The Effect Of Water/cement Ratio On Compressive Strength Of Palm Kernel Shell Concrete At 1:2:4 Nominal Mix

3.2.2        Specific Gravity
The specific gravity of any substance is defined as the unit weight of the material to the unit weight of distilled water at 40c. Substances with a specific gravity of 1 are naturally buoyant in water, those with specific gravity greater than 1 are denser than water and so (ignoring surface tension effects) will sink in it, and those with specific gravity of less than 1 are less dense than water and so will float. Table 4.2 on page 34  shows the result of specific gravity of palm kernel shell.
Specific gravity of saturated surface Dry Sample = Ws/((W_S+W_W )-W_A )
3.2.3 WATER ABSORPTION CAPACITY
Absorption capacity represents the maximum amount of water the aggregate can absorb. It is calculated from the difference in weight between the WS and WB stakes, expressed as a percentage of the WB Weight:
Water absorption capacity (%)= (WS-WB)/WB X100
The absorption capacity is used in mix proportion calculations. Most normal weight aggregates have absorption capacities in the range of 1 to 2%. Abnormally high absorption capacities indicate high-porosity aggregates, which may have potential durability problems.
3.2.4        Aggregate Impact Value
The aggregate impact value gives relative measure of the resistance of an aggregate to sudden shock or impact. The property of a material to resist shock is known as toughness. Due to the effect of moving loads on concrete pavement, the aggregates are subjected to impact resulting in their breaking down into smaller pieces.
Aggregate impact value = B/A X 100
Where,
B= Weight of fraction passing 2.36mm sieve
A= Weight of oven dried sample
3.2.5     Concrete Slump
Workability is the ease with which the ingredients can be mixed and the resulting mix handled transportation and with little loss in homogeneity. Unfortunately, workability cannot be measured directly. Engineers therefore try to measure the consistency of the concrete by performing a slump test. The slump test is useful in detecting variations in the uniformity of a mix. In the slump test, a mould shaped as the frustum of a cone, 305mm high with 203mm diameter base and 102mm diameter top is filled with concrete in 3 layers and subjected to 25 strokes of tamping rod each (ASTM Specification C143). Immediately after filling, the mould is removed and the change in height of the specimen is measured.
The change in height of the specimen is taken as slump when the test is done according to the ASTM Specification. A well proportioned workable mix settles slowly, retaining its original shape. A poor mix crumbles segregates and falls apart. The slump may be increased by adding water, increasing the percentage of fines (cement or aggregate), entrain air or by using an admixture that reduces water requirements.
Specification of concrete slump includes;
    mass concrete and road work slump is between 15mm to 50mm
    beams and slabs slump is between 50mm too 100mm
    columns, thin vertical section e.t.c slump is between 75mm to 125mm