What are the tips for using a concrete power trowel?

  Laser leveling concrete wear-resistant floor refers to the use of laser leveling machines to perform high-precision and rapid leveling operations on concrete, thereby obtaining a concrete wear-resistant floor that meets high standards in terms of flatness, levelness, density and strength.   The concrete laser leveling machine uses laser as the reference plane, and emits rotating laser through the laser transmitter. The laser signal is captured by the laser receiver on the leveling machine. The received signal is deeply analyzed by the laser measurement and control system, and any deviation will be accurately identified and fed back to the highly sensitive computer control system on the leveling machine. Based on this feedback information, the leveling machine will intelligently adjust the height of the scraper or leveling head to ensure the accuracy of the leveling operation. At the same time, the hydraulically driven vibration motor drives the vibration plate to vibrate the concrete to further compact the ground.   (1) Construction preparation Material preparation: Ensure the quality of concrete materials. Polycondensate high-efficiency water reducer can be added to reduce the risk of cracking. At the same time, prepare the required wear-resistant aggregates, interface agents and other materials. Equipment preparation: Transport and place laser leveling machines, trowels, trimmers, vacuum cleaners and other equipment to the designated location on site, and perform maintenance work to ensure that the equipment is in good standby condition. Base treatment: Mill the base to increase the adhesion between the leveling layer concrete and the base. Clean the surface of the concrete base plate and use a high-pressure water gun to thoroughly rinse the floor surface. Sweep mortar or apply special interface agent as needed. (2) Formwork setting and steel bar laying Formwork setting: Set the formwork according to the design requirements, ensure that the formwork support is on the same horizontal line as the elevation, and use a special formwork frame to set it at an inclined angle to facilitate subsequent construction. Rebar laying: Adding steel bars to concrete can effectively increase the tensile strength of concrete and prevent cracking. The steel mesh should be placed 20mm~30mm away from the floor surface, which not only increases the tensile strength of concrete but also protects the surface from cracks. (3) Concrete paving and laser leveling Concrete paving: The mixed concrete is pumped and spread on the crushed stone base. The paving speed should be appropriate, and manual leveling should be assisted quickly. Ensure that the concrete construction thickness meets the design requirements. Laser leveling: Use a laser transmitter to determine the height of the concrete paving construction, and use a laser leveling machine to perform leveling operations. During the leveling process, one person should be responsible for moving the laser leveling machine, and two people should be responsible for the front-end auxiliary leveling to ensure that the concrete surface remains at the designed height (4) Initial grinding and slurry breaking and throwing wear-resistant aggregates Initial grinding and slurry breaking: When the concrete is initially set, use a single-disc and double-disc trowel to repeatedly rub and level the concrete slurry. The best time is when there are no clear footprints left by people on the concrete. Spreading wear-resistant aggregate: Spread the specified amount of wear-resistant material evenly on the surface of the concrete just after the slurry is broken. Special materials can be considered as specific conditions and spread more than twice. After each spreading, use a trowel to grind and compact the aggregate. Finishing and maintenance Finishing operation: Depending on the degree of hardening of the concrete, perform at least three trowel operations without a disc. The speed and angle of the trowel should be adjusted according to the degree of hardening of the concrete. The corners can be manually scraped. Maintenance: After the construction is completed, it takes more than 28 days to maintain. Sprinkle water for maintenance and lay soil cloth to reduce water evaporation and keep the wear-resistant floor after construction in water. (5) Cutting expansion joints and subsequent treatment Cutting expansion joints: After the concrete has been sprinkled with water for a certain period of time (such as 24 hours), cut the expansion joints according to the design requirements. The setting of expansion joints should take into account the expansion and contraction space of concrete to prevent cracking. Subsequent treatment: Clean and fill the expansion joints after cutting to ensure the beauty and practicality of the floor.   