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Concrete Casting News from the Hill and Griffith Company

Stop by Booth 1427 at the 2020 Precast Show in Ft. Worth thru Saturday

Posted by Hill and Griffith Company on Mar 6, 2020 11:38:40 AM

HG 2020 Precast ShowIMG_2592 560

Left to right: Bob Waterloo, Tom Dempsey, Mike Lawry, Angela Cox and Barry Morgan will help you with your precasting needs.

The Precast Show is the largest precast-specific trade show in North America and the one place where you can find the industry’s most important suppliers and foremost equipment experts under one roof. We are looking forward to seeing you March 5-7, 2020, in Fort Worth, Texas.

The Precast Show is sponsored by the National Precast Concrete Association and the Precast Prestressed Concrete Institute with additional collaboration from the Canadian Precast Prestressed Concrete Institute and the Cast Stone Institute.

HG Concrete ad

Grifcote® and Cast-O-Magic Concrete Form Release Agents

VOC Compliant, NSF Certified and Biodegradable Release Agents for all Concrete Applications

THE PERFECT RELEASE

Industry Leading Performance and Quality
Trained technicians are available to visit your site, determine your needs and design the right product for you.

• Gricote FR-50 & PR-5S voe - Workhorse Release
• Grifcote LV-50 Plus - NSF Certified for Potable Water - Release
• Grifcote Bio-Gold - Environmentally Friendly Release
• Grifcote CC-1S0 VOC - Premium Seasoning Agent
• Cast-O-Magic, Con-Solver and Liquid Chisel
• Corrosion Inhibitor for Steel Forms

https://precast.org/theprecastshow/


More News from the Precast Show


Hill and Griffith Customer Service

We're known for our hands on approach. Let us visit your plant and recommend concrete release agents, packerhead concrete form releases, concrete form seasoning, potable water concrete form release, non-petroleum concrete form release, biodegradable concrete form release, rust inhibitors and concrete dissolver products that suit your needs.

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We are pleased to provide samples in quantities large enough to allow you to "try before you buy."
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On-site casting defect investigations, product testing, machine start-ups and much more. Also, lab facilities are available to provide testing upon request.
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 Bulletins and Technical Papers for Concrete Casting Products

Tags: Concrete, Casting Solutions, Concrete Casting Products, Concrete Casting Supplies, Concrete Casting, Precast Concrete, Precast Show, Concrete Form Release Agent, National Precast Concrete Association

Producers' Guide: Form Release Agents

Posted by M.K. Hurd on Mar 5, 2020 8:00:00 AM

Excerpt from the February 2000 Concrete Construction Article by M.K. Hurd

Concrete form-release agents represent only a small fraction of the cost of a manufactured concrete item, but they have a big influence on the quality and success of the concrete surface.

Though no American Concrete Institute or ASTM standards define these products, common usage suggests that form release agents are materials containing proprietary reactive ingredients specifically formulated for use on concrete forms. ACI 301-96, “Standard Specification for Structural Concrete,” does, however, give performance-based requirements for release agents. Section 2.2.1.30 says to use “commercially manufactured form-release agents that will prevent formwork absorption of moisture, prevent bond with concrete, and not stain concrete surfaces.”

Concrete Form Release Application photo

Today, precasters can choose from among hundreds of form-release products, and new ones are still being developed. Many changes have been introduced as manufacturers scramble to meet federal and state environmental regulations, particularly with respect to volatile organic compounds (VOCs).

With the myriad form-release products available, how do you select the best one for a particular application? Here are a few of the fundamental questions you should ask:

  • On what form surfaces can it be used?
  • Will it provide clean, easy release without damage to either the concrete or the form?
  • Will it produce a stain- and blemish-free concrete surface?
  • Is it compatible with admixtures in the fresh concrete and with surface coatings that may be applied later to the hardened concrete?
  • Is it ready for use without site mixing, and is it appropriate for anticipated casting and curing temperatures?
  • Is it user-friendly and compliant with environmental regulations?

The table on pages 61-68 answers some of these questions and summarizes manufacturers’ recommendations for many currently available form release products. How release agents work Release agents are classified by how they work rather than what they contain. Two basic categories are barrier agents and chemically active agents (also referred to as reactive agents). Some release agents are a combination of the two types. Barrier-type release agents create a barrier between the form surface and the fresh concrete, preventing the concrete from sticking to the form

Read More

Hill and Griffith Customer Service

We're known for our hands on approach. Let us visit your plant and recommend concrete release agents, packerhead concrete form releases, concrete form seasoning, potable water concrete form release, non-petroleum concrete form release, biodegradable concrete form release, rust inhibitors and concrete dissolver products that suit your needs.

