BCS土壤固化剂固化土的耐久性研究

Durability of stabilized soil by BCS

【目的】确定BCS土壤固化剂的最佳掺量,分析BCS土壤固化剂对土壤的加固机理,探讨增强固化土耐久性的方法。【方法】选用陕西杨凌的黄土,按黄土质量加入12%的水泥及不同掺量的BCS核心材料,并按0.6%的BCS核心材料掺量,在黄土中加入不同质量比的水泥基BCS固化剂,通过抗压试验分析确定最佳的BCS核心材料掺量和最佳的BCS固化剂掺量。采用无侧限抗压试验、渗透试验、水稳性试验、干湿循环试验、冻融循环试验等研究固化土的耐久性,采用扫描电子显微镜(SEM)观测BCS固化土的微观结构和水化产物,分析BCS固化剂的作用机理。【结果】BCS土壤固化剂核心材料的最佳掺量为水泥质量的0.6%;固化剂水化产物中主要有纤维状和网状的水化硅酸钙凝胶(C-S-H)、六方棱柱型的三硫型水化硫铝酸钙晶体(Aft)以及片状或叠片状的氢氧化钙晶体(CH);固化土的渗透系数较水泥土略低,最低可达3.8×10-8 cm/s;固化土的水稳系数随着固化剂掺量的增加而降低,随着龄期的延长而升高;干湿循环后固化土的强度有所下降,强度损失率最高可达19.8%,但其强度随着固化剂掺量的增加而增大;采用硅酸钠、氢氧化钠或饱和石灰水进行养护,可有效提高固化土的抗冻融循环次数。【结论】与水泥土相比,BCS固化土的工程性能有所提高,采用饱和石灰水养护可显著增强固化土的抗冻性能。

【Objective】Experiments on soil stabilized by BCS were conducted to determine the optimum content of BCS agent in stabilized soil,analyze consolidation mechanism of BCS soil stabilizer,and investigate methods for improvement of durability.【Method】Loess from Yangling,Shaanxi was chosen and 12%cement and different contents of BCS core material were added.0.6% BCS core material and BCS stabilizers with different mass ratios were also added.Optimal content of BCS core material and BCS stabilizer were determined by compression test.The durability of stabilized soil was investigated through unconfined compressive test,permeability test,water stability test,wetting-drying test and freezing-thawing test.Microstructure and hydration products were observed through the scanning electron microscope(SEM),and the mechanism of BCS was analyzed.【Result】The optimum content of core material of BCS stabilizer to the loess from Yangling was 0.6% of cement mass.Hydration products of BCS agent mainly consisted of fibrous and reticular calcium silicate hydrate(C-S-H),hexagonal prisms ettringite crystal(Aft),and sheet calcium hydroxide crystal(CH).The permeability coefficient of stabilized soil was slightly less than that ofcement soil,with the minimum of 3.8×10-8 cm/s.The water stability coefficient reduced with the increase of cement content,while the coefficient rose with the extension of curing period.Wet-dry cycles caused reduction of strength of stabilized soil by up to 19.8%,but the strength increased as the increase of BCS.The freeze-thaw resistance times of stabilized soil could be improved significantly by curing in sodium silicate solution,sodium hydroxide solution or saturated limewater.【Conclusion】Compared with cement soil,the engineering property of BCS stabilized soil was improved.Durability of stabilized soil was improved obviously by using saturated limewater.