The Ancient Chinese Stone Bridge Reinforcement Repair Method and Quality Control

China is known as the “land of bridge”, it architecture of bridge construction technology has a long history. A lot of this bridges, ancient stone bridge architecture has the creations in the history of world bridges that shows the wisdom of hard working craftsmen in ancient China. This research is to find out how damage ancient stone bridge are repair and quality control during the construction period. What’s more the author is ensuring the related repairing and stability measures according to the above situations the measures of reinforcing old bridges. In the actual repair method of the bridge, analyzing the actual damages and provide suitable design, reasonable reinforcement repair method to achieve the best in the aspects of proper control and reinforcement construction of the stone bridge so that we can achieve the quality service.


Introduction
Guifang stone bridge is located in the East Street of Donghu street, Linping, Yuhang District, Hangzhou city. It is built on shangtanghe River from north to south. The climate is subtropical monsoon humid climate, with abundant rainfall, warm and humid. The annual average temperature is 16 ℃, the annual extreme minimum temperature is -14 ℃, the annual extreme maximum temperature is 42.1 ℃, the annual temperature is 37 ~ 38 ℃. The bridge is situated in the downtown area of Linping City, surrounded by numerous buildings and as a passage connecting the block used by residents. It reached the Beijing Hangzhou Grand Canal in the East and the main urban area of Hangzhou in the West and used to be one of the main waterways for the prosperity of local economy and commodity trade. According to the records of Renhe county published by Jiajing of Ming Dynasty, "the old name of Mao bridge is Xu Xuan, who was born in the Song Dynasty, Diyin and Cuan, and dozens of people from Taixue, Fu que, wrote to attack Jia Sidao. Later, he was also a Jinshi, ranking first in the list. The name of the villager is one gate, three shows, and the bridge name is "Guifang". The bridge was faced with some diseases that called for urgent repair work in order to sustain it for normal operational use.

damage and disease of Guifang bridge stone
According to the field survey, the overall status of Guifang bridge is as follows: 1) there is a large gap in the bottom slab of the bridge; 2) there is a pull-out crack between the corundum and the eyebrow stone; 3) the corundum is damaged and missing. The surface strength of Guifang bridge stone is high, there is slight weathering phenomenon, and local weathering is serious. The surface strength of bridge floor is high, and the surface strength of arch ring and side wall on both sides is relatively low.

3.Repair material 3.1 Optimization of Field Material Ratio 3.2 Optimization and Debugging of Site Proportion
(1) Weigh on site according to the material foundation ratio; (2) After weighing, manual mixing shall be carried out, consistency test shall be carried out on site, and mix proportion shall be optimized according to consistency; (3) Mix again according to the optimized proportion, repeat the above steps, and finally carry out mold making, sample retention and on-site maintenance. After the curing period is completed, test the bond strength, bending resistance and compression resistance of the sample test block on site  Figure 2 Field Consistency Test (1) Wipe the sliding rod lightly with small lubricating oil so that the sliding rod can slide freely.

Field Consistency Test
(2) Wipe the container and cone surface with a wet cloth, and put the mortar mixture into the container once, make the mortar surface is about 10 mm lower than the container mouth. Vibrate the container evenly for 25 times, shake container for 5-6 times to make the mortar surface flat, and then place the container on the base of the consistency tester.
(3) Loosen the brake screw, move the sliding rod downward, when the tip of the cone just contacts the mortar surface, tighten the brake screw, loosen the pointer screw, adjust the position of the pointer to the zero scale line, and tighten the pointer screw.
(4) Loosen the brake screw and count the time. When it 10s, immediately tighten the screw and read the sinking depth (accuracy to 1mm) from the scale.
(5) The mortar in the slurry container is allowed to measure the consistency only once. When the measurement is repeated, the sample shall be taken again for measurement.
Finally, through the consistency test, the field test repair material from the original water to glue ratio of 0.5 consistency 66 to water to glue ratio of 0.45 consistency 45.

Optimization Results of Field Proportioning
Through the actual construction process on site, confirm the results of material proportion after optimization on site.

Material Protection Technology Construction Site Guidance 4.1 Site Material Preparation
On site, according to the optimized material ratio, the construction guidance of material preparation is carried out, and the construction is reminded to pay attention to the difference between grouting and repair material ratio.

Arch Missing Repair Construction 4.2.1Construction Process
First, clean the pollutants inside the crack with brush, high-pressure air and vacuum cleaner, then seal the crack with repair materials, and finally fill the repair materials; pay attention to observation while filling the repair materials to prevent leakage of slurry in other places. If leakage occurs, plug it in time and clean it with ethanol. After grouting, the outer surface shall be treated as old. If the bonding part is large, wooden board and other tools shall be used for fixing.

Production of Sample Test Block on Site A. Fabrication of Bond Test Block
Put water, lime, mineral powder and various additives into corresponding containers according to the repair ratio after material optimization (1).Mix manually and then mix evenly with mixer.
(2)Then make the drawing test block on the stone.
(3)Finally, the pull-out test block shall be cured for three days. (4)After forming, the formwork shall be removed and placed near or under the bridge for maintenance.  The test method is in accordance with the test method for strength of cement mortar (ISO method) (GB / T17671-199). The size of the test piece is 40mm × 40mm × 160mm. The test piece is demoded after pouring for three days. It is naturally cured near the Guifang bridge environment. The test curing period is 28d. A.Test Principle: RB=PL/BH 2 Where: RB -flexural (tensile) strength of concrete (MPa); P -ultimate failure load of test piece (n); L -distance between supports (L = 100mm); B -width of test piece (mm); H -height of test piece (mm).