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 Bulletins and Technical Papers for Concrete Casting Products

Tags: Concrete, Casting Solutions, Concrete Casting Products, Concrete Casting Supplies, Concrete Casting, Precast Concrete, Concrete Form Release Agent, Concrete Construction Magazine

Composition of Concrete Release Agents

Posted by Jonathan Meier on Feb 28, 2020 2:14:18 PM

Content from Civil Engineering

The quality of the concrete finish is affected by many factors. These include the concrete mix design and  its constituents, the formwork, the compaction, the temperature and the curing process and also the mold or formwork release agent used. The influence of the release agent is described below and advice is given on how to select and use concrete release agents correctly.

Composition of Release Agents

Release agents can be formulated from up to three different types of ingredients.

  • Release Film Formers
  • Additives
  • Thinners

Spraying Concrete Release Agent

Release Film Formers

These include the base materials, which are largely responsible for the release effect (usually various oils).
Used or waste oil was once the main concrete release substance, but these should not be used nowadays due to their quality fluctuations and also for environmental reasons. In addition to mineral oil distillates and simple raffinates (with a variable hydrocarbon content), there are now high-grade mineral oil products on the market (such as technical white oils and paraffin oils) and it is possible to obtain low-aromatic or practically aromatic free oils – depending on the refining process and conditions (e.g. medical white oil). The lower the aromatics content, the more environmentally friendly and easy to use this product is. Special synthetic oils can also be obtained from paraffin wax by the hydrocracking process. Some products which are used as release agents are rapidly biodegradable, such as vegetable oils, but these are extremely sensitive to temperature, unlike the synthetic oils, which can safely be used over a broader temperature range.

Additives

These are materials used to achieve additional or intensified effects and to improve product stability. They include release boosters (usually fatty acids or their derivatives), wetting agents, rust inhibitors, preservatives and surfactants required for emulsions. Most of the release agents in use today contain additives which react chemically with the concrete (to disrupt the setting process). It is then much easier to separate concrete from formwork and a more general-purpose product can be produced. This effect occurs because these fatty acids, or their derivatives, react with alkaline hydroxides in the cement to form calcium soaps and water.

Thinners

These products act as viscosity reducers for the release-film formers and additives described above. Their purpose is to adjust the workability, layer or coating thickness and the drying time before concreting can take place. Thinners are generally organic solvents (usually aliphatic hydrocarbons) or water in the case of water-based emulsion products.

Read More

Hill and Griffith Customer Service

We're known for our hands on approach. Let us visit your plant and recommend concrete release agents, packerhead concrete form releases, concrete form seasoning, potable water concrete form release, non-petroleum concrete form release, biodegradable concrete form release, rust inhibitors and concrete dissolver products that suit your needs.

Hill and Griffith Samples

Product Samples

We are pleased to provide samples in quantities large enough to allow you to "try before you buy."
Contact Us »

 

Hill and Griffith Customer Service

Technical Services & Support

On-site casting defect investigations, product testing, machine start-ups and much more. Also, lab facilities are available to provide testing upon request.
Contact Us »

 

 Bulletins and Technical Papers for Concrete Casting Products

Tags: Concrete, Casting Solutions, Concrete Casting Products, Concrete Casting Supplies, Concrete Casting, Precast Concrete, Concrete Form Release Agent, Civil Engineer Magazine

The Importance of Precast Concrete Cistern pH

Posted by Jonathan Meier on Feb 21, 2020 2:34:44 PM

Why you should only use a concrete tank to store drinking water

Jonathan Meier with Rain Brothers LLC covers the basics.

Concrete cisterns are, in our experience, the best type of tank to use for underground drinking water systems. Rainwater tends to have a lower pH (acidic), while concrete has a higher pH (alkaline). As rainwater fills a concrete tank, the concrete then actually helps neutralize the water and balance the pH, if not slightly alkalinize it, which is why, after the cistern has gone through a few empty-full cycles, a litmus test of your cistern water would reveal a pH of between 6-8 – the optimal range for a good drinking water system.

