Readymix Concrete - A Green Product

Introduction

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Some guidelines to assist plants

In SA, Sarma (Southern African Ready-Mix Association) does an annual audit on its member plants. The environmental issues that are taken into consideration are also audited.

Ready-mix concrete is in tune with the environment. From homes to office buildings to highways, using concrete as a construction material actually helps protect our natural resources and affords unique benefits to consumers. From an environmental standpoint, concrete has a lot to offer.

Ready-mix concrete is environmentally friendly in a variety of ways. The ingredients of concrete (water, aggregate, and cement) are abundant in supply and take a lesser toll in their extraction than other construction materials. Quarries, the primary source of raw materials, can be easily reclaimed for recreational, residential, or commercial use. Or they can be restored to their natural state.

As a nearly inert material, concrete is an ideal medium for recycling waste or industrial byproducts. Many materials that would end up in landfills can be used instead to make concrete. Blast furnace slag, recycled polystyrene, and fly ash are among materials that can be included in the recipe for concrete and further enhance its appeal. Waste products such as scrap tires and kiln dust are used to fuel the manufacture of cement. Even old concrete itself can be reborn as aggregate for new concrete mixtures.

Another environmental plus for concrete is energy efficiency. From manufacture to transport to construction, concrete is modest in its energy needs and generous in its payback. Since the materials for concrete are so readily available, concrete products and ready-mixed concrete can be made from local resources and processed near a jobsite.

Once in place, concrete offers significant energy savings over the lifetime of a building or pavement. In homes and buildings concrete's thermal mass, bolstered in insulating materials, affords high R-factors and moderates temperature swings by storing and releasing energy needed for heating and cooling. Rigid concrete makes it less costly to illuminate. Also, pervious concrete pavements can reduce storm water run-off and help recharge our natural ground water.

Further commendable characteristics of concrete are waste minimization and long life. Whether it's cast-in-place or pre-cast, concrete is used on an as-needed basis. Leftovers are easily reused or recycled. And concrete is a durable material that actually gains strength over time, conserving resources by reducing maintenance and the need for reconstruction.

The SARMA SHREQ Audit, with specific reference to "E" - Environmental issues

Some background to ready-mix concrete:

Ready-mix concrete manufacture can potentially place a significant burden on the environment if not controlled properly as explained above. The most important adverse impacts on the environment are related to quarrying of raw materials, nuisance impacts from dust discharges and discharges of high pH water to waterways.
Sarma has been aware of the potential problems and therefore developed its SHREQ audit. This audit being viewed as an industry initiative to have some self regulation.

Ready-mix concrete is manufactured at plants and delivered in concrete trucks. Due to the nature of the material, the manufacture of ready mix concrete is undertaken at plants close to the delivery site. There are many companies manufacturing ready-mix concrete in South Africa, from small companies to large construction companies. The majority of the ready-mix companies are members of Sarma.

To reduce the amount of material requiring quarry, ready-mix concrete plants are starting to use alternatives to raw aggregate with recycled concrete either being used or proposed.

The biggest impact from ready-mix concrete manufacture is the potential impacts from high pH runoff. This can occur during the manufacture at the ready-mix plant as well as runoff during pouring and curing of the concrete at the delivery site.

SOME SUGGESTED FOCUS AREAS WHICH PLANTS COULD ADOPT TO HAVE "BEST PRACTICE" OPERATIONS

Environmental issues: Legal requirements
The product "ready-mix concrete" must comply with the provisions of all relevant laws and regulations that are applicable during the product's life cycle.

Conformance with this requirement shall be demonstrated by providing a written statement on regulatory compliance. This statement shall be supported by documentation identifying the applicable regulatory requirements and demonstrating how compliance is monitored and maintained.

Relevant laws and regulations could, for example, include those that relate to:

  • Producing, sourcing, transporting, handling and storing raw materials and components for manufacture;
  • Manufacturing processes;
  • Handling, transporting and disposing of waste products arising from manufacturing;
  • Transporting product and;
  • Using and disposing of product.

The documentation required may include, as appropriate:

  • Procedures for approving and monitoring suppliers and supplies; and
  • Information provided to customers and contractors regarding regulatory requirements.

It is not intended to require Sarma member plants to accept increased legal responsibility or liability for actions that are outside their control.

Raw Materials

  • Cement
    The cement used in the readymix concrete shall meet the requirements of the SABS as set for the cement industry.
    Conformance with this requirement shall be demonstrated by providing a written statement on compliance. This statement shall be supported by evidence to demonstrate the cement product falls in line with the SABS standards.
  • Aggregate
    Quarries, from which materials are obtained, must have a mineral licence and preferably undergo the Aspasa ISHE and About Face Audits. (See Aspasa's website. www.aspasa.co.za for reliable quarries).
    In addition to this,

    There must be management plans including any policies and management procedures to minimize adverse effects from the following potential impacts:
    Noise
    Vibration
    Dust; and
    Discharges to surface water, groundwater, or land

  • A quarry rehabilitation plan.

Conformance with these requirements shall be stated in writing and signed by the authorized representative of the applicant company. This statement shall be supported by documentation, including:

Copies of the relevant management plans;
Records demonstrating the management plans are being effectively implemented (including monitoring results).