B.Evaluation of Test Results:
 The bending strength of each specimen is accurate to 0.1MPa.  Take the average value of the bending resistance results of a group of three specimens as the experimental results. When any of the three strength values exceeds ± 10% of the average value, the average value shall be taken as the experimental result of flexural strength after elimination. The experimental results are accurate to 0.1MPa.

(3)Compressive Strength Test
The test method is in accordance with the test method for strength of cement mortar (ISO method) (GB / T17671-199). The size of the test piece is 40mm × 40mm × 160mm. The test piece is demoulded after pouring for three days. It is naturally cured near the Guifang bridge environment. The test curing period is 28d. The relative error (accuracy) of indication shall not be greater than 1%. The range application shall make the expected failure load value of the test piece not less than 20% of the full range, nor more than 80% of the full range. The upper and lower part of the testing machine shall have sufficient rigidity, and one of them shall be equipped with spherical bearing, so that the contact between them and the bearing is even. Mold test, steel ruler: measuring range: 300 mm, division value: 1 mm.

A.Test Principle:
Rc=P/A Where: R -compressive strength of concrete (MPa); P -Ultimate failure load of test piece (n); A -Compression area (mm 2 ); Rc -compressive strength of concrete Rb, accurate to 0.01Mpa. B.Evaluation of test results:  The compressive strength of each specimen is accurate to 0.1MPa.  Take the arithmetic mean value of six compressive strength measured values obtained from a group of three test blocks as the experimental results. If one of the six measured values exceeds ± 10% of the six average values, this result shall be eliminated and the remaining five average values shall be taken as the result. If there are more than ± 10% of the five measured values, the results of this group will be invalid.
The experimental results are accurate to 0.1MPa. Figure 7 Bending Strength Test Figure 8 Compressive Strength Test

On Site Bridge Deck Crack Grouting Construction 4.3.1 Construction Observation
Firstly, the pollutants inside the cracks shall be cleaned with brush, high-pressure air and vacuum cleaner, and then the cracks shall be sealed with repair materials. After the sealing and repair materials are hardened, the hydraulic lime grouting materials shall be sucked by the grouting machine for pressure grouting treatment, and the grouting height shall not exceed 10-15cm each time. The time interval for step grouting shall be 24h, and the grouting shall be carried out after the previous grouting is completely solidified. The grouting sequence is from the bottom to the top. In case of slurry overflow, grouting shall be stopped; at the same time, attention shall be paid to grouting to prevent slurry leakage in other places. In case of slurry leakage, it shall be blocked in time.
After grouting, the external surface shall be pointed and trowelled with stone powder of the same material, and the old treatment shall be carried out at the same time.

The Appearance of Bridge Arch is Old
According to the special project of science and technology protection of Guifang bridge, after the repair, the external surface is treated as new ones so that there is no obvious construction trace on the appearance of the bridge. For the materials, the exterior color matching agent SA90 of Shanghai dessaibao is selected. steps  Red, yellow and black pastes shall be mixed, and the total amount of color pastes shall not exceed 3% of the total amount of color matching agent.  The base surface must be dry and clean, free of dirt, weathering, alkali, algae and moss.  Defects of the base surface, such as cracks, cracked joints, joints, rising steam, etc., must be repaired 27 first.  The product can be applied to the surface to be treated by brush or low-pressure spraying equipment.
The newly treated surface shall be protected from rain within 5 hours. Figure 11 Getting the Crack Old

On site construction effect detection
The visual inspection shows that the color of the repair construction site is similar to that of the stone on both sides.

Quality Control Measures
(1)Check whether all kinds of pollution on the surface of bridge are effectively clear before and after being clear through photo comparison, and restore the color of the stone of cultural relics; (2) The surface of bridge before and after cleaning shall be inspected by color difference meter. After cleaning, the color difference brightness will increase or remain unchanged; (3) Use hardness tester to test the surface hardness of cultural relics before and after cleaning. After cleaning, the surface hardness of cleaning parts increases or remains unchanged; (4)Detect the water absorption of the surface of the cultural relics after cleaning, indirectly judge that all kinds of blockage pollutants in the surface pores of bridge are effectively removed, and the water content of the surface increases or remains unchanged after cleaning.

Conclusion
The ancient stone bridge reinforcement repair method and quality control has been thoroughly researched. The repair procedure has been the best by the researcher in the order of how the whole repair process is been done. A conclusion is drawn after the whole work on how design princples are constantly maintain.
 Principle of "not changing the original state of cultural relics"  Principle of "safety first"  Principle of "quality first"  Prevention of protective damage  Principle of reversibility and reprocess ability The researcher finally notice the people of China and the government as a whole did not change the face of their cultural relics as far as stone bridge is concern to date but rather protecting it for new generation come.

Acknowledgements
This work was financially supported by the Science foundation of zhejiang province, China (LGF20E080005).