Abstract
Polycarboxylic acid-based superplasticizers are used in various types of concrete work. Wide variations in environmental temperatures are known to affect how well chemical admixtures perform as superplasticizers, influencing the properties of the concrete. However, little has been reported on changes in performance caused by thermal variations. Previous studies have reported that heating superplasticizers change the polymer structure, improving and sustaining cement particles' dispersibility. Moreover, the improved fluidity from thermal stimulation is not temporary. The effect has been observed to remain for about seven days, with the residual characteristics differing depending on the superplasticizers used. Therefore this study evaluates mortar stiffness when using thermally stimulated superplasticizers and evaluates how the stimulation affects construction performance using measures such as the flow and rheological properties (plastic viscosity) of fresh mortar, vane shear tests, blade viscometer tests, and mortar vibration box tests. Mortar's fluidity was found to improve by about 25% when using thermally stimulated additives, with plastic viscosity dropping by up to 45% and the stress likely to be needed for pumping also being reduced by about 16%. Filling speed was also found to increase by about 26%. Thus, thermal stimulation improves mortar and concrete construction performance, and it may be possible in the future to carry out the construction with fewer workers utilizing this technology’s benefits. The study indicates a need for further investigation of how thermal stimulation affects polymer molecules’ adsorption efficiency with cement to elucidate the mechanism at full scale and propose ways to adopt thermal stimulation at actual construction sites.
Highlights
Superplasticizers, such as high-performance water-reducing admixtures and air-entraining agents, are used widely because they are effective in both reducing water requirements and retaining fluidity
Thermal stimulation reduces the plastic viscosity by 12% for the PCa-type and about 45% for the RMC-type additive
Thermal stimulation improves the dispersibility of the cement particles, lowering their stiffness since it further reduces their cohesion
Summary
Superplasticizers, such as high-performance water-reducing admixtures and air-entraining agents, are used widely because they are effective in both reducing water requirements and retaining fluidity. Iranian Journal of Science and Technology, Transactions of Civil Engineering changing the balance of the molecular backbone, such as its molecular weight, molecular weight distribution, graft chain length, and the composition ratio of the components, waterreducing agents with different dispersibilities can be synthesized. Their active mechanisms and the degree to which they adsorb with cement particles can be affected (Qianping et al 2009; Sakai et al 2003). Their results suggest that longer and more entangled main and side chains reduce adsorption capacity with cement particles
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