Category Archives: concrete mender

concrete mender, Concrete Repair

All about Roadware 10 Minute Concrete Mender

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At Roadware, we encounter many two-component polymer concrete repair products that claim to be similar to Concrete Mender™. One product even refers to itself as “Quick Mender.” However, these products are primarily polyurea-based and are often too thick to effectively penetrate concrete surfaces. Additionally, they are highly reactive, becoming sticky and gooey just one or two minutes after mixing, making them difficult to trowel. When you examine the details, you will notice a significant difference between these alternatives and the genuine Roadware 10 Minute Concrete Mender™.

  • What is Concrete Mender? Proprietary Polyurethane Blend
  • Formulation: Classified
  • Manufacturing: South Saint Paul, Minnesota, USA
  • Origin: NATO program for rapid bomb damage repair on runways.
  • Function: To penetrate deep into concrete cracks, joints, and spalls, creating a structural repair in 10 minutes.
  • Military Use: Classified
  • Civilian Use: Repair cracks, joints, and spalls in commercial, industrial, and civil applications.
  • Service Life: Indefinite
  • Cure Time: 10 Minutes at 70°F (21°C)
  • Distribution: Worldwide Distributor Network

Surface Tension:

Surface tension measures a liquid’s ability to overcome its internal friction and penetrate materials such as concrete. Roadware 10 Minute Concrete Mender™ has a surface tension that is one-third that of water, allowing it to enter concrete cracks and fissures more quickly and deeply than water. This low surface tension enables Concrete Mender™ to infiltrate standard bond lines and promotes structural bonding with the concrete’s aggregate. For more details, please refer to the electron microscope slide below.

 
 

Low surface tension offers another hidden benefit: it enables Roadware 10 Minute Concrete Mender™ to be mixed with more than two parts sand while still remaining workable and easy to trowel. In contrast, if you try that with a polyurea, you’ll end up with a gooey mess.

Roadware 10 Minute Concrete Mender can be bucket mixed and applied like or mortar.
 
Roadware Microdoweling™ Technology:
 
The slab-to-slab micro-doweling action provided by Roadware 10 Minute Concrete Mender effectively links concrete slabs together, securing them in place while allowing for full traffic and dynamic load transfer within just 10 minutes. This micro-doweling action is more compatible with concrete and less reactive in harsh environments compared to poly-coated rebar. Millions of micro-dowels penetrate the slabs, bridging and bonding broken and jointed surfaces side by side. This remarkable technology is suitable for addressing hairline cracks, wide trench cracks, irregular cracks, cured control joints, and variable depth spalls.
 
Scanning electron microscope image of the interface between Concrete Mender™ and concrete.
 
In just 10 minutes at 70°F (21°C), this micro-doweled bond achieves compressive and shear strengths equivalent to those of poured and fully cured concrete. As a result, bond-line failures are now a thing of the past. Furthermore, parallel re-cracking, which is often seen when epoxies cure, is eliminated thanks to Roadware’s micro-doweling technology.
 

Structural Polyurethane

Roadware 10 Minute Concrete Mender™ is a polyurethane-based material designed to restore the structural integrity and aggregate interlock of distressed concrete. Its low surface tension and low viscosity allow it to penetrate concrete surfaces effectively. The product utilizes cross-linking polymer chains to bond directly to the concrete-aggregate matrix. This bonding action harnesses capillary forces to self-inject polymer chains into the surrounding concrete.

The material is engineered to have a modulus of elasticity that is lower than that of the surrounding concrete, ensuring it does not become brittle over time. Additionally, it can be mixed with manufactured sand to create a polymer concrete that is compatible with Portland Cement Concrete (PCC), enabling effective structural repairs for concrete cracks and spalls.

Advantages– One of the key benefits of this material is its very low surface tension and viscosity, which allows for effective saturation bonding of cracks without significant effort. This characteristic enables the repair process to be straightforward, requiring only minimal preparation, such as removing loose debris from the area before application.

Once applied, if the material is allowed to flow freely to the full depth of the crack, the repair can be classified as structural. To enhance the durability of the repair and prevent issues such as water pooling underneath the slab, it may be advantageous to incorporate manufactured sand or quartz into the mixture. This addition helps to optimize material usage and improve overall stability.

