Preparation And Performance Characterization Of Normal Temperature Asphalt Modified Cement Repair Mortar

The cement pavement under long-term load is prone to cracks,broken plates,falling corners and other defects,which affect the pavement service quality and even endanger traffic safety.The traditional repair materials of cement concrete pavement have some defects,such as long curing cycle,large brittleness;large shrinkage and so on.This paper proposes to use the reactive normal temperature asphalt modified cement mortar,analyzed the normal temperature asphalt and mineral admixtures on the modification mechanism of repair mortar,and discusses the influence on its performance.The main contents of this paper are as follows:(1)The main modifiers and admixtures suitable for the preparation of composite repair mortar were analyzed by orthogonal experiment,and the optimum mixture ratio of Portland cement normal temperature asphalt,silica fume,calcium sulfate whisker and slag powder was determined.The results of basic performance test show that the properties of composite repair mortar meet the requirements of fast pavement repair material.(2)The influence of normal temperature asphalt on the performance and early hydration of cement repair mortar was studied.The results showed that normal temperature asphalt modified repair cement mortar accord closely with the Bingham.model.The yield stress and plastic viscosity of modified repair mortar accelerate with the increase of normal temperature asphalt.The addition of bitumen at room temperature reduces the speed of cement hydration reaction and delays the hydration process.As the degree of normal temperature asphalt increased,the retardation for cement hydration was intensified.(3)The effects of normal temperature asphalt and other admixtures on mechanical properties,dry shrinkage properties and corrosion resistance of cement mortar were studied.The results show that with the increase of normal temperature asphalt content,the flexural strength of mortar increases obviously,and the increase of age at 28d reaches 103.26%,while the compressive strength decreases slightly,and the decrease is 14.24%at 28d,indicating that toughness is improved.The addition of normal temperature asphalt also improves the early cracking property of cement mortar.Silica fume improves fluidity and makes up for the loss of compressive strength caused by normal temperature asphalt.The maximum compressive strength of 7d is 52.8MPa.With the increase of the content of calcium sulfate whisker,the tensile strength of mortar increases significantly.When the content of calcium sulfate whisker reaches 7%.the tensile strength reaches 4.2MPa,and the drying shrinkage rate decreases.The corrosion resistance of mortar is improved by the addition of normal temperature asphalt.Among various kinds of chemical erosion,the resistance to sulfate erosion is the best,followed by alkaline erosion,and the resistance to acid erosion is weak.(4)The modification mechanism of normal temperature asphalt on cement repair mortar was studied.The results show that the normal temperature asphalt film covers the surface of cement hydration products.Bitumen membrane attached to the surface of cement hydration products or filler between the micro pore,the existence of bitumen membrane delayed the cement hydration,prevent the generation of micro cracks and expand at the same time,thus improve the flexural strength,improve the toughness.The bitumen film also isolates the contact between the corrosive medium and the hydration products,thus improving the resistance to erosion.