28-8.758 7,and the correlation coefficient r=0.95.The fitting curve of the density measured by the nuclear density meter and the density data measured by the irrigation method is γi=0.822 6γn+427.046 27,and the correlation coefficient r=0.90;the fitting curve obtained from the initial verification test of dam filling is γi=0.829 68γn+417.720 57,the correlation coefficient r=0.90. The fitting correlation coefficients obtained by the two test methods are both greater than 0.80,which meets the requirements of the project.The above test methods used have been verified and applied during the construction of the project,and also have been tested in parallel.It shows that the testing methods for the compressive strength and density of cemented sand and gravel described are effective and feasible,which may solve many existing problems in conventional testing methods,and may also provide a good reference for similar projects in the future.

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