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Myth busting facts about concrete/cement based flooring.

06 Nov 2019 by Permacolour

Although concrete is one of the most commonly used building materials there are quite a few misconceptions about what it is, what it can do, and how it can be used.  Here we bust some of the most common concrete myths

Myth #1Concrete is cold

This is a common misconception. Concrete finishes are not as cold as many think. Cement/concrete is actually fantastic at absorbing and retaining heat, to gradually release it throughout the day.  Concrete is actually warmer than having tiles due to its natural ability to absorb heat.

Concrete floors are also suitable for use with underfloor heating. If this is something you would consider, care needs to be taken in the initial stages of using the system. There will be a waiting period to allow the concrete to sufficiently cure before you can turn on the heating system, as this is critical to maintaining your finish. The temperature should be gradually increased over the course of a few weeks.

 

Myth #2: Concrete is not environmentally friendly

It’s no secret that the cement industry is one of the world’s primary producers of carbon dioxide and this tends to mean that people believe that concrete is bad for the environment. In reality, concrete is the most durable building material on the market and a properly constructed concrete building can last for hundreds of years. In fact, the majority of greenhouse gases produced by a concrete building over its lifetime are produced by the electricity run in the house, rather than the structure itself.

Myth #3: It’s easy to DIY concrete jobs

Although pre-mix concrete is readily available in hardware stores and an array of DIY tutorials available online, the reality is that installing concrete correctly takes skill and experience. Obviously small jobs can be done with a DIY approach  DIY provided you know what you are doing. Larger projects such as driveways, pathways, slabs or any sort of concrete construction and specialized finishing should be done by professionals.

Myth #4: Concrete is unattractive

Usually, when people think about concrete, they immediately imagine the dull, boring, grey type of concrete which is commonly used in construction or civil engineering. There are however so many options available in terms of coloring, textures, patterns, and finishing. Creating something truly unique and interesting has never been so easy.

Myth #5: Water weakens concrete

It is true that concrete mixed with too much water will be weaker and less structurally sound as well as increasing the chances of cracking, flaking, and blistering among others. Concrete does, however, require water to hydrate and strengthen during the curing process. Concrete curing is not a drying process but one in which water is vaporized. As long as there is sufficient moisture and favorable temperatures, the hydration of concrete will continue for some time. When fresh concrete dries out (usually below about 80% relative humidity), hydration stops. If the temperature of fresh concrete approaches freezing (below 5°C), hydration slows dramatically. In high temperatures, rapid moisture loss can increase the risk of cracking, hence the importance of regulating the moisture availability for the concrete to cure sufficiently. The longer you cure concrete, the stronger and more durable it will become.

Myth#6: Decorative overlays are repair products designed to hide major imperfections and/or cracks.

Decorative overlays are thin coatings and are not designed to disguise a crack or to prevent substrate blemishes from shadowing through. The phrase “a topping is only as good as what you put it on” is accurate when considering whether to overlay or not. Sometimes an overlay is considered due to some kind of surface defect, however suitable repair products, crack fillers and primers should be considered first prior to any decorative overlay coatings being applied.

Myth #7: Adding water to the mix is the only way to increase the slump.

Adding water to increase workability and slump will actually reduce the strength and substance of the concrete. Additional water dilutes the paste and increases the water-to-cement ratio (w/cm). Excessive water can also reduce concrete’s resistance to freeze-thaw cycles, increase drying shrinkage, and lead to other problems.

There are effective ways to increase concrete slump and workability. Aggregate gradation and the maximum size of the aggregate both greatly influence cement and water requirements, which affect mix workability. Water reducers and superplasticizers can also be used, to increase the slump while maintaining the water-to-cement ratio.

Myth #8: Concrete is impermeable.

Truth is even the densest concrete is somewhat porous.

Water and other substances in liquid or vapor form can still pass through concrete. Permeability can be reduced by using mix designs with a low water to cement ratio, well-graded aggregate and chemical admixtures like plasticizers. Surface treatments, like sealers, can also aid in reducing permeability and water/liquid absorption.

Myth #9: The higher the strength of the concrete, the more durable it will be.

Unfortunately, compressive strength alone does not determine the durability of the concrete.

Whilst compressive strength is an important characteristic of concrete, other factors are important for concrete durability in harsh environments. Usually, the principal causes for deterioration in concrete are corrosion of reinforcing steel, exposure to freeze-thaw cycles, alkali-silica reaction, and sulfate attack. Reducing permeability is the key to durability.

In areas of tension, structural reinforcement does not prevent cracking, but rather it holds the crack faces together. When concrete cracks, the tensile stress is transferred from the concrete to the steel, allowing reinforced concrete to withstand higher tensile loads than concrete alone.

Myth #10: No bleed water and a successful “footprint” test mean a “thumbs up” for concrete finishing.

