In order to meet the development requirements of circular economy and resource-saving society, the State advocates the use of premixed mortar, and it is imperative to adopt industrial production of premixed mortar; the wall of traditional plastering mortar and construction technology often has quality problems such as hollowing and cracking, and the use of premixed mortar and spraying construction technology can solve the problem of hollowing and cracking, but the subsequent treatment of spraying construction is difficult and inefficient, It seriously affects the spread and application of premixed mortar spraying technology. In order to solve the above problems, a vibrating plastering tool is developed. Combined with the construction of mortar spraying machine, the field tensile bond strength and construction efficiency of plastering mortar are greatly improved. Through the comparison of spray vibration plastering and manual construction, the comprehensive cost of plastering mortar can be saved by one third. It is suggested to adopt advanced spray vibration plastering construction technology, change the traditional construction method, and make the popularization and application of ready mixed mortar enter the fast lane.
1. The mechanism of improving the tensile bond strength of mortar by spraying vibration trowel
The vibrating plate of the vibration troweling tool exerts a vibration action on the mortar sprayed on the wall, which makes the mortar enter into the vibration motion, and the particles of the mortar get the pulse, so they vibrate in the unstable and balanced position. At this time, the mortar has the property of "thick liquid". Under the influence of pulse, the particles of mortar will vibrate continuously around the middle position of some unstable equilibrium. As a result of the displacement of adjacent particles, a hole will be formed and the vibration will continue at the new unstable equilibrium position. Therefore, in addition to the downward vertical displacement, the mortar particles may have other Displacements: upward, toward and away from the vibrator. Under the action of vibration force, the air in the mortar will become the shape of bubble and separate out from it; the mortar may have any shape and cause the pressure on the side elevation of the vibration plate, that is, the side pressure, which is distributed in a triangle state. When a vibrator is used to make the mortar compact and smooth, its particles will be close to each other and air will be discharged, which will become many bubbles rising to the mortar surface. Only some bubbles with a certain diameter can float on the surface of mortar. The buoyancy of bubbles with a diameter less than a certain limit value is not enough to overcome the internal friction, which ensures that a more compact mortar can be obtained under the condition of vibrating mortar.
2 spray vibration plastering construction process
The plastering vibrator is composed of transformer (6-24vdc power supply), metal shell, micro vibration motor and handle. After receiving the 220V AC power, the mortar is sprayed and the plaster vibrator is opened. As long as the mortar is pressed lightly, the metal bottom plate of the plaster vibrator can vibrate to make the convex mortar flow to the concave, so that it can be smoothed one to two times on the mortar surface to be smoothed, and the finish is not pressed at one time. It can replace the traditional tools aluminum alloy scraper, iron trowel, and foam small rub. The plastering vibrator shall be cleaned after the completion of the plastering construction to ensure the normal use of the equipment.
The construction process of spraying and vibrating plastering includes: base treatment - mechanical preparation - commodity mortar preparation - pumping - spraying - vibrating plastering - floor ash cleaning.
Base course treatment includes: inlaying door and window joints, making corner protection lines, making signs and marked bars, watering and wetting, etc.
Mechanical preparation includes: installation of mortar delivery pump, plastering vibrator, mortar pump, pipeline assembly and scaffold erection.
Pumping refers to pouring the ready mixed mortar into the hopper of the pump body, relying on the force of the pump body to press the mortar into the pipeline and deliver it to the mortar pump. Spraying refers to that the mortar is sprayed evenly from the nozzle of the spray gun to the wall by the pressure of compressed air. Vibration plastering refers to the use of a plastering vibrator to level the mortar on the standard reinforcement along the surface of the standard reinforcement, remove the height and make up the low, make the standard reinforcement surface, and compact the mortar surface. Cleaning floor ash refers to the timely cleaning and recycling of mortar dropped on the ground in the process of spraying, vibration plastering, etc.
The preparation before spraying and vibro plastering construction plays an important role in ensuring the construction quality. Before construction, the construction area, specific room and construction sequence shall be determined (in principle, the construction shall be carried out from the inside to the outside), and the usage amount of ready mixed mortar shall be estimated according to the construction area and wall conditions, and then the mortar pump shall be placed in place, connected with water and electricity in the correct way, and the machine shall be started to make the equipment in standby state. In addition, the required construction machine is equipped with mortar pipe and suitable spray gun according to the spraying thickness. Auxiliary tools include 0.2m plastering vibrator, 0.5m plastering vibrator, 1.2m plastering vibrator, spade, cart, bucket, ash trough, 2m guiding ruler plate, plumb bob, steel tape, ash supporting plate, iron trowel, broom, rubber water pipe, small bucket, powder line bag, small white line, etc.
