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Is Water Ponding on Carpark Floors Normal?

Date: 15.07.2020 By: Dr. Zack Lim Nowadays water ponding has become a common construction dispute as any water appearing stagnant on the floor surface us generally not acceptable by owners and/ or architects. Hence, is water ponding normal or should it be rectified? Two issues are commonly encountered when rectification is made to water ponding. Firstly, if the affected area is rectified, there is a tendency that a new puddle of water my be created adjacent to the rectified area. Secondly, it is very difficult to carry out thin topping repairs on low areas successfully. Any mason can repair a floor but what is the assurance that the repaired area will not delaminate or fail months later? Before understanding the causes and finding a solution, everyone should know the difference between 'flat' and 'level'. Flatness relates to the bumpiness of the floor surface and levelness relates to the tilt or slope of the floor. To describe a floor profile clearly, flat and level are two inseparable entities with different types of floor profile as shown in Fig 1. Water ponding is common on concrete floor surfaces, especially at today's large carpark areas. This problem is unavoidable as most finished floor levels are specified to meet a 'perfect level', and even on a floor that is constructed to be super-flat and super-level, the water will still stagnate on the floor surface as the water has nowhere to fall. Therefore, the only way to eliminate ponding problem is to design and build the floor surface to fall or slope to facilitate water flow. Thus, the expectation of the property owners and architects by not having any water ponding (unless to fall) is not realistic. There must be an acceptance of reasonable tolerance on the level of ponding. What causes water ponding? Large areas of water ponding or small localised ponding known as birdbaths are results of depressions created on the concrete floor surface during concrete strike-off (screeding) and power trowelling. The other reason for water ponding can be resulted by a deflection of a floor slab caused by the weight of the slab itself after the removal of scaffoldings or a possible change of floor profile on an elevated slab after post-tensioning the slab. Idealistically, to avoid water ponding, concrete floor need to be built with a surface profile that is very flat but not level (designed to fall), to cater for water runoff from a higher to lower elevation. However, modern carpark floors are so large that it is impractical to build floors with gradients, as concrete at the centre need to be much thicker to enable water to fall to the lower perimeter scupper drains. Alternatively, the formworks to receive the concrete can be installed to tent-shape so that the concrete can be laid with consistent thickness with falls. However, it is extremely difficult for builders to actually control and do it precisely. As floors are generally designed and built without gradients, any high spots will restrict water to flow freely to any low-lying areas which then trap and hold water, resulting in water ponding. Floor specification and acceptance The QLASSIC standard mentioned that specification for floor surface evenness allowed is 3mm over 1.2-meter starightedge whereas BS8204-2:2003 (refer Table 1) has three classifications of floor flatness for different usages. For example, SR3 specification, which is a 10mm tolerance under 2-meter straightedge is generally recommended for carpark floors. Fig 2 shows how a SR floor is measured using a 2-meter straightedge placed anywhere on the entire floor surface and uses a slip-gauge to measure the gap under the straightedge. This only measures the flatness of the floor but does not measure the level tolerance from the control datum or finished floor level (FFL). As mentioned earlier, flat and level are two inseparable entities, therefore floor level tolerance also needs to be specified for the entire finished floor. For example, +/- 15mm tolerance from the finished floor level is a very stringent specification imposed on levelness control. If a level tolerance of +/- 15mm is also specified from the finished floor level, logically water ponding of up to 30mm may be observed over the entire floor area. Rectification of water ponding Generally, the method of repair is carried put by grinding the high spots that caused water damming and topping up the low areas with suitable cementitious materials. However, if the high areas are grinded down too much, it will cause new ponding areas around the newly filled up areas. As such, rectification works to eliminate water ponding may backfire as most repair areas will looked worse than original and any repairs not carried out professionally may results in delamination. It is near impossible to build a concrete floor with no water ponding. As such, if the depth of water ponding is very little (not more than 10mm deep), it is bearable and acceptable as it can easily be removed. As today's carparks are mostly dry, any slight imperfections on the floor profiles are unnoticeable when dry. Low spots are evident only if waters is present. Understanding of Surface Regularity (SR) Theoretically, a floor specified to SR2 tolerance accepts 5mm water ponding on every localised measurement using a 2-meter straightedge. However, the common misinterpretation of SR2 is assumed to be a +/- 5mm level tolerance from the control datum (level control), which is near to impossible to achieve. As a result, huge spending for repairs are incurred due to such misunderstandings in complying to the SR standard. Another ambiguity of this standard is that it does not indicate how many bumps are allowed if measurements need to be taken. Generally, at least 5% of the floor area should be measured. For example, for a floor area of 500-square meters, twenty-five equally spaced out points need to be selected and measured randomly. Conclusion Without water stagnation on the floor, any low spots may not be noticeable. Any corrective action taken on insignificant ponding areas is unfavourable, as any repair carried out may make the smooth floor appear worse than before. If the repairs is not carried out properly, in addition to patchiness and colour variations, the repaired area may delaminate. The only areas where water ponding is unacceptable are main walk paths, vehicle turning points and areas which may be a safety hazard, causing people to slip and fall or a vehicle to skid. Thank you

