On-site concrete mixing choices create much debate at the planning stage to achieve the best results. Many factors must be considered to achieve desired outcomes, such as location, machinery required and the personnel complement.
Small Construction Sites – Residential building and Renovations
Works Managers face challenges such as access to the site, whether there are confined spaces to operate in, and if designated material storage areas exist. The standard practice regarding concrete requirements is to hire a small mixer (if not owned) which can mix between 0.75 m3 and 1.35 m3 per cycle, and which requires:
- Resources – aggregate loaders and labour to transfer mix where required.
- Materials – sand, stone and cement delivered either by truck/pickup in raw material form or pre-bagged.
- Space – area for the concrete mixer and materials.
- Access to a faucet or delivery of a water tank.
Equipment, such as aggregate loaders, and the relevant staff to operate it, make up a high percentage of cost allocations. Material waste is often an unwanted consequence, as the various loads of aggregate arrive in small quantities. Poor planning can cause over- or under-estimating order volumes. If the latter occurs, project margins will shrink as small quantities purchased to complete the operation come in at a much higher cost.
Space issues are also a consideration when selecting on-site concrete mixing options on these smaller sites. Residential properties, for example, often do not have sufficient ground for vehicles together with construction materials, such as brick piles, storage and equipment.
Manual labour processes, such as the mixing of materials and the consistency, vary from mix to mix, as no two shovel loads of aggregate are ever identical.
Medium to large Sites – office construction, industrial builds and shopping centres
Preparation for this type of sites takes many hours of discussions with sub-contractors and project planners. Generally, volumetric mixers are utilised for an operation of this size.
Timing is one of the essential components – all trucks involved in the job have to leave the mixing plant at designated times, ensuring that all personnel and machinery are ready at the receiving end. Slight errors in judgement of traffic patterns, for example, can impact the project in both time and capital outlay. On large pours, truck flow and numbers of vehicles needed in the various locations require pinpoint planning accuracy.
Choosing the correct concrete mixer is critical
In the world of batch, drum and continuous mixers, there are many solutions to suit specific functions and situations. BLEND’s concrete mixing plant solutions offer owners and contractors both mobile and stationary units, with the E-Series of equipment providing excellent flexibility and compact design.
For smaller operations where distance is a problem, having a concrete pump on standby is an advantage. The E-Series can produce between 5m3 and 50m3 per hour, depending on requirements. As the equipment can pour the precise MPa1 required by the contractor, costs are better controlled, achieving the precise volumes desired for any project.
For the larger sites where the stationary plant is separated for a batching area, efficiencies are gained by having a few volumetric mixers on standby. Once a fresh batch is loaded, it can be delivered immediately without fear of the slump value changing in the specified mix. As the plants in the BLEND E-Series are dry mix, continuous batching units, operators can make the mobile equipment available as needed.
BLEND Plants offer a precise measurement of concrete with a specific mixture according to the application, across a variety of end products such as:
- stabilisation cement,
- bridge mix,
- laboratory specified mix,
- coloured cement,
- backfill,
- shotcrete,
- cold asphalt or
- standard concrete.
MMI Zimbabwe has a range of BLEND stationary and mobile batching plants suitable for a variety of applications. Contact Blend Plants for more information on your specific needs.
1 Concrete is measured by its strength capacity. MPa (megapascals) is the metric measurement for psi or pounds per square inch. Many countries’ building codes require a minimum MPa for specific concrete projects.