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On the grouting in the Treatment of Old Cement Concrete Pavement

Author: ZhuXiaoBin From: www.yourpaper.net Posted: 2010-07-08 22:43:49 Read:
Abstract: This paper Old Cement Concrete Pavement squirt mud, formed to analyze the causes of the Void the vacuum grouting technology as the applicability of the above two types of common diseases harm Governance program.
Keywords Old Cement Concrete Pavement; grouting; technology applications

Cement concrete pavement is one of the main form of China's highway pavement, account for a large proportion in the composition of China's highway network. It has the advantages of high strength, stiffness, and little affected by temperature, long service life. Cement concrete pavement joints are more prone, more sensitive to overloading, Void, jack mud cracks early disease, resulting in damage to the road. How governance and the prevention of Void, jack mud and other diseases, do a good job in the conservation of the cement concrete pavement, to extend the service life of the road, to improve its capacity and is economical. Is still a subject not yet conclusive. I have participated in Guangdong Province cement concrete pavement of a highway reconstruction project construction, the project uses the grouting technology to settle the original cement concrete pavement, and achieved good results. The following from the cement concrete panel jack mud, Void formation of the main reasons and mechanism of grouting technology mechanism and implementation details the aspects.

The Cement Concrete panel jack mud, Void formation of the main reasons

Squirt mud and void diseases produce its internal factors and external factors: internal factors is the quality of the grass-roots level itself, the composition and condition of the concrete panel joints; external factors is the vehicle load and climate change. China's road base material layer (pad) are generally selected stable class aggregates, the elastic modulus is much smaller than the elastic modulus of the concrete surface. Cement Concrete Pavement in the heavy vehicle loads repeatedly under the plate under the base (cushion) layer will have a cumulative plastic deformation, the local scope of the concrete slab is no longer maintain continuous contact with grass-roots, so Cement Concrete Pavement Base with the base (cushion) tiny gap between the layers will appear, that the local board of void or void areas known as the original. Changes of temperature, humidity, and a non-linear distribution of temperature in the plate, causing the plate up or down warping, accelerate the separation between the plate and the foundation, the formation of Slab Hollow. Void appear to create conditions for water immersion timely pavement joints or cracks conservation, rainwater from the breakage invade the grass-roots level, the infiltration of water will be formed under the board the hydrocephalus (free water). Fine material in the stagnant water in the base material to form a slurry, and splashes out along the panel seams gap, to form a squirt mud. Squirt mud further exacerbated by the emergence of the Void the end of the board. This cycle, a vicious cycle, eventually leading to damage to the road surface.

Two vacant concrete slab determine

(A) Void plate method for determining
Void board artificial observation, Measurement of Deflection method can be used to determine. Artificial observation by the naked eye seams, cracks, jack, mud preliminary determination Void. When re-dealers can feel the concrete slab vertical displacement, or after it rains, significant squirt mud phenomenon plate, that is Void. The disadvantage of this method is subjective, even experienced engineers can not avoid wrongly, Missing. Measurement of Deflection angle deflection of the test board, exceeds a certain limit, which is considered to exist Void. China's Ministry of Industry Standard Highway Cement Concrete Pavement Maintenance Technical Specifications (JTJ073.1-2001) (hereinafter referred to as the "Code") is also clear that the Cement Concrete Slab the empty position determination can be used Measurement of Deflection.

