11 minute read
Product Focus
TOOLS & LIGHT EQUIPMENT
Makinex Lift Assist
The Makinex Lift Assist is a simple, easy to install attachment for 60-90-lb. pneumatic hammers. The ergonomically designed Lift Assist reduces operator stress and fatigue, resulting in higher productivity. • Pushes and lifts 350 lbs. of force—not only lifting the weight of the hammer, but also releasing the buried chisel from the ground and allowing each of the 1,200+ blows to have a smooth exit and transition to continue the cut or demo. • Its "foot" extends out of the bottom to lift up the tool and enable easy repositioning of the bit before breaking material again • Designed to reduce operator stress and fatigue, improve efficiency and productivity, and reduce risk of jackhammerrelated back injuries • Weighs just 9 lbs., is quick and easy to assemble to any 90-lb. pneumatic jackhammer, and shares the tool's existing air supply
ForConstructionPros.com/21497132
Valtec's VP614 OmniPoly Poly Trowel Blade
Designed to control dark burnish marks on new concrete floor installation, Valtec Group LLC's VP614 OmniPoly Poly Trowel Blades (patent-pending) are now available in a 6 by 14-in. size for 36-in. rotors for walk-behind and ride-on power trowels. • A rigid main body for producing a hard and uniform finish • Its flush bottom surface eliminates voids that collect fines that could later cause scratches • Made from non-rusting materials make it easy to clean, handle, and store • The long-lasting abrasion-resistant material reduces blade changes • Operator friendly and low noise for highperformance use • Cost per SF is better than steel making it valuable as an everyday blade
ForConstructionPros.com/21521215
The Steele Mixer by SteeleHouse Industries
The Steele Mixer by Steele House Industries is manually-powered, weighs 34 lbs., and can mix a 60-lb bag of concrete ready-to-pour in less than 45 seconds. Water and dry materials are poured into the pivoting mixing drum. Rocking the drum from side to side via the wooden handles incorporates the materials thoroughly and can produce ready-to-pour concrete faster than an electric mixer. It can make a wide variety of cement-based concretes and mortars including ordinary concrete, masonry mortar, stucco, deck mud, fat mud, self-leveling underlayment, and other water-mixed materials, up to a 90-lb bag of premixed dry material at a time.
Due to the drum’s design, mixing performance is thorough and highly efficient, so it can produce structurally sound concrete using the specified quantity of water. It also eliminates the temptation to add extra water, protecting the final strength of the concrete. In third-party testing, a commercial premixed bag of concrete produced in the Steele Mixer exceeded the specified 4,000 psi compressive strength in less than 28 days.
The Steele Mixer, built from wood, steel, and 100% recycled low-density polyethylene (LDPE) is light enough to be used in remote locations that remain inaccessible for electric mixers. It can be picked up and carried, full of concrete, and taken to the pour, and is also compact enough to operate inside a small residential bathroom. Its size, portability, and affordability make it an ideal tool for general contractors, plasterers, tilesetters, masonry, landscapers, fencing contractors, farmers, ranchers, and DIY homeowners.
Steele House partnered with Habitat for Humanity, donating one mixer for every 100 units sold.
ForConstructionPros.com/21821425
The PowerLite HN120 concrete/steel pinner can shoot one pin per second unlike P.A.T.’s which require operators to either load a single pin and powder load one at a time to fire each shot or load a maximum of 10 pins along with powder loads. Traveling back and forth between your work area and the place where you keep the pins and powder reduces productivity. The difference in reloading time when using PowerLite tools saves operators time and time is money. • Magazine holds 50 pins and shoots pins from 1 to 2 1/2 in. long • Attachment parts available for wood to concrete, drywall to concrete, and wood to steel applications • Eliminates the need for gas or powder • Durable metal housing
ForConstructionPros.com/10083928
Simpson Strong Tie's RCA-C Rigid Connector Angle
Simpson Strong-Tie's RCA-C rigid connector angle is an ideal solution for attaching cold-formed steel (CFS) stud framing to concrete supports. • 2 by 2-in. legs for plenty of room to make attachments to structure and stud framing • Multiple screw pattern options for different load rating options on stud framing • Prepunched holes for attachment of screws to stud framing and concrete • A range of load applications—the connector can be used either to form a heavy-duty shear and tension connector or to form a light-duty moment connection
Designed to save installers time and reduce the cost of drilling connector holes at the jobsite, the RCA-C provides the most anchor options available, including holes for a 1/2-in. diameter anchor screw or bolt, or for two 1/4-in. diameter concrete screws positioned to allow a variety of fastening options.
