<img alt="" src="https://secure.hims1nice.com/150891.png" style="display:none;">

Concrete Casting News from the Hill and Griffith Company

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

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, 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

Concrete Overview

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.

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

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.

1906_ro_afinitas

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.

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 Plant International Magazine

5 Rules of Watertightness to Reduce Porosity and Permeability

Posted by Hill and Griffith Company on Jan 2, 2020 4:32:39 PM

Manufacturing specified watertightness in precast concrete products is straightforward if you play by the book.

Excerpt from the November 2012 issue of Pre-Cast Inc. by Claude Goguen

Dutch legend has it that there was once a small boy on his way to school who noticed a slight leak in a dike where the seawater trickled in through a small hole. Knowing that the dike held back the sea from flooding his village, the boy poked his finger into the hole, and so stemmed the flow of water. Sometime later, a passerby saw the boy and went to get help. Thus the villagers arrived, repaired the dike and sealed the leak.

If that dike had been made of quality precast concrete, this legend wouldn’t exist, and the boy would have gone to school without fanfare. A good precaster would have known the seawall’s intended use and would have followed industry guidelines to ensure a leak-proof and watertight dike.

Concrete_From_Release_2

Two “P’s” of watertightness

“Watertight” is a term we often hear in describing many precast products. Whether above-ground or underground products, in many instances, we want to prevent fluid from getting from one side of the concrete wall to the other. In making our structures watertight, there are two areas where we’re concerned: the concrete itself, and joints and penetrations.

Let’s start with the concrete. When discussing watertightness of concrete, we must consider the two P's: porosity and permeability.

Porosity is the ratio of the volume of openings (or voids) to the total volume of the material. It represents the storage capacity of the material. Concrete is inherently porous, although a sealer can be added to the concrete surface to prevent water penetration. It’s practically impossible to make an absolutely nonporous concrete where water won’t penetrate even a fraction of an inch. However, we can control the size and distribution of those pores and limit the penetration. The pores, which are tiny voids, reside in the cementitious paste (see Figure 1) and can be subdivided into two types: gel pores and capillary pores. The gel pores exist in every system and are part of the glue that forms around the aggregate to make concrete what it is. Gel pores are very small and not a real problem.

Permeability is the measure of the ease with which fluids can flow through a porous material. Permeability is expressed in terms of speed (in./s or mm/s) as opposed to porosity, which is expressed in volume per volume (cu in./cu in. or mm3/mm3).

Permeability depends on other factors, such as aggregate gradation and density. In high-quality concrete, infiltration is very slow, around the order of 3.94×10-11 in. / s (1.00076 x 10-12 m/s). To give you an idea of how slow that is, it would take about 4,800 years for water to breach a 6-in.-thick wall – well beyond the terms of your warranty for sure.

Watertightness Rule #1:
Use a low w/c ratio mix design
The w/c ratio is the most important factor in concrete design. The water content in a mix controls the moisture’s rate of entry (which may contain aggressive chemicals) and the movement of water during the freeze-thaw process. Compare the leading causes of low durability versus high-quality concrete listed in Figure 2. A mix design for durable, watertight concrete should have a maximum w/c ratio of 0.45 and require a well-graded mixture of fine and coarse aggregates.

The more excess water in a mix, the lower the strength, durability and watertightness. Excess mix water results in capillary pores – entrapped air pockets in hardened concrete that will reduce its resistance to leakage. On the other hand, too little water can cause placement difficulties and undesirable effects such as honeycombing. The effect w/c ratio has on the watertightness of a concrete mix is illustrated in Figure 3.

Durability and densification can also be improved with admixtures. Many admixtures can be used to improve concrete’s workability, durability and densification. In controlling our water content while trying to maintain workability, water-reducing agents can be used. Air entrainment agents produce near-microscopic independent bubbles that improve the watertight performance of hardened concrete. Air entrainment also improves concrete’s freeze-thaw performance and overall durability in addition to easing the placement process.

Watertightness Rule #2:
Meet minimums for cementitious material
Rich concrete mixes provide a denser, more impermeable and superior finished product. Consequently, specifying that cement content does not exceed a minimum amount is recommended. In the case of watertight structures, a minimum cement content of 564 lbs/cu yd is suggested (the effect of cement content on concrete permeability is illustrated in Figure 4).