The construction requirements of laser-leveled concrete wear-resistant floor are strict, covering material selection, construction equipment, construction process, construction environment and other aspects. The following is a detailed summary of these requirements: (1) Material requirements: Concrete Strength grade: C25~C30 concrete, 28-day strength not less than 25MPa. Water-cement ratio: not more than 0.5, no water should be added at will during the feeding process. Cement: ordinary silicate cement with a grade not less than 42.5 should be used. Bone material: well-graded, coarse bone material is crushed granite or pebble, with a maximum diameter not more than 25mm; fine bone material is clean river sand, with a fineness modulus of 2.4~2.7. Concrete mix ratio: cement dosage is not less than 350Kg/m³, and the sand ratio is controlled at 35%~40%. Concrete slump: 14±2cm, maximum 16cm. Setting time: The initial setting time is controlled within 3-5 hours. Wear-resistant aggregate: The amount of wear-resistant aggregate is not less than 5kg/㎡, and it is evenly spread in batches to ensure wear resistance and flatness. (2) Construction equipment requirements Concrete laser leveling machine: Ensure that the laser transmitter and receiver work normally, without dead corners, and can monitor and control the ground elevation in real time. Other auxiliary equipment: Including concrete mixing station, pumping equipment, trowel, trimmer, vacuum cleaner, etc., to ensure that the equipment is intact and meets the construction requirements. (3) Construction process requirements Preparation work: Including laying the base, steel mesh, setting the transmission rod, placing the buffer zone, etc., to ensure that the foundation is firm and flat. Concrete paving: Pump concrete to the site and manually assist in leveling to ensure that the concrete is evenly distributed. Laser leveling: Use a laser leveling machine for high-precision leveling to ensure that the ground flatness and levelness meet the requirements. Initial grinding and breaking of slurry: When the concrete is initially set, use a trowel to perform initial grinding and breaking of slurry to remove the concrete slurry. Spreading of wear-resistant aggregate: Spread wear-resistant aggregate evenly in batches and compact and grind with a trowel. Finishing: Perform multiple finishing operations according to the hardening of the concrete to ensure that the floor is smooth and free of defects. Maintenance: After the construction is completed, perform maintenance for more than 28 days to ensure the strength and durability of the concrete. (4) Construction environment requirements Temperature: Avoid construction in extremely high or low temperature environments to prevent the concrete from drying or condensing too quickly. Humidity: Keep the construction environment moderately moist to prevent the concrete from losing water too quickly and causing cracks. Avoid wind and rain: The newly constructed concrete floor should not be exposed to sunlight, wind, rain and other environments that are unfavorable to the health of concrete. (5) Other requirements Cutting expansion joints: Cut expansion joints in time to prevent concrete from cracking due to expansion and contraction. Construction sequence: Ensure that the construction sequence such as concrete feeding speed, leveling speed, polishing time is reasonable to avoid problems such as cold joints. Personnel coordination: Manual and mechanical construction to ensure construction quality and efficiency. Safety requirements: Comply with construction safety regulations to ensure the safety of personnel and equipment.   (1) Protection principles Timeliness: After the construction is completed, protective measures should be taken as soon as possible to prevent the floor from being polluted and damaged. Comprehensiveness: The protective measures should cover the entire floor, leaving no dead corners, to ensure comprehensive protection. Targetedness: Develop targeted protection measures for different construction environments and floor uses. (2) Protection measures Covering protection Maintenance blanket or non-woven fabric covering: Within 5-10 hours after the construction is completed, use a maintenance blanket or special maintenance non-woven fabric to cover the floor and water it to keep it moist to prevent the floor from drying out too quickly and causing cracks. Film covering: In certain circumstances, such as before the steel structure is hoisted, a film can be used to cover the floor to prevent components from falling and damaging the floor. Isolation protection Set up guardrails: Set up guardrails for the completed floor area to prohibit people from entering at will to prevent trampling and pollution. Warning signs: Set up eye-catching warning signs at places such as doors where people frequently enter and exit to remind people to pay attention to protecting the floor. Anti-collision protection Fully spread earth cloth or wooden formwork: During the hoisting operation, the floor is protected from collision by fully spread earth cloth or densely spread