THE RIX GROUP Shotcrete Solutions was established in March 2000 specialising in – all shotcrete contracting, civil work & construction of mobile phone base stations. The RIX Group has offices in Queensland & New South Wales. RIX are expanding rapidly. RIX now specialise in Civil Tunnel Contracts, Rail Construction Contracts, Specialised Drilling, Rockbolts, Rockfall Netting, Soil Nails & Shaft Lining.
RIX also have Underground Robotic Shotcrete Equipment and a Remote Shotcrete Shaft Liner for ground support in mines and tunnels. RIX have in-house Engineers with the experience to help you with your more challenging projects. The RIX team are regularly travelling to all parts of Australia to provide our clients with shotcrete solutions. If you have a project requiring Civil or Rail Construction, Shotcrete, Rockbolts, Soil Nails, Drilling, Underground Robotic Shotcrete Application, Rockfall Netting or other forms of geotechnical stabilization you have found the right website.
As you read on, you will see some of our more challenging civil & rail construction projects.  

SHOTCRETE  -  ENABLING CONCRETE TO OVERCOME GRAVITY

In the USA where the process was invented, Shotcrete is commonly called Gunite. Since its inception in the early 1900's shotcrete application has advanced.
Technically the definition of Shotcrete is the " the spraying of concrete via air or hydraulic pressure". This can be achieved by two methods.

1. using mechanics & hydraulics to force wet concrete through a hose, where compressed air increases the Shotcrete's velocity at the discharge end.

2. using compressed air to blow a dry mix through a hose, where water is added at the discharge end.

In Eastern Australia method one is commonly called Shotcrete & method two is commonly called Dryshot.
Both Shotcrete & Dryshot use compressed air to increase discharge velocity. This increases the ability of the shotcrete to adhere to surfaces that normal concrete would not adhere to. For example tunnel roofs, rock faces, steep batters etc.
Shotcrete is used extensively in civil construction, tunnelling, shotcrete pools & geotechnical stabilization around roads, railways & other forms of excavation.
Both Shotcrete & Dryshot differ from normal concrete in the size of the aggregate. Normal concrete generally has an aggregate size of 20mm where as Shotcrete generally has an aggregate size of 10mm & dry shot has an aggregate size less than 10mm.

Shotcrete is best used in situations that require:

· quantifiable water/mix design

· large quantities & fast application

· consistent admixture/concrete ratios

· minimal rebound, or aggregate loss

· Steel fibres or Barchip use

Dryshot is best used in applications that require:

· smaller quantities (<20m³)

· application via Rope Access

· artificial rock simulation (mock rock)

· remote areas

SHOTCRETE APPLICATIONS

1) Civil Construction - Shotcrete & Dryshot can be shaped, contoured, levelled, coloured, moulded, imprinted, smoothed & reinforced. Common terms for the myriad of Shotcrete finishes include:

· gun finish (rough)

· wood, float, sponge (rendered look)

· steel trowel (smooth)

· oxide (colour)

· mock rock (carved)

Shotcrete has been used to construct multistorey hotels, wheat silos, hydroelectric tunnels, underground sewers, bridge abutments, artificial white-waterways (Penrith Whitewater Stadium - Sydney Olympics), dam slipways, car parks, skateboard ramps, nuclear missile shafts, water reservoirs, & retaining walls.

2) Tunnelling - Shotcrete is extensively used in mines & tunnels due to its ease of application & ability to adhere to surface that normal concrete would not. With the addition of silica fume shotcrete has great characteristics for use in mines.
Shotcrete’s popularity in tunnelling & mining rocketed once steel mesh that took days to install to a mine tunnel was substituted with steel fibres & or Barchip additives.
Of these additives Barchip is preferred. As Steel fibre leaves a sharp surface that can easily tear the skin were as the polymer Barchip alternative has no OH&S issue, while achieving comparable tensile strengths.

3) Culvert Construction & Maintenance - Culverts are under the spotlight at the moment due recent failures that have resulted in numerous fatalities. Culverts that have been constructed from galvanised iron are reaching the end of their service life, rusting out & failing.
Shotcrete & reinforcement have been selected in many cases to increase the strength of the failing culvert while minimising the restriction to flow volumes.

4) Geotechnical Stabilization - Shotcrete is used extensively with rock bolts, soil nails, temporary anchors, Maccaferri rockfall mesh, reinforced steel & steel fibres to reinforce loose ground conditions, hazardous geology & rock fall. 

5) Landscaping - Shotcrete is used in the creation of decorative landscapes. Due to shotcrete’s ability to be coloured, shaped, contoured & carved the possibilities & creations are endless. Mock or artificial rock like that used recently in the Great Southern Oceans Precinct in Tooronga Zoo, can be incorporated around pools to resemble natural features like rock ledges or waterfalls.