Cement content or total cementitious content needs to be based on the guiding specifications, but generally, cements with a higher fineness (> 600 m²/kg Blaine fineness) will benefit workability and reduce bleeding, both of which are beneficial for watertight concretes.

The use of supplementary cementitious materials such as fly ash, slag and silica fume can also increase concrete’s density, thus reducing capillary porosity and permeability.

Watertightness Rule #3:
Use well-graded aggregates
Gradation of the aggregates is an important factor and should be of primary consideration. Shape and texture of the particles will also affect workability. Aggregate moisture needs to be accounted for when adjusting the mix design so that additional surface water from aggregates does not contribute to a more porous hardened product. Concrete mixtures that are not well-graded can permit water to pass through the finished structure, as illustrated in Figure 5.

Watertightness Rule #4:
Follow quality manufacturing processes
Quality concrete manufacturing processes are critical to the production of durable, watertight concrete products. Proper attention to important pre-pour activities such as maintaining prescribed mix proportions, form cleanliness, and specified reinforcement placement and minimum cover is very important. For concrete products permanently exposed to earth or moisture, increased concrete cover, as specified in ACI 318, is recommended to ensure the corrosion protection and proper bonding of concrete around the reinforcement. Adequate consolidation of freshly placed concrete is an extremely important factor to produce a high-quality, dense concrete. Added emphasis on consolidation is required for a desirable low w/c ratio concrete, as it requires a higher compactive effort (a summary of preferred practices is illustrated in Figure 6).

The degree of consolidation can have a marked effect on the watertightness of concrete. As illustrated in Figure 4, a 5% reduction in concrete consolidation can result in a 20% reduction in watertightness. This figure also shows that higher cement content improves watertightness. Defect-free surfaces produced by using smooth forms and appropriate release agents can considerably improve the impermeability of a precast concrete product. Concrete must be adequately cured if its optimum properties are to be developed. An adequate supply of moisture, either by covering or other means, is important to ensure full hydration and reduce the porosity level such that the desired durability is attained, as shown in Figure 7. Although a period of moist curing significantly reduces permeability, the effects of curing are less pronounced with lower w/c mixes.

Watertightness Rule #5:
Execute joints and penetrations carefully
A system is only as strong as its weakest link. Close attention to all jointed, connected and sealed areas is necessary to ensure watertightness. Potential differential settlements and thermal movements must be addressed in the design and manufacture of joints and penetrations.

Little Dutch boy or precaster: Rules matter
Whether you’re building a septic tank in Wisconsin or a dam in Holland, precast concrete products are well-suited for durable, watertight applications. The best strategy for manufacturing a durable, watertight concrete structure is to play by the book and pay close attention to all recommended concrete manufacturing and installation details. Like the legend of the little Dutch boy, the price of ignoring the rules can be enormous.

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, Precast Inc Magazine

Understanding Biodegradable Concrete Form Release Agents

Posted by Hill and Griffith Company on Dec 19, 2019 11:59:10 AM

Excerpt from the May 2018 issue of Concrete Products

As consumers become more eco-conscious and more informed about how the materials they buy affect the environment, the desire for environmentally friendly products is on the rise. This holds for concrete producers and contractors as well. Whether it’s to meet specific federal and state requirements on biodegradability, volatile organic compound (VOC) exposure limits, or because customers are requesting “green” materials, owners, contractors and architects want products on their job sites that are less harmful to the environment.

There are multiple ways to measure a product’s environmental impact. These include carbon offsets, whether or not the ingredients are compostable, non-toxic, ozone-safe, recyclable, refillable, and the percentage of recycled content in the product. When it comes to chemicals used in concrete production and construction, biodegradability is a primary measurement of eco-friendliness.

WHAT QUALIFIES AS BIODEGRADABLE?

A product is classified as biodegradable when it is capable of returning to its natural, raw material state quickly through biological means. A truly biodegradable material will break down into carbon dioxide, water, biomass and other natural minerals that don’t adversely affect the ecosystem.

The Federal Trade Commission’s (FTC) Green Guides, last updated in 2012, states that for marketers to make an unqualified claim on degradability, they must prove that the “entire product or package will completely break down and return to nature within one year after customary disposal.” This issue of “customary disposal” is key because the characteristics of the environment in which the material is disposed can greatly affect its ability to break down. 