Precast Concrete Cistern for Drinking Water

While concrete cisterns help neutralize acidic rainwater, initially, the residual concrete dust from the manufacturing/casting of the tanks will elevate the water's pH to high alkaline levels (10-11). This is completely normal, though for new concrete cisterns, precautions should be taken to get water down to 7-9 range. There are two approaches to managing this initial alkalinity:

1) Flush the tank. For this method, we recommend hauling in a load of water from a local water hauler (in Ohio, a list of water haulers can be obtained through your County's Department of Health or from the Ohio Department of Health Office of Environmental Health). You can then use the hauled water to rinse the walls of the tank to remove as much concrete dust residue as possible. Do not drink this water, but instead either pump it out after a few days or use it for non-potable applications (flushing toilets, showering, irrigation, etc.). Occasionally, it may take two and sometimes three full empty-fill cycles before the water inside the tank reaches a safe pH level of 9.

2) Pressure wash/scrub. For this method, once the tank has initially been installed, use a pressure washer with a 55-gallon drum of clean water and a cup of unscented chlorine bleach to pressure wash the walls of the tank. You may also use a scrub brush with a bucket of water/chlorine mix and hand scrub the walls. Doing so will remove the majority of concrete dust from the side walls. Then, when possible, pump out the water from the bottom of the tank (note: you may have to put more water into the tank to be able to pump the "dirty water" out). If it is not possible to pump out the bottom of the tank after pressure washing/scrubbing, then get a load of hauled water into the tank but do not drink water from this load. Again, use that first load for non-potable uses only.

(Washing the tank will also remove the NSF approved concrete form release. Forty-eight U.S. states have legislation, regulations or policies requiring drinking water system components to comply with, or be certified to, NSF/ANSI 61.)

These precautions may sound intimidating, but the reality is that the work on the front end is minimal compared to the lifetime of fresh, clean water you will receive from a concrete cistern. 

As always, thanks for reading.

(Thanks to Rain Brothers LLC for this article and video below.)


For additional information on the proper concrete release agent to use for concrete drinking water tanks, read these articles published in Precast Inc. by the Hill and Griffith Company:

Precast Concrete in Google News and NPCA, National Precast Concrete Association


Hill and Griffith Customer Service

We're known for our hands on approach. Let us visit your plant and recommend concrete release agents, packerhead concrete form releases, concrete form seasoning, potable water concrete form release, non-petroleum concrete form release, biodegradable concrete form release, rust inhibitors and concrete dissolver products that suit your needs.

Hill and Griffith Samples

Product Samples

We are pleased to provide samples in quantities large enough to allow you to "try before you buy."
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Hill and Griffith Customer Service

Technical Services & Support

On-site casting defect investigations, product testing, machine start-ups and much more. Also, lab facilities are available to provide testing upon request.
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 Bulletins and Technical Papers for Concrete Casting Products

Tags: Concrete, Casting Solutions, Concrete Casting Products, Concrete Casting Supplies, Concrete Casting, Precast Concrete, Concrete Form Release Agent, NSF/ANSI 61 Potable Water, Precast Concrete Drinking Water Tanks

Formwork Lubricants - Types and Uses of Release Agents for Formworks

Posted by Hill and Griffith Company on Feb 13, 2020 4:51:40 PM

Excerpt from The Constructor Magazine by Kavita Pai

Concrete formwork lubricants are high-quality form seasonings that are applied to the inner surface of a formwork before pouring concrete. Formwork lubricants are also known as form or mold release agents.

Uses of Formwork Lubricants

Release Agents are used for the following reasons:

  1. Application prevents sticking of formwork to the concrete surface thereby permitting easy stripping of formwork after the concrete has hardened.
  2. Protects the formwork and hence the formwork can be reused several times.
  3. Provides good finishing surface of the concrete with minimum defects.
  4. In the case of wooden formwork, prevents water absorption from concrete by the wooden formwork.
  5. Reduces leakage of water during the curing process.
  6. Prevents steel formwork corrosion.

Precast Concrete Form Seasoning 2

The performance of release agents are largely dependent on the type of formwork used. For wooden formwork, straight refined, pale, paraffin-based mineral oil and oil-phase emulsion have been successfully used. The oil that is chosen should be capable of penetrating the wood to some extent while leaving the surface slightly greasy to touch.

There should not be any free release agent on the wood surface. The form release agents that are good for wooden formwork are not always suitable for steel formwork. And hence the choose form release agents based on the type of formwork used for construction.