(B) detection method
The author participating in the construction of a road test section of a highway, built in i997, design plate thickness 24cm. Deflection indicators to determine the vacant concrete slab. First select cement concrete panel to load the most adverse effects of position as the detection point, should select a point near the transverse joint and longitudinal seam. Use of of two 5.4m pole deflectometer and BZZ-100 standard axle load (rear axle axle load 10t) Determination car. Detection point of the main points, sub-points. The main point is located before the board Joints 10cm, loading and unloading. Vice-point in the transverse joint 10 cm, no load (normal direction of traffic for the former). A deflectometer on the main point, that determination of the middle of the car wheel gap; another deflectometer placed in the sub-point. Were measured Lord, Vice-point deflection (right wheel test in the forward direction). Right wheel in the longitudinal seam about 30 cm. The road repair manual "provides that, where the deflection value is more than 0.635mm, plate Void. According to the actual situation of China's highway construction status and detection equipment, the experts recommended that where more than 0.2mm deflection value should be identified as the panel Void (see specifications). In the experimental section of double-index control, that is the main point of deflection greater than 0.2mm or differential deflection (the main point of the vice point) is greater than 0.06mm, are of the view that the bottom of the plate may appear Void phenomenon. (C) Reinforcement Mechanism
Existing concrete pavement design theory, the concrete slab as a small deflection thin elastic plate, on the assumption that full contact between the panel and the foundation (Void). Concrete slab is a quasi-brittle materials, high compressive strength, flexural poor performance. Under normal circumstances, the panel is evenly supported, regardless of the load acting position, the stress is small. Once Void, board corner due to the loss of basic support in a cantilever state, the board will have a large stress, shear, concrete slab soon reached the limits of life. Cement concrete panel grouting grouting pipe, exert a certain pressure slurry evenly into the bottom of the plate gap plate base (cushion) layer, filling, penetration, crowded dense way, get rid of the bottom of the board, the grass-roots fissures plot water, air occupies its position after manual control for a period of time, the slurry will the original loose particles or fractured cemented as a whole, the formation of a good "stone body. The grouting improved board the end of the original stress state to restore the continuity of the plate body and foundation. To achieve the purpose of reinforcement based on governance diseases.
One of the basic requirements of slurry material
Top material slurry comprising: cement, fly ash, water and admixtures. The slurry was made of 7.07 7.07 7.07cm cube specimens, the standard conservation 7d, its compressive strength to 5MP a. Slurry should have a good pumpability, workability, water retention, the paste is too thick can not be uniformly covered with the bottom of the plate gap, the paste is too thin, the shrinkage of. In the construction, I believe that in order to prevent the shrinkage of the slurry, the slurry should be mixed with a certain amount of bulking agent. Fluidity are the main factors to affect groutability, generally the higher the degree of liquidity, irrigation, the better. Not to do this in the existing norms clearly defined reference Precast Slab Grouting experience, the use of cement slurry consistency test funnel (volume 1725ml 5M1) to paste all the free flow after time as fluidity to control (see See technical specifications for road bridges and culverts JTJ041-2000 Appendix G-11). Wherein under ambient conditions, the efflux time of pure water for 10 s (indoor test result). Under standard conditions, the flow between the different water-cement ratio, the ratio of different materials and specimen strength. Cement paste regardless of doped or without superplasticizer, better mobility than their mobility under the same conditions cement fly ash pastes. Therefore, it can be seen that the water demand of the secondary fly ash per unit volume greater than cement. For cement paste without superplasticizer, the fluidity of not less than 16s; slurry water-reducing admixture can be reduced to 12s fluidity should not be greater than 26 s. In the construction, I believe that the fluidity of paste should not be too small, better control between 20-3 0s. Or will cause bleeding phenomenon.
2 test data
In the case of the same water-cement ratio, liquidity changes with the proportion of cement and fly ash. Meanwhile, the proportion of fly ash also affect the late strength of the grout. Under the same conditions, the greater the water-cement ratio, the strength of the slurry will be gradually reduced, and therefore, should not be too large water-cement ratio. According to the above test results, the ratio of the slurry used in the construction of: cement: fly ash: water: early strength agent = 1:0.5:0.7 0.5%. Obtain large liquidity to ensure the strength of the slurry.

(D) the implementation of the grouting technology
Holes layout is generally 3-5 hole, should be determined according to the size of the concrete panel cracks conditions and filling machinery. Grouting hole size should be the same size and perfusion mouth, usually about 5cm. Filling the order from the large place of settlement, from far to near, from big to small. The grouting pressure control should be considered damage to the concrete slab and Lost specifically identified. When the slurry emerge from the seams or another grouting holes can be considered to complete the hole grouting, grouting stop, quickly moved to another orifice to continue the job. Pressure is generally controlled between 1 MPa-4 MPa and stay 3min-5min better.
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