wooden formwork. Take anti-fall measures: Small objects such as tools and screws (caps) should be packed in special tool bags to prevent them from falling and damaging the floor. Anti-pollution protection Apply special concrete sealing wax: Apply special concrete sealing wax on the floor surface to form a surface wax coating to prevent pollution and damage. Receiving bucket setting: During the hydraulic test of electromechanical installation, arrange the water inlet and outlet positions to prevent the test water from flowing into the floor. At the same time, place the receiving bucket at the joint position to prevent leakage from polluting the floor. Repair measures Small pit repair: If the floor has small pits and other damage, it can be repaired with a special adhesive SBR. Finished product protection team: Establish a special finished product protection team to be responsible for daily inspection and maintenance of the floor, and promptly discover and deal with damage problems. (3) Protection period and supervision Protection period: According to the specific situation of the floor and construction requirements, determine a reasonable protection period to ensure that the floor is fully protected during the maintenance period. Supervision and inspection: Regularly inspect the floor to ensure that the protection measures are effectively implemented. Violations of protection measures will be corrected and punished in a timely manner.     ①Material preparation: Ensure the quality of concrete materials. The concrete specifications must meet the design requirements, such as C25~C30 concrete, and the 28-day strength is not less than 25MPa. The aggregate grading is good, the maximum particle size of coarse aggregate is not more than 25mm, and the fineness modulus of fine aggregate is moderate. Ordinary silicate cement with a cement grade of not less than 42.5. Equipment inspection: The laser leveling machine and auxiliary equipment (such as mixing station, pumping equipment, trowel, etc.) should be intact and overhauled to ensure normal operation during construction. Check whether the laser transmitter and receiver are working properly, ensure that the laser signal has no dead corners, and can monitor and control the ground elevation in real time. Base treatment: The base should be flat, solid, free of oil and debris to ensure good bonding between the concrete and the base. After the base is treated, it should be inspected and accepted, and the next step can be carried out only after it is qualified. ② Matters needing attention during construction Concrete paving: The minimum hourly feeding speed of concrete should be determined according to the ground thickness and pouring area to avoid cold joint problems. When manually assisted leveling, attention should be paid to the uniform distribution of concrete to avoid large piles falling. Laser leveling: When using the laser leveling machine, the measured height of the vertical pole should be accurate to ensure the leveling accuracy. During the leveling process, the laser leveling machine should be integrated with the paving machine to maintain good rigidity and avoid excessive vibration affecting the construction quality. Operators of laser leveling machines need to undergo professional training and be familiar with the performance and operating procedures of the equipment. Spreading of wear-resistant bone materials: Wear-resistant bone materials should be spread evenly in batches, and after each spreading, they should be compacted and polished with a trowel to ensure wear resistance and flatness. Finishing and maintenance: The finishing operation should be polished multiple times according to the hardening of the concrete to ensure that the floor is smooth and flawless. The floor should be kept moist during maintenance, and a maintenance blanket, non-woven fabric or film should be used to cover and moisturize the floor to prevent the concrete from drying out too quickly and causing cracking. ③ Precautions after construction Cutting and expansion joint treatment: After the construction of the laser-leveled concrete wear-resistant floor is completed, the expansion joint should be cut in time to prevent the concrete from cracking due to expansion and contraction. Professional personnel should be assigned to the cutting operation to ensure that the cutting depth and spacing meet the design requirements. Finished product protection: Guardrails and warning signs should be set up for the completed floor area to prevent people from stepping on and contaminating. Use maintenance blankets, non-woven fabrics or films to cover and protect the floor from external damage. Quality inspection and acceptance: After the construction is completed, the floor should be inspected for quality, including flatness, levelness, density, strength and other indicators. It can only be delivered for use after acceptance to ensure that the floor meets the design requirements and usage functions.  