For cracks measuring greater than 0.125 inches in depth, it is recommended to mix the polyurethane with sand at a ratio of two parts sand to one part polyurethane. This not only extends the volume of the repair material but also significantly increases its strength. The inclusion of sand provides the added benefit of aligning the thermal coefficient of expansion of the repair material more closely with that of the surrounding concrete, thereby minimizing the risk of future cracking due to temperature fluctuations.

Another notable advantage of these polyurethanes is their versatility in application temperatures. They can be effectively applied in a wide range of substrate temperatures, making them particularly useful for repairs in freezing conditions and cold storage environments. These materials can even be applied in extremely low temperatures, as low as -20°F (-23°C), ensuring that repairs can be conducted year-round, regardless of weather conditions.

Finally, one of the practical benefits of this repair material is its quick curing time. Typically, repairs will be fully ready to accommodate traffic in approximately 10 minutes when applied at a temperature of 72°F (22°C). This rapid turnaround time minimizes downtime and allows for efficient maintenance of surfaces in both commercial and industrial settings.

 

Toughness:

Roadware 10 Minute Concrete Mender™ mixed with sand gets about as hard as concrete, yet it’s modulus of elasticity is slightly less than concrete so it will move with the slab, not work against it.

 
 
Common uses for 10 Minute Concrete Mender™
 
Spalled control joints and cracks.
 
 
 
Spalls and holes.
 
 
Delamination Repair
Uneven slabs and thresholds.
 
 
Crack Injection using gravity:
 
Typical crack injection repair techniques involve epoxy, ports, pumps, and pressure to force thick epoxies into a crack.  Roadware 10 Minute Concrete Mender™ with its low surface tension can do same job in less time, less mess, and better performance.
 
 
 

Easy Floor Crack Injection using cartridges:

Roadware 10 Minute Concrete Mender can be injected into a wide range cracks and delaminations using a simple cartridge and special Soft-tip injection mixers.  Successful full-depth repairs have been made in 24″ of concrete.

Concrete Mender crack injection into 24 inches of concrete.
Slowly injecting Roadware 10 Minute Concrete Mender into 24″ of concrete using 600ml cartridge and soft-tip injection mixers.

Diagram showing Concrete Mender Soft-tip mixer injection into a concrete slab.

The core sample shows full depth repair down 24 inches.
The core sample shows full depth repair down 24 inches.
Hairline cracks repaired using Roadware 10 Minute Concrete Mender and Easy Injection application.

Vertical Crack injection

For fast and easy vertical crack injection on walls and structures, we recommend the Gebbie Tech System 

THE GEBBIE TECH SYSTEM TRANSFORMS VERTICAL CONCRETE WALL REPAIR

  • Comprehensive testing by Opus International Consultants – repairs have consistently achieved results higher than the manufactured panel.
  • Full training in the system – a step by step training video and instructional booklet is included within each kit.
  • Save time and money! Conventional repair methods with epoxy have longer repair times, additional downtime and are more expensive.
  • Use a hand gun – no need for expensive pumps! The Gebbie Tech System uses the cost effective Roadware 10-Minute Concrete Mender™ hand gun to repair walls.
  • Complete penetration. Due to the composition of the Roadware 10-Minute Concrete Mender™ the resin travels easily from the injection point.
  • The approved vertical wall repair system. The Gebbie Tech System is listed in Roadware’s 10 Minute Mender Concrete Data Sheet as the approved method of vertical concrete wall repair.
  • Repairs cracks from a hairline through to quarter inch. Walls are repaired within 2 – 12 hours depending on the temperature, and the length of the cracks.

Polishable:

Polishing your floor to a mirror like finish? Repairs made with Roadware 10 Minute Concrete Mender™ will not smear into the surrounding surface or gum-up diamond polishing pads.  You can even add natural sand to match the grain and color of the surrounding concrete.

 
Polished concrete repair with Concrete Mender™ Off-white.
 
The repair pictured above shows  Roadware Concrete Mender™ Off-white blended with plain concrete sand and a small amount of portland cement. This water-thin polyurethane is almost translucent. When we add nearly any type of dry sand or aggregate, we get a fast-curing polishable repair that blends beautifully with the surrounding concrete. Since this material is almost translucent, it resists shadowing effects due to over-banding when applied.
 
 
 

Lower Cost:

By adding two parts silica or quartz sand to a gallon of Concrete Mender™ you will yield about 2.2 gallons of repair material.