 

Types of Release Agents:

1. De-Shuttering Oil (DSO)

This is a water-based mold release agent, which produces clean and stain-free, high-quality concrete. It is available in a sprayable form and ready to use as a direct application on required places. It should be applied in light film either by brush or sprayer. If it is over applied, excess release agent should be drained before it dries. Pools of DSO cannot be allowed to dry as it causes surface retardation of concrete.

Advantages of De-Shuttering Oil are as follows:

  • DSO is economical to use.
  • It is non-toxic and non-hazardous.
  • It can be used for all types of concrete formworks.
  • It helps reduce the cleaning efforts before reusing of the formwork.
  • DSO provides a damp proof interface that protects the formwork and ensures even texture and color of concrete.

Read More


More News The Constructor Magazine

Concrete Sweating – Phenomenon, Causes and Prevention

Pre-Concrete Checks for Formwork and Release Agents


Hill and Griffith Customer Service

We're known for our hands-on approach. Let us visit your plant and recommend concrete release agents, packerhead concrete form releases, concrete form seasoning, potable water and non-petroleum concrete form release, biodegradable releases, rust inhibitors and concrete dissolver products that suit your needs.

Hill and Griffith Samples

Product Samples

We are pleased to provide samples in quantities large enough to allow you to "try before you buy."
Contact Us »

 

Hill and Griffith Customer Service

Technical Services & Support

On-site casting defect investigations, product testing, machine start-ups and much more. Also, lab facilities are available to provide testing upon request.
Contact Us »

Tags: Concrete, Concrete Form Release Agents, Biodegradable Concrete Form Release, Concrete Casting Products, Concrete Release Agents, The Constructor Magazine

Get More from Your Mix - For Less

Posted by Hill and Griffith Company on Feb 6, 2020 8:00:00 AM

Excerpt from the July/August 2012 issue of Precast Inc. Magazine by Chris Von Handorf, P.E.

New material technologies and intelligent mix designs can significantly decrease production and labor costs.

Reducing material and labor costs makes sense for any manufacturing company, and increasing profits is even more imperative during a slumped economy. Companies in every industry have been forced to look at ways to lower production costs to remain competitive in our rapidly evolving marketplace. The precast concrete industry is no exception. Concrete constituents are only a portion of the costs incurred by a precast concrete manufacturing facility. This article shows how a smart mix design can help you cut costs. The important point to remember is that a lower-cost concrete does not always result in an inferior product. In fact, in some cases, lowering the cost of your mix design may actually yield a higher-quality concrete product.

Admixtures offer many cost-saving options
The cost of the materials that make up concrete is but one of the many expenses incurred by a precast concrete manufacturing facility. Another major expense is the labor cost to place and finish the product. This cost varies widely depending on a plethora of factors including: the type of product; the climate; the experience level of workers; and reinforcement required.

Here are just a few of the admixtures available that, in the right application, have the potential to significantly lower production costs:

1. Supplemental Cementitious Materials: The use of supplemental cementitious materials, such as silica fume and blast furnace slag, has the potential to enhance the performance of concrete while reducing any bleeding that may occur. When used properly, silica fume can improve concrete’s resistance to chemical attack. It can also increase concrete strength while reducing the permeability of the concrete.

2. Accelerators: The use of accelerators in precast applications has some obvious advantages. The faster concrete reaches the required stripping strength, the quicker the forms can be cleaned, prepped and used again. For a precaster, a quicker strength gain is huge if you are looking to go from pouring once per day in a given form to twice per day.

3. High-range water reducers: High-range water reducers (HRWRs) are excellent for nearly every precast concrete application. A good high-range water-reducing admixture will allow you to produce concrete batches with more consistent air entrainment and more consistent ultimate strengths. 

4. Release agents: While release agents are not a constituent of the mix, the use of a high-quality release agent is essential for a better-looking, lower-cost, finished product. As with HRWRs, release agent technology has improved significantly in recent history. Although many new release agents are more expensive per unit, most of them do allow for a lighter application than traditional release agents. As a result, the cost per square foot of coverage is often significantly lower using the newer form release agents.

Emerging technology and processes surrounding the concrete industry are rapidly advancing. Admixtures that cost only $1 to $2 per cubic yard may have the potential to save you hundreds of dollars or more in labor and rework. Many of these admixtures were not available a few years ago. Some material testing techniques that were not available years ago, or were very expensive, are now relatively inexpensive. Therefore, it is no longer economical or wise to continue precast production methods with a familiar, long-standing mix design simply because it has been the traditional way of doing things for the last 20 or 30 years.