Stamped Concrete Finish in Malaysia – An Introduction

Date:05 April 2020 By :Eric L.S, Soong Simon K.K, Soong #stampedconcrete #concreteimprint #textureconcrete Stamped concrete popularized in the United States in the 1970s was beginning to make its way to Malaysia in the late 1980s. The systematic method of concrete stamping was introduced by a gentleman named Brad Bowman in the 1950s. After making its foray into Malaysia, this new trend of decorating concrete began slowly to gain momentum in the county. Once dominated by plain concrete finishes, interlocking pavers and floor tiles, today stamped concrete has been trending throughout the county and found favour among the local architects and designers. Stamped concrete exhibits a unique trait in being able to blend a variety of colors and patterns together. This special property is what makes it a popular feature for decorating roads, driveways, walkways, patios and many more places. It also offers a variety of pattern options ranging from wood textures to slate textures. Other benefits of using stamped concrete include among others its affordability, the durability of the product and its requirement of not needing much maintenance. The Early Years In the early years of stamped concrete, the works were largely concentrated in individual luxury houses. In the late 1980s and early 1990s as the trend began to pick up, stamped concrete was being installed in larger volume and scale. Stamped concrete began to feature prominently in many housing developments as it accords a uniqueness to the development. Specifically the stamped concrete works in these developments would generally adopt a single pattern with a two- tone color system to attain a more realistic feel to the design. The blending of colors were typically achieved by combining different products such as colored release powders The Later Years Forty years since stamped concrete was first introduced in Malaysia, it continues to be one of the pillars in both the residential and commercial building sector and is a common product offered among decorative concrete contractors. However, customization and differentiating designs are the new normal in this day and age. Designers and architects are now adding their creative touches to the finishing design by using existing moulds and other decorative products to give it a unique outlook. In order to realize this new feat, contractors are turning to hand tools to create the finer designs such as customized groove and post coloring techniques, for example stains, to blend multiple colors. Challenges The stamped concrete industry do have its challenges. Some of the challenges encountered by decorative concrete contractors often include, among others, issues such as surface delamination, crusting cracks and lack of pristine textures on the final product. Many contractors shared the common problem on surface delamination, though in many ways it is not a reflection of the stamped concrete product itself. The main culprit more often than not is that insufficient time to allow the excessive bleed water to escape before broadcasting the color hardener onto the concrete surface. A little concrete bleeding will be beneficial to facilitate working with the dry shake color hardener but excessive concrete bleeding is one of the causes for delamination when the bleed water and air accumulated under the dense hardened color hardener, unable to escape. Another major cause of delamination is over-layering resulted from broadcasting the color hardener onto hardened concrete, followed by wetting and floating the surface. This issue can be mitigated by adjusting the concrete mix design to reduce concrete bleed water and to improve the workability with sufficient time for finishing. Crusting cracks is another issue seen on some finished works. Whilst the cracks themselves do not generally affect the durability of the concrete slab; their appearance is unsightly on the finished product. These cracks are mainly found near the stamped joints near the edges of the imprinted texture. This occurs as the surface loses water rapidly and has hardened before the rest of the concrete is allowed to set and tends to amplify during hot and windy days. Small cracks are formed around the stamped joints as the stamp mats are pushed into the crusted surface, and the surface tears apart due to stresses. This issue however could minimized by erecting a shade when casting during a hot day and by putting up temporary wind barriers to reduce the wind velocity on the surfaces. Lack of texture on the finished products is a common issue faced in the industry. A major factor that causes this issue is the type of concrete mix used during the stamping process. Concrete mix with large amount of coarse aggregates could interfere with the impression of the stamping process. One way that this could be minimised is to thus ensure the appropriate size and type of aggregates contained in the concrete mix, and in this regard, the experience of the decorative concrete contractor matters. Moving Forward A better understanding of concrete behavior and how the work surroundings could impact upon the final product are essential in bringing up, and capitalizing on, the many great features accorded by decorative stamped concrete products. These factors together with the growing diversity in stamped concrete designs as well as the continuing advancement in concrete technology in Malaysia will be strong sustaining driving forces to propel the decorative stamped concrete industry forward.

