Technical Data MM80 - Crack & Joint Repair

1 Technical DataMM80 - Crack & Joint Repair mm80 10 INTRODUCTION Metzger/McGuire and Norton Construction Products are pleased to provide this guide on a number of common floor problems and our recommended common sense correction methods. These field proven methods and materials were developed through years of experience as restoration/ Repair PRINCIPLES FOR SUCCESSFUL REPAIRD etermine CauseDid slab movement cause or contribute to the problem?Can a change in your operation (different wheels etc) ease future damage? Is the concrete itself adequate?Match Materials To ProblemDon t use high strength concrete in joints/cracks that are likely to move. Would a liquid or mortar best fill the defect? Does the cure time match the limits you have? Match Materials to Methods How deep must material be applied?

2 What tools are required to obtain that depth? Can you wet saw cut, or must the floor be totally dry for maximum adhesion? Match System to ConditionsWill dry cutting create unacceptable dust? Will odour from epoxy or solvent be a problem? Us epoxy cure time adequate for the type of work involved? Preparation Is VitalNever feather edge! Always make a vertical edge at the end of the Repair . Remove all foreign substances and structurally unsound concrete to ensure best SEPARATIONMM80 is installed long before a slab has completed its shrinkage and may separate adhesively as joints open. Gaps can be filled with Crack Fill if mm80 is firmly in Norton Construction Products GuideFig 1. Typical FailureFig 2. Saw cut past the edge of breakage Width (mm) Depth (mm) 3-30 12-20 30-100 20-25 Fig 3.

3 PreparationClean out debris, blow out and choke off base with silica 4. Install mm80 flush/slightlycrowned Width (mm) Filler (%) <12 0 >12 250 Fig Damage > 30mm wideBrush apply a primer coat of epoxy. Install filled epoxy. Inset expansion strip making sure bot-tom extends below epoxy and it is verticalFig 6. Typical FailureFig 7. Saw CutSaw cut past the edge of breakage to a depth of 25mmFig 8. PreparationClean out debris, flow mm80 liquid into any 9. Install mm80 Width (mm) Depth (mm) Filler (%) <30 25 250 >30 refer to Fig SPALLED JOINTS/ Crack KEYWAY JOINTSFig 10. Filler separationMM80 is installed long before a slab has ompleted its shrinkage. Where mm80 separates adhesively but is still firmly in place, voids can be filled with Crack FillBETTER SOLUTIONS FOR CONCRETE FLOORSMM80 - Crack & Joint RepairFig 11.

4 Typical FailureSPALLS WITH PREMOULDED FILLERFig 12. Saw cut to 20-25 mm deepFig 13. Prepare the SurfaceRemove filler and concrete laitance to a depth of 25-30 mm. Form a barrier by applying tape or a thin layer of or sandFig 14. Install mm80 Width (mm) Depth (mm) Filler (%) <30 25 250 >30 25 500 CRACKS & DETERIORATED JOINTS IN YOURCONCRETE FLOORDo you remember when you first moved into your warehouse or distribution centre? The joints were sharp and narrow, and you had only a few isolated , random cracks. Now as you walk through the facility you see that all the Joint edges are severely crumbled and random cracks are everywhere. What happened? How did your great new floor turn into a nightmare that causes materials handling vehicles to slow down and wheels to deteriorate?

5 This article will help you understand concrete floors in general, and more specifically, why floors Crack and joints deteriorate. To do justice to the subject would fill a book, so I ll focus on just the most common problems we see in our company. Hopefully the condensed information contained here will help you avoid the same problems on future floors and offer some solutions to make your present floor deterioration causes generally fall into one or more of the following categories: Deficiency in design Deficiency in construction Owner (or tenant) abuse or article will focus on design and construction deficiencies since they are by far the most prevalent cause of deteriorated floors. A high quality floor can tolerate some owner neglect, but even top notch maintenance can not overcome built in PRIMER ON CONCRETEC oncrete is basically a combination of Portland Cement, large aggregate (rocks), fine aggregate (sand), and water.

