Why does dry density decrease after optimum moisture content?

How moisture content affects the dry density? If water is added beyond the optimum moisture content, the water will occupy the extra space since there is no air volume and dry density will reduce. This change in dry density values with respect to water content is shown by the compaction curve below.

Why the dry unit weight first increases and then decreases with the increase in moisture content in soil after the soil compaction?

As the soil compacts the voids are reduced and this causes the dry unit weight ( or dry density) to increase. Initially then, as the moisture content increases so does the dry unit weight.

What increases the dry density of soil?

The mass of compacted soil and the volume of the mold gives bulk density of the soil. From the bulk density the dry density can be determined for the water content used (w). The same procedure from (1-8) is repeated by increasing the water content in the soil by 2 to 3\%.

What happens to the maximum dry unit weight and optimum water content when the compaction energy is increased?

For all types of soil and with all methods of compaction, the effect of increasing the compactive energy is to increase the maximum dry density and to decrease the optimum moisture content.

What is the primary factor that affects the dry unit weight and the optimum moisture content from the compaction test?

The degree of compaction is measured by dry unit weight and depends on the water content and compactive effort (weight of hammer, number of impacts, weight of roller, number of passes). For a given compactive effort, the maximum dry unit weight occurs at an optimum water content.

How does increased effort affect the compaction curve?

This means that, as the effort increases, the compaction curve shift towards the theoretical point in which all porosity is erased and the dry density becomes equal to the density of the soil particles.

How can the dry density of a mixture be increased?

As in any of the particulate material with the interaction of water, the dry density increases and then decreases. At f/b ratio of 0.2, the mix would attain maximum dry density for all the fluids. It can be seen that compaction characteristics would be marginally affected by the fluid medium.

Why does the density of soil decrease with increase in water?

This is the reason for lower dry density attainment. When the soil particles are lubricated with the increase in the water content, the soil particles will be densely packed resulting in increased density. Now beyond a limit (OMC) the addition of water will not bring a change in dry density or will decrease the dry density.

What happens to the density of water at different temperatures?

At temperatures well above freezing, the molecules move faster and get further apart. The density decreases as temperature increases. At temperatures near 0 °C, the water still contains many ice-like clusters. These clusters are free to move relative to each other, so water is still liquid.

How do you find the theoretical maximum dry density of water?

The theoretical maximum dry density can be determined by the equation Eq.4 G = specific gravity of solids; = mass density of water; w= water content; The theoretical zero void line can be drawn by plotting the theoretical maximum dry density in the compaction curve if the value of ‘w’ and G is known. Modified or AASHTO Proctor Test