Pigmented Concrete Facade Finishing (Part 1)

Date: 9 April 2020 By: Oscar R.H.Teng Tony Teng #GFRC #GRC #Façade #Pigmented #Concrete Façade, have you ever wondered how do you read this word? Have you come across this word around while being in the construction industry? There have been multiple pronunciations in the construction industry especially in Malaysia. According to the Cambridge Dictionary, the proper pronunciation is /fəˈsɑːd/ (Cambridge University Press, 2020), which in other words, it is similar to “Far – Sud”. According to the above dictionary, façade is defined as; the front of a building, especially a large or attractive building (Cambridge University Press, 2020) where in lay-man term, the make-up of the building. Among the range of façade materials, concrete façade has its own unique character. It is believed that concrete façade serves to bridge between the design of ancient stone façade of castle like buildings to modernized unique curvy designs. This is due to concrete being ‘malleable’ which enable the shape of the concrete to be limitless as long as the mould can be fabricated. With the advancement of concrete technology and knowledge, concrete façade has developed from painted concrete to stained concrete and further to pigmented concrete as the replacement of conventionally dull color concrete. To further explain pigmented concrete, it is the mixture of color pigments dispersing in the medium of cement mortar (binder) in order to create colored concrete when cured. One of the recent building in Malaysia was constructed with it’s entire building covered with pigmented concrete as their façade curtain wall with combinations of aluminium-frame and glass is The Chow Kit Hotel located in Kuala Lumpur, Malaysia. Unsurprisingly, such distinguish design has won itself multiple press featurings including but not limited to; Monocle (UK);’Key Opening’ and The New York Time Onlne; ’52 Place To Go in 2020’ (Ormond Group, 2019). The beauty of pigmented façade is the huge contrast of color depending on the time, light, and weather effect on the concrete. With all theses features, this is one of the reason why The Chow Kit was featured. At noon, the façade is more towards brown in color while evening, the color will turn slightly reddish. Even better, as night falls, the building will appear more amazing when the color appear to be brownish-red especially when the spot lights illuminated the façade. (Left)The Chow Kit by Ormond Group, evening sun (Ormond Group, 2019) (Right)Side view of The Chow Kit by Ormond Group, night view(Ormond Group, 2019) Apart from Malaysia, pigmented concrete is being used all over the world as façade. Pigmented concrete can be shaped into different shapes just like normal concrete. Below are some buildings from all over the world which are featured in both ‘Archdaily‘ website that present architecturally interesting building internationally and ‘Concrete Construction’ website where usage of concrete is often discussed. The Casa das Historias Paula Rego (ArchDaily, 2020) Built in year 2008, designed by architect Eduardo Souto de Moura. This building have two iconic red pigmented concrete pyramid-shape towers. Being a museum, having a timeless design using pigmented concrete has always been a choice by many architects. L23 House (ArchDaily, 2020) Built in 2011, designed by Pitagoras Group. This is a private house located on a slope of a higher point of Guimaraes city, Portugal. In order to outstand the house itself on a slope full of greens, black pigmented concrete façade was selected as a contrast on the hill. Textilmacher (ArchDaily, 2020) Built in 2013, designed by Tillicharchitektur. Textilmacher is an office building/showroom located in Munich, Germany. The building is designed for a company that does textile print and embroidery. Hence, the iconic geometry folded design is combined with grey pigmented concrete façade to represent the character of the textile company. Nevertheless, depending on the season, time, light shining on the building and the weather, the pigmented façade will change it character continuously. Pigmented concrete façade is not limited to rectangular panels but can be designed to any forms. With different texture/shapes of pigmented concrete, we can achieve various kinds of finishing effects. We shall discuss about the finishing textures available for pigmented concrete in the next article. TO BE CONTINUED References ArchDaily. (2020, Mar 24). The Possibilities of Pigmented Concrete: 18 Buildings Infused With Color. Retrieved from ArchDaily: Cambridge University Press. (2020). Cambridge Dictionary. Retrieved from LUXBEE. (2019). Chow Kit Hotel work in progress. Retrieved from Facebook: Ormond Group. (2019). The Chow Kit. Retrieved from Press: Ormond Group. (2019). The Chow Kit. Retrieved from Gallery:

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