Quality Control

✓Written by Help The Engineer TeamReviewed by Er. Inderjit Sharma (Retd.), Punjab PWD Why test sulphates? Some soils and groundwater contain dissolved sulphate salts (sodium, magnesium or calcium sulphate). Sulphate attacks concrete: it reacts with the cement and forms new crystals that expand, crack and soften the concrete of foundations, piles and buried pipes. What

✓Written by Help The Engineer TeamReviewed by Er. Inderjit Sharma (Retd.), Punjab PWD What is CBR? The California Bearing Ratio (CBR) tells you how strong a soil is compared to standard crushed stone. A 50 mm plunger is pushed into the soil, and the load needed is compared with the load needed for the same

✓Written by Help The Engineer TeamReviewed by Er. Inderjit Sharma (Retd.), Punjab PWD What is the plastic limit? The plastic limit (PL) is the lowest water content at which soil can still be moulded. In the lab, it is the water content at which a soil thread just starts to crumble when rolled to 3

✓Written by Help The Engineer TeamReviewed by Er. Inderjit Sharma (Retd.), Punjab PWD What is the liquid limit? As you add water to clay, it changes from hard, to soft and mouldable, to a thick liquid. The liquid limit (LL) is the water content at which the soil just starts to behave like a liquid.

✓Written by Help The Engineer TeamReviewed by Er. Inderjit Sharma (Retd.), Punjab PWD Why a hydrometer? Sieves can only separate particles down to 75 µm. Silt and clay are much smaller, so they are measured by letting them settle in water and checking how fast they settle. This is the hydrometer (sedimentation) method. What does

✓Written by Help The Engineer TeamReviewed by Er. Inderjit Sharma (Retd.), Punjab PWD What is grain size analysis? It finds how much of a soil is gravel, sand, silt and clay by shaking it through a stack of sieves with smaller and smaller openings, and weighing what stays on each one. Why does it matter?

✓Written by Help The Engineer TeamReviewed by Er. Inderjit Sharma (Retd.), Punjab PWD What is specific gravity? Specific gravity (G) of soil tells you how many times heavier the soil particles are than the same volume of water. If G = 2.65, a cube of soil solids weighs 2.65 times as much as a cube

✓Written by Help The Engineer TeamReviewed by Er. Inderjit Sharma (Retd.), Punjab PWD What is water content? Water content (moisture content) tells you how much water is in a soil compared to the dry soil. It is written as a percentage. Why does it matter? Almost every soil property depends on water. It is needed

✓Written by Help The Engineer TeamReviewed by Er. Inderjit Sharma (Retd.), Punjab PWD Why prepare soil samples? Soil brought from the site is wet, lumpy and mixed with roots and stones. Before any lab test (water content, liquid limit, CBR, compaction and so on), it must be dried, cleaned, broken down, sieved and reduced to

✓Written by Help The Engineer TeamReviewed by Er. Inderjit Sharma (Retd.), Punjab PWD Why keep codes in the lab? Every test result must follow a standard method and be checked against a standard limit. Indian Standards (IS), IRC codes and MoRTH specifications tell you how to test and what result is acceptable. This page lists