Abstract
Internal curing can help to improve the durability of concrete by preventing and minimizing initial cracks due to autogenous shrinkage and plastic shrinkage. Using a reliable internal curing agent is essential to the effectiveness of the internal curing process. This paper investigates the reaction kinetics of a starch graft anionic nonionic type polymer. The results demonstrate that initiator monomer concentration, and starch concentration are positively correlated with graft reaction rate Rp. Based on the research, the kinetics equation of this cassava starch graft anionic nonionic-type polymer has also been developed, which coincides well with the law of free radical polymerization. The obtained Rp equation is a first order dependence of the monomer concentration and the square root of the initiator concentration. And Rp is further correlated to the reaction temperature based on a sigmoid function instead of a linear function. It is also found that the polymerization reaction is characterized by the coexisted disproportion termination and coupling termination.
Highlights
Concrete, as the most commonly used material, creeps and shrinks during its service life
The above three characteristics are a clear indication that the monomer AM and monomer AMPS were grafted onto the cassava starch and formed the anionic and nonionic polymer starch graft copolymer AM-AMPS (STAGAA)
It shows that the mean monomer mass grafted onto starch backbone increases linearly with the increasing reaction time during the early 30minutes, but it increases slowly after that. This indicates that the reaction rate is approximately constant in early reaction time (30 minutes) and it can be considered as the initial reaction rate
Summary
As the most commonly used material, creeps and shrinks during its service life. Early-age cracking is a predominant problem especially for high strength concrete/high performance concrete (HSC/HPC) due to the high autogenous shrinkage (self-desiccation) caused by its low water-to-cement ratio (w/c) and the usage of fine or ultra-fine mineral admixtures. These cracks would affect the durability and service life of concrete. Yu et al (1999) studied the copolymerization kinetics of graft acrylonitrile onto starch by using benzoin ethyl ether as initiator, and derived the reaction rate equation and calculated the activation energy. This would serve the purpose to predict synthesis reaction with eligible explanation
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