Synthesis and Characterization of Quaternary Polymers as Superplasticizer and Assessing Their Effectiveness on Micronized Cement Particles

Different macromonomers having polyethylene glycol branches were synthesized via esterification reactions in various conditions. Quaternary polymers were prepared using synthesized macromonomers of polyoxyethylene acrylate and methacrylate with a PEG molecular weight of 600-3000 g/mol, and sodium acrylate, sodium methacrylate and sodium maleate. The superplasticizers were synthesized by free radical polymerization in water medium at 65-80oC. The recipe and polymerization conditions have a direct effect on the structure of superplasticizers. The structures of the synthesized quaternary polymers were characterized by 1H NMR, Fourier transform infrared spectroscopy (FTIR) and gel permeation chromatography (GPC) analyses. The efficiency of a superplasticizer depends on the size of main chain, the chemical structure of repeating unit, molar ratio of monomers, chain-to-ion molar ratio (B/I) and size of the branches. These structural parameters affect the geometrical restriction, adsorption and the interaction between the superplasticizer chains and cement particles. FTIR, thermal gravimetric analysis (TGA) and X-ray powder diffraction (XRD) methods were also used to characterize the effect of superplasticizer structure on the hydration reaction of the cement pastes. FTIR spectroscopy was used to explore the effect of superplasticizer structure such as branch length and chain-to-ion molar ratios on the structure of the hydrated calcium silicate gels, polysilicate (SiO4-2) and calcium hydroxide generated during 7 days hydration. The results of XRD indicated that the structure of superplasticizer affects the content of anhydrous phase and hydrated products during hydration. The increase of PEG branch length slightly increased the decomposition temperatures of the hydrated calcium silicate gels and calcium hydroxide crystals. Furthermore, the size of calcium hydroxide crystals changed with the superplasticizer branch size

Superabsorbent Microparticles for Production of Concrete Using Ultrasound: A Performance Study

Hypothesis: Superabsorbent polymers are modifiers that have broad applications. One of their applications is in concrete production industry. The use of these materials for supplying water to cement materials and their curing process has attracted the attention of researchers. Using SAPs in concrete is a valuable tool for areas where conventional curing is very difficult, such as extreme weather conditions that can lead to excessive evaporation and freezing. It also saves water.Methods: Modified carbopol was prepared using poly(ethylene glycol) methyl ether methacrylate as a monomer with a molecular weight of 300 in amounts of 1, 2 and 3 g and with azobisisobutyronitrile (AIBN) as the initiator by ultrasound method. The properties of the prepared microgel and its effect on the properties of cement paste are investigated. The prepared microgel has been studied using FTIR analysis, scanning electron microscopy, particle size determination and swelling properties. In addition, the effect of prepared microgel on different properties of cement paste, such as rheology, compressive and flexural strength and hydration, is investigated.Findings: The results of FTIR and microscopic images showed that the monomer was modified. According to the swelling results, it was observed that carbopol has no absorption and it is dissolved. After modification, the swelling and absorption properties are obtained. The swelling capacity in water and saline solution has increased first and then decreased with increasing monomer concentration. The resultant cement pastes show that the compressive strength of samples is decreased in the presence of modified carbopol. In addition, the strength of the cement paste prepared with commercial superabsorbent (polyacrylic acid sodium salt) has increased with the same water:cement ratio. The flexural strength is reduced in all samples compared to the reference. According to the results, the modified carbopol has increased the viscosity of the cement pastes. According to the XRD results, hydration and curing of samples with superabsorbent have completed within 28 days compared to the control cement. Therefore, it can be concluded that superabsorbents generally cause a delay in hydration, and besides the hydration of the superabsorbent-cement specimens is decreased by reducing the monomer