Read More


More News from Precast Inc.

Protecting What Matters Most

For the Long Haul


Hill and Griffith Customer Service

We're known for our hands-on approach. Let us visit your plant and recommend concrete release agents, packerhead concrete form releases, concrete form seasoning, potable water and non-petroleum concrete form release, biodegradable releases, rust inhibitors and concrete dissolver products that suit your needs.

Hill and Griffith Samples

Product Samples

We are pleased to provide samples in quantities large enough to allow you to "try before you buy."
Contact Us »

 

Hill and Griffith Customer Service

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On-site casting defect investigations, product testing, machine start-ups and much more. Also, lab facilities are available to provide testing upon request.
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Tags: Concrete, Concrete Form Release Agents, Biodegradable Concrete Form Release, Concrete Casting Products, Concrete Release Agents, Precast Inc Magazine

Avoiding Surface Imperfections in Concrete: bugholes, crazing, dusting, flaking, honeycombing and popouts

Posted by Hill and Griffith Company on Jan 30, 2020 12:01:12 PM

Excerpt from the July 2008 issue of Cement, Concrete and Aggregates Australia

Bugholes

What are bugholes

Bug holes are individually rounded or irregular cavities that are formed against the formwork and become visible when it is stripped. Small bugholes (less than, say, 10 mm) tend to be approximately hemispherical, while larger ones are irregular and often expose coarse aggregate particles. They tend to be more prevalent towards the top of a concrete placement than at the bottom, due to the increased compaction and static head at the bottom layer of the pour. Generally, they are regarded as an appearance problem though a concentration of large bugholes may lead to loss of durability. Under AS 3610 Formwork for Concrete, the size/extent of bugholes is, therefore, one of the criteria by which an off-form surface finish can be evaluated. This Standard incorporates full-size photographs, which enable a particular surface to be assessed for compliance with the specified class of finish. When using normal (i.e., impermeable) forms, it is impossible to achieve a bughole-free surface. However, the use of permeable forms may significantly reduce, if not eliminate, the incidence of bugholes.

toa-heftiba-WeW4RbApL6s-unsplash cropped

What Causes Bugholes?

Bugholes are caused by the entrapment of air against the inside face of the formwork. The extent to which they occur is dependent on:

  • the texture and stickiness of the formwork surface,
  • the inclination of the surface (the incidence of blowholes is increased where the formwork surface slopes inwards), 
  • the use of a poorly proportioned or sticky concrete mix, and
  • the amount of vibration.

Practices to Minimize the Occurrence of Bugholes

To minimize the incidence of bugholes:

  • Use rigid well-braced formwork.
  • Avoid the use of inwardly-sloping forms where possible.
  • Apply a thin coat of a form-release agent that spreads evenly and is not sticky.
  • Where appropriate use permeable formwork.
  • Avoid "sticky" concrete mixes, e.g., ones that may be over-sanded or have a high percentage of air-entrainment, and mixes that are too lean.
  • Place concrete at a rate such that its rise up the form is not less than 2 m/h vertically.
  • Ensure that the member is adequately compacted (see Compaction of Concrete data sheet for guidance on size of vibrator, spacing of insertion points and technique).
  • Pull vibrator up slowly through the concrete layer allowing time for the entrapped air to rise to the surface. 
  • Ensure the concrete against the surface is properly compacted.
  • Re-vibrate the top placement layer at about the same time as if a further layer was being placed on top.

Read More

Crazing

What is Crazing?

Crazing or craze cracking (sometimes referred to as map cracking) is a network of fine random surface cracks spaced from 10 to 70 mm apart, dividing the surface up into irregular hexagonal areas. They are always most prominent when the surface has been wet and then dries off, leaving the damp cracks outlined against the dry surface. They are a surface feature and though unsightly, are unlikely to lead to structural or serviceability problems. There is no repair method; thus it is best to take precautions, as outlined below, to avoid them.

What causes Crazing?

Crazing is caused by the shrinkage of the surface layer relative to the base concrete. Usually, it occurs because one or more poor concrete practices are adopted, for example: 

  • Using too wet a mix
  • Finishing of the surface too early, i.e., while bleed water is present
  • Overworking the surface, thus bringing too many fines to the surface
  • Adding driers to the surface to try and remove bleed water
  • Not commencing curing early enough (three hours after completion of finishing is too late) or using inadequate curing procedures (such as intermittent wetting and drying).
On formed surfaces, it usually occurs where shiny, impermeable formwork is used and this is coupled with inadequate curing.

