Production Process and Equipment of Dry-Mixed Mortar
2025-11-23
Dry-mixed mortar (also known as dry powder mortar) is a "dry-mixed" ready-mix commercial mortar produced industrially through sand preprocessing (including drying and sieving), batching and metering, mixing, storage, packaging, or bulk delivery by advanced computer-controlled automatic dry-mixed mortar mixing stations (towers). Due to strict weighing and proportioning during production, and the addition of corresponding chemical additives according to different functional requirements of mortar, the quality of mortar is greatly improved. The application of dry-mixed mortar avoids quality defects caused by on-site manual mixing, ensures construction quality, reduces urban waste and environmental pollution, and improves the level of civilized construction. It is a green and environmentally friendly new building material with broad market prospects.
Dry-mixed mortar is used in construction projects.
I. Production Process of Dry-Mixed Mortar
Dry-mixed mortar refers to a homogeneous mixture processed by scientific formulation, which consists of initially dried and sieved sand, a small amount of cementitious materials (cement, gypsum), and trace high-tech additives. The finished mortar has properties such as shrinkage resistance, crack resistance, thermal insulation, and moisture resistance according to different uses. The product can be transported to the construction site in packaged or bulk form, and can be directly used after mixing with water in the specified proportion. Its production process is as follows:
1.Sand preprocessing includes quarrying, crushing, drying, (grinding), sieving, and storage. For river sand, only drying and sieving are required; where conditions permit, finished sand can be directly purchased and sent to the sand silo.
2.Cementitious materials, fillers, and additives are delivered to corresponding silos.
3.Batching and metering are carried out according to the formula.
4.Various raw materials are put into the mixer for mixing.
5.The finished mortar is sent to the finished product silo for packaging or bulk delivery.
6.The product is transported to the construction site. Bulk dry-mixed mortar must be transported by special bulk silos or bulk transport vehicles to prevent segregation, which may affect construction quality.
7.Dry-mixed mortar is put into a mortar mixer and mixed with water in proportion.
8.The mixed mortar is transported to the construction site using a special mortar pump or directly applied by on-site shotcreting.
II. Production Equipment of Dry-Mixed Mortar
Dry-mixed mortar production equipment is a combined device used for centralized mixing of ordinary mortar and special mortar, also known as a dry-mixed mortar production plant. There are various types of dry-mixed mortar production equipment:
By mixing method: Single-mixing type and double-mixing type;
By structure: Simple type, serial type, and tower type.
The product has flexible and diverse structural forms, strong adaptability, and can be modularly expanded. The control methods include manual, semi-automatic, and full-automatic; dry sand methods include vibrating fluidized bed and mechanical drum type; mixing hosts include gravity-free double-shaft paddle mixers, horizontal ribbon mixers, and plow blade mixers, which are divided into batch type and continuous type according to the working method.
The main equipment for dry-mixed mortar production and construction includes: sand preprocessing (drying, sieving, conveying) system, various powder material storage systems, batching and metering system, mixing system, packaging and bulk system, dust collection system, electrical control system, logistics transportation, and mixing-spraying construction equipment.
1. Sand Preprocessing System
Sand is the main component of dry-mixed mortar, accounting for about 70% of the proportion. The moisture content of sand varies greatly, but the moisture content of sand used for dry-mixed mortar must be controlled between 0.2% and 0.5%, and it must be stored in sealed containers; otherwise, the storage time of finished dry-mixed mortar will be seriously affected. Therefore, the original sand purchased from the market must undergo moisture content determination, drying, sieving, and conveying.
1) Sand Moisture Content Determination
Ensuring no moisture in the finished mortar is the key to guaranteeing the quality of dry-mixed mortar. To accurately control the rotation speed of the sand dryer drum, the moisture content of the sand must be measured. An automatic microwave moisture meter with a microwave moisture sensor installed on the sand silo wall can be connected to the computer control system's closed-loop control program to automatically adjust the sand drying speed according to the measured moisture content. Alternatively, laboratory determination methods can be used to preset the drying speed.
