Astm C29 موضوع مهم لكل المهندسين المدنيين

Introduction: We intend to find the unit weight and the percentage of voids in fine aggregates upon putting them in a cylinder of height (h) 32.5cm and radius (R) of 10cm.

Procedure: We weigh the cylinder of the mentioned dimensions when it is empty and record its weigh as 10.2kg then we put the gravel in it successively while using a 16mm rod to remove any presence of voids until it’s filled, then we measure its weight and by subtracting it from the weight of the empty cylinder we obtain the weight of the solid Ws.
Then calculate the total volume of the cylinder by using the formula VT1=pi*R2*h, then VT1=10205 cm3, another way to find the total volume of the cylinder is to fill the cylinder with water and find its weight which VT2= 9.83Kg then find the average (VT1 +VT2)/2=10.0175Kg. To find the volume of voids we must fill the cylinder full of aggregates with water 1L at a time, so we find that it needed 4.55L of water to be filled and its all over weight is 29.2 Kg. To find the unit weight (u.w) we use the equation u.w= Ws/ VT=1.47 g/ cm3.knowing that sp.gr=2.7 then
%Voids=(sp.gr-u.w)/sp.gr*100=45.4%.

Conclusion: We conclude from the preceding experiment that voids fill about 50% of the total volume of the cylinder. There are two ways to get rid of these voids:
1- Use different types of aggregates (different sizes) especially smaller ones to minimize the % of voids.
2- Compact the soil to the maximum in such a way to eliminate any voids that may cause damage upon using.