 

A gallon of polyurea or epoxy will yield a gallon of repair material.  That makes polyurea more expensive to use even at half the material cost! This does not even factor in the hidden costs of short repair life, damage to the surrounding concrete caused by pre-mature failure, or the cost of redoing the repairs when they fail.

4030 Grit manufactured quartz sand is the standard sand used with Roadware 10 Minute Concrete Mender.
4030 Grit manufactured quartz sand is the standard sand used with Roadware 10 Minute Concrete Mender.

Packaging:

Roadware 10 Minute Concrete Mender™ hand packed with state-of-the-art packaging materials.  They have to be good. The very low viscosity and surface tension require it.

 
Bulk Application:
 
Due to the the extended working time formula, bulk mixing of Concrete Mender™ is easy.  Unlike polyureas that start to gel up instantly, Concrete Mender will remain workable and flowable for several minutes before curing begins.  Much less wasted product setting up in buckets.
 
Roadware 10 Minute Concrete Mender can be easily mixed in a bucket with sand or used neat. No pumps of special equipment needed.
 
 
Pin-point Application:
 
With a Roadware needle tip mixer, you can apply Concrete Mender™ within-point accuracy delivering product to where it is needed most. Our needles come as small as 1.2mm in diameter.  If you can get a finger nail in the crack, we can get some Concrete Mender in there as well.
 
 
Use Roadware needle tip injection to repair hairline cracks in concrete floors.
 
 
 
 

Freezers:

Working in the cold?  We’re from Minnesota. We know first hand what it takes to work in freezing temperatures. Roadware 10 Minute Concrete Mender™ can be applied at temperatures below -30 F ( -34C).  That is really cold.  Exposed flesh will freeze in seconds.  That is almost too cold to go ice fishing. Most repair products would freeze solid before curing and quickly fail.  Roadware 10 Minute Concrete Mender™ generates its own heat. Curing will take several hours, but you will still get the same great performance.

Colors:
 
Roadware Concrete Mender™ comes in two standard colors.  Concrete Grey and natural off-white. Since a typical repair is made up of two parts sand to one part liquid, the color of the sand will determine the color of the finished repair.  By adding colored quartz sand to off-white Concrete Mender, you can make custom colors as needed.
 
Use Concrete Mender Off-white to make your own colored repair by adding different colored sand at the time of application.
Use Concrete Mender Off-white to make your own colored repair by adding different colored sand at the time of application.
 
 
Specialty Applications:
 
We also custom make Concrete Mender in Safety Yellow, Red, Blue, and Black.  Use Concrete Mender Yellow to create permanent safety lines and marks in difficult areas like cooler and freezer floors.
 
 
 
Safety:
 
Roadware 10 Minute Concrete Mender™ is completely self-reacting and does not out-gas solvents or VOC’s when curing.  This material meets FSIS guidelines for work is federally inspected meat and poultry plants.
 

History:

For over twenty years, Roadware 10 Minute Concrete Mender™ has performed without fail in thousands of applications. Many times outliving the facility itself.

Supervalue warehouse cold storage floor
repairs with Concrete Mender™.
Concrete Mender repair in a cold storage warehouse after 15 years of heavy forklift traffic.

Utilizing technology developed to repair bomb damaged runways for NATO, Roadware 10 Minute Concrete Mender™ was reformulated and brought to commercial markets in the early 1990’s.  You can find us in nearly every industry that has concrete floors, decks, slabs or surfaces.

Links:
Roadware 10 Minute Concrete Mender™

Availability:

Roadware 10 Minute Concrete Mender is made in the USA and is available from Roadware authorized distributors and dealers worldwide. Call 1-800-522-7623 or 1-651-457-6122 to find a dealer near you.