READILY VS. INHERENTLY VS. ULTIMATELY BIODEGRADABLE

The U.S. Environmental Protection Agency and the FTC recognize biodegradability by two classes, readily and inherently. (A third class, ultimately biodegradable, covers both readily and inherently biodegradable and more.) Readily and Inherently biodegradable products have the natural ability to biodegrade to their natural state when subjected to sunlight, water and microbial activity. The difference lies in how quickly they achieve complete biodegradation. To measure the speed of biodegradability, EPA recognizes a 28-day half-life. Half-life is the time required for one-half of a given component to decay.

Readily biodegradable: Product is capable of biodegrading from 60-100 percent in 28 days or less. In other words, these materials achieve complete biodegradation at a quick rate.

Inherently biodegradable: The product is capable of biodegrading from as low as 20 percent to less than 60 percent in 28 days. Such products will achieve less biodegradation than readily biodegradable products in the same time span, but eventually, they all get to the same place.

Concrete Form Release Agents Help Form Removal

BIODEGRADABLE RELEASE AGENTS

As with any industry, concrete interests have set federal guidelines for classifying products as eco-friendly. Just as federal VOC regulations are put in place to protect the ozone, biodegradability standards are in place to protect land and water from contamination. Keep in mind, states can apply more stringent requirements.

Water-based release agents are suitable for most concrete form surfaces to include steel, plastic, fiberglass and bare or overlaid plywood. They can be used on many rubber and closed-cell foam forms and are safe for use in enclosed building sites. Water-based formulations are free of conventional form oil, diesel oil and kerosene. Because they are water-based, these release agents are susceptible to freezing, usually require mixing before use, and can have a shorter shelf life due to emulsion. While water-based release agents are typically inherently biodegradable, they are not always readily biodegradable. Even a water-based formulation must meet the EPA requirements of the 28-day half-life of 60 percent or more to be considered readily biodegradable.

When temperatures allow, an environmentally responsible, water-based release agent can produce smooth, uniform concrete surfaces without staining and with minimal surface voids while providing a crisp, positive release. With proper research and due diligence, concrete producers and contractors can find an environmentally responsible option that yields quality results in a readily or inherently biodegradable formulation.

Read more


Hill and Griffith Customer Service

We're known for our hands on approach. Let us visit your plant and recommend 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 Products Magazine

Properly Applying Concrete Release Agents

Posted by Hill and Griffith Company on Dec 13, 2019 8:31:59 AM

Reprinted from the National Precast Concrete Association Tech Notes

Release agents, when properly used, aid in the stripping process, assist in producing sound defect-free concrete surfaces, simplify form cleaning and increase the working life of quality form surfaces.

There are two main categories of form release agents:
• Barrier – those that provide a physical barrier between the form and the concrete (such as petroleum-based products, soaps, synthetic resins, waxes) 
• Reactive – those containing fatty acids or other ingredients that react with the free lime in fresh concrete to produce a metallic soap interface between the form and the concrete (such as proprietary products and vegetable oils that are typically found in petroleum-based carrying agent products).

Concrete_From_Release_1.pngApplying Release Agents

Release agents should be applied to a clean form before the reinforcement has been placed to reduce the likelihood of inadvertently applying it to the reinforcement. If the release agent does come in contact with reinforcement it should be wiped clean before placing the concrete.

When applying a release agent it is best to follow the manufacturer’s instructions. When too much form release is used, it is not only wasteful and inefficient, but it leads to a number of other associated problems with the finished product. He who holds the wand determines the amount of material being applied, so proper training is crucial. As a rule of thumb, remember: Less is better. The amount needed to affectively coat a form is only about 0.005 inches thick. The actual cover thickness will depend on the application method and viscosity of the product, which is related to the ambient temperature. Typically, the colder it is in the plant, the thicker, or more viscous, the release agent will be. The warmer it is the plant, the thinner, or less viscous, it will be. Different measures can be taken during the application process to account for changes in material temperature (viscosity) throughout the year.

Spraying

Spraying is probably the most efficient and common method for applying release agents. Keep the wand moving when applying form release. Broad nozzle/ flat spray tips have been found to give the thinnest and most uniform cover. It should be noted that as the temperature drops and viscosity increases, the spraying pressure should be increased and the nozzle orifice size reduced. As temperatures rise, reduce pressure and increase nozzle size. It is a good practice to soak or mop up any puddles that may have formed at the bottom of the form Remember: Less is better. Only through experience and training will you learn what works best for your plant’s production line.

