Quality Control Methods for Ensuring Uniform Distribution of Wear-Resistant Aggregates

With the advent of laser leveling machines, are you still using the old vibrating leveler to vibrate the beam? When it comes to construction, everyone knows that only with a short construction period and high quality can we save costs, improve efficiency and increase profits. If you want to save costs quickly during construction, construction tools are a very important choice. An efficient, convenient and fast tool will make construction work more effective with half the effort! On the contrary, choosing inappropriate tools will extend the construction period, increase costs, and reduce profits. Take the floor construction under construction as an example! The flatness of the floor is more difficult to grasp. Leveling is usually done manually. Even if you use an old-fashioned floor machine, the effect and cost are not particularly ideal. The emergence of a laser leveling machine has greatly solved many problems that arise during construction. During the construction process, it can solve the problems of hollowing, shelling, cracking, and uneven ground after general construction. It can make the final effect exceed Party A's floor quality requirements, reduce costs, and Improved work efficiency. Many industries require factories, as well as shopping malls, large warehouses and other construction sites that require large areas of ground, to have much higher standards. Attention has been greatly increased to the strength, flatness and level of the ground quality. It is difficult to meet the requirements using old-fashioned flooring methods, and labor costs will increase exponentially. The construction principle of the laser leveler is very simple and clear. It can perform several construction processes such as leveling and vibration at the same time, further ensuring the quality of the construction and completely saving labor costs. The advantage of construction is that the construction speed is fast and the quality is high, ensuring that the overall integrity of the ground is good and cracks are not prone to occur. The amount of support and disassembly is reduced compared with the traditional method. Moreover, the reduction in the number of workers ensures an increase in final profits.

Concrete pressure strength detection method 1. Rebounder or Schmitt Hammer (ASTM C805) Method: The hammer is activated by a spring release mechanism, which presses the plunger and presses it into the concrete surface. The rebound distance from the hammer to the concrete surface is in the range of 10 to 100. The measurement results are then associated with the strength of the concrete. Pros: Relatively easy to use and can be done directly in the field. Cons: To ensure accurate measurementresults, pre-calibrated concrete samples are required. Different states of the surface and the presence of rebar under large aggregates or test sites can affect the test results. 2. Penetration test (ASTM C803) Methods: When carrying out a penetration test, a pin or probe is drilled into the concrete surface with a special device. The strength and depth of drilling required to drill into a concrete surface are related to the strength of the poured concrete. Pros: Relatively easy to use and can be done directly in the field. Cons : The data are greatly influenced by conditions such as surface state, template type, and aggregate used. Accurate strength measurements require multiple sampling of concrete samples for early calibration. 3. Ultrasonic pulsation detection (ASTM C597) Method: This method is used to judge the velocity of the vibration energy pulsation in the ground floor. The ease with which this energy penetrates the floor plate reflects the results of the concrete's ability to elastic, resist deformation or stress, and density. The data is then associated with the strength of the concrete slab. Pros: This is a non-destructive testing method and can also be used to detect defects such as cracking or honeycomb holes inside concrete. Cons: The method is seriously affected by the enhancement method, the moisture in the aggregate and the concrete material. Multiple samples and calibrations are also required to obtain accurate test results. 4. Pull-up test (ASTM C900) Method: The main principle of this method is to pull the metal rod, which is poured inside or installed afterwards, out of the concrete. The cone after pulling out and the amount of force required to pull out from the concrete are related to the strength of the pressure. Pros: Easy to use, can be done in both old and new building structures. Cons: This detection can cause the concrete to break or damage. To obtain accurate test results, a large number of test samples need to be selected at different locations on the floor plate. 5. Drill core method (ASTM C42) Method: The drill core method is used to extract solidified concrete sample blocks from the floor plate. These samples are then compressed in the machine to monitor the strength of their concrete. Pros: These samples are more accurate than field solidification samples because the concrete of strength is tested by actual heat and solidified on site. Cons: This is a destructive detection method that requires the destruction of the structural integrity of the concrete slab. The position of the core needs to be patched after the fact. The strength data must be obtained by the lab. 6. Poured concrete cylinder detection method (ASTM C873) Method: The cylindrical mold is placed in the position of the pouring area. Fresh concrete is discharged directly into these molds, which are retained in the floor board. After the floor plate solidifies, remove the specimens and pressurize them to detect their strength. Pros: This method is considered to be more accurate than on-site cured specimens because the concrete undergoes the same solidification process and conditions as the site floor plate; Cons: This is a destructive detection method that requires the destruction of the structural integrity of the concrete slab. The hole position left after the specimen is removed needs to be repaired afterwards. The strength data must be obtained by the lab. 7. Wireless Maturity Sensor (ASTM C1074) Methods: The principle of this method is based on the direct relation of concrete strength and its hydration temperature history. Before starting pouring, the wireless sensor is placed in a concrete template and secured on the rebar. The sensor receives temperature data and uploads it to any smart device APP with a wireless connection. According to the maturity calculation formula of the setting number in the APP, the collected information is used to calculate the pressure strength of the concrete element at the current position. Pros: Anti-pressure strength data is fed back in real time and updated every 15 minutes. At the same time, because the sensor is embedded inside the template, the data accuracy and reliability are also ideal, i.e. the curing data collected is consistent with the in situ concrete element. This also means that you don't have to spend time waiting for a third-party lab to provide the test results. Cons: Each batch of mating concrete needs to create a maturity curve using a test method of a collapse dwelling barrel and complete a one-time calibration.