2) Drying of Raw Sand
The drying of raw sand is achieved by sand dryers, which mainly include two types: vibrating fluidized bed dryers and mechanical drum dryers.
a) Vibrating Fluidized Bed Dryer: This equipment has advanced technology and low operating costs. Compared with drum dryers, it has the advantages of high efficiency, economy, almost no radiant heat loss, no mechanical movement, low wear, low maintenance costs, short start-up time, low noise, and good environmental performance. During operation, materials jump forward under the action of exciting force in a given direction, and hot air at a certain temperature is input from the bottom of the bed to make the materials in a fluidized state. The materials fully contact with the hot air, and the mixed gas is drawn out from the outlet by an induced draft fan to achieve the ideal drying effect.
b) Mechanical Drum Dryer: This equipment can be divided into double-drum separate drying and cooling type, single-drum drying forced air cooling type, and single-drum triple-pass drying and cooling type. It has a relatively simple structure and convenient maintenance but occupies a large area. The burner can be configured with various forms such as oil-fired, gas-fired, and coal powder-fired according to user needs, and the drying speed can be manually or automatically adjusted according to the moisture content of the sand. Among them, the single-drum triple-pass drying and cooling type has a compact structure, reliable operation, low energy consumption, good drying effect, convenient fuel sourcing, and low cost, making it suitable for supporting small dry-mixed mortar production equipment.
3) Sieving of Dry Sand
The sieving of dry sand is achieved by vibrating sieves, which mainly include two types: projection type probability vibrating sieves and horizontal linear vibrating sieves.
a) Projection Type Probability Vibrating Sieve: Adopting the principle of probability sieving, by reasonably selecting the sieve mesh size and sieve surface inclination angle, difficult-to-sieve material particles can quickly pass through the sieve. The equipment has a small volume and reliable operation; even under overload conditions, the sieve mesh will not be torn due to the inclined setting. At the same time, the sieve mesh can be equipped with two, three, or four layers as needed, suitable for small and medium-sized dry-mixed mortar production equipment.
b) Horizontal Linear Vibrating Sieve: A traditional domestic model with a large floor area and low output. The improved vibrating sieve adopts sieve mesh vibration technology, with small vibration power, low energy consumption, low noise, and little dust pollution, making it a new energy-saving and environmentally friendly sieving equipment.
4) Conveying of Dry Sand
The conveying of dry sand is different from that of cement, lime powder, and industrial waste coal fly ash, and should be carried out by bucket elevators or belt conveyors.
a) Bucket Elevator Conveying: This machine installs several steel buckets at certain intervals on flexible traction components such as belts or chains to continuously convey materials upward. Bucket elevators have the characteristics of small floor area, large conveying capacity, high conveying height (generally 30-40m, up to 80m), and good airtightness, so they are the key conveying equipment for dry sand.
b) Belt Conveyor: The advantages of using belt conveyors are high production efficiency, no influence from climate, continuous operation without easy failure, and low maintenance costs (only regular lubrication of certain moving parts is required). To improve environmental conditions, prevent aggregate scattering and rainwater mixing, a protective cover can be installed on the belt conveyor.
2. Material Storage System
In addition to aggregates (dry sand), dry-mixed mortar also includes cementitious materials such as cement, gypsum powder, thickening powder, and fly ash, admixtures, and high-tech materials such as chemical additives. Due to the moisture-proof characteristics of dry-mixed mortar, all materials must be stored in sealed silos. Except for special additives that are manually fed, other materials are conveyed by air flotation discharge systems and screw discharge systems to ensure accurate batching and metering of various materials.1) Sealed Silos
Silos can be set into multiple same or different specifications according to equipment configuration. Silos are generally made of steel plate welding, but some are made of plastic plates.
Feeding into the silo can be done by pipeline pneumatic conveying, bucket elevator conveying, or screw conveyor conveying. Feeding from the silo to the mixer is generally done by pipeline pneumatic conveying and screw conveyor conveying.
To prevent material arching and blocking inside the silo, silos are generally equipped with different types of arch breaking devices to ensure continuous feeding; to detect the storage capacity in the silo, various level indicators are installed inside the silo; to eliminate dust pollution, a roof dust collector is used for dust removal.
2) Air Flotation Discharge System
The air flotation discharge system is composed of floating sheets uniformly installed at the conical bottom of the silo. Compressed air forms a suspension layer of materials on the surface of the floating sheets, allowing the materials to slide freely under gravity and flow smoothly. This effective silo discharge method is applicable to almost all fine dry powder materials.
