Research On The Development And Performance Optimization Of Multi-compound Portland Cement Based Grouting Materials

Traditional Portland cement based tunnel grouting materials have poor grouting effect due to its long setting time,high bleeding rate and poor durability of hardened slurries,which further leads to the occurrence of flooding accidents and brings severe challenges to the security of tunnel construction.Consequently,it is of tremendous consequence for engineering construction to improve the performance of traditional Portland cement based grouting materials.In this paper,red clay,sodium silicate and sulfoaluminate cement were used to modify Portland cement based grouting materials.The optimal dosage range of modified materials was determined by single factor test,and the modification mechanism was explored.On this basis,the response surface methodology(RSM)was used to establish the correlation model between the content of each modified material and the working performance(setting time,2 h bleeding rate,fluidity and compressive strength)of multi-compound Portland cement based grouting materials.The impact of the interaction between the modified materials on the performance of the multi-compound Portland cement based grouting materials was investigated,and the optimal dosage of each modified materials was determined.Finally,the durability of the multi-compound Portland cement based grouting materials and the traditional Portland cement based grouting materials was compared.The results of single factor test show that: the red clay in Portland cement slurry reduces the 2h bleeding rate of Portland cement based grouting materials by adsorption,ion exchange and electrostatic force.The reaction of calcium hydroxide and sodium silicate produces more calcium silicate hydrate gel,which improves the compressive strength of Portland cement based grouting materials.Sulfoaluminate cement consumes calcium hydroxide and gypsum in Portland cement at the same time,which promotes hydration of calcium silicate and weakens the retarding effect brought by gypsum,shortening the setting time of Portland cement based grouting materials.In addition,the optimal dosage ranges of red clay,sodium silicate and sulfoaluminate cement in Portland cement based grouting materials are 10%-20%,1.5%-2.5%and 10%-20%,respectively.In order to overcome the defect that the modified materials are difficult to realize the multiperformance optimization of Portland cement based grouting materials by single admixture,the Portland cement based grouting materials were modified after compounding red clay,sodium silicate and sulfoaluminate cement.Response surface analysis shows that the interaction between sodium silicate and red clay has the most significant influence on the 2 h bleeding rate and compressive strength of Portland cement based grouting materials.The interaction between sodium silicate and sulfoaluminate cement has the most significant effect on the setting time and fluidity of Portland cement based grouting materials.The optimal dosage scheme of composite modified materials was obtained by Design-Expert Numerial function as follows: the dosages of red clay,sodium silicate and sulphoaluminate cement were15.52%,1.81% and 12.92%,respectively.Compared with the traditional Portland cement based grouting materials,the modified multi-compound Portland cement based grouting materials reduced the 2 h bleeding rate by 96.67%,and the initial and final setting time shortened by 485 min and 546 min,respectively.The compressive strength of 7 d,14 d and 28 d increased by 0.79 MPa,2.72 MPa and 3.89 Mpa,respectively,and the cost of grouting material per ton was reduced by 8.05%Compared with the traditional Portland cement based grouting materials,the multi-compound Portland cement based grouting materials have better volume stability,water corrosion resistance and frost resistance.In the multi-compound Portland cement based grouting materials,sodium silicate stimulated the activity of red clay and generated more calcium aluminate hydrate and sodium aluminate hydrate polymer gels with low Ca/Si ratio,which has low solubility,good stability and better water corrosion resistance.In addition,the hydration of sulfoaluminate cement in the multi-compound Portland cement based grouting materials generates more ettringite,which is filled in the hardened slurries,further improving the hardened slurries compactness,and thus improving the volume stability and frost resistance of the hardened slurries.