 

shivanshu-gaur-tYans8xqIHw-unsplash

Flaking

What is Flaking?

Flaking is where discrete pieces of the surface become detached, leaving a rough indentation behind. The pieces are usually flat, hence the name "flakes." Scaling should not be confused with flaking. Scaling is delamination of the concrete surface when exposed to freeze-thaw cycles, and although the appearance is similar, the mechanism is different.

What Causes Flaking Floors?

Flaking is caused by inappropriate finishing techniques that seal the surface and trap the water, which would otherwise have risen to the surface as bleed water. This water accumulates below the surface, forming a plane of weakness and resulting in delamination of the surface layer. Premature sealing of the surface can be caused by:

  • Commencing finishing too early because the ambient conditions dry the bleed water from the surface and the lack of sheen suggests that bleeding has finished. Note that some finishing tools more than others tend to seal the surface, e.g., a hand strike-off with a magnesium straightedge tends to seal the surface while a strike-off with a wood or magnesium bull-float pass leaves the surface open5.
  • The use of driers on the surface to absorb bleed water

andrew-buchanan-XUbIShMDGSM-unsplash

Read More

What is Dusting

A dusting floor surface is marked by an accumulation of fine material requiring to be swept up after the floor has been used. Also, a hand rubbed over the surface of a dusting floor will be coated with a fine powder

Read More

What is Honeycombing?

Honeycombing refers to voids in concrete caused by the mortar not filling the spaces between the coarse aggregate particles. It usually becomes apparent when the formwork is stripped, revealing a rough and 'stony' concrete surface with air voids between the coarse aggregate. Sometimes, however, a surface skin of mortar masks the extent of the defect. Honeycombing may extend some depth into the member. Honeycombing is always an aesthetic problem, and depending on the depth and extent may reduce both the durability performance and the structural strength of the member.

Read More

Popouts

Popouts are roughly conical depressions in the concrete surface created by localized pressure within the concrete, usually occurring after the concrete has been in place for some time. They can be categorized as small, medium or large depending on whether the diameter of the cavity is 10 mm or less, 10 to 50 mm, or greater than 50 mm respectively.

Read More


More News from Cement, Concrete and Aggregate Australia

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Concrete Puts Its Stamp on Shaw Wines' Success


Hill and Griffith Customer Service

We're known for our hands-on approach. Let us visit your plant and recommend concrete release agents, packerhead concrete form releases, concrete form seasoning, potable water and non-petroleum concrete form release, biodegradable releases, rust inhibitors and concrete dissolver products that suit your needs.

Hill and Griffith Samples

Product Samples

We are pleased to provide samples in quantities large enough to allow you to "try before you buy."
Contact Us »

 

Hill and Griffith Customer Service

Technical Services & Support

On-site casting defect investigations, product testing, machine start-ups and much more. Also, lab facilities are available to provide testing upon request.
Contact Us »

Tags: Concrete, Concrete Form Release Agents, Biodegradable Concrete Form Release, Concrete Casting Products, Concrete Release Agents, Cement, Concrete and Aggregates Australia

Formwork Rust: Reasons and Prevention

Posted by Hill and Griffith Company on Jan 23, 2020 8:00:00 AM

Excerpt from the April 2007 issue of Concrete Construction by Peter Boos and Reiner Haerdtl

Rust on steel formwork leads to stains on the concrete unit

Introduction

Steel formwork is used in prefabrication operations because of its robustness and reusability, as well as its ability to produce prefabricated units with smooth surfaces. On these steel molds, brownish-reddish rust spots sometimes form while the concrete hardens. This rust could lead to brown or red spotty discolorations on the concrete surface lower the concrete element's appearance. Removing these discolorations by sanding and resurfacing is costly and time-consuming.

Rusted Concrete Form

Reasons for corrosion

There are several reasons for metal corrosion, and thus different forms: contact corrosion, crack corrosion, inter-crystalline corrosion, pitting corrosion, etc. The corrosion of iron and/or steel is an electrochemical process in the presence of water and oxygen. Metal corrosion occurs at the spot with the higher electro-negative potential. Here, the metal ions dissolve from the surface into the solution and when they collide with hydroxide ions they precipitate as iron hydroxide.