Hazardous Substances
No, substance shall be used in the production processes that are classified as toxic, carcinogenic, harmful to the reproductive system or genetically harmful (excluding cement).

Conformance with these requirements shall be stated in writing.

This statement shall be supported by documentation that:

- Lists all hazardous substances and products included in the concrete
- Includes Material Safety Data Sheets for hazardous substances
- Identifies the classifications that apply to each substance.

Water and Water re-use

a) The ready-mix concrete manufacturer must have and implement effective water management policies and procedures and/or a water management programme.

b) Accredited Sarma plants must report on water management, including:

    - Total water use;
    - Breakdown or water sources including water sourced from the local water supply, on site bore or recycled.
    - Water use related to production; and
    - Initiatives taken to reduce water use.

Conformance with this requirement shall be stated in writing. This statement shall be accompanied by documentation that includes:

  • Copies of the water management policies, procedures and programmes;
  • Records demonstrating the policies or procedures are being effectively implemented (including monitoring results) and
  • Annual reports on water use and management.

Discharge of Water

a) Discharges to the natural environment (natural water bodies or groundwater) shall not exceed the criteria as per the area were the plant operates

b) Discharges of contaminants to the natural environment (natural water bodies, groundwater, ocean or land) excluding those pollutants shall be demonstrated to result in acceptable and environmentally sustainable level of impact on the quality of the receiving environment.

c) The ready-mix concrete manufacturer must have and implement a management plan for discharges to surface water, groundwater or land.
Conformance with these requirements shall be demonstrated by providing a written statement on compliance. The statement shall be supported by the following:

  • Test results demonstrating that the above pH limit is being met; and an independent assessment of quality of discharges and impacts on the receiving environment completed by a person or agency competent to complete such an assessment. The assessment may be based on the quality of discharges from the point at which the discharges from the site or any relevant combined or municipal waste collection and treatment system discharges to the natural environment; or from the plant in situations where the plant discharge is mixed with other organisations' waste streams and the combined waste stream and its treatment before it is discharged to the natural environment is outside the control of the plant or licence applicant and suitable information is not available on the quality of the combined discharge.
  • Copies of the relevant management plan and records demonstrating the management plan is being effectively implemented (including monitoring results).

Cement Silo's

a) All cement silos shall be fitted with the following:

- Fabric filters to capture cement emissions during loading of the cement silos; and
- Overfill sensors to detect overfilling.

b) All cement transfer shall be undertaken pneumatically and shall be fully enclosed.

Conformance with this requirement shall be stated in writing. This statement shall be accompanied by:

  • Information from the supplier of control equipment confirming that the equipment meets the criteria or evidence that the equipment required to meet the criteria is installed and operational (eg: photographs) and;
  • A copy of the plant's preventative maintenance plan for all the equipment required to meet the criteria.

Dust Management Plan
Criteria
The ready-mix concrete manufacturer must have and implement a dust management plan covering all areas of the operation including access ways, concrete plant and associated activities.

Conformance with this requirement shall be stated in writing. This statement shall be supported by documentation, including a copy of the plant's dust management plan and records to show it is being effectively implemented.

Truck Washing
All ready-mix concrete trucks shall be washed out at a location where all wash water and wash solids are collected and re-used or disposed of to a licensed facility.
Conformance with these requirements shall be stated in writing. This statement shall be supported by documentation including:

  • A copy of the site layout plan showing designated truck wash areas;
  • Delivery procedures stating that no truck washing is to be undertaken off the concrete manufacturing site; and
  • Records of material disposed.

Truck Driver Training
The ready-mix concrete manufacturer must ensure a training programme is in place to ensure all drivers are knowledgeable of procedures to minimize impacts on the environment in the event of a spill or potential discharge.

Conformance with these requirements shall be stated in writing. This statement shall be supported by documentation, including a copy of the companies training programme for truck drivers and records of training.

Product Information
The ready-mix concrete manufacturer shall have consumer information available on the potential impacts on the environment from the use of ready-mix concrete and instructions on appropriate use and actions to be taken to minimize the impact on the environment including actions to avoid contaminated water entering stormwater or surface water.

Conformance with these requirements shall be stated in writing. This statement shall be supported by documentation, including a copy of the manufacturer's consumer information and procedures to provide this to customers.

Waste Management

a) The concrete product manufacturer must have effective waste management policies and procedures and/or waste management programme covering manufacturing operations; and

b) The Sarma accredited plant must report on waste management, including:

- quantities and types of waste recovered for reuse internally and externally;

- quantities and types of waste recycled internally and externally;

- quantities and types of waste disposed of to landfill;

- information on disposal locations for all wastes; and

- initiatives taken to reduce waste generation and improve recovery/recycling of waste.

Conformance with this requirement shall be stated in writing. This statement shall be accompanied by documentation that:

  • describes the waste management policies, procedures and programmes.

Energy Management
The concrete manufacturer must have effective energy management policies and procedures and/or an energy management programme covering the ready-mix plant and delivery of ready-mix concrete.

The Sarma accredited plant must report annually on:

  • total energy use including fuel used for delivery vehicles;
  • breakdown of total energy use to types of energy used;
  • energy use related to production