To calculate the quantity of sand required for 8 cubic meter brickwork with cement mortar (1:3), we need to follow the below steps:

Step 1: Find the volume of brickwork

The volume of brickwork is given as 8 cubic meter.

Step 2: Find the proportion of cement mortar

The proportion of cement mortar is given as 1:3 i.e. 1 part of cement and 3 parts of sand.

Step 3: Find the volume of cement mortar

To find the volume of cement mortar, we need to first calculate the total proportion of the mixture.

Total proportion = 1+3 = 4

Now, we can calculate the volume of cement mortar as:

Volume of cement mortar = (1/4) x volume of brickwork

Volume of cement mortar = (1/4) x 8

Volume of cement mortar = 2 cubic meter

Step 4: Find the quantity of sand required

As per the proportion of cement mortar, the quantity of sand required will be three times the quantity of cement.

Quantity of sand required = 3 x quantity of cement

As we know the volume of cement mortar is 2 cubic meter, we can calculate the quantity of cement as:

Quantity of cement = (1/4) x volume of brickwork

Quantity of cement = (1/4) x 8

Quantity of cement = 2 cubic meter

Now, we can calculate the quantity of sand required as:

Quantity of sand required = 3 x 2

Quantity of sand required = 6 cubic meter

Therefore, the quantity of sand required for 8 cubic meter brickwork with cement mortar (1:3) is 6 cubic meter.