新型具側鏈羧酸系強塑劑的合成與對水泥漿流動性的影響

Abstract

強塑劑是促進混凝土有良好工作性的關鍵組成。本研究利用聚乙二醇（PEG）、馬來酸酐（MA）合成具側鏈之改質單體(PM)，並藉由PEG分子量及PEG/MA莫耳比例之改變，得到不同鏈長與不同結構的改質單體。接著由2-丙烯醯胺-2-甲基丙烷磺酸（AMPSA）、甲基丙烯酸（MAA）與改質單體依不同比例行自由基聚合，反應以過硫酸銨為起始劑及2-甲基丙烯磺酸鈉為鏈轉移劑，利用鏈轉移劑濃度之改變得到一系列不同分子量之新型具側鏈羧酸系強塑劑(PAMP)。以FT-IR、1H-NMR與13C-NMR鑑定合成之改質單體及PAMP結構；GPC測PAMP之分子量；EA測PAMP之C、H、N、S含量比例。 強塑劑對水泥漿與混凝土工作性之研究分別以PAMP單體比例、分子量、側鏈長度與側鏈結構為變因分別進行探討，以強塑劑對水泥漿體顆粒之吸附行為實驗來解釋之，並與商用之羧酸系HP-100及磺酸系HPC1000進行比較。研究結果顯示，PAMP在AMPSA/MAA/PM = 2/3/0.5的比例下，具有最佳之分散效果與坍度維持性，飽和劑量為0.5wt%；最適重量平均分子量為M(—)w=5.0~8.0×104；吸附實驗結果顯示當PAMP之初始吸附量少，達吸附平衡時間長，有最佳之漿體流動促進性；研究並證實PAMP藉由改質單體側鏈長度與結構的調整，有助於提升水泥漿體之坍度維持。

Superplasticizers are key components to promote the workability of concrete. In this research, monomers(PM) with different side chain lengths and different reactant ratios were prepared from polyethylene glycol (PEG) and maleic anhydride (MA). A noval carboxylate-based superplasticiser PAMP with 2-acrylamido-2-methylpropane sulfonic acid (AMPSA), methacrylic acid (MAA), and the monomers aforementioned were prepared by free-radical polymerization using ammonium peroxodisulfate as the initiator and sodium methallylsulfonate as the chain transfer agent. The prepared monomers and PAMP have been confirmed by FT-IR、1H-NMR, and 13C-NMR；the molecular weight of PAMP was determined by the Gel Permeation Chromatography (GPC) and the composition of the polymer was determined by the Elemental Analysis (EA). The effects of the reactant ratio, molecular weight, and side chain lengths of PAMP on the cement paste and the workability concrete were investigated. The dispersion properties of PAMP fluidity were compared to those of the commercial superplasticisers, i.e., HP-100 (carboxylate-based) and HPC1000 (sulfonate-based). The test results indicate that the cement pastes containing PAMP with AMPSA / MAA / PM = 2 / 3 / 0.5 shows the highest initial spread diameter and the lowest slump loss; the saturation dosage was 0.5wt%, and the optimum-weight average molecular weight (M(—)w) are 5.0~8.0×104. It is indicated that when the amount of PAMP was less adsorbed initially and the equilibrium adsorption time was longer, then the resulting cement pastes show better fluidity. PAMP with proper side chain length will promote the slump-retention of the resulting cement pastes.