6) Shotcrete Pool Construction -  Quality construction assures you in getting the maximum life out of your shotcrete pool. Steel Reinforcement gives the shotcrete pool tensile strength. This is installed usually on a previous day. The steel is often certified by a Structural Engineer prior to shotcrete application.
Shotcrete Pools can be completed in a single day. Shotcrete pools have no construction joins. This minimises the potential for leaks & cracks.
As opposed to formwork, shotcrete pools mix design can be greater controlled due to the reduced application time.
Shotcrete Cutters & Finishers have honed their skills over years of shaping shotcrete. Shotcrete can be worked to produce sharp, straight & parallel edges equal to that of a formed structure, but without the construction joins & in a fraction of the time. The possibilities for shotcrete are endless in the hands of a craftsman.
Shotcrete stairs can be shaped on site to the client's individual design.
Subtle additions to your pool are not a problem with shotcrete construction.
Shotcrete enables seamless construction & sleek design.

AN EXAMPLE - GEOTECHNICAL STABILIZATION WITH SHOTCRETE

Following are some of the steps in a typical shotcrete application.

This typical scenario will look at the securing of ground that has been assessed to be geologically unstable by a Geotechnical Engineer:

1. Site Assessment

The site will need to be assessed by a Geotechnical Engineer who will identify areas of geological instability. Taking the geotechnical assessment, an Engineer with expertise in structural strength will then formulate a design for retaining the ground in question. The Engineer's design will then be implemented as the solution.

This design may incorporate:

· Maccaferri Rockfall Mesh or Netting

· Rockbolts or Ground Anchors

· Soil Nails (rockbolts for soil)

2. Shotcrete Contractor Selection

The Site Owner or Primary Contractor will then Tender out the job. It is in the Site owner's best interest that the wining tender addresses all the safety & environmental requirements as laid out by the tender package. A Site Owner or Primary Contractor will normally ensure that the winning Shotcrete Contractor has: 

· a proven track record

· quantifiable OH&S culture

· environmental awareness

· quality assurance & control

· sound plant 

· an adequate corporate skill base

Once the contract has been awarded to the Shotcrete Contractor, preparations for mobilising on site begin.

3. Site Safety

Assess the site & task for potential hazards. Implement controls that will minimise the potential for these hazards to harm.
Design a work methodology for the task that isolates these hazards, or if they can't be removed, minimises them to a level of acceptable risk. Ensure that all employees & the surrounding public are aware of the hazards & are isolated from harm.

4. Site Establishment

Gain access to the geologically defective area. This may need to be done through:

· Industrial Rope Access

· Elevated Work Platforms

· Manitou

· Crane

5. Site Preparation

De-vegetate the site to be treated. This may need to be done by trained Arborist’s who have proven competency in chainsaw use. Often if the geologically defective area is at height this is achieved best by Arborist’s with Industrial Rope Access competency.
Next it is important to remove all loose rock & soil to give the shotcrete a strong key to the geologically defective area. This is called scaling the site & once again if the geologically defective area is at height this is achieved fastest & cheapest via a team of Industrial Rope Access technicians.

6. Mesh & Drainage Installation

Once the area is scaled & deveged the geologically defective area is ready to mesh.
If the area is significantly large the Engineer may decide that only the most severe areas are to have Shotcrete applied. If this is the case Maccaferri Rockfall Netting may have been chosen to stabilise areas with a lesser hazard rating. This can now be installed along with the steel mesh intended for shotcreting.
Once again Industrial Rope Access technicians are valuable in getting this mesh up the fastest & cheapest. For detail on Maccaferri Rockfall Mesh we recommend visiting www.maccaferri.com.au for more technical data.
Areas designated for shotcrete are usually meshed in a galvanised steel mesh of the SL series. Under this mesh a drainage system is normally installed to relieve water or hydrostatic pressure.
The rockfall netting, galvanised mesh & drain can be temporarily located with dowels prior to rockbolt installation & shotcrete application.

7. Rock Bolt Selection

The rockfall netting & steel mesh will need to be anchored to secure ground surrounding or within the area being stabilised. Rockbolts may have been selected. Rockbolts come in all shapes and sizes. Rockbolts can be either fibreglass or steel. They can be simple bar or mechanical shell bolts.
We recommend visiting the DSI Australia site www.roofbolt.com for a more comprehensive range of rockbolts.
What ever the design or make up of rockbolts generally they will need to be grouted to achieve both corrosion protection & stability in the sites geology.