6 Sometimes additives may be used to accomplish certain objectives such as workability, etc. For concrete to prove durable, all components must be in a proper balance. Too much or too little of any component can cause problems later. For example, let s look at the water serves to react (hydrate) the cement, make the mix homogeneous and make the concrete workable and placeable. But too much water can result in excessive shrinkage and weakened a Crack has no islands , no edge chipping and is less than a credit card thickness it should not be saw cut open. Brush apply a protective coating of liquid wider than credit card thicknesses apply a bead of Crack Fill and allow to seep into the Crack . Reapply until no further penetration. Allow to cure. Razor cut of SPALLSMake cuts a minimum of 12mm deep at edges.

7 Remove concrete within cut area to at least 12mm depth. Remove all dust and loose concrete. Mix and brush in liquid mm80 as a primer coat. Add 500% silica sand to mm80 liquid to make a mortar and apply. Trowel smooth or broom finish during epoxy cure for non-skid TO PLASTIC JOINTSS palls often occur where plastic zip strips are used as control joints. Saw cut both sides of the T Joint along edge of spall to a depth of 12-20mm. Remove concrete rubble and zip strip. Overfill resulting Joint with mm80 and grind flush. If Joint width exceeds 12mm, mix mm80 with 250% silica sand to form a data mm80 10 All concrete mixes contain more water than is actually needed to hydrate the cement. The excess water eventually evaporates. One primary objective is to retain the water until the cement is fully hydrated, then let it evaporate slowly over a prolonged period of time.

8 This moisture retention process is called curing the concrete loses moisture it shrinks in dimension, usually at the rate of 3mm in every 6m of slab. If concrete were left as it is placed, it would Crack in random Crack patterns. To avoid random cracking we create joints at regularly spaced intervals, thus weakening the slab in a grid pattern. These joints, called control (or contraction) joints force the cracking to occur in straight lines beneath the Joint , so actually producing a designed slabs shrink at a relatively slow rate because all the moisture must evaporate through the top of the slab. A reasonable shrinkage rate estimate is: 30% in the first 30 days50-60% in the next 335 days80-90% in the first yearIn other words, the slab is still shrinking long after you have taken occupancy.

9 Thus joints will continue to open up and new random cracks may occur at any point in the first year or we create the control joints we caused interruptions in what would otherwise ideally be a continuous surface. To restore the floor s surface continuity for the purpose of material handling vehicle flow, we must refill the joints. The filler must accommodate two conflicting objectives: Be hard enough to support hard-wheeled traffic Allow the Joint to continue to open until the shrinkage process is completeSO WHAT WENT WRONG WITH YOUR FLOOR?In the design and construction process there are literally hundreds of mistakes that can be made. The following are the most common that we causes of Random CrackingShallow JointsThe joints were not cut deep enough to induce the Crack , leaving the slab to Crack randomly.

10 Slab ThicknessIf the slab thickness varies, the slab contraction will encounter restraint, causing the slab to SpacingJoints were spaced too far apart and the concrete cracked between the joints rather than at the JointingThe shrinkage stresses in the slab exceeded the strength of the concrete before the joints were BaseThe base under the slab must be smooth and evenly, densely compacted. Uneven bases create restraint, causing the slab to Causes Of Cracking Concrete mix too weak (too much water etc) Additives may cause excessive curl Slab was subjected to wind or sun, causing rapid drying and early stresses Steel reinforcing was improperly positioned Floor was designed for light loads, but operations imposed are heavy loads Slab was not properly cured to prolong water retention Base was not adequately compacted, especially common near foundation walls, docks, RR RestraintIf the dowels at construction joints are misaligned, or if rebar is used instead of smooth, greased dowels, the joints will be restrained and random cracks will occur, usually parallel to the LoadsIn tilt-up construction the crane s outrigger may rest on a panel corner and break it EdgesAll concrete curls upward at the end of the pours.