New mixes were prepared according to the EFNARC self-compacting concrete criteria with synthesized polycarboxylate-type superplasticizers. For this purpose, superplasticizers possessing different side-chain lengths and cross-linkages were produced to overcome the workability and workability-retention problems in selfcompacting concrete (SCC) by time. Not only the fresh properties but also hardened properties of SCCs were improved. With this study it was determined that, cross-linked polycarboxylate-type superplasticizer shows better performance in SCC compared to its counterparts and commercial polycarboxylate. It provides better self-compaction by discharging its bubbles during molding. Besides, the effects of water-powder ratio and superplasticizer dosage were also examined and discussed in this study.
Various combinations of zinc borate (ZB), alumina trihydrate (ATH) and magnesium hydroxide (MH) were used to retard the flammability of PVC composite. Flame retardancy of samples were investigated with limiting oxygen index (LOI) test. Further testing was achieved to expose the individual and synergistic effects of flame retardant additives on heat stability, Vicat softening temperature, fusion time, microstructure, mechanical and thermal characteristics. Microstructural and thermal analyses were performed by scanning electron microscopy and TG/DTA respectively. The LOI results showed that, high levels of ZB-ATH combination provided the highest LOI value of 53.4%. Although ZB and its combinations improved the fire performances of composites, they caused a small reduction at tensile strengths. When compared with plain PVC, flame retardant composites had better thermal stability. In addition to the advantages of ZB, when test results were evaluated with a holistic approach ZB-ATH-MH combination was understood to be an effective flame retardant alternative with this research.
Copolymers of methoxy polyethyleneglycol (meth)acrylate (mPEG(M)A) and 2-acrylamido-2-methyl-1-propanesulfonic acid (AMPS) were synthesised, characterised with Fourier transform infrared spectroscopy and gel permeation chromatography, and the effects of molecular architecture on the properties of cement-based systems were investigated. Superplasticiser (SP) adsorption was determined with a total organic carbon analyser, while spread and mechanical properties were assessed according to European standards. The rheological behaviour of cement pastes at different copolymer dosages was also studied. Sufficient fluidity and fluidity retention over time are requirements for the mixing, transportation, pumping and moulding of concrete at construction sites. The synthesised SPs with long side chains provided mortars with high fluidity, high dispersing power per adsorption ratio and low mechanical strength compared with the SPs with short side chains. They were also effective at decreasing the shear yield stresses and plastic viscosities (at high dosages) of the cement pastes. Additionally, mortars dosed with mPEG(M)A-co-AMPS had higher fluidity and fluidity-retaining properties compared with mortars prepared with lignosulfonate-type SP.
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