Concrete Synthetic Cricket Wicket (page 2)
See the previous discussion under Funding.
You will need one person to manage the project, an expert concrete finisher to supervise laying the slab, a carpet layer to install the synthetic mat, and several labourers. These will be required as two teams, one to lay the concrete slab (the concrete finisher and at least four labourers) and one about a week later to lay the synthetic (carpet layer and two labourers).
e) Concrete slab
The tasks here are:
Prepare and level the site
Levelling the site can be done at any time, but preferably just before you set up the formwork (so no one stuffs it up).
Set up the form work
Lay and finish the slab
Keep everyone off it until it dries
Setting up the formwork and reinforcing should take two to three hours and be done late on the afternoon before you pour the concrete.
The concrete should be poured around 8:00 in the morning which means the finishing will be done by lunch time and the formwork can be removed. You will then need someone to act as security guard to keep everyone off it until late afternoon by which time it will be hard enough to stop people carving their names in it.
Make sure that the slab goes down in one piece. DO NOT include any expansion joints otherwise the separate slabs will drift over the years and create dangerous joints. It is quite OK for the slab to develop cracks, the reinforcing will ensure that these cracks are not accompanied by dangerous changes in surface levels. In any case, the surface cracks will be covered by the synthetic mat.
Make sure that you DO NOT finish up with a glazed surface. If you do it will be extremely dangerous when wet. When finishing the concrete the final process is to go over it with a broom to give a textured finish that will provide grip to rubber soled shoes in wet conditions.
Prepare and Level the site
The idea is to use a grader to remove 50mm of topsoil from where the wicket will go leaving an exposed, flat soil surface 35 by 5 metres. Since the slab will be 100mm thick, the final surface of the wicket will be 50mm above the surrounding ground level. After construction, top soil will be battered up to the edge of the slab with the final result that rainwater will run off the wicket area. When you grade off the topsoil, keep it handy to put back as batter. You may choose to use a turf cutter to remove the turf before grading. This turf can be re-laid after the batter is put in place. If you use a turf cutter, remember to count the soil removed as part of the 50mm.
When taking off the topsoil you want to finish up with a surface that looks level to the naked eye. If it is perfectly level then the resultant wicket will be so level that water will not run off it. A 1 in a 100 fall to the left or right would be ideal. If it has humps or hollows in it you will finish up using too much concrete.
When levelling the site, make sure you leave room to put in place your formwork.
It is best if you use 100mm C sections in 5 metre lengths. Using steel C sections makes it easier to use a screed to get the surface of the slab level. Using 5m lengths fits neatly with the dimensions of the wicket and flares.
Place the two wooden blocks so that they will make voids through the slab where the stumps are to go. The centres of these blocks should be 20,120mm apart.
Place the plastic sheeting so that it covers most of the dirt within the formwork box. Do not let the plastic extend beyond the edge of the slab (within 50mm of the edge will do, if it extends beyond the edge it will interfere with grass growth).
Ideally the reinforcing mesh should be 7mm bars at 200mm centres (F72), but you can get by with a lesser grade. Because of its size the slab will crack (that's OK), what we need the reinforcing to do is to stop the various pieces from moving up and down in relation to each other. Place the reinforcing mesh so it is no more than 50mm above ground level and not within 50mm of the edge of the slab. Overlap and tie all joins.
The concrete does not need to be of superior construction quality. The standard brew for footpaths should do the job. We suggest 20mpa with a working time of 3 to 4 hours.
The idea is to pour the slab in one piece, starting at one end and working to the other. The should be NO expansion joints. Make sure the reinforcing stays in place on its bar chairs and is not trampled down to ground level. Make sure you don't knock out of place the wooden voids for the stumps.
If you used 100mm C sections for formwork then you will find a 5m length of C section makes an ideal screed for getting the surface of the slab roughly level. Simply giggle it along the top of the formwork.
Once the concrete is in place and roughly level, gradually work it to give a smooth flat surface and work the edges with an edging trowel. Don't forget to use the edge trowel around the voids for the stumps. Remove these wooden blocks once the concrete has "gone off" otherwise you will never get them out.
Remember, you do NOT want a glazed finish. You should finish the surface with a broom to give a slight textured finish that will not be slippery when wet.
Once the concrete has set firm you can carefully remove the formwork and patch up any imperfections along the edges.
On the top of one edge, adjacent to the stumps at one end, you may discreetly mark the date in letters 50mm high.
What you don't want is every kid in the neighbourhood carving his name in your handiwork, so it is wise to have some of your people watch over the wicket for the rest of the day.
