Accelerants, or accelerators, are
substances that increase the rate of a natural or artificial
chemical process
In a scientific sense, a chemical process is a method or means of somehow changing one or more chemicals or chemical compounds. Such a chemical process can occur by itself or be caused by an outside force, and involves a chemical reaction of som ...
. They play a major role in
chemistry
Chemistry is the scientific study of the properties and behavior of matter. It is a physical science within the natural sciences that studies the chemical elements that make up matter and chemical compound, compounds made of atoms, molecules a ...
, as most
chemical reaction
A chemical reaction is a process that leads to the chemistry, chemical transformation of one set of chemical substances to another. When chemical reactions occur, the atoms are rearranged and the reaction is accompanied by an Gibbs free energy, ...
s can be hastened with an accelerant. Understanding accelerants is crucial in
forensic science
Forensic science combines principles of law and science to investigate criminal activity. Through crime scene investigations and laboratory analysis, forensic scientists are able to link suspects to evidence. An example is determining the time and ...
,
engineering
Engineering is the practice of using natural science, mathematics, and the engineering design process to Problem solving#Engineering, solve problems within technology, increase efficiency and productivity, and improve Systems engineering, s ...
, and other fields where controlled chemical reactions are essential. Accelerants function by either altering a
chemical bond
A chemical bond is the association of atoms or ions to form molecules, crystals, and other structures. The bond may result from the electrostatic force between oppositely charged ions as in ionic bonds or through the sharing of electrons a ...
, speeding up a chemical process, or changing the reaction conditions. Unlike
catalyst
Catalysis () is the increase in rate of a chemical reaction due to an added substance known as a catalyst (). Catalysts are not consumed by the reaction and remain unchanged after it. If the reaction is rapid and the catalyst recycles quick ...
s, accelerants may be consumed during the process.
They are commonly used in contexts such as
fire investigation
Fire investigation (sometimes referred to as origin and cause investigation) is the analysis of fire-related incidents. After firefighters extinguish a fire, an investigation is launched to determine the origin and cause of the fire or explosi ...
where they can indicate
arson
Arson is the act of willfully and deliberately setting fire to or charring property. Although the act of arson typically involves buildings, the term can also refer to the intentional burning of other things, such as motor vehicles, watercr ...
, in
construction
Construction are processes involved in delivering buildings, infrastructure, industrial facilities, and associated activities through to the end of their life. It typically starts with planning, financing, and design that continues until the a ...
to speed the
curing of building materials, and in
sulfur vulcanization
Sulfur vulcanization is a chemical process for converting natural rubber or related polymers into materials of varying hardness, elasticity, and mechanical durability by heating them with sulfur or sulfur-containing compounds. Sulfur forms cros ...
to produce rubber products such as
tyres. In fire investigation, accelerants are often detected through laboratory analysis of fire debris. Various types of accelerants exist, including liquids, solids, and gases, each with specific properties and applications.
Applications
Vulcanization
Vulcanization of rubber can be categorized primarily into two types: sulfur and peroxide vulcanization. Both chemical processes are examples of using an accelerant.
Sulfur vulcanization, the more traditional method, uses sulfur to create cross-links between rubber polymer chains, enhancing flexibility and durability. Sulfur vulcanization is a chemical process crucial to the rubber industry, transforming raw rubber into a durable, elastic material. This process is suitable for a wide range of rubber products.
On the other hand, peroxide vulcanization uses organic peroxides to form cross-links, resulting in rubber that withstands higher temperatures and chemical exposure better than sulfur-vulcanized rubber. Each method offers distinct properties to the rubber, tailored to specific applications and performance requirements.
Cement and concrete
Cement accelerators are available as
admixtures for use in
concrete
Concrete is a composite material composed of aggregate bound together with a fluid cement that cures to a solid over time. It is the second-most-used substance (after water), the most–widely used building material, and the most-manufactur ...
,
mortar,
render, and
screed. The addition of an accelerator speeds the setting time and thus
curing starts earlier.
[Justnes, H. (2000): Accelerator Blends for Portland Cement. Proceedings of Cement and Concrete Technology in the 2000s, September 6–10, 2000, Istanbul, Turkey, Vol. 1, pp. 433–442] This allows concrete to be placed in winter with reduced risk of
frost damage.
[ACI 306R-88: Cold Weather Concreting. ] Concrete is damaged if it does not reach a strength of before freezing. Typical cement accelerators are
calcium nitrate (),
calcium formate (), and
sodium nitrate
Sodium nitrate is the chemical compound with the chemical formula, formula . This alkali metal nitrate salt (chemistry), salt is also known as Chile saltpeter (large deposits of which were historically mined in Chile) to distinguish it from ordi ...
().
Fire
In
fire protection
Fire protection is the study and practice of mitigating the unwanted effects of potentially Conflagration, destructive fires. It involves the study of the behaviour, Compartmentalization (fire protection), compartmentalisation, suppression and inve ...
, the term ''accelerant'' is used differently from its use in chemistry, to refer to any material that initiates and promotes the development of
fire
Fire is the rapid oxidation of a fuel in the exothermic chemical process of combustion, releasing heat, light, and various reaction Product (chemistry), products.
Flames, the most visible portion of the fire, are produced in the combustion re ...
, including in cases of
arson
Arson is the act of willfully and deliberately setting fire to or charring property. Although the act of arson typically involves buildings, the term can also refer to the intentional burning of other things, such as motor vehicles, watercr ...
, whether a chemical or not. Chemists distinguish an accelerant from a
fuel
A fuel is any material that can be made to react with other substances so that it releases energy as thermal energy or to be used for work (physics), work. The concept was originally applied solely to those materials capable of releasing chem ...
, such as gasoline. This usage of ''accelerant'' is also referred to by the term ignitable liquid.
A fire is a self-sustaining,
exothermic
In thermodynamics, an exothermic process () is a thermodynamic process or reaction that releases energy from the system to its surroundings, usually in the form of heat, but also in a form of light (e.g. a spark, flame, or flash), electricity (e ...
oxidation reaction that emits heat and light. When accelerants such as oxygen-bearing liquids and gases (like
) are used, fires produce more heat, consume fuel more quickly, and spread quicker. Fires involving liquid accelerants like gasoline burn quicker, but at the same temperature as fires involving ordinary fuels.
See also
*
Chemical kinetics
Chemical kinetics, also known as reaction kinetics, is the branch of physical chemistry that is concerned with understanding the rates of chemical reactions. It is different from chemical thermodynamics, which deals with the direction in which a ...
*
Rate equation
In chemistry, the rate equation (also known as the rate law or empirical differential rate equation) is an Empirical relationship, empirical Differential equation, differential Expression (mathematics), mathematical expression for the reaction rat ...
*
Retarder (chemistry)
References
{{Wiktionary
Firefighting
Rubber