The resulting iron minerals are formed, depending on temperature and air humidity. Due to constant recrystallization, no permanent protective rust layer is formed on the surface that would prevent further corrosion. Corrosion is prevented by protective coatings, such as greasy lubricants, a coat of varnish or other metals that prevent air and moisture from contacting the iron surface. Unfortunately, under the daily production load of a prefabrication plant, no protective layer will last long.

The appearance of rust on steel formworks can look quite different. While some steel molds rust over their whole surface, others show rust spots arranged linearly like pearls on a string. In other cases, rust spots occur only along the edges of the casting tables near the clamps. Frequently, rust appears periodically in certain seasons and disappears. Most causes for rust formation can be classified as process-related causes or environmental causes and causes related to concrete technology.

Process-related causes

Steel in direct contact with concrete forms a protective passivation layer in the alkaline milieu of concrete, which suppresses rusting. This hardened non-carbonated concrete is the best corrosion protection for reinforcement. Release agents are used to ensure reliable separation of the concrete from the formwork. This means that it acts like a contact barrier between steel formwork and concrete. Due to that, the formation of the protecting passivation is either slowed down or totally suppressed. Nevertheless, release agents prevent the direct contact of water to the steel surface. But a reliably effective form release agent is no rust protection agent for steel formwork, although a release agent may well contain small amounts of rust inhibitors. By taking the thinness of the release agent layers into account, no rust protection can be provided in this way.

In concrete's alkaline state, the metallic oxidation of the steel required for this effect to materialize does not take place. Rust can therefore develop only where water films or specific chemical elements and compounds enable oxidation, for example, in case of condensation water. It is always recommended to consult the supplier of the release agent when problems with rusting arise.

Magnets can promote rusting of steel casting tables, especially in contact with water. Clamps are placed over the magnets and positioned on the steel tables. When the magnets are placed on the casting tables before the surface has been sprayed and protected with release agent or when the steel surface underneath the clamps are not fully covered by the release agent, rust is more likely to occur. Typically, linear rust spot patterns are due to magnets.

Removing rust mechanically, such as by sanding, can lead to "activated" steel surfaces, which are especially prone to rust. Some manufacturers of casting tables sand the steel surfaces as a service. After sanding, the surface is treated with waxes and chemicals that penetrate deeply into the pores of the steel, which protect it from rusting for a period of time. Without such a treatment the formwork will definitely show rusting.

But this provides no long-term solution unless the real reason of the rust problem is eliminated. In the long-term, new rust will develop and the protective layer will wear off in the course of ordinary mechanical load. When the cause of rusting is analyzed and eliminated the rust spots will generally encapsulate themselves on their own (deeply embedded black rust).

Using chemicals to remove rust or attempts to form a protective coating on the casting tables, such as by phosphorizing, are usually no solution. The black coating that is produced in the process is not resistant to the mechanical load imposed on the surface during production and chips off, so steel surfaces can rust again. This chemical treatment may even lead to additional black discolorations on the concrete surfaces.

Environmental Causes

Read more

Technological Causes

Read more

Recommendations for Prevention

Read more


Hill and Griffith Customer Service

We're known for our hands-on approach. Let us visit your plant and recommend concrete release agents, packerhead concrete form releases, concrete form seasoning, potable water and non-petroleum concrete form release, biodegradable releases, rust inhibitors and concrete dissolver products that suit your needs.

Hill and Griffith Samples

Product Samples

We are pleased to provide samples in quantities large enough to allow you to "try before you buy."
Contact Us »

 

Hill and Griffith Customer Service

Technical Services & Support

On-site casting defect investigations, product testing, machine start-ups and much more. Also, lab facilities are available to provide testing upon request.
Contact Us »

Tags: Concrete, Concrete Form Release Agents, Biodegradable Concrete Form Release, Concrete Casting Products, Concrete Release Agents, Concrete Construction Magazine

Applying Concrete Form Release Agent

Posted by Hill and Griffith Company on Jan 16, 2020 8:00:00 AM

Excerpt from the August 2010 issue of Concrete Construction

Q: How often should concrete release agent be applied to plywood form panels?

A: Plywood forming panels usually are treated with a concrete form release agent at the mill, but it's still important to evaluate their condition carefully before using them for the first time. Unless the mill treatment is reasonably fresh, the panels may need another treatment of release agent before the first use. Even medium-density overlays should be treated with a chemical release agent before the first use and between each pour. 

