Development of Rapid-hardening, Expansive, High-strength Grouting Mortar

In order to solve the problem that the cement-based anchoring material has low early-strength and its volume contracts obviously, it is necessary to develop anchoring material which has characteristics of early-strength, expansion, high strength etc. Based on the ettringite with characteristic of early strong and expansion, the properties of the grouting mortars modified with alunite and gypsum were studied. The results show that at early stage the expansion is rapid and expansion is stabilized at later stage. The setting time can be controlled in 0.5～1.5 hours, and compressive strength of 1 day and 3 days reaches 20 and 40Mpa, respectively. The micro-analysis shows that with the increase of curing-time there are plenty of expansive ettringite crystals and porosity decreases. The limit load test shows that the pullout force of 1metre sample at 14 days is 93 KN, which is larger than the average lever of 1.5～2 meters samples.     

Activation and Toxicity of Slag-fly Ash-fluorgypsum Cementitious Material

Effect and mechanism of activation of activator to fluorgypsum, strength, softening coefficient and leaching toxicity of composite cementitious material are studied. Through activation testing of NaOH, Na2SO4 and NaF, the optimum adding quantity was defined as 1%. On the basis of it, 80% fluorgypsum was further processed to improve its quality with slag, fly ash and clinker. With 1% Na2SO4, 25% slag, 5% fly ash and 89% fluorgypsum, the cementitious material properties were excellent; the 28-day compressive strength could reach 12.25 MPa; the softening coefficient was 0.70; and the concentration of fluoride could be reduced to 0.7485 mg/L. The analysis of SEM and XRD show that gypsum, a few calcium silicate hydrate, ettringite and calcium fluoride are filled and packed each other, which hampers water enter particle structures, increases the water resistance of cementitious material and reduces leaching toxicity of cementitious material.     

混凝土膨胀剂MEA的膨胀作用机理

分析了混凝土膨胀剂MEA产生体积膨胀的原因及其对（普通）硅酸盐水泥强度的影响机理。X射线衍射分析结果说明膨胀剂MEA的膨胀作用与水泥强度发展是协调的。根据试验结果确定了混凝土膨胀剂MEA中石膏掺量的范围为30％～50％（质量分数）;试验结果证明,与混凝土膨胀剂MEA配合使用的（普通）硅酸盐水泥中以（C3S）＝45％～55％和3（C3A）＝6％～10％为宜。