Preparation And Properties Of Geopolymer Materials For Road Repair And Oil Well Cementing

Geopolymers are three-dimensional inorganic polymer networks composed of Si O₄and Al O₄tetrahedral structures,which are synthesized from alkali activators and solid materials.These materials exhibit excellent mechanical properties,high bond strength on inorganic substrates,and good fluidity,so that they can be applied in a wide range of fields.To meet the requirements on the rapid repair of roads,the geopolymer grouting material was modified by adding high-alumina cement,and the effect of high-alumina cement content on the mechanical properties of geopolymer grouting material was studied.In addition,for the problem that the cement slurry cannot effectively bond the two cementing interface caused by the residue of mud cake,the geopolymer cementing material was modified by choosing the addition amount of metakaolin（MK）and the modulus of waterglass.We prepared the geopolymer cementing material with low viscosity and high permeability,and explored its influence on cementing performance.The main result are listed below:1)For a rapid repair of road,the time for open-to-traffic（compressive strengthδ_c>1MPa）should be as short as possible.In order to meet the demand of rapid road repair,metakaolin-based geopolymer materials were modified by adding high-aluminum cement to prepare a geopolymer grouting material with early strength and excellent late-stage high strength properties.The setting time test results showed that the addition of high-alumina cement can significantly shorten the setting time of geopolymer grouting materials,and the addition of 25%high-alumina cement can shorten the initial setting time from 20 hours to 20minutes.The compressive strength（δ_c）can achieve 1.5 MPa（which fits with the standard for early-stage-traffic）in 2 hours.Meanwhile,after curing for 28 days,theδ_c,flexural strength（δ_f）,and bond strength（δ_b）of the materials were detected to be 30.5,3.0,and 1.5 MPa,respectively.According to the results of low-field nuclear magnetic resonance,it was proposed that an appropriate amount of high-alumina cement was able to absorb water produced in the process of geopolymerization and therefore to catalyze further geopolymerization,which was the important reason for the ultra-early strength of this kind of geopolymer grouting materials.2)The solidification of mud cake was the key to solve the problem of two cementing interfaces.We prepared modified geopolymerwith low viscosity and high permeability through sodium silicate and metakaolin.Mechanical properties results showed that the modified geopolymer（M=1.5,MK addition=2.5%）can effectively penetrate into the mud cakes.Under normal pressure and high pressure,the value ofδ_cof the cured mud cakes（at90°C for 10 hours）achieved 3.0 and 1.0 MPa,respectively.The cementation strength of formation-cement interface and casing-cement interface were 0.6 MPa and 1.0 MPa,respectively.The cementing strengths of the formed‘stratum-cement’interface and‘casing-cement’interface was detected to be 0.6 and 1.0 MPa,respectively.X-ray diffraction data indicated that the addition of MK was not the factor to modify the crystallization but the key for improving the strength of the final cured mud cakes.