Expermental Research On A Super-early Strength Cement-based Grouting Material

With the continuous development of infrastructure construction,especially the success of world-class super projects such as Hong Kong-Zhuhai-Macao Bridge,and under the background of the high attention paid by the state to environmental protection,the requirements for grouting materials for bridge supports and early-strength repairing materials technology are constantly increasing.Facing the important repairing projects in alpine regions of China,grouting materials are required to reach a very high early stage under low temperature conditions.Strength makes it possible to carry out construction in winter and high-cold areas,and can greatly shorten the construction period of the project.Therefore,it is imperative to study high-flow super-early strength grouting material.Based on the single and multiple admixture tests of sulphoaluminate cement and high alumina cement,the effects of different mixing ratios of two kinds of cement and ordinary Portland cement on the properties of ultra-early strength grouting material are systematically explored,and the reference mix ratio of cementitious material is preliminarily determined.On the basis of this benchmark mix ratio,the single factor tests of four mineral admixtures,fly ash,ultra-fine mineral powder,silica fume and micro-beads,were carried out successively.The experimental results show that ultra-fine mineral powder has the greatest influence on the initial fluidity of ultra-early strength grouting material,and silica fume has the greatest influence on the 30-minute fluidity of ultra-early strength grouting material.The effects of two important parameters,i.e.cement-sand ratio and water-binder ratio,on the properties of ultra-early strength grouting material were investigated.Through comparative tests of tartaric acid,boric acid,borax and sodium gluconate in the same dosage,it was found that tartaric acid and sodium gluconate had the greatest influence on the initial fluidity and 30-minute fluidity of ultra-early strength grouting material under the same dosage condition;tartaric acid and sodium gluconate were compared.The compressive strength of coagulant in 2 h is about 13 MPa.The results showed that the retarding effects of four retarders were tartaric acid,boric acid,borax and sodium gluconate in turn.Hydroxypropyl methyl cellulose(HPMC)and polycarboxylic acid water reducer were introduced to replace the traditional retarder at low temperature.By adjusting the water-binder ratio,a low temperature super-early strength grouting material with compressive strength of 2 h > 20 MPa was successfully prepared at-10 ℃.The experimental results show that the compressive strength of ultra-early strength grouting material decreases by 10 % and 8 % respectively in 2 h and 1 D and 4 MPa in 28 d when HPMC is in the range of 0.15 % to 0.25 % at water temperature of 15 %,that is,HPMC is negatively correlated with the compressive strength of grouting material at all ages.