Most current testing of lime quality involves discovering the neutralising value of the lime based on method P33, which uses hydrochloric acid to react with the Calcium Carbonate neutralising the acid. The more acid that can be neutralised by a determined sample of the lime product the higher the Calcium carbonate content of the lime. Fortunately your soil is nowhere near the acidity of Hydrochloric acid. If it was then you would need a lot of lime in order to grow anything.
Another lesser known test is the Hars/Resin test, which uses an acid with a pH value close to the average pH value of soil to give you a more accurate indication of how much of the product is going to be readily available and how much is going to need a good amount of time for the soil to slowly break it down. Much like the ocean breaks away at the limestone cliffs of our coastline except without the pounding action of millions of tones of seawater everyday.
Wet versus Dry Particle Size Analysis
The analysis of particle size distributions has become increasingly important in industrial and agricultural processes. Particle size is recognized to be fundamental to the control of operations as diverse as grinding, crystallization, emulsification, agglomeration, and more. Particle size determination has traditionally been relegated to the laboratory, and is performed by slow, labour-intensive methods such as sieving, sedimentation columns, and the like.
Applications of the wet sieving apparatus are the fields of agriculture and land conservation (research on soil erosion, land degradation/ conservation, salinization, agriculture, sustainable agriculture). Determining aggregate stability will give information on the sensitivity of soils to water and wind erosion, which might be prevented e.g. by mulching the soil surface. Information on soil aggregate stability can also improve tillage programs, adapted to the specific soil type and crop demands.
What is Wet Sieving?
Wet sieving is a procedure used to evaluate particle size distribution or gradation of a granular material. It’s also used to prepare a granular material for particle size analysis by removing fines that may impede the separation process.
Materials and Applications
Wet sieving is an ideal sample preparation process for specimens with a high fraction of granular materials and enough fines content present to make sieving difficult. The fines can stick together in clumps, preventing an accurate assessment by sieving. Wet sieving is also useful for direct particle sizing of problem materials including:
- Soils and mineral aggregates with high fine contents
- Agricultural soil with a high clay content
- Clay suspensions
- River sediments
- Contaminated soil (brownfields)
- Materials that are fragile but not soluble, such as coal or other minerals
- Lightweight powders
- Sludge and glazes
- Kaolin and fillers
- Micro granulations
How Do the Testing Procedures Work?
Wet sieving is usually performed with one of two purposes in mind. Either the operation is performed to determine a fraction retained on a sieve or sieves, or it is a method of sample preparation that allows a later particle size analysis to be performed more easily or accurately.
It’s important to be aware that any wet sieving method has the potential for sample loss during the process. Some material may be washed away during agitation or decanting or may be forced into crevices of the sieve and become trapped. The percentage loss is very small and the accuracy and efficiency of wet sieving compared to dry sieving is worth the process if necessary for your application.
A sieve analysis (or gradation test) is a practice or procedure used to assess the particle size distribution (also called gradation) of a granular material by allowing the material to pass through a series of sieves of progressively smaller mesh size and weighing the amount of material that is stopped by each sieve as a fraction of the whole mass.
The size distribution is often of critical importance to the way the material performs in use. A sieve analysis can be performed on any type of non-organic or organic granular materials including sands, crushed rock, clays, granite, feldspars, coal, soil, a wide range of manufactured powders, grain and seeds, down to a minimum size depending on the exact method. Being such a simple technique of particle sizing, it is probably the most common.
Limitations of sieve analysis
Sieve analysis has, in general, been used for decades to monitor material quality based on particle size. For coarse material, sizes that range down to #100 mesh (150μm), a sieve analysis and particle size distribution is accurate and consistent.
However, for material that is finer than 100 mesh, dry sieving can be significantly less accurate. This is because the mechanical energy required to make particles pass through an opening and the surface attraction effects between the particles themselves and between particles and the screen increase as the particle size decreases. Suspending the particles in a suitable liquid transports fine material through the sieve much more efficiently than shaking the dry material.
Sieve analysis assumes that all particle will be round (spherical) or nearly so and will pass through the square openings when the particle diameter is less than the size of the square opening in the screen. For elongated and flat particles a sieve analysis will not yield reliable mass-based results, as the particle size reported will assume that the particles are spherical, where in fact an elongated particle might pass through the screen end-on, but would be prevented from doing so if it presented itself side-on.
Gradation affects many properties of an aggregate. It affects bulk density, physical stability and permeability. With careful selection of the gradation, it is possible to achieve high bulk density, high physical stability, and low permeability. This is important because in pavement design, a workable, stable mix with resistance to water is important. With an open gradation, the bulk density is relatively low, due to the lack of fine particles, the physical stability is moderate, and the permeability is quite high.
Methods Of Sieve Size Analysis
Wet Sieving Sieve analysis is a simple but proven method of separating bulk materials of all kinds into size fractions and to ascertain the particle size and distribution through weighing the single fractions. Usually, sieving processes are carried out on dry material. However, when dry sieving cannot produce an adequate degree of separation between the individual fractions and even sieving aids cannot improve the quality, wet sieving is called for.
ISO 20977:2018-Liming materials – Determination of size distribution by dry and wet sieving. The dry sieving of powdered material containing individual particles can be carried out quite easily. This simple, quick and cheap method enables the determination of the particle size of water-soluble materials. Therefore, the dry sieving method should always be used first. However, the sieve apertures can become blocked by sample particles, a phenomenon known as blinding. Blinding is mainly caused by caking and the production of electrostatic charges, particularly on sieves with small apertures.
Dry sieving of very wet material can also lead to blinding. These difficulties are not encountered with the wet sieving method, which is applicable to any kind of material such as powders (dry or wet), paste-like products or granules except those containing water-soluble constituents. In order to ensure the comparability of results, all masses of size fractions are expressed as dry matter.
|Method A - the dry sieving method
| Method B - the wet sieving method