    Concrete engineering construction involves multiple links such as material transportation, mixing, pouring and curing. The working environment is complex (such as high-altitude, edge and heavy machinery operation), which is prone to cause safety accidents such as collapse, fall from height and mechanical injury. For common safety issues, response measures should be formulated throughout the entire process of "prevention – control – emergency response". Specifically, they can be classified by risk types as follows:   The spacing of the vertical rods of the formwork support is too large, there is no base plate at the bottom of the vertical rods/the foundation is unstable. Improper sequence of concrete pouring (such as not pouring in layers, resulting in local load exceeding the limit); The formwork was removed too early (the concrete strength did not meet the design requirements). The foundation pit/slope support was inadequate, causing deformation due to the load of concrete pouring. Preliminary design and verification The formwork support and scaffolding must be designed by professionals in accordance with the specifications, calculating the load-bearing capacity of the vertical rods, the spacing of the horizontal rods, and the setting of the sweeping rods to ensure the anti-overturning and anti-deformation capabilities. The foundation pit/slope support plan should be specially designed in combination with geological conditions (such as soft soil and quicksand layers). When necessary, support forms such as sheet piles and soil nail walls should be adopted. Over-excavation is strictly prohibited. Construction process control Before setting up the support, the foundation should be leveled and compacted. Wooden pads or steel sections should be placed at the bottom of the vertical poles to prevent uneven settlement. Concrete pouring should follow the principle of "layering, symmetry and gradual progress". The thickness of each layer should not exceed 30cm (for pumped concrete). It is prohibited to stack materials on one side or pour them in a concentrated manner, which may cause the support to be biased. Before the formwork is removed, the concrete strength must be tested (by the rebound method or the same condition test block test). It can only be removed when it reaches 75% (for beams and slabs) or 100% (for cantilever components) of the designed strength, and the removal sequence follows the principle of "remove the later supports first, and then remove the later supports". For high formwork (height ≥8m) and deep foundation pits (depth ≥5m), "deformation monitoring" should be implemented. Daily data on the settlement of supports and slope displacement should be recorded. Work should be immediately halted for rectification if the warning values are exceeded (such as settlement ≥10mm).   The pouring platform and scaffolding have no guardrails or toe boards, or the height of the guardrails is insufficient (less than 1.2 meters). The worker is not wearing a safety belt, or the safety belt is not fastened to a secure support point. No closed protection or warning signs have been set up at the edge openings (such as elevator shafts and stairwells). Standardization of protective facilities For high-altitude pouring platforms (such as floor slab and beam pouring), 1.2-meter-high guardrails must be set up, with 18-cm-high toe boards at the bottom, and close-mesh safety nets (flame-retardant type) hung on the outside of the guardrails. Elevator shafts and reserved openings shall be sealed with "tools" (such as steel mesh + cover plates), and it is strictly prohibited to temporarily block them with debris. The scaffold working layer is fully covered with scaffold boards, with no gaps between the boards. The probe boards (extending more than 15cm beyond the crossbars) must be fixed or removed. Personnel operation specifications Workers engaged in high-altitude operations must wear "double-hook safety belts" and use them "high up and low down" (the safety belt's hanging point should be higher than the work position). It is strictly prohibited to walk on the edges of unprotected beams and slabs. Before starting work, check the integrity of protective facilities. If loose railings or damaged safety nets are found, stop work immediately for repair. High-altitude concrete pouring operations are prohibited in severe weather conditions such as heavy rain and winds above level 6.   The concrete mixer and vibrator have no protective cover or the protective cover is damaged. The equipment operators work without a license and operate in violation of regulations (such as cleaning the residue in the mixer by hand). There are irrelevant personnel staying within the working radius of pump trucks or tank trucks, causing collisions or crushing. Intrinsic safety of equipment The transmission parts of the mixing plant and vibration equipment (such as gears and belts) must be equipped with "fixed protective covers", and the strength of the protective covers must meet the requirements of impact resistance. The material rods and outriggers of the concrete pump truck are equipped with "limit alarm devices", and steel plates are placed under the outriggers (to prevent subsidence). Before operation, make sure the outriggers are stable. Before using the equipment, conduct a "pre-shift inspection", with a focus on checking the braking, steering and leakage protection devices. Do not start the equipment if they are not up to standard. Personnel and on-site control Equipment operators must pass training and assessment and hold a "Special Operations Operator Certificate" to work. It is strictly prohibited to operate without a certificate or after drinking alcohol. When cleaning or maintaining the mixer, it must be "powered off and locked" (with a warning sign), and there must be a dedicated person to supervise. Live operation is strictly prohibited. The operation areas of pump trucks and tank trucks are set up with "warning zones" (isolated by warning tapes or guardrails), and irrelevant personnel are prohibited from entering. Drivers should observe the surrounding environment before operation.   