    Cutting the joints is a crucial step in maintaining the flatness of the ultra-smooth floor. The timing and method of Cuttinging are of vital importance. To avoid damaging the millimeter-level precision achieved by the laser leveling machine, the key lies in "early" and "stability". "Early" means cutting the guiding joints before the concrete has developed internal stress; "stability" means the equipment operates smoothly, without bouncing or chipping. Based on this principle, there are mainly two types of equipment available on the market that are suitable for cutting joints in ultra-smooth floors. The core difference between them lies in the time window for cutting. To make it easier for you to compare, I have listed their features as follows: Comparison dimension Early-Entry Cutting Conventional Cutting The timing of the cut Within 1-4 hours after the concrete has been polished (commonly known as the "initial setting" stage) After 6-12 hours or longer of concrete curing (usually overnight waiting) Core Strengths Prevent cracks from forming at their source: Cut the joints before the concrete begins to contract, guiding the cracks to develop in a regular pattern. This is the best way to protect the flatness of the super-level floor. High flexibility: Suitable for all types of concrete, including hardened floors. Smooth cuts: Special blades and patented sliding plates are used, resulting in almost no chipping during cutting, and the joints are aesthetically pleasing. Adjustable depth and width: Capable of cutting deeper and wider joints. Potential risks The time window is narrow, and high requirements are placed on construction organization. Special cutting blades must be equipped. May cause random cracks: If the cutting is done too late, the internal stress of the concrete may have already caused micro-cracks or warping on the floor before the joint is made, thus damaging the flatness. The key to the decision lies in your ultimate pursuit of flatness and the scheduling of the project. Preferred solution: Early Cutting If your project aims for a super-flat floor with FF/FL 35 or above, or if the floor will be used in high-shelf warehouses or precision instrument workshops, then the early Cutting is the only recommended option. It actively guides the cracks before stress is formed, maximizing the protection of the perfect foundation created by the laser leveling machine. Alternative solution： Traditional precision joint Cutting If your project requires a slightly lower level of flatness (such as for ordinary commercial floors), or if you missed the early Cutting window due to construction schedule reasons, then choosing a high-precision, smooth-running traditional joint Cutting is necessary. The key lies in the stability of the equipment. No matter which equipment you choose, there are two points to keep in mind: Special blades: For the initial cutting, you must use the blades specifically designed for this purpose. The blade head connection and formula are specially tailored for un-hardened concrete, which can prevent the blade head from falling off and ensure the cutting quality. Smooth operation: The weight balance of the equipment and the design of the blade guard (such as whether it has a stabilizing slide) will directly affect the stability during cutting, and thereby influence the final flatness.   I hope the above information can help you make a clearer choice. If you want to know more about how to select the appropriate blade type based on the specific concrete mix ratio (such as whether fibers are added), I can help you organize more detailed information for you.   Contact us NOW   Note: The parameters provided in this document are for reference only and are not mandatory. Due to differences in technical characteristics between different brands and models of laser levelers, please consult the manufacturer for a suitable solution before actual operation. This reference document assumes no responsibility for any issues arising from failure to follow the manufacturer's instructions.    

  Concrete pavement occupies a vital position in modern transportation infrastructure, and its quality is directly related to the service life, driving safety and comfort of the road. In order to ensure the quality of concrete pavement, comprehensive and scientific quality inspection is indispensable. With the continuous advancement of science and technology, advanced equipment such as concrete laser leveling machine is increasingly widely used in concrete construction, which also puts forward higher requirements for quality inspection methods. The following will introduce the quality inspection method for concrete pavement in detail. As the key cementing material of concrete, the quality of cement has a profound impact on the performance of concrete. When testing cement, the following aspects should be paid attention to: Strength: According to relevant standards, the 3-day and 28-day compressive and flexural strength of cement is measured through cement mortar strength test to ensure that it meets the design requirements. For example, for 42.5-grade ordinary silicate cement commonly used in road engineering, the 28-day compressive strength should not be less than 42.5MPa. Set time: Use a setting time meter to detect the initial and final setting time of cement. Generally speaking, the initial setting time of ordinary Portland cement shall not be earlier than 45 minutes, and the final setting time shall not be later than 10 hours, so as to ensure that the concrete has sufficient operation time during the construction process and can harden in time. Stability: The boiling method is used to test the stability of cement to ensure that the volume change of cement during the hardening process is uniform, without abnormal phenomena such as cracking, so as to avoid quality problems such as cracks in the concrete pavement due to poor cement stability. Aggregates include coarse aggregates (such as crushed stone and pebbles) and fine aggregates (such as natural sand