3) Screw Discharge System
The screw discharge system controls the feeding of cement (fly ash) by controlling the rotation and stop of the screw blades of the screw conveyor. Screw conveyors have the characteristics of large conveying inclination angle (up to 60°), strong conveying capacity, and good dustproof and moisture-proof performance. To improve conveying capacity, variable screw conveying blades are adopted: the filling volume is large in the feeding section, and decreases with the increase of screw pitch, which can effectively prevent the backflow of high-fluidity powder materials during conveying.
3. Batching and Metering System
Batching and metering is an important process in the production of dry-mixed mortar, directly affecting the proportioning quality of the product. Therefore, accurate and efficient batching and metering equipment and advanced automatic control means are reliable guarantees for producing high-quality dry-mixed mortar.
The batching and metering system adopts precise full-electronic scales and advanced computer control, with functions such as drop tracking, automatic weighing error compensation, and fault diagnosis. The reliable feeding and discharge system ensures uniform and smooth material discharge to achieve accurate metering effect and effectively guarantee product quality.
4. Mixing System
Mixing is an extremely important process in the production of dry-mixed mortar. Because the mortar formula requires cementitious materials, admixtures, and chemical additives to be uniformly distributed on the surface of aggregates, only by uniformly mixing various ingredients can high-quality finished dry mortar be obtained. According to the production characteristics of different dry-mixed mortar varieties, the main supporting mixers include three types: gravity-free double-shaft paddle mixers, horizontal ribbon mixers, and plow blade mixers.
1) Gravity-Free Double-Shaft Paddle Mixer
This mixer uses the principle of instantaneous weightlessness to make materials produce all-round composite circulation under mechanical action in the machine body, with extensive interlacing and no dead ends, thereby achieving uniform diffusion and mixing. The mixing process is gentle, no segregation occurs, and the original physical state of materials is not damaged. It has a large mixing ratio, high uniformity, and fast mixing speed. The discharge adopts a bottom-discharge large door, with fast discharge and little residue; the discharge door is reliably sealed with no material leakage. The machine has a compact structure, beautiful appearance, stable performance, low noise, no dust, and no environmental pollution, making it a fast, efficient, energy-saving, and high-quality mixing equipment.
2) Horizontal Ribbon Mixer
This mixer is a new generation of mixing equipment successfully developed by absorbing advanced technologies at home and abroad, belonging to batch mixers. This product adopts a bottom-discharge large door discharge method and a safe and reasonable pneumatic control mechanism system. It has the characteristics of wide applicability, beautiful appearance, gentle mixing process, no segregation, good uniformity, stable performance, little material residue, and convenient maintenance. It is an ideal equipment for mixing and processing powder materials.
3) Plow Blade Mixer
This mixer has a wide range of applications and can mix dry or wet materials, powder materials, and various coarse bulk materials. It has high mixing uniformity; during mixing, multiple high-speed small flying knives are installed in the mixer to ensure uniform mixing when producing high-quality chemical materials or colorants. The discharge door can be equipped with a large door or small door, with fast discharge speed and no residual material. When changing to produce different products, there is no need to clean the mixer.
All three types of mixers are equipped with automatic sampling devices for on-line detection to ensure product quality.
5. Packaging and Bulk System
The finished product can be packaged by packaging machines or placed into special bulk silos or special bulk transport tank trucks.
1) Packaging
The packaging machine is mainly composed of a weighing display controller, high-precision load cell, high-speed screw conveyor, electrical control cabinet, pneumatic executive components, automatic bag turning mechanism, and pneumatic vibrator. It adopts stepless speed regulation to control the feeding speed of materials, with the characteristics of fast filling speed and accurate metering. This machine can be equipped with a chain mesh conveyor, bag pressing machine, weight sorter, and long belt conveyor to form a main packaging line, improving labor efficiency. The equipment is equipped with a dust collector to ensure no dust pollution to the environment, with a beautiful appearance and convenient maintenance.
2) Bulk
A special automatically telescopic bulk head is installed under the bulk silo. After the bulk silo or special bulk transport tank truck is in place, the bulk head automatically extends into the feeding port for feeding. The bulk head is equipped with a level sensor and a dust collection device, which can automatically control the feeding amount and prevent dust from flying.