Concrete_From_Release_1

Applying a thin film of concrete form release agent to both reused panels and new panels that are not freshly mill-treated will:

  • prolong the panel's life
  • enhance its release characteristics
  • minimize the potential for staining the concrete

Apply the release agent a few days before using the forms for best results.

You also should determine whether an edge sealer was applied at the mill, and if not, seal any cut edges with two coats of polyurethane paint or varnish before the first pour. Otherwise, the forming panels will absorb moisture and swell at the edges.

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Tags: Concrete, Concrete Form Release Agents, Biodegradable Concrete Form Release, Concrete Casting Products, Concrete Release Agents, Concrete Construction Magazine

Cutting-Edge Production Management System is a Game-Changer for Canadian Precast Manufacturer

Posted by Hill and Griffith Company on Jan 9, 2020 8:00:00 AM

Excerpt from issue 6 of Concrete Plant International by Claude Goguen

Traditional wetcast production plant setups make it nearly impossible to drive productivity because there are too many variables and there is no linear process flow that can be easily tracked, measured, analyzed and optimized. The Prima wetcast system offers a solution to this by organizing the different work processes in the plant and by tracking and measuring these processes for analysis and evaluation. Precast producers like M-Con Pipe & Products Inc have found that Prima helps them organize the wetcast production of many different kinds of products and is the solution they were seeking to drive efficiency while maintaining high quality.

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The Problem: Inefficiency and Floor Space

Doug Galloway had a problem and an idea. The president of Ontario-based M-Con Pipe & Products Inc., Galloway was out of space on his wetcast production floor and looking for ways to work more efficiently.

That was the problem. The idea? Some type of carousel system that would move forms to workstations set up on a production line - like an auto assembly plant. Instead of moving buckets of concrete and production teams around the plant to strip, prep and fill the forms, bring the forms to the workers. 

Galloway took the idea to HawkeyePedershaab in 2013, and, little more than a year later, the Precast Industrial Management System, or Prima, was born. The HawkeyePedershaab engineering and sales team took Galloway's concept and brought it to life, creating a wetcast production system that saves space, reduces labor, increases the throughput of products and provides comprehensive analytics to management.

Based in Ayr, Ontario, just west of Toronto, Canada, M-Con Pipe is known as an innovative leader in providing precast concrete infrastructure products throughout Central and Southwestern Ontario. Even though they have a 100,000 sq. ft. (approximately 9300 m2) manufacturing facility, things were tight on the production floor.

"We were doing a lot of wetcast products, and they were taking up a lot of floor space," Galloway said. "The floor space was crammed with products and forms, and we were having to move them with lift trucks to strip the product and to pour concrete. So, we were looking for a more efficient way to manage wetcast forms. That's when we started thinking of this system. Because of the work we had done in the past with Hawkeye, we approached them about putting together this carousel-type system that they eventually called Prima."

The Solution: Prima Automated Wetcast Production

To understand how Prima works, let's follow one form down the production line. At the beginning of the day, the form is located in its assigned spot on the floor, monitored by an RFID tag. As the production line starts, the previous day's product is stripped from the form and moved out to the yard by a chain conveyor.

The form sits on a cart that rides on a moving conveyor that sends it to the next station, where the form is cleaned, oiled and set up for pouring. From there, it moves to the reinforcement station, where the steel is placed. At this stage, there may be an option to pull the form offline if it needs any special preparation, reinserting it after the additional prep.

The next stop is the form filling station, where the operator confirms that all the preparation has been completed and the concrete is poured into the form. An automated overhead manipulator then moves the green product to predetermined curing location where the product cures in the form until it is ready to return to the production loop to start the process over. There is more to the system, of course, according to Randy Beelman, Eastern North America Sale Manager for HawkeyePedershaab.

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Hill and Griffith Customer Service

We're known for our hands-on approach. Let us visit your plant and recommend concrete release agents, packerhead concrete form releases, concrete form seasoning, potable water and non-petroleum concrete form release, biodegradable releases, rust inhibitors and concrete dissolver products that suit your needs.

Hill and Griffith Samples

Product Samples

We are pleased to provide samples in quantities large enough to allow you to "try before you buy."
Contact Us »

 

Hill and Griffith Customer Service

Technical Services & Support

On-site casting defect investigations, product testing, machine start-ups and much more. Also, lab facilities are available to provide testing upon request.
Contact Us »

Tags: Concrete, Concrete Form Release Agents, Biodegradable Concrete Form Release, Concrete Casting Products, Concrete Release Agents, Concrete Plant International Magazine

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