Definition: a kind of material that can cause volume expansion through physical and chemical reactions. Its volume expansion can be used in many fields such as material production, silent blasting, etc.

Application: concrete expansion agent, refractory expansion agent, mainly used to compensate the shrinkage in the hardening process of materials and prevent cracking. In recent years, according to the characteristics of materials, static blasting agents have also been developed, mainly through the volume expansion of materials to cause damage to the structure.

Core: its technical core is volume expansion with controllable period and controllable quantity.

Theoretical basis

Expansion agent materials are mainly used in the production of materials, the more common are concrete expansion agent and refractory expansion agent. During the hardening process of concrete and unshaped refractories, cracks are often caused by the shrinkage characteristics of raw materials. The purpose of using expansion agent is to introduce quantitative volume expansion, compensate the shrinkage value of the material itself, prevent the material from shrinkage cracking, and affect its structure, function and appearance. In recent years, with the extensive research and development of composite materials, expansive materials have been paid attention to by various industries and widely used in the production and manufacturing of materials.

Technology core

The materials that can cause volume expansion can be processed into expansion agents. The technical core of expansive agent is to control the period and expansion rate. The strength of the composite is from zero to some, and its shrinkage mainly occurs in the pre hardening process. At this time, a certain range of expansion can bring favorable results. However, in the later stage of hardening, the strength and structural morphology of the composite have become stable. The volume expansion can not bring favorable results, but will cause structural damage. To sum up, the technical core of expansive agent materials is not expansion, but when and how much expansion. A good expansive agent must be controllable in period and expansion rate.

 Application characteristics

1. Generally, it is necessary to strengthen the maintenance: the expansion agent in the field of materials usually reacts with water to produce a volume increased unit cell (such as ettringite) and then causes expansion, so it is necessary to give sufficient curing in the process of use;

2. Expansion agent is not cementitious material: the raw materials of strength type composite materials are generally divided into coarse aggregate (coarse aggregate), fine aggregate (fine aggregate), cementitious material (binder), and functional additives (such as water reducer, accelerator and retarder, etc.). Expansion agent is usually in the form of solid powder, its purpose is not to bond, can not replace the role of cementitious materials.

3. About mixing method: it is usually divided into two kinds: internal mixing and external mixing. It describes a calculation method of material consumption. Internal mixing means that "the expansion agent is regarded as cementitious material in the calculation of the ratio". The external mixing is the quantitative addition of the original proportion, which usually requires a small amount of water reducing agent to be added.

4. Current situation at home and abroad: Germany and Japan are the most mature countries in the application of this technology. In China, the research institutions of expansive agent technology are mainly China General Academy of building materials science, Shanghai Silicate Research Institute of Chinese Academy of Sciences (hereinafter referred to as "Shangsi Institute"), Tsinghua University, material Department of Beijing University of science and technology, School of materials and metallurgy, Wuhan University of science and technology .

5. Main application fields: common in non-metallic, non sintering composite production industry, such as concrete and unshaped refractories.