To keep them occupied they can carefully replace the topsoil over the still exposed earth and replace the turf on
f) Synthetic surface
You should leave the slab cure for about a week before laying the synthetic grass mat on top. Make sure the slab is clean and free of dirt, water and oil before you start.
The mat should be laid in one piece 22m long and 1.83m wide. Since the slab is 2m wide this will leave a strip of bare concrete about 85mm wide down either side of the mat. This is deliberate, the bare strips are used to stop grass from growing underneath the mat.
Firstly, without using any glue, place the mat in position so you can see how it is going to fit. Using some glue, anchor one end in place and carefully roll the other end up to it. Now, applying the glue as you go, work the mat up to the other end, unrolling it as you go. You do not need to stretch the mat tight, but you do need to roll out any bubbles and wrinkles as you go. Make sure that the edges are well stuck down, and take particular care at the four corners and where the bowlers run up.
Cut out the rectangular holes where the stumps go.
Mark the creases and leave the synthetic mat sit for one day before using it.
g) Marking creases
With white paint and a 1 inch brush you will need to mark a Bowling Crease and a Popping Crease at either end of the wicket. You will not be able to mark Return Creases as they fall outside the edges of the concrete slab. If in doubt, get an umpire to show you where the creases go - it's very embarrassing if you put them in the wrong place.
The Bowling Crease is a line one inch thick running across the wicket so that its back edge would pass through the middle of the three stumps.
The Popping Crease is a line one inch thick running across the wicket so that its back edge is exactly 1.22m (four feet) in front of the back edge of the Bowling Crease. ie the back edge of the Popping Crease is 1.22m in front of the middle of the stumps.
If you are careful, you may mark a small line (10mm x 30mm) across the middle of the Popping Crease to show where "centre" is. This will discourage batsmen from wearing a hole in the synthetic when they mark their guard when coming in to bat.
Care and maintenance
In normal conditions a synthetic mat should last up to ten years or even longer. The worst problems are vandals, golf players and dirt or sand.
Vandals are your problem, but you should ensure that golfers do not practice their chip shots on your synthetic wickets - they leave little L shaped cuts on the surface.
If gritty dirt or sand gets into the surface it will grind and cut the base of the pile. The best solution is to use a high pressure water pump to blast the mat clean at the start of each season or as required.
You can repair cuts or holes in the synthetic mat by patching in a piece of synthetic with similar use. You can cut pieces out of the "spare" synthetic behind the stumps to effect repairs to damaged parts of the wicket.
When you reach the stage of replacing a synthetic wicket, keep what you can of the old one - it will be handy for practice wickets and repairs.
If your wicket needs to be covered during the off season so other sports can use the ground, ensure that a plastic sheet is placed over the synthetic before dirt or sand is placed on top.
Do not allow players to wear spikes on synthetic.
Local rules for synthetic wickets
When playing on synthetic wickets it is normal to adopt the following Local Rules:
a) On concrete or synthetic wickets a ball pitching off the wicket is a no-ball and is called as soon as it pitches.
Note that this is a No-ball as opposed to a Wide. The batsman cannot be out from a No-ball, but he may be out from a Wide. It can be embarrassing if the umpire calls Wide and the ball deflects from the grass at the edge of the pitch and hits the stumps or is taken as a catch. The bare concrete strip along the edge of the synthetic is not regarded as part of the wicket, so a ball pitching on the bare concrete or on the very edge of the synthetic is a No-ball.
b) A bad bounce from a join in a synthetic wicket is called Dead Ball and is replayed.
Fielders should be encouraged to be careful when returning the ball to the keeper or bowler. If it bounces on the bare concrete flares it will damage the ball. You may place synthetic to cover the concrete on the flares to overcome this problem.
Variations on a theme
We have found that the above gives an ideal concrete synthetic wicket. In particular, the flares at either end of the slab are desirable to stop erosion from bowlers and wicket keepers; the slab should be wider than the synthetic to help control grass which wants to grow under the synthetic; the slab should be laid in one piece without expansion joints to avoid "floating" over the years; and the top of the slab should be above natural ground level to allow storm water run-off.
The plastic liner under the slab is optional depending on local conditions. If the soil is dry it can tend to extract too much moisture from the slab while curing.
You can place a synthetic mat onto an existing concrete slab. This may mean foregoing the flares at either end, or that the slab is narrower in which case you may forego the protective strip down either side, or that the wicket is narrower.
If you can get hold of some spare or recycled synthetic you can use it to cover the bare concrete on the run-up flares. Looks good, makes the bowlers happy and protects the ball.
You can purchase synthetic wider than 1.83 metres. You may choose to install a wider wicket which will encourage batsmen to use their feet and go for strokes when the ball is pitched wide of the stumps.
Dubbo Dustrict Cricket Association