Performance Study On The Fly Ash Based Geopolymer Material For Cement Pavement Rapid Repair

Cement pavement is a common-seen road surface pattern.Under the interference of modern vehicles and natural factors,the pavement occurs diseases such as crack,arch,breakage and fracture.Conventional repairing materials for cement pavement have some significant deficiency,mainly the poor durability,high producing cost,great carbon emission and complicated construction process.In order to develop a new repairing material,under the compound stimulation of sodium silicate and sodium hydroxide alkaline solution and with blast furnace slag and fibers added,fly ash,the main raw material,was employed to manufacture geopolymer mortar which could quickly repair cement pavement.And the relation between mix design and properties was also explored in this research.The diseases causes and curing methods were analyzed.On the basis of this,the applicability and economy of the fly ash based geopolymer neat paste and mortar were also investigated.The main conclusions are listed as follows.1.The performance of this material was mainly influenced by four factors,water-binder ratio,alkali-activator proportion,blast furnace slag replacement ratio and the module of sodium silicate,respectively.The reasonable value range of sodium silicate module was 1.2 ~1.8.For saving the costs,the alkali-activator with1.8 sodium silicate module was allowed to be used to manufacture the geopolymers.And the reasonable values of water-binder ratio and alkali-activator proportion was approximately at the level of 0.28 and 0.14 respectively.The blast furnace slag replacement ratio was the most significant influential factor for the properties of the geopolymers.Its reasonable value was 0.4.Considering that the strength of this material had considerable surplus when applied to repair cement pavement,it was also allowed to increase the water-binder ratio and reduce alkali-activator proportion,so as to save the costs.2.With fibers or styrene-butadiene latex added into the fly ash based geopolymer neat paste,the fluidity became smaller,and the fluidity loss of PVA fiber is less than that of PP fiber.The fiber plays a role in promoting the coagulation of fly ash based geopolymer,and the styrene-butadiene latex has a retarding effect。Fiber had little effect on compressive strength,but it can significantly improve the flexural strength and tensile strength.The styrene-butadiene latex can only improve the long-term flexural strength,and it cause the reduction of the compressive strength,early flexural strength and tensile strength.The fiber can improve the durability of the fly ash based geopolymer neat paste,reduce the creep shrinkage and enhance the frost resistance,while styrene-butadiene latex can not.3.Fibers can significantly improve the toughness of fly ash base polymer,and the toughening effect of PVA fiber was better than that of PP fiber.The mechanism of fiber toughening lies in two aspects:First,the flexural strength of fly ash baded geopolymer improved with fibers added,Another aspect is also the most important aspect,The addition of fibers increased the ductility of the geopolymer so the toughness was improved,and the toughening effect of PVA fiber was better than that of PP fiber.4.In order to reach satisfying fluidity and mechanical strength,the rational value range of water-binder ratio and binder-aggregate ratio of fly ash based geopolymer motar were 0.4~0.42 and 0.45~0.5 respectively.The strength of medium sand and the coarse was greater than the fine kind.The better technology category,the higher strength.Specifically,the mechanical strength of this geopolymer mortar was comprehensively influenced by the thickness degree and gradation of sand.Therefore,it is advocated to use well-graded medium or coarse sand to manufacture geopolymer mortar.5.The fly ash based geopolymer mortar can quickly reach high compressive strength,3d compressive strength can reach more than 35 MPa,and 7d compressive strength can reach more than 50 MPa.The addition of PVA fiber had little effect on the compressive strength,and the compressive strength decreased greatly after adding styrene-butadiene latex.PVA fiber can improve the early flexural strength,tensile strength and toughness of fly ash based geopolymer mortar,but it has no significant improvement in long-term flexural strength.The styrene-butadiene latex can obviously improve the long-term flexural strength of the fly ash based geopolymer neat paste.The flexural strength,tensile strength,bond strength and toughness of fly ash based geopolymer mortar at different ages were improved after PVA fiber and styrene-butadiene latex mixed together,The reasonable composition is 0.5% volume of fiber and the mass of the amount of styrene-butadiene latex 8%.6.The fly ash based geopolymer mortar has good performance of anti-shrinkage,anti-sulfate and good durability.The addition of PVA fiber can reduce creep shrinkage to a certain extent and improve frost resistance.Styrene butadiene emulsion has a slight negative effect on the durability of fly ash based geopolymer mortar.7.The fly ash based geopolymer neat paste was mainly suitable for the rapid repair of cement pavement cracks,The fly ash based geopolymer mortar was mainly suitable for the cement pavement and the rapid repair of cement slab.The price of the fly ash based geopolymer neat paste material was about 1300 yuan,and the fly ash based geopolymer mortar was almost 700 yuan,Compared with similar products,they were economical applied into repair of cement concrete pavement crack sealing,mix patching and bottom sealing.