6. Dust Collection System
Dust collection equipment refers to equipment that can separate dust from the air. Dust collection is an important means to improve the on-site working environment of dry-mixed mortar production equipment. Dust collection is required when powder is pneumatically transported to the powder silo and when the mixture and powder enter the mixer. Currently, commonly used dust collection equipment includes cyclone dust collectors and bag filters.
1) Cyclone Dust Collector
A cyclone dust collector is a dust collection device that separates dust from gas by using the centrifugal force of particles. It is often used as a dust collection device for powder silos and drying parts. It is composed of an outer cylinder with a conical cylinder, an air inlet pipe, an exhaust pipe, an ash discharge pipe, and an ash storage box. Cyclone dust collectors have a simple structure, good performance, low cost, and easy maintenance, but the dust collection efficiency can only reach about 90%, so they can only be used as primary components of the dust collection system.
2) Bag Filter
A bag filter is a purification equipment that uses natural fibers or inorganic fibers as filter cloth to filter dust from gas. Because the filter cloth is made into a bag shape, it is generally called a bag filter. Bag filters are often used for dust collection from mixed dust sources. This method has a significant effect in the initial stage of installation, but if the dust accumulated on the bag wall is not cleaned for a long time, the dust removal effect will be poor. Therefore, the dust collector of dry-mixed mortar production equipment must regularly clean the accumulated dust. The commonly used bag filters with this function are mechanical vibration type and negative pressure cylindrical type.
a) Vibrating Bag Filter: Mainly composed of a vibration ash cleaning device (installed on the top, which shakes the filter bag in the middle of the dust collector through a rocker, vibration rod, and frame to achieve ash cleaning), filter bags, filter chamber, dust hopper, air inlet and outlet pipes, and screw conveyor. The vibrating bag filter has a simple structure, few failures, and easy maintenance, and has become one of the standardized bag filter products in China.
b) Negative Pressure Cylindrical Bag Filter: This machine is composed of a dust collection fan, filter element, controller, discharge port butterfly valve, and shell. The air inlet of the machine is connected to the mixer or other parts with dust sources. Under the control of the control system, it works intermittently or continuously, collecting dust on the outer wall of the filter element, and then reversely blowing the inner wall of the filter element through high-pressure air program circulation to press out the dust and fall into the recovery chamber. The machine has a simple structure, high dust collection efficiency, and low energy consumption.
7. Electrical Control System
The electrical control system adopts advanced programmable logic controller (PLC) and PC control methods, which can perfectly handle the automatic control of the entire production process such as batching, weighing, and mixing; it has PC monitoring and control functions for formulas, records, statistical displays, and databases; it has system expansion and network functions for client-server databases. With the assistance of a multi-point safety monitoring system, operators can understand the key working parts of the entire production line in the control room. It can provide all basic management modules for controlling dry-mixed mortar production equipment, from order receiving to scheduling to invoice issuance. The interface simulates and displays the entire dynamic production process of the dry powder production line, with intuitive, simple, and convenient operation.
8. Logistics Transportation
The finished dry-mixed mortar is available in two forms: packaged and bulk. Packaged dry-mixed mortar can be directly transported to the construction site by ordinary trucks for use; bulk dry-mixed mortar must be transported by special bulk silos or bulk transport tank trucks. Bulk silos must be transported to the construction site by special tank trucks and directly placed on the construction site for use. The bulk dry-mixed mortar transported by bulk transport tank trucks is sent to the bulk storage silos owned by the construction site using the on-board pneumatic conveying device after arriving at the construction site. However, the transport tank trucks must be special bulk dry-mixed mortar transport tank trucks with anti-segregation devices; otherwise, the quality of dry-mixed mortar and construction will be seriously affected.
9. Mixing and Spraying Construction Equipment
Mechanized construction of dry-mixed mortar has obvious advantages, with higher technical content, which can further improve the uniformity of dry-mixed mortar, ensure project construction quality, and achieve high quality and efficiency. It can reduce comprehensive costs, achieve no dust pollution and no waste materials, greatly reduce labor intensity, and truly achieve civilized construction. Currently, the construction machinery for dry-mixed mortar