and machine-made sand). The key points of quality inspection are as follows: Particle grading: The particle grading of aggregates is determined by screening tests to ensure that it meets the requirements of relevant standards. Good particle grading can make the aggregates compactly stacked in concrete, reduce the amount of cement used, and improve the strength and durability of concrete. For example, the maximum particle size of coarse aggregates is usually no more than 1/3 of the thickness of the concrete slab, and should meet the requirements of continuous grading. Mud content and mud block content: Excessive mud and mud block content will reduce the bonding force between aggregate and cement paste, affecting the strength and durability of concrete. The mud and mud block content of aggregates are determined by the water washing method. Generally, the mud content of coarse aggregates is required to be no more than 1%, and the mud block content is no more than 0.5%; the mud content of fine aggregates is required to be no more than 3%, and the mud block content is no more than 1%. Robustness: The sodium sulfate solution immersion method is used to test the robustness of aggregates and evaluate their durability under the influence of climate and environmental changes. Aggregates with good robustness can effectively resist the erosion of external factors and extend the service life of concrete pavements. Admixtures can significantly improve the performance of concrete and need to be strictly tested before use: Water reduction rate: The water reduction rate is an important indicator for measuring the performance of water reducers. By comparing the water consumption of concrete mixtures with and without admixtures, the water reduction rate is calculated to ensure that it meets the requirements of the product manual. Generally, the water reduction rate of high-efficiency water reducers should not be less than 15%. Setting time difference: Detect the effect of admixtures on the setting time of concrete. The initial setting time difference and the final setting time difference should meet the construction requirements to avoid abnormal setting time of concrete due to admixtures, which will affect the construction progress and quality. Compressive strength ratio: Determine the compressive strength ratio of concrete with admixtures and benchmark concrete at different ages, evaluate the effect of admixtures on the strength development of concrete, and ensure that admixtures will not reduce the final strength of concrete. The water used for concrete mixing and curing should meet relevant standards and should not contain harmful substances that affect the performance of concrete. The test items include pH value, insoluble matter, soluble matter, chloride, sulfate, etc. For example, it is generally required that the pH value of water used for concrete is not less than 4, and the chloride content (measured in Cl⁻) does not exceed 500mg/L (reinforced concrete) or 1000mg/L (plain concrete). Slump is an important indicator for measuring the fluidity of concrete mixture. At the construction site, a slump cone is used for testing. The concrete mixture is loaded into the slump cone in three layers, and each layer is rammed 25 times. Then the slump cone is lifted vertically to measure the height difference between the cone height and the highest point of the concrete specimen after collapse, which is the slump value. According to the construction requirements, the appropriate slump can ensure the uniformity and density of the concrete during the paving process. For example, when concrete laser leveling machine is used for concrete paving, the slump is generally controlled at 30-50mm to ensure that the concrete can be paved smoothly and can achieve good flatness under the action of the laser leveling machine. For dry and hard concrete mixtures, a Vebe consistency meter is required to detect its Vebe consistency. This indicator reflects the consistency of the concrete mixture under vibration. During the test, the concrete mixture is loaded into the slump cone, and then the slump cone is placed in the container of the Vebe consistency meter. After lifting the slump cone, the vibration table is turned on and the stopwatch is started at the same time. When the concrete surface changes from uneven to flat, the stopwatch is stopped. The recorded time is the Vebe consistency value. The Vebe consistency value should meet the design and construction requirements. Generally, the Vebe consistency of dry hard concrete is between 10-30s. The air content has an important influence on the frost resistance and durability of concrete. The air content of the concrete mixture is tested using an air content meter. The appropriate amount of air content can form tiny bubbles inside the concrete, relieve the stress caused by the freeze-thaw cycle, and improve the frost resistance of the concrete. Generally, the air content of the concrete is required to be controlled between 3% and 5%, and the specific value is determined according to the environment and design requirements of the project. The temperature of the concrete mixture has a significant impact on its performance and construction quality. In a high temperature environment, if the temperature of the concrete mixture is too high, it will accelerate the cement hydration reaction, resulting in too fast slump loss and even false setting; in a low temperature environment, if the temperature of the concrete mixture is too low, it will delay the cement hydration reaction and affect the strength growth of the concrete. Use a thermometer to measure the temperature of the concrete mixture at the mixing site and the pouring site. According to the ambient temperature and construction requirements, take corresponding temperature control measures, such as cooling the raw materials in high temperatures in summer and heating and insulating the concrete in low temperatures in winter. Flatness: The flatness of the base directly affects the thickness