8. Drilling of holes for Rock Bolts

Holes will need to be drilled. The Engineer will specify both depth & diameter.
Drilling can be achieved with various plant:

· Excavator drill

· Rock drill

· Hand drill

These Rock Drills can be pneumatic drills or hydraulic drills. Excavator drilling will deliver the largest diameter hole but may be hampered by height or access restrictions. Hand rock drills will deliver the smallest hole but are light enough to be carried into remote sites. If needed Hand Rock Drilling can be used by Rope Access Technicians at height.
If the drilling contractor is large enough then rock drills of all sizes & shapes will be owned to deliver the desired diameter hole in the desired location.

9. Grouting of the Rockbolts

Once drilled the holes are then cleaned. If the rock bolt is steel these holes will need to be large enough to house both the rock bolt & an encapsulating layer of corrosion protection. This corrosion protection may be cement or an epoxy grout.
Plunge grouting is the most common method for grout insertion into the hole. This enables grout volumes to be monitored thereby ascertaining any grout leakage into subsurface voids. Once the hole has been filled with grout, the rockbolt is installed. The grout will need to be left to cure. This is so the grout achieves maximum strength before the plates are put on & the nuts are tensioned securing the mesh.

10. Anchoring of Mesh

In the case that Maccaferri rockfall netting is used, wire cables are integrated into the rock mesh. These cables need to be located under the rock bolt plates for maximum strength. Tension the rock bolts & the mesh is now secure and ready for shotcrete application. As for other mesh used locate the plate in the weld areas of the mesh prior to rock bolt tensioning.

11. Shotcrete Pump Selection

Shotcrete pumps come in all shapes & sizes. If a large Shotcrete Contractor has been selected they will own a good range to suit the majority of sites.
If the pumping distance is large between the geologically defective area & the closest vehicle access point relay trailer pumps, cranes or Dryshot can be used.

12. Shotcrete Application

Shotcrete is delivered to site via agitator trucks. The mix is normally sampled & tested in a laboratory for compressive strength.
An experienced nozzle man can manipulate the shotcrete to most surfaces & gradients without too much waste or over-break.
It is important that all voids are filled with no air-pockets. Normally the shotcrete is sprayed from left to right & from bottom to top.

13. Shotcrete Finishing

This is the business end for most project managers as this is what the client & public will see.
In the finishing of shotcrete there are many possibilities. Shotcrete can be:

· Unfinished (Gun Finish)

· Cut, wood floated & sponged, this results in a finish that is indistinguishable from a rendered block look.

· Cut, wood floated & steel trowelled for a sleek finish. This is often used in areas where the shotcrete wall will later be treated to repel water in sub-surface or sub-sea level sites.

· Shotcrete can be carved & coloured to simulate to rock features or sandstone block work. Examples of this can be seen in Tooronga Zoo’s new attraction Great Southern Oceans Precinct. This mock rock can then be further softened with plants to reduce any visual impact.

Curing compound can be applied to the shotcrete surface. This curing compound reduces the potential for surface cracking.

If the shotcrete contractor has been chosen carefully, a Quality Control procedure was rigorously followed during the project & the product will enjoy design life defect free.

SILICA FUME 

Silica fume is an ultra-fine powder 100 times smaller than a grain of cement. When introduced into shotcrete these fine particles assist to fill any voids. Silica fume significantly enhances the overall compressive strength of the shotcrete mix.

Characteristics of Silica Fume in Shotcrete

· enhanced compressive strength

· reduced permeability

· improved corrosion resistance

· improved shotcrete pump ability

· improved cohesion resistance to segregation

· improved adhesion to tunnels, culverts, steep geology

· improved abrasion resistance

· improved resistance to most sulphates and various other forms of chemical attack

SAFETY FOR SHOTCRETE CONTRACTORS

Safety has high priority in Australia especially in New South Wales & Queensland. Government Authorities in all states regulate, inspect & monitor workplaces in attempt increase safety awareness & safer work practices. Shotcrete contractors are required by law to protect their employees from work injury.
Shotcrete contractors are required to keep their:

· shotcrete plant maintained & safe

· processes & work methods safe

· chemicals & hazardous substances stored correctly & MSDS’s available.

Shotcrete application has inherent risks including:

· moving mechanical parts

· pressurised shotcrete

· projected aggregate

· chemicals

· vehicle traffic

· airborne dust

· manual handling

RIX take their responsibility to providing a safe workplace seriously.
At The RIX Group Shotcrete Solutions our Occupational Health, Safety and Rehabilitation Policy is based on a belief that the well-being of people employed at work, or people affected by our work, is a major priority and must be considered during all work performed on our behalf.
People are our most important asset and their health and safety is our greatest responsibility as shotcrete & geotechnical contractors. The public shall be given equal priority to that of our employees.