Unfortunately, there is no absolute rule of thumb to determine the readiness of concrete for finishing. Improper finishing can cause surface defects like blistering, dusting, crazing, and delaminating. It takes skill and experience to know when to start the finishing process. Relying on  “old rule of thumb” type methods for testing readiness may not always apply,  given there are several external factors that need to be taken into account, such as different mix designs, weather conditions, and finishing tools. Relying on the absence of a sheen of water on the surface to determine when bleeding has stopped is not a reliable method, since bleeding may still be occurring even though it isn’t obviously visible. Bleeding must be completed for the entire slab thickness before finishing operations begin. Choosing the appropriate time to begin the finishing process takes skilled and experienced judgment and knowledge of the materials being used. The timing can change based on current weather conditions, mix designs, placement rates, and a variety of other issues. Experienced finishers take all those factors into account.

Myth #11: Concrete that is flat and level after placing and finishing will remain so.

Concrete changes in volume while setting, hardening, and drying.

Curling of slab edges is caused by differences in the moisture content and temperature of the top and bottom of the slab. The edges of slabs at the joints tend to curl upward when the top surface of the slab is drier or cooler than the bottom surface. A “reverse curl” occurs when the top surface is wetter or warmer than the bottom. The possibility of curling occurring can be reduced by using techniques that minimize shrinkage differentials and the temperature and moisture-related volume changes that cause them.

Even after placement of the concrete, movement and/or settlement in the ground can all cause the concrete to sag over time, resulting in uneven, cracked concrete.

Myth #12: Reinforced concrete will not crack.

If only it were so! Structural reinforcement does not absolutely prevent concrete from cracking due to volume change.

Concrete that is prevented from moving during volume changes (during setting and drying) may crack since concrete is weak in areas of tension.  Structural reinforcement does not prevent cracking, but rather it holds the crack faces together. When concrete cracks, the tensile stress is transferred from the concrete to the steel, allowing reinforced concrete to withstand higher tensile loads than concrete alone.




Permacolour
New Zealand
New Zealand's Longest Leading Manufacturer And Supplier Of Products For The Decorative Concrete IndustryPermacolour, formerly New Zealand Decorative Concrete Supplies, was established in 1992 and is now recognised as New Zealand's longest-leading manufacturer and supplier of Concrete colourants including Iron Oxides, sealers, additives, tools and other products for the decorative concrete industry.Permacolour is owned and managed by Brian O’Keeffe who has been in the concrete industry for over 32 years. With considerable experience ranging from owning a concrete contracting business to manufacturing and distribution, he is extremely knowledgeable and provides valuable practical assistance to customers.Permacolour can provide solutions for your decorative coating needs, such as:> Walls (Internal and External)> Floors (driveways, patios and internal floors)> Stamped Concrete> Sealers> Additives> Waterproofing> Concrete Admixtures> Anti-slip coatings and additives> Concrete Tools> Hiring of equipment (grinders, stamped concrete mats)In 2006 Brian O’Keeffe signed a sole distributorship contract with Cathay Pigments which is now the second largest manufacturer of pigments (Iron Oxides) in the world. Purchasing directly from the manufacturer has enabled Permacolour to be the most competitive supplier of iron oxides in the industry.Permacolour has been marketing a range of iron oxides in water soluble bags that have become extremely popular. The range comprises of 36 standard colours and we offer a custom blending service at the manufacturing plant in New Plymouth so offering an unlimited range of colours for supply. The product is bagged to suit one cubic metre and 0.2 cubic metre concrete loads, for 20-25mpa. For high mpa custom bagging is available.Permacolour, in partnership with Cathay Pigments, can offer ready-mixed companies and paving manufacturers, the Cathaymat 100 Colour Batching System that can be programmed with up to 100 colours.These are produced to handle the companies FF grade iron oxide and titanium dioxide. The Colour Batching System can be installed at larger ready mixed and paving plants where there is a high demand for colour.Permacolour (New Zealand Decorative Supplies) has been innovative with its research and development in high quality, aesthetically pleasing finishes reflecting nature in concrete. We provide factory direct, state of the art products and services to:> Architects> Ready Mix> Specifiers> Landscape designers> Concrete placers> General Contractors and Builders> Decorative applicators> Homeowners> ManufacturersYour One-Stop-Shop For A Complete Range Of ProductsPermacolour is a one-stop-shop for the complete range of Permacolour colourings, release powders, imprinting mats (sale and hire), decorative overlay products, hand tools, machinery, sealers and specialist additives.With warehouses in Auckland, New Plymouth and Christchurch and distributors in the North and South Islands as well as a national freight network, Permacolour is able to provide an efficient, cost-effective service New Zealand wide as well as to the export market.With our 30 years of expert knowledge and experience in the industry, you can rely on Permacolour for a friendly, comprehensive technical backup service.All our staff are trained to put the customer first and pride themselves on Customer Service, giving you the best possible options to meet your requirements and make your journey with Permacolour a memorable one.

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