uniformity and driving comfort of the concrete pavement. Use a 3m ruler or a flatness meter to detect the flatness of the base surface, and the allowable deviation is generally not more than 10mm. For parts that do not meet the flatness requirements, they should be trimmed to ensure that the base surface is flat, providing a good foundation for the construction of the concrete pavement. Compactness: Insufficient compaction of the base will cause road subsidence and other diseases. The compaction degree of the base layer is tested by sand filling method, water filling method or ring knife method to ensure that it meets the design requirements. For example, for lime-stabilized soil base layer, the compaction degree is generally required to be not less than 95%. Strength: The strength of the base layer is the key to ensuring the bearing capacity of the pavement structure. The strength of the base layer is tested by making specimens for unconfined compressive strength test through on-site core sampling. The strength of the base layer should meet the design requirements to ensure that it can withstand the vehicle load transmitted from the concrete pavement. Casting thickness: During the concrete pouring process, the pouring thickness of the concrete is regularly tested using a steel chisel or other measuring tools to ensure that it meets the design requirements. The thickness deviation of the concrete slab is generally controlled within the range of +10mm, -5mm. Insufficient thickness will affect the bearing capacity and service life of the pavement, while excessive thickness will cause material waste. Vibration quality: Vibration is a key link to ensure the compactness of concrete. The vibration effect can be judged by observing the surface condition of the concrete, such as whether there is slurry overflow and bubble discharge. At the same time, an inserted vibrator can be used to detect the density of the concrete inside to ensure uniform vibration without missing vibration or over-vibration. For concrete pavements constructed with a concrete laser leveling machine, it is necessary to ensure that the concrete has been initially vibrated and compacted before the laser leveling machine is operated to ensure that the laser leveling machine can play a better role and achieve high-precision flatness control. Rebar arrangement (if any): For reinforced concrete pavements, check whether the type, specification, quantity, spacing, position of the steel bars, and the connection method and anchorage length of the steel bars meet the design requirements. Improper steel bar arrangement will affect the structural performance of the concrete pavement, such as bearing capacity and crack resistance. At the construction site, a steel ruler is used to measure the spacing and position of the steel bars, observe the connection and anchorage of the steel bars, and ensure that the quality of the steel bar project meets the standards. 3m ruler method: This is a commonly used road surface flatness detection method. Place a 3m ruler along the longitudinal direction of the road surface and measure the maximum gap between the ruler and the road surface to assess the road surface flatness. Measure 2 locations every 200m, and measure 10 feet continuously at each location. Judge whether the road surface flatness meets the requirements based on the gap value. Generally, the allowable deviation is no more than 5mm. Continuous flatness meter method: This method can continuously measure the road surface flatness, with high detection efficiency and more accurate results. The continuous flatness meter travels along the road surface, collects the elevation data of the road surface through sensors, and calculates the flatness index (such as the International Roughness Index IRI). After the concrete pavement construction is completed, this method can be used to conduct a comprehensive inspection of the road surface to provide detailed data for road surface quality assessment. For roads constructed with concrete laser leveling machines, the continuous flatness meter test results can intuitively reflect the construction effect of the laser leveling machine. The IRI value should generally be controlled within a certain range, such as no more than 2.0m/km, to ensure that the road surface has good driving comfort. Vehicle-mounted bump accumulation meter method: The bumpiness of the road surface is measured by the bumpiness of the vehicle when it is driving on the road. The vertical vibration acceleration of the vehicle is measured by a sensor installed on the vehicle, and the bump accumulation value (VBI) is converted. This method has a fast detection speed and is suitable for rapid detection of large-area road surface flatness. When conducting quality inspection on concrete pavement, the road surface flatness condition can be evaluated according to the VBI value, and verified with other detection methods to fully grasp the road surface quality. Structural depth: The structural depth reflects the macro texture depth of the road surface and has an important impact on the road surface skid resistance. The road surface structural depth is detected by sand spreading method or laser structural depth meter. The sand spreading method is to spread a certain amount of standard sand on the road surface, flatten the sand into a circle with a push plate, measure the coverage area of ​​the sand, and calculate the structural depth value. The laser structural depth meter uses laser scanning technology to quickly measure the road surface structural depth. Generally, the structural depth of cement concrete pavement is required to be between 0.7 and 1.1mm to ensure that the road surface still has sufficient skid resistance under adverse conditions such as moisture. Friction coefficient: The friction coefficient is a direct indicator of the road surface skid resistance. Use a pendulum friction meter or a dynamic friction coefficient tester to detect the road surface friction coefficient. The pendulum friction meter