氧化镁掺量对硅酸钠激发矿渣砂浆收缩及力学特性的影响研究

Effect of MgO content on the shrinkage and mechanical properties of sodium silicate activated slag mortar

硅酸钠等强碱性激发剂引发的较大自收缩是限制碱激发胶凝材料(AASM)发展应用的关键因素之一。为此,在硅酸钠激发矿渣体系中外掺MgO,研究不同掺量的MgO对AASM的新拌性能、水化产物、孔结构、多尺度力学性能和收缩特性的影响。结果表明:MgO可协同硅酸钠促进矿渣水化,加速水化产物的析出,并生成膨胀性水化产物水滑石。更多水化产物的生成可填充水被消耗后产生的孔隙,减少AASM孔隙率,同时提高了水化产物的堆积密度,促进弹性模量提高。MgO碱当量最高为8%时,砂浆28d抗压强度提升了29.5%,自收缩减少了51.8%。此研究为AASM的发展与应用提供了理论依据。

The significant autogenous shrinkage induced by strong alkaline activators like sodium silicate is one ofthe key factors limiting the development and application of alkali-activated slag materials(AASM). To address this,external additions of MgO in sodium silicate-activated slag systems were investigated to study the influence of differentMgO content on the fresh properties,hydration products,pore structure,multi-scale mechanical properties,andshrinkage characteristics of AASM. The results indicate that MgO can synergize with sodium silicate to promote slaghydration,accelerate the precipitation of hydration products,and generate expansive hydration product hydrotalcite.The increased production of hydration products can fill the pores formed after water consumption,reducing the porosityof AASM while also increasing the packing density of hydration products,promoting an increase in elastic modulus.When the alkali equivalent of MgO reaches its maximum at 8%,the compressive strength of mortar at 28 days increasesby 29.5%,and autogenous shrinkage is reduced by 51.8%. This study provides a theoretical basis for the applicationof AASM.