Table of Contents

1. Introduction
2. Quality testing of sand
3. Silt content test
4. Particle size distribution
5. Organic impurities test
6. Bulking of sand 

Introduction

Sand is one of the basic raw materials used for construction. It is a fine aggregate that is either extracted from natural sources or made artificially in factories by crushing bigger rocks or gravel. Its size lies between 150 microns to 4.75 mm. Fine aggregate consists of natural sand, stone dust, crushed sand, gravel, fly ash, and broken brick. It should be well-graded to ensure that all its particles are of the same size.  

Sand is mixed with concrete and is used to fill the voids between coarse aggregates. Sand helps in increasing the workability of the concrete. It is used in brickwork, plastering work and RCC work.

Quality testing of sand

Sand is considered ideal if it is durable, inert, clean and free from organic matter, and the presence of iron pyrites, alkalis, salts or coal can affect the quality of concrete and cause corrosion. The presence of harmful materials in the sand must not exceed 5%.

4 major tests are conducted to determine the quality of sand

1. Silt content test
2. Particle size distribution
3. Organic impurities test
4. Bulking of sand

Silt content test

Take some sand in a beaker and add a glass of water to it. Stir it well and wait for the mix to settle down. Observe after an hour, and you’ll see that the clean sand has settled at the bottom and a layer of silt containing clay particles or other impurities will be formed at the top.

The amount of silt in the sand shall not exceed 8%. The presence of clay can make the sand cohesive and it is ideal for sand to have fewer traces of silt. If the silt is more than the recommended amount, it should be washed to bring the silt within allowable limits. 

Particle size distribution

It is also known as testing for the grade of sand. Fine aggregate is divided into 4 zones based on its size. Sand is meant to be coarser for RCC works and plastering works it is meant to be finer. The following table gives the details about different grades of sand

If other than 600 micron IS sieve, the grading falls outside of the limits of any particular grading zone of the sieve, by an amount not exceeding 5 per cent, then it will be considered as falling under that grading zone. 

Organic impurities test

It is also called the test for deleterious materials in the sand. It is necessary to check the sand for the presence of materials like salts, iron, pyrites, alkalis or other organic impurities like mica or shale, as these materials can affect the quality of concrete and affect the durability, strengthening and hardening capacity of the mortar. The maximum amount of clay, fine silt and organic impurities must not exceed 5% by mass and the organic impurities that determine the colour of the liquid should be lighter.

Bulking of sand

Fine aggregates have the same volume in a dry or saturated state, but it increases when there is dampness. If it is damp at the time of proportioning of ingredients of concrete, then the volume must be suitably allowed to bulk.

The table below gives the relation between bulking and moisture content.

Testing of sand is done in order to determine if the sand is fit for usage or not. Different grades of sand are used for different purposes. There are various types of construction sand, that include pit sand, artificial sand, river sand, beach sand, coarse sand, utility sand, fill sand and utility sand. All these types of sand have different properties and textures.

Explore our different categories of sand in our sand product listings for seamless construction experience.