Preparation And Properties Of Rapid Repair Materials For Cement Concrete Pavement

The damage of cement concrete pavement or concrete pavement for short not only influences the road service capacity but also brings hidden dangers for vehicle in normal state.The traditional repairing technique needs to close to traffic for a long time which obviously can not satisfy the economic progress and the requirements of pavement function for people.To meet the demands of concrete pavement quick repair,this paper aims at developing a concrete pavement quick repair material which can achieve traffic requirements of flexual strength greater than 3.5MPa within 8 to 24 hours.By compounding portland cement(PC),sulphur aluminate cement(SA)and early strength retarder,their performance matching and adaptability are studied.Finally,the mass ratio of SA to PC,the dihydrate gypsum dosage,the polypropylene fiber dosage and length are chosen as control parameters to prepare a concrete pavement quick repair material named fiber reinforced concrete made with PSAG ternary system of cement and its strength,elastic modulus,shrinkage performance and abrasion resistance,etc are studied.Several main conclusions have been obtained as follows:(1)It is feasible to confect fiber reinforced concrete made with PSAG ternary system of cement used for concrete pavement quick repair by compounding PC and SA as a main cementitious material.The flexual strength of the concrete can achieve greater than 3.5MPa,and the later strength at age 1 year develops well.While gypsum shows a significant influence on early strength of the concrete,it has no obvious effect on the later flexual strength.The optimal dosage of gypsum ranges from 0%to 2.5%.The fiber dosage has much more influence on concrete strength than the fiber length has.The later strength reduces with the increase of fiber dosage,but with proper quantity,fiber can improve the toughness of concrete to some extent.To make sure that the fiber can take effect in the internal concrete and avoid adverse effect on mechnical property of concrete,the best fiber dosage should control around 0.1%of the concrete volume.(2)Fiber dosage,dihydrate gypsum dosage and fiber length have a very significant influence on elastic modulus,while the influence of SA/PC is significant.The impact trends of fiber dosage and gypsum dosage on elastic modulus keep the same,and the elastic modulus decreases with the increase of dosage.The mathematical model between elastic modulus Ec and compressive strength fcu and apparent density ?c can be described as Ec=1.4734 fcu0.1096?(?)2.4345×10-7,and the relativity is signnificant under level a=0.01.(3)By adding appropriate amount of PC to SA,it can improve the minerals composition content of cement component and make a more reasonable composition and structure of hydration products so that the cement stone is denser and the cement blocks and aggregate at the surface of concrete are not easy to come off which improve the anti-abrasion ability of concrete.The improvement of abrasion resistance will be the most significant when the fiber dosage is 0.1%and when the dosage is excessive it will bring adverse effects.(4)After SA/PC by 7/3 distribution,the concrete not only can compensate its own internal shrinkage at early stage,but also have certain extra expansion which plays a positive role to improve the durability of concrete.(5)The later shrinkage of concrete is minimum when the dihydrate gypsum dosage is 5%and the fiber dosage is proportional to the concrete shrinkage rate.During the trial design shrinkage age,the SA/PC is the main factor to influence the concrete shrinkage.When the fiber length is 12mm the shrinkage rates are all minimum.The mathematical model between the maximum shrinkage rate ?max at the age of 180 days of fiber reinforced concrete made with PSAG ternary system of cement and the factors parameters can be described as ?max=10.43x1+32 166.67x2-7.39x3+92.85 and the relativity is remarkable under level a=0.01.(6)The strength at different ages of fiber reinforced concrete made with PSAG ternary system of cement have been studied and the concrete gains an optimum strength when the SA to PA is 9 to 1,the gypsum dosage is 5%,the fiber dosage is 0.3%and the fiber length is 9mm.It is found that the hydration products mainly are C-S-H gel,CH crystal and ettringite without other crystalline phases after the micro-analysis of optimal group and comparision group.The mechanical performance of optimal group is good not only because it can generate more hydration produces at the same age but also because the composition and structure are much more reasonable in the products to make the cement stone denser which leads to a better mechanical performance in macro.