measures the friction force of the pendulum sliding on the road surface when it swings freely from a certain height, and calculates the friction coefficient of the road surface (BPN value). The dynamic friction coefficient tester simulates the friction between the tire and the road surface during vehicle driving and measures the friction coefficient in real time. According to different road grades and usage requirements, the road friction coefficient should reach the corresponding standard value. For example, the BPN value of general urban roads should not be less than 45 to ensure driving safety. Core drilling method: The core drilling method is the most direct and reliable method to detect the strength of concrete pavement. After the concrete pavement is hardened, a core drill is used to drill a core sample on the pavement. The diameter of the core sample is generally not less than 100mm and not less than 3 times the maximum particle size of the aggregate. After the core sample is processed into a standard test piece, a compressive strength test is carried out, and the strength of the concrete pavement is evaluated based on the test results. The core drilling position should be representative, and at least 1 core sample should be drilled every 3km for each lane. The compressive strength of the core sample should meet the design requirements. For example, for a concrete pavement with a design strength grade of C30, the average compressive strength of the core sample should not be less than 30MPa, and the minimum value should not be less than 25.5MPa. Rebound method: The rebound method is a non-destructive detection method. The rebound value of the concrete surface is detected by a rebound hammer. The strength of the concrete is estimated based on the correlation between the rebound value and the concrete strength. When using the rebound method, the measurement areas should be evenly arranged on the pavement. The area of ​​each measurement area should not be greater than 0.04m², and the number of measurement areas should not be less than 10. At the same time, the influence of the carbonization depth of concrete on the rebound value should be considered and necessary corrections should be made. The detection results of the rebound method have certain limitations. It is generally used as an auxiliary detection method of the core drilling method for the preliminary evaluation of the strength of large-area concrete pavements. Ultrasonic rebound comprehensive method: This method combines the advantages of the ultrasonic method and the rebound method. By measuring the ultrasonic sound velocity and rebound value of concrete, the strength of concrete is comprehensively estimated. Ultrasonic sound velocity reflects the density and uniformity of concrete, and the rebound value reflects the hardness of concrete surface. The combination of the two can more accurately evaluate the strength of concrete. The ultrasonic rebound comprehensive method is suitable for batch testing of concrete pavement strength. The accuracy of the test results is relatively high, but the operation is relatively complex and requires professional testing equipment and technicians. Core drilling method: The drilled core sample can not only be used for strength testing, but also can intuitively measure the thickness of the concrete pavement. Use a caliper to measure the thickness of the core sample with an accuracy of 0.1mm. Drill sample cores at 2 locations on the left and right within every 100m of pavement paving width to test the thickness of the board. The pavement thickness deviation should meet the design requirements, and the general allowable deviation is +10mm, -5mm. Radar detection method: Use ground penetrating radar to emit high-frequency electromagnetic waves to the pavement, and detect the thickness of the concrete pavement based on the reflection characteristics of the electromagnetic waves at the interface of different media (such as concrete and base). The radar detection method has the advantages of fast, non-destructive, and continuous detection, and can obtain thickness data of large-area pavements in a short time. However, this method requires professional radar equipment and data analysis software, and the detection results are greatly affected by factors such as the material properties and water content of the pavement structure layer, and calibration and verification are required before use. Appearance inspection: Observe the surface of the concrete pavement with the naked eye to check whether there are cracks. Record the location, direction, length, width and other information of the cracks. For cracks with smaller width, a crack observation instrument can be used to measure and accurately measure the crack width. Generally, cracks with a width of no more than 0.2mm are considered to be small cracks and can be closed on the surface; cracks with a width of more than 0.2mm need to analyze the cause and take corresponding repair measures, such as grouting repair. Non-destructive testing technology: In addition to appearance inspection, non-destructive testing equipment such as ultrasonic flaw detectors and infrared thermal imagers can also be used to detect whether there are cracks inside the concrete pavement. The ultrasonic flaw detector transmits and receives ultrasonic waves, and judges whether there are defects and cracks inside according to the reflection and refraction characteristics of ultrasonic waves when propagating inside the concrete. The infrared thermal imager uses the difference in temperature distribution on the surface of the object to detect internal defects. When there are cracks inside the concrete, a corresponding temperature abnormality area will be formed on the surface, which can be intuitively displayed through infrared thermal images. Non-destructive testing technology can detect hidden cracks inside the pavement, provide a basis for timely prevention and control measures, and ensure the integrity and safety of the pavement structure.