Advanced Materials Research Vol. 857

Abstract: The stress concentration will appear in cement concrete around joint dowel set in contraction joint of cement concrete pavement with repeated loads. And concrete around joint dowel will damage gradually.In this paper, the stress of concrete around joint dowel and deflection of concrete slab are analyzed when joint dowel loosing. It is indicated that the shear stress is key to damage of concrete around joint dowel. when the loosing width reaches certain extent. With loosing width increasing, load transfer capacity will decrease gradually. And it is shown that the load transfer capability will lower rapidly when the loosing width comes in 4cm.

Abstract: Three-dimensional structure model on Winkler foundation considering inter layer contact status was established. The effect that base modulus, thickness and inter layer contact status between slab and base to maximum stress of slab bottom and base bottom, shear stress between slab and base, warping of slab was calculated. The results showed that: interlayer contact status had great influence on slab stress and warping. Maximum stress of slab bottom dropped while bonding status decreased and slab warping increased obviously while bonding status weakened. Base modulus was the primary factor for base stress. Maximum stress of base bottom increased while modulus increased, and decreased while bonding status weakened. Interlayer shear stress occurred mainly at slab edge, and decreased while the bonding status weakened, almost had no correlation to base modulus and thickness.

Abstract: This paper, in terms of structure design, mainly considers the unfavorable load position of cement concrete pavements and the finite element software is used to establish three-dimensional solid model for analysis and calculation of load stress. The results show that fatigue stress along the transverse direction is much larger than that along the longitudinal direction, and slabs are most likely to have cracking along the longitudinal direction under the combined effect of load and temperature. It is of certain significance for the prevention of longitudinal cracking of concrete pavements and the extension of pavement life.

Abstract: Supported by the Guozigou-bridge, the paper studied the Frost-resisting property of bridge concrete in alpine frigid region. Researched the effect of water-binder ratio, fly-ash content, water consumption and air-entraining agent consumption, and reveals the impact mechanism of frost-resisting property of bridge concrete in alpine frigid region. Analyzed the influence rule of frost-resisting property and showed reference value of concrete's ingredient rate in alpine frigid region. The result showed that low water-binder ratio and water consumption can effectively improve the deicer-frost resistance of concrete and the influence of water consumption is more significant. Best air content between 4.5% ~ 4.5%.

Abstract: Based on field tests and numerical simulation methods, distribution characteristics of early-age built-in temperature of cement concrete pavement constructed in different seasons and pouring time were analyzed firstly. Then considering effect of creep, characteristics of early-age zero stress temperature in cement concrete that built-in temperature of cement concrete pavement constructed in different seasons and pouring time has a great difference. The distributions of built-in temperature along the thickness present nonlinear obviously, and they have four typical types: concave and positive gradient type, concave negative gradient type, convex positive gradient type and convex negative gradient type. Zero stress temperature gradient shows prominently developing process compared with built-in temperature of slab at different ages by the effect of creep. Zero stress temperature of slab poured on am7:00 in summer firstly increase and then decline. Besides, the positive gradient change to negative gradient gradually, and the gradient of zero stress temperature trend to decrease. At last, it is recommended to calculate zero stress temperature of slab consideration of base temperature and the nonlinear distributions characteristics, and the combined effect of creep and age.

Abstract: Transforming the cement concrete mixer, simulating twin-shaft mixing process on large mixing plant, adding real-time acquisition equipment of torque and speed, and achieving the online monitoring of concrete mixing process. The influences of speed and stirring time on the liquidity of fresh cement concrete was deliberated, so that it were analyzed from three indicators of concrete slump, stirring torque and compressive strength to determine the optimum stirring speed 48r/min, reasonable mixing time 40s ~ 50s, and mixing time less than 100s.

Abstract: It is difficult to control quality for precast concrete girders in curing, so we set up the curing system of precast concrete girders with computer networks, automatic control of drip irrigation technology, database technology and two-dimensional code technology, With which we can control concrete girders curing continuously. Achieve well curing results, and storage the precast girders curing process temperature and humidity data, provide the data basis for quality assessment and acceptance of post-concrete structure.

Abstract: To carry out frost resistance, resistance to chlorine ion permeability, abrasion resistance and flexural tensile strength test for different mixture ratio of concrete, the influence of salt frost was systematically analyzed on the other concrete road performance. The results show that the salt frost made the decrease of strength of concrete, resistance to chloride ion penetration reduce, but had a little effects on abrasion resistance.

Abstract: Extensive crack width and crack spacing data from recently constructed continuously reinforced concrete pavements (CRCP) sections in China were collected and statistically analyzed in this study. A total of 29 CRCP sections were observed which lead to 1171 crack data. Kolmogorov-Smirnov test result shows that CRCP crack spacing follows a four-parameter Dagum distribution. ANOVA tests show that slab thickness does not have a significant impact on crack spacing. However, slab thickness does have a significant impact on crack width. Further ANOVA test shows that crack width reduces with the increasing of slab thickness. This preliminary result is not consistent with the crack spacing formula in MEPDG where the crack spacing is directly related to slab thickness.

Abstract: Cross-prestressed concrete pavement, without setting expansion joints, can extend its service life, improve its bearing capacity and make the continuous construction possible. In recent years, it has been successfully applied to toll plazas, short subgrade of the highway and the overweight or overloaded road. Materials choosing, construction method of the cross-prestressed concrete pavement was presented in details and some relevant problems during the construction have been discussed in this paper.