The cables of mobile equipment such as vibration rods and water pumps are damaged and the insulation layer is aged. The temporary power supply did not adopt the "three-phase five-wire system", and the grounding and zero connection protection was missing. Waterproof electrical appliances were not used in damp environments (such as pouring basements or working during the rainy season). Standardization of temporary electricity usage Temporary power supply at the construction site must be laid by professional electricians, strictly adhering to the principle of "one machine, one switch, one leakage protector, one box" (each device is equipped with an independent switch and a leakage protection device). The operating current of the leakage protection device should be ≤30mA, and the operating time should be ≤0.1s. The cables of mobile devices shall adopt "wear-resistant and waterproof rubber-sheathed cables". It is strictly prohibited to drag or crush the cables. The cable joints shall be sealed with waterproof tape. Distribution boxes and switch boxes should be installed in dry and rain-proof locations. The grounding resistance of the box body should be no more than 4Ω. The box door should be locked and a "Electrical Safety Sign" should be affixed. Working environment and operation protection When working in a damp environment, operators should wear "insulating shoes" and "insulating gloves", and insulating sleeves should be added to the handles of the vibration rods. Lighting fixtures should use "36V safe voltage" (such as in basements and deep well pouring), and the use of 220V ordinary bulbs is strictly prohibited. Regularly test the insulation resistance of temporary power lines. Replace the cables immediately when the insulation value is lower than 0.5MΩ.   The tools and materials piled up on the concrete hopper and scaffolding were not fixed and fell, injuring the people below. Workers working at heights randomly throw tools and waste materials (such as bolts and broken formwork). There is no horizontal protective layer for cross-operation (such as pouring above and cleaning below). Material management The amount of concrete and tools stacked on the aerial work platform shall not exceed the load-bearing limit of the platform, and they shall be firmly fixed (such as binding the hopper with iron wire). It is prohibited to stack irrelevant sundries on scaffolding and formwork. After work, waste materials should be cleared in time to avoid accumulation. When transporting materials vertically (such as using a tower crane to transport concrete hoppers), the hoppers must be covered, overloading is strictly prohibited, and a "warning zone" should be set up below. Cross-operation protection When performing cross-operation up and down, a "horizontal safety protection layer" (such as fully laid scaffolding boards or safety flat nets) should be set in the middle, and the spacing between the protection layers should not exceed 10 meters. Workers working at heights are strictly prohibited from throwing any objects downward. Tools should be placed in tool bags to prevent them from falling. The personnel working below must wear "safety helmets", with complete brims and chin straps, and the chin straps must be fastened tightly.   The construction site is equipped with a "first aid kit" (including tourniquets, bandages, fracture fixation splints, etc.), and 1-2 part-time first aid workers are trained. Special emergency response plans should be formulated for accidents such as collapses and electric shocks. An emergency drill should be organized once every quarter to ensure that personnel master escape and first aid skills. An "emergency passage" is set up on site, with a width of no less than 1.2 meters and no debris blocking it. Emergency lighting (automatically activates after power failure) covers key areas. When a collapse occurs, immediately stop the operation, organize personnel to evacuate to a safe area, and strictly prohibit blind rescue (to prevent secondary collapse). At the same time, contact professional rescue teams (such as the fire department). When an electric shock occurs, first "cut off the power supply" or use an insulating tool to remove the injured person from the power source, and then perform cardiopulmonary resuscitation (send to the hospital if necessary). When mechanical injury occurs, immediately stop the operation of the equipment, stop bleeding and bandage the wound. For those with fractures, avoid moving them at will and send them to the hospital promptly.   The safety management of concrete engineering should adhere to the principle of "prevention first and combination of prevention and control". Through the triple guarantee of "technical measures (such as support verification, protective design) + management measures (such as personnel training, on-site inspection) + emergency measures (such as plan drills, first aid preparations)", risk control should be integrated throughout the entire construction process, and at the same time, the safety awareness of all personnel should be strengthened. Eliminate the "three violations" behaviors of "illegal command, illegal operation and violation of labor discipline", and reduce the occurrence of safety accidents from the root.   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.