Study On Preparation And Performance Of Rockburst Prevention Materials

Rockburst is a sort of geological disaster that greatly threaten the safety of constructionpersonnel and equipment. Now, material that be used for rockburst prevention are shotcrete.But ordinary concrete have many fatal flaws. For example: high brittleness, low flexuralstrength, high porosity and poor durability, used for material can cause crack and desquamate.So the research on high performance rockburst prevention material is significant tounderground engineering to be smoothly carried out.The objective of paper is to prepare a kind of mortar with high flexural strength, excellentbondability and good toughness for rockburst prevention engineering. In this thesis, polymerlatex and fiber are mainly applied to modify cement mortar, then proceeded to study theinfluences of sand grading, cement sand ratio and admixture on properties of rockburstprevention cement mortar.Firstly, this thesis research the effect of styrene acrylic ester copolymer latex (SAE) andacrylic copolymer emulsion (ACE) with different addition amount on setting time, flexuralstrength, compressive strength, bondability, toughness and total porosity of sulpho aluminatecement mortar. The results indicate that the optimal content of ACE and SAE latex in mortar is12%. The flexural strength increases firstly, and then decreases with the increment of latexcontent. However, the compressive strength decrease slowly. Both of latex can improvetoughness and bond flexural strength, decrease the porosity and prolong the setting time ofcement mortar. The results of SEM and XRD analysis show that latex could defer the earlyperiod hydration process of cement mortar. As ACE belongs to reactive latex, the modificationeffect of ACE is better than that of SAE.The influences of polypropylene fiber (PP) and polyvinyl alcohol fiber (PVA) added onthe flexural strength, compressive strength and toughness of the hardened mortar were studied.The results show that the flexural strength and compressive strength increases firstly, and thendecreases with the increment of each fiber content and the optimal content of PVA and PP fiberin mortar is1.6kg/m~3. Both of fiber can improve the toughness of mortar. Because of thedifferent surface characteristic of each fiber, the effect of PVA fiber reinforced cement mortar isbetter than that of PP fiber. The influences of curing methods of latex modified mortar and mixing process of fiberreinforced cement mortar on strength of mortar. The results indicate that wet curing firstly andthen dry conservation is the best curing method. Under the condition of two mixing process,(Ⅰ)has a better effect, the methods is that Add and mix fiber to sand and cement first, and thenmixing with water.On the foundation of previous conclusions, the effect of latex and fiber added together onthe strength of mortar were studied. The results indicate that the mechanical property of fiber-latex added together is better than that of two matters added separately. The optimal componentfor fiber-latex hybrid is:12%of ACE+1.6kg/m~3of PVA. Fiber can restrain the crackdevelopment effectively. In addition, latex can increase the bondability between matrix andfiber by SEM photograph. Physical properties of cement mortar will get the furtherimprovement by the cooperation of fiber and latex.Further more, the paper studies the influences of sand grading, cement sand ratio, mineraladmixtures and admixture on strength and bondability of rockburst prevention material. Theresults show that sand grading, cement sand ratio, mineral admixtures and admixture inrockburst prevention material have notable impacts on physical properties and durability. Theexperimental data show that the best sand grading is40~70:70~140=1:0.8, the optimal cementsand ratio is1:1, early strength agent choose CaO and dosage is2%, quick-setting agent selectLi2CO3and dosage is0.04%, water reducer agent is FDN and dosage is1.5%. Both silica fumeand slag powder can increase the water requirement, decrease the strength and bondability ofrockburst prevention material. Compare with silica fume, slag powder has minor infection onphysical properties of rockburst prevention material.Finally, The optimal component for rockburst prevention material are(mass fraction):ACE is12%, PVA is1.6kg/m~3, FDN is1.5, Li2CO3is0.04%, CaO is2%, tributyl phosphate is0.5%, cement sand ratio is1:1, water cement ratio is0.25. Preparing a kind of rockburstprevention material according to the optimal component, which flexural strength can beimproved by80~90%and bond flexural strength of the material can be improved by40-50%.