How to Choose Sand

How to choose sand at LimeWorks.us. When selecting sand for making mortars with Saint-Astier® Natural Hydraulic Limes, it is essential to ensure that the sand meets ASTM C-144 standards. ASTM C-144 is a specification for aggregate used in masonry mortar established by the American Society for Testing Materials (ASTM). Although people often use the term “aggregate” instead of “sand” because it encompasses recycled materials that can substitute for sand, the specification provides valuable guidelines for choosing sand based on cleanliness, shape, composition, and grain size distribution.

LimeWorks.us supplies pre-bagged, washed, dried, and graded sands that meet the ASTM C-144 standards. Bulk sand may are used if it meets the ASTM Standard but may have some problematic issues. The bulk sand may contain undesirable impurities or not be uniform between loads. Bar Sand may be too smooth in one load due to separating during trucking, which pushes larger grains to the top of the truck as it travels long distances. There may be a suitable gradation in other loads from the same quarry. Still, when the transported sand is dumped into storage bins and separated, it will vary when pulled from a lower part of a storage bin yielding sand different in gradation than from the top of the storage bin at the same place that sells sand. If you plan to obtain sand from a nearby creek, be sure it is legal to do so, and be prepared to wash the sand of silt and sift it until you obtain the ideal gradation for the application. Use beach sand sparingly for a few reasons. Salt and other contaminants in the sand can not be controlled very well. Rounded grains from wave action allow mortars made with beach sand to potentially roll apart instead of having interlocking grains of sharp, well-graded sand which helps with the overall performance of the lime mortar using locked-in angular grains. The composition of the aggregate affects the long-term performance of the mortar. Some aggregates can even cause delayed expansion and failure of the mortar, so suitable sand is essential. 

Grain size distribution is the most critical factor when choosing an aggregate. The sand should have a wide range of sizes in its composition. Good distribution significantly impacts workability and durability. If possible, obtain a sieve analysis and look for a bell curve when the data is plotted on a graph. This indicates the presence of a few large pieces, an increasing number of medium sizes, and a small quantity of fines or powder. Excessive fines in the sand result in poor workability, often leading to the addition of excess water, which compromises durability.

When clean and dry, good sand should have a theoretical void ratio of 33%. This means that within a given volume of sand, there should be an ideal air space ranging from 33% to 66% between the grains.

Here’s how you can perform your own sand test:

1. Take two clear containers, one at least twice the size of the other.
2. Fill the small container with water and pour it into the large container, making a mark.
3. Refill the small container with water and pour it into the large container, ensuring that the first water measure remains in the container. Make a mark at the level of the second measure.
4. Create six evenly spaced lines between the two marks, resulting in six marks on the large container.
5. Empty the large container and fill the small container with water.
6. Pour the water from the small container into the large container, filling it up to the bottom of the six lines.
7. Fill the dry small container with dry sand and pour it into the large container.
8. After everything settles, observe the amount of water displaced.
9. Starting from the top line representing 0%, each line moving down the large container represents 20%.
10. The resulting percentage represents the void ratio, indicating the minimum volume of lime required to create a good mortar.

Poor sand can have ratios above 50% and will increase the amount of lime required, thus resulting in added expense for your project. So when in doubt, conduct a small test on the available sands. Choose the one that has a ratio closest to 33% to save on the amount of lime required and sleep easier knowing that you have decent sand.

For engineered material that offers convenience and reliability immediately, you can purchase directly from LimeWorks.us, The Ecologic™ Graded and Dried Sand Blends. Our Ecologic™ Graded and Dried Sand Blends are available in Pale Brown Coarse (G) and Fine White (F) grades. They are ideal for making a lime mortar, which is planned for laying brick or stone, parging, and for pointing and grouting deep voids. Contact us to discuss which grade should be used for a corresponding application when mixing an Ecologic™ Graded and Dried Sand Blend at specific ratios with Saint-Astier® Natural Hydraulic Limes. Both types of washed sand can also be used in art projects or for a child’s play sandbox and many other non-construction uses. The Ecologic™ Graded and Dried Sand Blends Conform to ASTM C144 and NYS DOT STANDARD #703-03 for Masonry Sand.