Construction can start when everything is ready. The first step of construction is to first treat the base course, remove the dust, oil and other attachments of the base course, and make the base course clean. The second step is to fill the reinforcement. Use a 2m guiding ruler plate and a plumb line to measure the straightness of the wall. Use a rigid straight reinforcement with a diameter of 8-12mm to fill the reinforcement every 1.3m (the width of the reinforcement should be controlled within the length of 1.2m plastering vibrator). Stick it to the wall and fix it with general plastering mortar. It should be noted that the screed must be flat, straight and firm. The third step is spraying, adding materials to the mortar pump, adjusting the appropriate mortar consistency, spraying, the spraying thickness should be slightly higher than the standard bar by about 1mm, the specific requirements are as follows: the gunner should spray according to the standard bar situation, and try to be even and level according to the wall leveling situation; guide the gunner to move back and forth quickly in the horizontal direction at a constant speed, and can't spray in a circle; spray on the wall surface When plastering, make sure the spray gun is slightly upwarped, otherwise it will always spray on the wall at right angles; the distance between the spray nozzle and the wall should be 10-30cm. The fourth step is vibration troweling. After the completion of mortar spraying, the troweling construction needs to be carried out immediately. Start the plastering vibrator, press the mortar gently from the bottom to the top along the standard bar, walk on the mortar surface to be troweled once or twice, and try to trowel once. If the mortar is too thin, it is not suitable to vibrate and plaster immediately. It should be carried out after the mortar is slightly hard. The fifth step is to clean up the site to ensure the normal use of the equipment.
Compared with traditional manual construction, the simultaneous interpreting of the above technical regulations is very important for mechanized construction. Within the team, strict division of labor, mutual cooperation, equipment as the core, one equipment equipped with a construction team. In addition, follow-up treatment shall be reasonably arranged according to the nature of the material. Generally, mortar suitable for mechanized spraying construction shall have good water retention, without segregation, with high bond strength and relatively long opening time. It is better to use premixed mortar. The last point is not to use the traditional method of making points and screeding to find the square for construction, which can not achieve the efficient mechanized construction requirements at all.
3. The influence of plastering construction technology on the field tensile bond strength of mortar
In GB / t25181-2010 ready mixed mortar, the performance requirements of clause 6.1 in the 14d tensile bond strength standard of wet mixed plastering mortar, dry mixed ordinary plastering mortar and dry mixed thin layer plastering mortar are as follows: M5 ≥ 0.15Mpa, M7.5 ≥ 0.20mpa, wet mixed waterproof mortar ≥ 0.20mpa, dry mixed ordinary waterproof mortar ≥ 0.20mpa. It can be seen that the tensile bond strength is an important performance index of plastering mortar.
Because of the poor adhesion between the traditional on-site mixing mortar and the new wall materials, the quality problems such as hollowing and cracking often appear in the masonry, which seriously affect the promotion and application of the new wall materials. In order to solve the above problems, China has vigorously promoted the premixed mortar. Engineering practice proves that the bond strength of mortar and base course is not only related to the mix proportion of mortar materials, but also related to construction technology. The experimental data show that the field tensile bond strength of spraying vibro plastering is more than 1 times higher than that of traditional manual plastering, and it is also higher than that of mechanical spraying + manual plastering.
A large number of experimental data can show that the field tensile bond strength of mortar constructed by premixed mortar and mechanized spraying vibro plastering process is far greater than that of traditional manual construction under the condition of ensuring the same mortar mix ratio; therefore, in order to ensure the quality of the project, we should actively promote the use of advanced spraying vibro plastering construction process and change the traditional one Construction method.
4. Economic benefit analysis of new technology construction for premixed mortar
The construction area of a project is 40905m2, and the total amount of mortar is expected to be 8000 tons. In order to meet the requirements of project quality, construction period and civilized construction, the owner decided to use the premixed mortar produced by our company and adopt the new technology.
5. Actual price comparison (decrease): 50.45-34.39 = 16.06 yuan / ㎡
It can be seen from the above table that the cost per square meter of the project has been reduced by 16.06 yuan and the work efficiency and quality have also been improved after the spray vibration plastering process and premixed mortar are used. In addition, according to the preferential policies for the promotion and use of premixed mortar, the project using premixed mortar will be fully returned to the special fund for cement and the fund for wall renovation. In fact, the owner not only gets the guarantee of project quality, construction period and civilized construction, but also reduces the cost of the project.
Conclusion:
The newly developed vibrating plastering tool, combined with the construction of premixed mortar spraying machine, greatly improves the bonding strength and construction efficiency of plastering mortar, and can save one third of the comprehensive cost of plastering mortar; from the perspective of the construction company, the productivity of transportation, mixing and construction of traditional mortar is about 35 m2 per work, while the premixed mortar and its corresponding supporting vibration are used The productivity of plastering tools, from transportation, mixing to construction, can be increased to more than 90m2 per work. The work efficiency is obviously improved and the cost is reduced, which plays a great role in reducing the total construction cost and accelerating the construction progress. It can be seen that the best choice for the construction company is to adopt advanced spray vibro plastering construction technology and change the traditional construction method. Spray vibration plastering construction technology is in the initial stage, and the wall decoration requirements are higher and higher. But architectural design, construction, building material quality and other aspects can not cooperate with each other very well, which often becomes the main reason of poor quality in wall plastering engineering. In many years of engineering construction practice, through the observation and analysis of the cracks and hollows in the wall plastering engineering, we have summarized the spraying vibration plastering construction technology, which can reduce the comprehensive cost by about 30% compared with other mechanized construction technology.