Specifications:

Concrete Mender™ Data Sheet

concrete mender, MatchCrete

Repair polished concrete with Concrete Mender™

1 Comment
Stop repairing polished concrete with polyurea joint fillers. They look like plastic, do not bond well, and do not hold-up over time. Concrete polishing lets the natural beauty of stones, sand, and rock shine through.  Your repair product should as well.

cbec1b48d1534cf9a2862736e4d80d23

We took the proven Microdoweling™ properties of Roadware 10 Minute Concrete Mender™ and combined it with natural sands, aggregates and pigments to make repairs that not only look great, but perform better than epoxies and polyureas.

polished-repair450

The repair pictured above shows  Roadware Concrete Mender™ Off-white blended with plain concrete sand and a small amount of portland cement. This water-thin polyurethane is almost translucent. When we add nearly any type of dry sand or aggregate, we get a fast-curing polishable repair that blends beautifully with the surrounding concrete. Since this material is almost translucent, it resists shadowing effects due to over-banding when applied.

concrete mender

Uncontrolled Epoxy Injection

Question: How do you epoxy inject cracks in floor slabs on grade when you do not have access to the bottom of the slab? What keeps the product from running out the bottom and all over the place?Answer: We make these type of repairs all the time. The first thing to do is dump the epoxy.  It is too thick, too brittle, and takes too long to set.  Fast setting materials like 10 Minute Concrete Mender allow you to control set points deep in the crack and prevent material seepage.Roadware 10 Minute Concrete Mender™ has an ultra low viscosity of 8cps and will gravity inject into the smallest of cracks. We make the repair in stages adding fine silica sand into the crack as necessary to prevent the material from running out the bottom. The product can be injected with needle tip mixers as small as 18 gauge. With careful technique and experience you can make structural repair that will restore aggregate interlock and restore the slab.

Start out by adding a small amount Concrete Mender to the prepared crack and noting where material in running beyond the slab.  Add a light dusting of silica sand or fine quartz to the crack and some more Concrete Mender. The Concrete Mender will combined with the particles of sand to form a quick setting, “mud” at the bottom of the crack. Repeat as necessary and repair the full depth of the slab.

This will be a structural repair with no ports, no pumps, and almost no down time.

Roadware 10 Minute Concrete Mender™ needle tip application.

 

concrete mender, Concrete Repair

Extreme Concrete Repair and Polish

How do polish a floor when your concrete is like this?

Deep cracks and surface spalling can make polishing jobs costly and difficult.  A lot of the top surface has to be removed to get to a smooth finish.

Roadware 10 Minute Concrete Mender™ is a great choice for filling out all the cracks, spalls and holes before polishing.

 
This floor was repaired by troweling down a thin layer of Concrete Mender and sand, then ground smooth. A liquid hardener completed the restoration and the floor was polished.

 

The floor shows zero failure shown here 3 years later in 2007.  The floor continues to perform today.

 

concrete mender, Concrete Repair

Vertical Wall Repair at Club Warehouse Store

Use Roadware 10 Minute Concrete Mender™ and sand to repair damaged concrete block walls in an hour or less. Sent in by Dave Wilson at Myspec Integrated Concrete Repair Group in Georgia.  770-335-9123 Roadware 10 Minute Concrete Mender™ is great for repairing cracks and spalls in floors. This ultra-low 8cps viscosity material gravity flows deep into concrete and makes repairs from the bottom up.  To repair a holes in a block wall, mix the Concrete Mender™ with fine silica sand to make a trowel-able mortar.

 
 Step 1: Prepare the area and remove any loose block, paint or dirt.

Step 2: Mask off the area like shown. In a clean bucket, mix one part AB blended Concrete Mender with 3 parts sand to make a stiff mortar and trowel into the repair area. You may want to tape a plastic sheet over the repair area to hold the Concrete Mender mixture in place while it cures for 10 minutes. See bulk mixing instructions here.

Step 3: After approximately 10 minutes depending on the ambient temperature, pull the masking and blend in the repair with a rubbing brick.

Step 4: Roadware 10 Minute Concrete Mender™ can be painted as soon as it cures.  Paint the repair area to match the surrounding wall.

With Roadware 10 Minute Concrete Mender™ you can do a job in less than an hour that used to take two days. No more waiting for hours or days while traditional cement based materials to set and cure.

concrete mender

Roadware Contraction Joint Repair

Why are my contraction joints spalling and what can I do to stop it?