ForConstructionPros.com/21952818
The History of the Internal Concrete Vibrator & The Rise of the Controlled Frequency Design
Industry studies have highlighted separation issues, vibration energy, surface defects and mix incompatibilities — leading to the development of a more predictive concrete placement experience.
Adobe Stock Images | By Branko Over the last 60 years, concrete vibrators have evolved into a necessary machine for concrete jobs. Industry studies have highlighted separation issues, vibration energy, surface defects, and mix incompatibilities— leading to the development of a more predictive concrete placement experience.
Concrete vibration dates to the late 1960s when Thomas Reading, an engineer from the U.S. Army Corps of Engineers, set vibration placement recommendations through vibration tests. At the time, the normal slump of structural concrete was three to four inches, had a “peanut butter” like consistency, and placed in forms by a concrete bucket.
Reading used a larger horsepower motor to maintain a maximum vibrator speed that ran the vibrator heads for the current consistency of mixes. Reading concluded that the vibrator frequency should never exceed 10,000 vibrations per minute (vpm) due to his observation of concrete material separation. At that time, the American Concrete Institute (ACI) 309 Consolidation Guidance Specification reflected Reading’s research and limited the vibrator frequency to that maximum frequency.
Ten years later, mix designs were being transformed by a water-reducing agent (WRA) to allow for a more workable concrete mix for the future of economical concrete placements by pumping instead of concrete buckets. By the end of the next several decades, the volume of pumped commercial concrete reached 80%. The increased use and type of WRAs (plasticizers) allows for more possibilities of bleeding.
With the increased bleeding in pumpable mixes, present concrete mix designs started to take on a "soup-like" consistency. While the vibrator design remained the same, manufacturers began to increase the amount of vibrator frequency. As a result of this vibrator design frequency disconnect, surface defects began appearing on the form face of freshly poured concrete surfaces. These surface voids were mistaken for entrapped air and even more vibration energy was added by contractors to try to alleviate the problem.
Through today’s research, we’ve come to understand that surface blemishes come from vibrationfrequency-forced bleed water.
The available water is a product of the WRA-induced hydration delay that makes pumping easier. In these WRA mixtures, the higher the vibrator frequency, the more water is moved to the form faces.
THEN, EVERYTHING STARTED TO CHANGE
In the late 1980s, the Federal Highway Administration (FHWA) and pavement industry representatives evaluated the long-life road design that was constructed in Europe. From the implementation of European road designs in the U.S., the pavement vibration approach had to be changed to meet new pavement mixes. By developing a controlled frequency vibration (CFV) system in coordination with an FHWA study, many vibrator design specifications were changed along with the product: the vibrator offcenter weights were increased; vibrator frequency was limited to 4,000 to 8,000 vpm; and vibrator centers were lowered from 24 to 16 in.
The study used data that came from the vibration monitoring and control system to set pavement construction specifications to limit the material separations, which were causing surface bubbling and scaling, aggregate displacement, and uneven patches of surface texture. The developed standards are in use today by individual state department of transportations (DOT), airport construction, and several other infrastructure placement practices.
THE EFFECT ON VIBRATOR DESIGNS FROM CONCRETE MIX FORMULAS
Learnings from resolving concrete paving vibration issues have been applied to commercial-use concrete that has been over-vibrated since the mid-1980s. The lack of vibration industry controls, field research, standards, or innovative designs to deal with the rising level of over-vibration was becoming an issue with the increase of form face defects. These surface defects are originated from the available water movement caused by high vibrator frequency.
While FHWA studies were conducted for roads, commercial concrete studies were not funded to evaluate the origins of having to patch freshly poured concrete.
