On-Site Concrete Plants in Mining Areas

[edit] Introduction

On-site concrete plants can be used to produce concrete close to construction activities on mining projects and other remote infrastructure projects. They can reduce the distance over which fresh concrete must be transported and can provide greater control over production and delivery schedules. This can be particularly relevant where construction sites are remote, road access is difficult, or concrete demand is sufficiently high or continuous to justify on-site production.

Mining developments can require substantial quantities of concrete for processing facilities, equipment foundations, access roads, retaining structures, tunnels, workshops, drainage infrastructure and other supporting works. An on-site batching plant allows concrete to be produced according to the project's mix requirements and programme rather than relying entirely on deliveries from an external ready-mix supplier.

[edit] Requirements for on-site concrete production

Remote mining projects can present different logistical conditions from construction projects in urban areas. Sites may be located considerable distances from established infrastructure and may have restricted access, difficult terrain or limited availability of construction materials and services. The time required to transport fresh concrete can therefore become an important consideration.

Fresh concrete has a limited period during which it can be transported, placed and compacted while maintaining the specified properties. The available time depends on factors including the concrete mix, temperature, admixtures, transport arrangements and project requirements. Long or unpredictable journeys can make delivery planning more difficult and may increase the risk of concrete arriving outside the required specification.

An on-site batching plant can reduce the distance between production and the point of use. Aggregates, cementitious materials, water and admixtures can be stored at or near the plant and batched in controlled proportions. Production can then be scheduled according to the construction programme and demand.

The suitability of an on-site plant depends on more than transport distance. The project must have sufficient demand to justify the plant and must be able to provide suitable space, access, power, water, material storage and arrangements for operation, maintenance and environmental control.

[edit] Plant types and site requirements

Concrete batching plants can be stationary, semi-mobile or mobile. Stationary plants are normally intended to remain in one location for an extended period and can be appropriate where substantial production is required throughout a long construction programme. Mobile and compact plants can be transported and reconfigured more readily and may be appropriate where construction activities move between work fronts or where the plant is required for a temporary project.

Rapid assembly can reduce the time required to establish production, but the extent of site preparation required depends on the plant configuration and site conditions. A plant may require suitable foundations or hardstanding, access for delivery and maintenance vehicles, aggregate storage, cement storage, water supply, electrical power, drainage and measures for managing dust, noise and wash water.

Mining sites can also experience challenging environmental conditions, including high altitude, extreme temperatures, heavy rainfall, dust and unstable ground. These factors can affect the selection, installation, operation and maintenance of batching equipment.

[edit] Factors to consider when selecting a plant

Selection should be based on the concrete production and logistical requirements of the project rather than equipment capacity or purchase price alone. Important considerations include:

• Concrete demand: Estimate average and peak production requirements and consider the required rate of supply to individual work fronts.
• Project duration: A temporary project may favour equipment that can be installed, dismantled and relocated efficiently.
• Site conditions: Assess ground conditions, available space, access, drainage, power, water supply and environmental constraints.
• Materials: Establish the availability, specification, transport and storage requirements of aggregates, cementitious materials, water and admixtures.
• Plant configuration: Consider batching and mixing capacity, aggregate storage, cement storage, weighing systems, control systems and the number and type of concrete mixes required.
• Transport and installation: Consider the dimensions and weight of plant components, access roads, lifting requirements and the equipment needed for installation or relocation.
• Maintenance and support: Establish arrangements for inspection, maintenance, spare parts, breakdowns and operator competence, particularly where the site is remote.
• Environmental management: Consider dust emissions, noise, water use, wash water, waste concrete and the management of contaminated water and materials.

[edit] On-site production compared with external supply

The choice between an on-site batching plant and externally supplied ready-mixed concrete depends on project-specific conditions. External supply can be suitable where a reliable concrete supplier is located within an appropriate transport distance and the required delivery rates can be maintained. It avoids the need for the contractor to establish and operate a batching facility on the project site.

An on-site plant requires capital expenditure or hire costs and introduces additional responsibilities for material procurement, storage, batching, mixing, quality control, maintenance and plant operation. It may nevertheless provide logistical benefits where concrete demand is substantial, delivery distances are long or access conditions make regular external deliveries difficult.

The comparison should therefore consider the whole-life cost of the concrete supply arrangement. Relevant costs can include plant purchase or hire, transport and installation, site preparation, aggregates and cementitious materials, storage, labour, fuel or electricity, maintenance, testing, environmental controls, external concrete deliveries and the consequences of delays or interrupted supply.

[edit] Applications in mining construction

On-site concrete plants can support a range of mining-related construction activities, including:

• Foundations for processing plants and other equipment.
• Equipment bases and hardstandings.
• Access roads and associated infrastructure.
• Retaining walls and drainage structures.
• Workshops, warehouses and service buildings.
• Tunnel and underground mining infrastructure.
• Worker accommodation and other supporting facilities.
• Other concrete structures requiring regular or high-volume supply.

The appropriate concrete production arrangement will depend on the scale, location, duration and sequencing of the works. Some projects may require a single fixed plant, while others may benefit from a mobile plant that can be relocated as construction progresses.

[edit] Planning concrete supply

Concrete production should be considered as part of the wider construction logistics strategy. The location of the plant should be coordinated with material delivery routes, aggregate and cement storage, vehicle movements, concrete delivery routes and the location of the principal work fronts.

Production capacity should also be considered in relation to the construction programme. Peak demand can arise during activities such as large foundation pours, structural works or the construction of extensive infrastructure. The plant and delivery arrangements should be capable of maintaining the required rate of production and supply during these periods.

Quality control is also essential. Concrete should be produced in accordance with the specified mix designs, with appropriate control of constituent materials, batching accuracy, mixing, sampling and testing. The requirements for quality control should be established as part of the project's concrete specification and quality management arrangements.

An on-site concrete plant can be an effective component of construction logistics where the project's concrete demand, transport distances and site conditions justify local production. The decision should be based on the complete supply arrangement, including capital and operating costs, site requirements, production capacity, quality control, environmental management and the duration and sequencing of the construction works.

[edit] Related articles on Designing Buildings

• Concrete batching plants
• Concreting plant
• Types of Concrete Batching Plants
• Concrete
• Construction logistics plan
• Logistics management in construction
• Construction logistics manager
• Construction strategy
• Ready-mix concrete
• Testing concrete