Contraction joints (or control
joints) are joints cut into a slab shortly after pouring. The purpose of these joints is to control the cracking of the slab as it cures. Most concrete slabs shrink and sometimes curl for the first 12 months after pouring. Contraction joints allow the
slab to crack at pre-determined intervals instead of natural random cracking. Joint filler is used to protect the joints from spalling and chipping caused by traffic on the slab.
 control-joint-filler-original

As the slab cures for the first
12 months, it shrinks in size and may even curl up at the joints. The contraction joints will expand as the slab shrinks. This causes the joint filler to split apart or dis-bond from the sides of the joint leaving them exposed to traffic.

control-joint-filler-curled
When loads are rolled over the
joint. The force of the load has to transfer from the wheel, to the concrete, and to the base. If the slab is even slightly curled and the joint is expanded, the force of the load will impact on the joint causing cracking and spalling. You may even get stress cracking parallel to the joint. You can sometimes feel the uneven load transfer across the joint if you stand with one foot on either side of the joint and have someone else roll a heavy load across the joint.
control-joint-filler-curled-dynamic-load
Eventually, you get a spalled contraction joint. The joint filler has completely failed or is missing. Wheels go “thunk, thunk” every time they go over the joint. Productivity suffers, and the joint fills with dust and debris.
 control-joint-filler-curled-spalled
A popular and effective way to repair spalled contraction joints is to lock them back up with Roadware 10 Minute Concrete Mender™. Once the slab is 12 months old, the shrinkage and curling has finished. There is no longer a need for contraction joints. Now you can use Concrete Mender™ and silica sand to bond the slab back together from the base all the way up to
the top. This will stabilize the slab, restore aggregate interlock,
and allow for complete and even load transfer from the wheels all the way down to the base. Your contraction joint problems are solved.
control-joint-filler-curled-spalled-repaired
NOTES: Locking up contraction joints
is recommended for interior controlled environment applications with sound concrete and base. Exterior applications may have different results. Always test a small section
of large repair for compatibility.
 See how this repair was made by clicking here.
Diagram of a spalled contraction joint repair using 10 Minute Concrete Mender headers.
concrete mender, Concrete Repair

Buy a gallon and make two. Good deal!

One gallon of Concrete Mender™ goes a long way.

 

Yield of Concrete Mender verses epoxy and pylurea.

 

One gallon of Concrete Mender™ will make 2.2 gallons of repair material when typically applied with 2 parts sand. That makes Concrete Mender™ a better value then most epoxies and polyureas. No other product we know of goes as far and performs as well.  Any way you look at it, Concrete Mender™ is a better value even it it was twice the price.

 

concrete mender

Freezer threshold repair with Roadware 10 Minute Concrete Mender™.

Freezer, chiller and cooler thresholds have been an ongoing challenge to floor repair contractors and the USDA since the 1950’s. Recognizing the need to keep refrigerated and frozen food storage areas clean and sealed so they will not harbor lichen, fungus and pests, the USDA has issued zero tolerance guidelines for floor cracks and spalls in all food processing and refrigerated food lockers. Unsealed and opened joints also come under the watchful eye of those charged with keeping America’s food supply safe. Because thresholds are freezing cold on one side and at room temperature on the other, the thermal stress on the concrete is unrelenting and unforgiving. Couple this with forklift and wheeled cart traffic and you have a formula for disaster.

 

Fortunately, 10 Minute Concrete Mender™ has become the accepted repair material for these very harsh conditions. The agency itself is forbidden from recommending one product over another, but the personal choice among active USDA inspectors is Roadware 10 Minute Concrete Mender™. It’s thin, it gets in, it won’t pop out.

Some minimal prep work is required when working in the cold. Have the cracks and spalls as clean and dry as possible. This may not be easy, but it’s a step professionals know better than to ignore. Next, apply Mender to the base and sidewalls to seal off any free moisture movement into the repair area. Immediately follow by filling the spalled area or crack, almost to the top, with manufactured sand or approved quartz. Flood the sand to refusal, making sure the Mender saturates each grain. For larger areas, a bulk mixed mortar of Mender and sand may be easier to handle and install. Keep all materials at room temperature or warmer to speed up cure time. Even then, one should plan on an hour or more if temperatures are extreme. However, since all conditions vary, onsite testing is the best way to insure the time at which freezer floors and thresholds will be traffic-ready. Contractor field reports are very solid in reporting that 10 Minute Concrete Mender is the only thing that works in these tough repair situations. Click here for step by step bulk application instructions.

 

1. Remove existing concrete to wood base.

2. Saw key-way at a 45° downward angle on the cold side of the

threshold toward the freezer.

3. Using a diamond shaped pattern, drive sheet rock screws into

the base leaving 3/8″ of the screw sticking up, to act as a

dowel pin for the finishing lift of 10 Minute Concrete

Mender and sand aggregate.