CAUTION: Fatty acids will react with brass, bronze, aluminum, grey ductile and malleable iron and mild steel, as well as some petroleum-based products used for making blockouts and other embedded items. It is best to use stainless steel, nickel or plastic for your spraying systems and to test for possible reaction of embedded materials prior to full implementation.

Swabbing and Painting

Swabbing and painting by hand is an acceptable application method, with the benefit of eliminating the majority of airborne particulate. On the negative side, applications tend to be thicker than necessary, leading to wasted material and the potential for additional problems.

Wiping

Wiping is often the method of choice for architectural precasters concerned with a blemish-free surface. Wiping on release agents with a sponge or rag will normally result in the thinnest coating, but it is very labor intensive.

Dipping

Automated dipping systems are fast, labor efficient and ensure complete coverage. Excess material will usually drip back into a holding tank, reducing material waste. The application coat is often thicker than necessary, however, again creating the potential for future problems.

Concrete_From_Release_2.pngSeasoning

Reactive form release agents, the most commonly used release agents in precast and pipe production, typically contain fatty acids. Fatty acids are mild acids composed of animal fats and vegetable oils. These fatty acids have a natural affinity for metal. They react with metal to form a protective barrier, which is a coating of metallic oleate. This process is known as seasoning. This protective layer prevents further application of fatty acids from migrating to the metal of the form and allows the fatty acid to remain on the surface of the form to react with the free lime on the surface of the casting. Seasoning serves two purposes. First, it enhances the easy separation of the form from the castings. Second, it enables free air to rise more easily on the vertical surfaces of the castings, resulting in fewer surface defects. Seasoning of forms is a very basic requirement to help minimize the amount of labor involved when forms are stripped or pipes are tipped out. If forms, pallets and headers are properly maintained, labor cost and better looking castings are the end result.

New forms, pallets and headers will frequently arrive with a protective coating on them to help prevent rusting in transit or until the forms are sold and delivered. In order to season these forms, the protective coating can be removed with solvents or grinding and the form release applied liberally, allowing it to set for a minimum of four hours. A 24-hour period is better, as it allows more seasoning to take place. Also, forms that are exposed to the sun will season more quickly, as higher temperatures increase the reactivity with the metal forms and rings.

Care of forms and rings

At times, you may be storing forms inside or outside for short or long periods of time. Release agents can be used to protect this vital equipment from damage. For short-term or long-term storage, a good quality VOC-compliant petroleum solvent-based form release can be used by applying a liberal coating on the form. If the forms are stored outside, even for a short period of time, a quick walk-by is often necessary to ensure that the form release has not washed off from rain. If any evidence of rust is present, apply another coat of the form release on the forms and rings as quickly as possible. A biodegradable form release is preferred, as over-application is desired and some of the material will end up on the ground.

Identifying Potential Problems

Concrete is a highly variable material because it is comprised of raw materials that potentially have a lot of variability. It is often difficult to pinpoint exactly what causes a problem because it may be a combination of a number of factors. The following are two examples of common problems often associated with excessive form release agent coverage.

• Staining has been linked to the use of excessive release agents and the use of dirty forms. Dirt, dust, rust or grease can easily be transferred from a dirty form to the finished surface of the concrete product. Once a form has been properly cleaned and coated with release agent, proper measures should be taken to minimize the potential for dust and debris to collect on the form before casting.

• Excessive bugholes occur when barrier-type release agents are applied to heavily. Barrier-type release agents tend to encapsulate free air along the vertical sidewalls, which leads to surface defects. In contrast, the metallic soap formed when using a reactive release agent allows the free air on the vertical walls to rise more easily to the surface. Proper vibration practices also reduces bugholes. The potential for bugholes and staining can be reduced by selecting an application method that produces the thinnest coat of release agent in accordance with the manufacturer’s recommendations. Release agent should not be allowed to collect and pool in the forms. Applying a thin coat, wiping up puddles and avoiding contact with reinforcing steel greatly improves the odds of producing a defect-free concrete product.

