Curing agents. They are all white powders. The dry products are extremely unstable and can cause explosions upon friction, impact, exposure to heat, or contact with reducing agents. The BPO content in the curing agent paste, strictly speaking, is the effective oxygen content, which is an important testing target for the curing agent paste. The effective oxygen content directly affects the gel time of the anchorage agent, particularly evident in medium-speed types of anchorage agents. The higher the effective oxygen content, the faster the gel time, but there is an upper limit. In ultra-fast anchorage agents, DC is used for assistance.
Accelerators (promoters). To accelerate the curing reaction and increase the initiation speed of the curing agent, a small number of compounds are called accelerators or promoting agents. The combination of dimethylaniline and benzoyl peroxide provides a fast cold curing speed and good performance. The amount of DMA doping directly affects the gel time of the anchorage agent. When combined with the curing agent, it can conveniently adjust the gel time of the anchorage agent to meet the required targets. However, the doping amount of DMA is not the greater the better. After a certain amount, it has little impact on the gel time but will, to a certain extent, reduce the strength target of the anchorage agent. If too little, it cannot separate a sufficient amount of free radicals, and the effect is also not good.
Fillers. The addition of fillers in the anchorage agent is important. It can relatively reduce the dosage, lower costs, adjust the consistency, increase thixotropy, prevent outflow in the anchor hole, increase the compactness of the anchorage agent, reduce the shrinkage rate, improve the bonding reliability, and during the rapid curing process, timely absorb the heat generated by the chemical reaction to prevent the occurrence of thermal runaway. The selected fillers should be inert materials without water and should not undergo chemical reactions with the curing agent and accelerator. Many mineral materials can be used as fillers, such as dolomite powder, quartz powder, limestone powder, porcelain powder, calcium carbonate powder, as well as yellow sand, small granite particles, limestone, and quartzite. Currently, the most commonly used filler by domestic anchorage agent manufacturers is limestone because of its low cost and high quality, and wide availability of materials.
Thixotropic agents. Compounds that can maintain a high viscosity and non-flowing state when at rest but can become a flowing liquid under external forces (such as during stirring) are called thixotropic agents. Commonly used thixotropic agents include soluble polyvinyl chloride powder and active silica. Active silica, also known as white carbon black, is produced by precipitation method and gas phase method. The doping amount of white carbon black produced by the precipitation method in the anchorage agent should be above 2%, while that of white carbon black produced by the gas phase method can achieve the effect at generally 1% or even lower. It has a high thixotropic index. Regardless of the type of white carbon black used, the stirring speed requirements in the anchorage agent are relatively high. The higher the stirring speed, the better the thixotropic property. Thixotropic agents are used in thinner anchorage agents to prevent outflow from the anchor hole and can also prevent the sedimentation and stratification of fillers during storage in general anchorage agents.
In addition, depending on the purpose and formulation of the anchorage agent, shrinkage-preventing expanding agents such as polystyrene particles can be added, and defoaming agents that generate a large number of bubbles during stirring, such as silanes, can also be added.