4. Place 10 Minute Concrete Mender to grade. When fully cured

(about an hour at 32F, 0C) sawcut the warm side joint and fill

with Roadware Flexible Cement II™.

5. Reopen to traffic when Flexible Cement II is fully cured.

Continue reading Freezer threshold repair with Roadware 10 Minute Concrete Mender™. →

concrete mender

New Roadware Estimator App

UPDATE: The new online Roadware product estimator runs on most browsers and mobile devices including iOs and Android. Click here for the Roadware Online Product Estimator.

Announcing the Roadware Product Estimator App for iOS devices.

 

Users of iOS devices such as the iPhone or the iPad now have a convenient way to estimate the amount of Roadware 10 Minute Concrete Mender™ needed to repair a concrete crack, joint or spall.  Since Concrete Mender may be extended with sand at a ratio of two parts sand to one part liquid, estimating product usage is more challenging. The Roadware App eliminates the guesswork and gives users an estimated usage in 600ml cartridges and gallons of material. Sand ratios can be adjusted from none, 2:1 and 3:1 for special applications. An internet connection is not necessary when using the App so you can make an estimate from anywhere.

The Roadware App can be downloaded for free at the iTunes store by searching for Roadware or by clicking here.

 


Enter the crack dimensions in English feet and inches or metric meters and millimeters.

Set sand ratio. Default is two parts sand two one part mixed Concrete Mender.

Click the Calculate button at the top.

 

The resulting screen shows:

Total cubic centimeters need to fill the repair area.

Total gallons of mixed repair material needed.

Number of 600ml cartridges of Concrete Mender needed.

Number of gallons of Concrete Mender needed.

 

concrete mender, Concrete Repair

Roadware 10 Minute Concrete Mender™ Best Practices

 

ROADWARE 10 MINUTE CONCRETE MENDER™

Buildings marked for demolition in Christchurch, New Zealand.
Recently, our Roadware distributor in New Zealand requested a list of best practices for using Roadware 10 Minute Concrete Mender™.  Contractors in Christchurch are using Concrete Mender to repair many meters of cracks following recent earthquakes.   
Best
Practices
Storage
and Transportation
1.
Keep cartridges in original foil bag and store in
an upright position.
2.
Store on a cool dry place between 10-28 degrees
C (50 – 80 F). If cartridges are allowed to freeze below – 10 C (14 F) some material separation
can occur.  Return material to 25 C (75 F)
and shake or mix to re-blend before use.
3.
Handle with care. Punctures to the bag can cause
moisture contamination. Rough handling can cause cartridge cracking and
leakage.
4.
Ship in upright orientation in original shipping
containers.
Usage
1.
Read and follow illustrated instructions.
2.
Use gloves and safety glasses.  Concrete Mender is very thin and can
splash back if applied erratically.
3.
Make sure the flow-restrictor and mixer seat
properly.
4.
Use a new flow-restrictor and mixer every time.
5.
Small cracks less than 2mm should be cut open to
5mm for best results.  The 5mm cut
will form a, “well” for the product to accumulate as it soaks down into the
crack and will reduce material spreading on the surface away from the repair
area.
6.
Once material is flowing from the mixer, keep the
tip pointed down.  Use the thumb
release on the gun to stop the flow.
7.
Discharge the material from the cartridge
firmly.  Working too slowly can
cause poor mixing.
8.
Always apply a coating of Concrete Mender into the crack or spall before adding sand. This will give you better penetration and bonding.
9.
When applying with sand, make sure the sand and
repair area are completely saturated with Concrete Mender.
10.  Use a shop vacuum or compressed air to remove as much dust and contaminates from the
repair area.
11.  If you suspect there is water on the bottom of the crack that you cannot remove, repair the bottom half first and allow it to cure (turn grey) before repairing the top half.
12.  When working at below 0 degrees C, use a propane torch or similar method to remove any surface frost from the concrete before applying the material. Keep Concrete Mender and sand at room temperature before use.

13.  Needle tip mixers are great for better control and pinpoint application. They also can easily clog up when left filled with mixed product. Do not try and force a mixer or tip to clear by adding more force to the gun. You can blow out the rear seals and cause a mess.  Get a new mixer or tip and start over.

Concrete Mender™ is injected into cracked walls in Christchurch, New Zealand.