Even without a funding source, the concrete material separations of water, aggregates and micro air by vibration frequencies in commercial construction still needed to be addressed. The
industry vibrators that were used to vibrate concrete in the U.S. were brought in for evaluation as part of a study. An identical vibrator in horsepower, shaft size and head diameter was obtained from five leading manufacturers and evaluated. The study concluded that all evaluated vibrators ran higher frequencies than the original ACI specification, and all ran differently from manufacturer to manufacturer, meaning the vibrator user had a very little chance of solving vibration patching issues.
The chosen method of evaluating the issues with commercial concrete placement by vibration was to control the energy that came out of a vibrator, predict the effects of that energy, and evaluate the energy against a changing concrete variability in batching, transport, and placement.
A VIBRATOR ENERGY WORKABILITY CURVE
Pavement control technologies and field study procedures have been adopted and helped achieve empirical behaviors for today’s types of commercial concrete mixtures. From these pre-construction trials, vibrator frequency was lowered from the standard 13,000 to 17,000 vpm range to a compatible range of 6,000 to 10,500 vpm in field trials. This change reduced the phenomenon of driving available mix water of pumpable mixes to the surface of concrete forms.
These unwanted blemishes become visible on the form surface of freshly placed concrete and are routinely misidentified by vibrator operators as air voids from under-vibration when instead, they could be easily avoided.
Although most types of material separation can be traced to vibrator frequency, it is often difficult to understand concrete viscosity versus vibrator frequency compatibility. Now, simplified and easily digestible vibrator energy wave concepts are used in clinical analysis. These concepts will also be used in the future to help users understand the predictive behavior of both vibrator and concrete variability tendencies upon truck delivery.
The wave concept of a vibrator examines the two waves that propagate from the same vibrating head source. In vibrator wave behavior, the elevated pulsating pressure waves (p-waves) are better in the consolidation effort than the elevated shear waves (s-waves) that contribute to material separation.
Vibration research has used CFV to study forces at wave values and report performance back to the user. The load curve shows the resistance against the workability of the concrete being vibrated. A workability log can be studied to bridge the gap between predictive vibration energy versus changes due to inconsistent quality in batching, transporting and pumping. In understanding vibration wave energy behaviors, higher p-wave values can be applied for consolidation while limiting s-wave values to limit material separation.
With science-backed research, mapping the concrete vibrator’s behavior and the changes in the concrete workability curve can be understood and better managed. The adjustment to the vibration frequency or wave manipulation creates a more predictive consolidation result.
CONCRETE CONTROL TESTS
In the past two years, there has been a large increase in vibration research and funding for future investigations into the issues caused by vibrator frequency and mix incompatibilities. There are several field trials that are conducted annually to look at using the right amount of vibration energy at pre-construction trials to make the construction outcome more predictive. This is done when the contractor prepares several wooden boxes built into 24-in. cubes to test the concrete when pouring their mock-up forms prior to actual construction. The trial boxes are marked by the vibrator frequency that the contractor selects—normal trial frequencies are 10,500; 8,000; and 6,000 vpm. During the pre-construction delivery to the mock-up forms, the boxes are filled and analyzed the day after for evaluation of surface issues.
Researchers are working on quality control tests that can add more data for contractors on the mixture’s bleed tendency or slump variance from the original mix design. The work has helped develop an easy, accurate and repeatable workability meter to dial in on concrete variances and how they will affect concrete construction.
Using CFV and evaluating vibration curves as a source of controlling batching or transporting variances, contractors can receive help in understanding the data that’s being logged by the manufacturer. In collecting job electronic data, the CFV will report a curve that can be compared to the curve that is reported at pre-construction trials.
The variety of industry concrete vibrators all act differently against concrete loads, and to limit patching needs, vibration control and evaluation are the first steps in a predictive outcome. Vibration compatibility testing should be done in pre-construction trials and contractors should always get help from the manufacturer of the trial vibrator.
Concrete vibrators are a vital part of the workability system. Through years of research and trials, issues caused by over-vibration and concrete material separation are being addressed and limiting the potential patching costs once associated with the vibrator model designs from the 1960s.
Close-up of a poured wall with surface imperfections due to vibrators running too fast.
Minnich Manufacturing
Paul Jaworski is the products manager at Minnich.
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