Daniela Lucia Manea

NMR relaxometry study of plaster mortar with polymer additives

The cement mixed with water forms a plastic paste or slurry which stiffness in time and finally hardens into a resistant stone. The addition of sand aggregates, polymers (Walocel) and/or calcium carbonate will modify dramatically the final mortar mechanic and thermal properties. The hydration processes can be observed using the 1D NMR measurements of transverse T2 relaxation times distributions analysed by a Laplace inversion algorithm. These distributions were obtained for mortar pasta measured at 2 hours after preparation then at 3, 7 and 28 days after preparation. Multiple components are identified in the T2 distributions. These can be associated with the proton bounded chemical or physical to the mortar minerals characterized by a short T2 relaxation time and to water protons in pores with three different pore sizes as observed from SEM images. The evaporation process is faster in the first hours after preparation, while the mortar hydration (bonding of water molecules to mortar minerals) can be still...

Physical and Mechanical Property Characterization of Hemp Shive Reinforced Gypsum Composite Board

Known and used since Antiquity, the hemp plant comes back to the attention of the researchers focused on making new ecological products used to reduce the environmental impact in the construction sector. A sustainable building environment needs to develop relations with renewable raw materials. This study aims to make an investigation in the products based on gypsum and hemp shives, where hemp shives are an agricultural plant and gypsum a natural resource produced by burning gypsum plaster. Using the multicriterial analysis, the best performing formula is identified, in order to satisfy thermal insulation, sound insulation, mechanical and fire related requirements and in which the variable is the hemp shives percentage in the composite material. The three recipes prepared were compared with the normative and other studies. The results presented at the end of this study shows that in terms of acoustic absortion and thermal conductivity, the insulating materials are best when the volume of hemp grows. Meanwhile the positive aspect of growing the volume of hemp for insulation materials becomes a disadvantage from the mechanical point of view, where to have high values of strength is recomanded a low volume of hemp.