Characteristics of Mortar Containing Sodium Polyacrylate Absorbent Synthesized by Inverse Emulsion Polymerization

摘要

This study examined the effect of sodium polyacrylate (PAANa) absorbent on the characteristics of mortar. PAANa was synthesized through inverse emulsion polymerization with varying amounts (e.g., 0.150.60 mol%) of cross-linking agent N,N'-Methylene Bisacrylamide (MBA). The polymerized PAANa was added to cement in amounts of 0.5%, 1.0%, and 1.5% (v/v) to produce mortar. Flow, compressive/flexural strength, Field-Emission Scanning Electron Microscopy (FE-SEM) analysis and porosity characteristics of the as-prepared mortar were subsequently measured. The test result shows that the flow properties of mortar decreased with the volume of PAANa added whereas it increased with the MBA mixing ratio. The sample prepared with 15% of MBA and 1.0% of PAANa (e.g., C15CA1.0) showed the highest compressive strength (29.0 MPa) after an aging of 28 days, which represents 31% improvement in strength compared to plain mortar (22.1 MPa). Compressive strength was observed to drop as the amount of MBA in the mixture increased. C15CA1.0 material also showed the highest flexural strength (2.7 MPa) after 28 days aging, which represents an 8% improvement over plain mortar. C30CA1.0 and C45CA1.0 materials showed moderate improvements in flexural strength (5% and 2%, respectively) whereas, a further increase in MBA (C60CA1.0) led to poorer performances (2% lower flexural strength) compared to plain mortar. FE-SEM analysis of C15CA1.0 revealed the presence of high amounts of acicular C-S-H crystals where the space between particles is filled with PAANa. The content of acicular structure in mortar was found to increase with the MBA mixing ratio. The modified materials showed lower porosity values compared to plain mortar, and these values increased with the amount of MBA in the mixture.