This publication is designed to provide accurate and authoritative information, however the National Precast Concrete Association does not guarantee the validity or accuracy of any data, claim or opinion appearing in this publication. If engineering, legal or other professional services are required, the services of a competent professional should be obtained. The National Precast Concrete Association does not assume and hereby disclaims liability to any person for any loss or damage caused by errors or omissions in this publication, regardless of whether such errors result from negligence, accident or any other cause whatsoever.

Read the NPCA whitepaper in its entirety.


Hill and Griffith Customer Service

We're known for our hands on approach. Let us visit your plant and recommend 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 Casting Products, Concrete Release Agents, National Precast Concrete Association, NPCA

Choosing and Using a Form Release Agent

Posted by Hill and Griffith Company on Aug 15, 2019 3:16:52 PM

Excerpt from the article by M.K. Hurd in the October 1996 issue of Concrete Construction

Concrete Form Release Agents Help Form Removal

Most form materials require the application of a release agent to prevent adhesion of concrete to the face of the form. Many form oils and other release agents adequately prevent sticking, but using the correct type of agent for the form material can also help to minimize concrete color variations, staining, bugholes, and poor surface durability. Article discusses the two basic types of release agents (barrier and chemically active), how to select a release agent for different form materials, and release-agent application methods. It also describes the newer types of water-based release agents, which are formulated to meet environmental regulations limiting volatile organic compounds (VOCs).

Photo caption: Forms will strip cleanly and easily if you use the correct form release agent and apply it properly. - Photo by Bob Sawyer

With the wide range of release agents available today, how do you choose the best one for your forms?

Types of Release Agents Historically, form release agents have been grouped in the following categories :
• Petroleum oils
• Emulsions—either water- or oil-based
• Nonreactive coatings with volatile solvents
• Chemically active agents
• Waxes

Though products in these categories are still available, new products and new formulations are being introduced to meet environmental regulations limiting volatile organic compounds (VOCs). Also, manufacturers may combine release-agent types, such as a chemically reactive product and an emulsion, to produce a product that has the advantages of both. Many newer form release agents, therefore, do not fit neatly into the above categories. Because environmental restrictions have caused changes in the commercially available agents, and because of the great variety of chemical formulations, manufacturers now simply classify release agents in terms of how they act instead of what’s in them. The two basic categories are barrier agents and chemically active agents. Read More.

Precautions in Selecting A Release Agent

A release agent may be incompatible with concrete that contains a number of admixtures. Compatibility problems have been reported when chemically active agents were used with concretes containing microsilica, high-range water reducers, and unusually high amounts of admixtures. Be sure to discuss possible compatibility problems with the admixture and release-agent suppliers. Read More.

Application Methods

Use enough release agent to prevent adhesion, but don’t apply too much. When overapplied, the material runs to low points in the form face where it can retard cement hydration or produce staining. Most manufacturers recommend a thin, uniform coating. With some products, the thinner the better; sometimes as little as 1 ⁄2 mil (0.0005 inch) is recommended on nonabsorbent form surfaces. Read More.

Precautions to Take During Release Agent Application

•Keep release agents off construction joints and reinforcing steel. To avoid spilling release agent on rebar, apply it before placing the steel.

• Never use release agents containing wax or silicone if the concrete surface is to be painted.

• Follow manufacturer recommendations for when to apply release agent. Some agents must dry or cure before concrete is deposited, while others can be applied only minutes ahead of concrete placement. Generally, the shorter the time between applying release agent and placing concrete, the better. Too long a wait can result in the agent drying out, running down the form face, or being washed away by the rain. (Note: Some agents are rainproof.)

• If there is any ponding or puddling of release agent, be sure to wipe away the excess material.

• After coating form faces, protect them from contamination and weather.

SELECTING A RELEASE AGENT FOR DIFFERENT FORM MATERIALS

Read the complete article in Concrete Construction Magazine


Additional News from Concrete Construction Magazine

Tilt-Up Innovations

Three Key Lessons About Moisture in Concrete


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 Form Release Agents, Biodegradable Concrete Form Release, Concrete Release Agents, Concrete Forms, Concrete Form Seasoning, Concrete Casting Supplies, Concrete Voids, Concrete Form Release, Concrete Construction Magazine

Subscribe to Concrete News

Concrete Posts

Concrete Casting News Categories

see all