Saturday, 29 July 2017

Using Bamboo in place of 'Iron Rods' in Concrete - Engr. Osaz’ ENOBAKHARE

There are now sufficient reasons to appreciate suitable alternatives in today’s construction. Whether it’s due to cost considerations or environmental factors, exploring alternatives is highly welcomed. Being the world’s most commonly used building material, nearly all our buildings have a signature of concrete on them. Unfortunately, the cost of a cubic-metre of concrete produced in Nigeria has nearly doubled in recent times. The price of iron rods (or steel rebars) is also largely unstable; swinging here and there like a triggered pendulum. 

There seem to be absence of any serious price regulation mechanism and the manufacturers also have their own side to the story – exchange rate issues, increased cost of raw materials, taxation and all sorts. It is not clear whether the building industry has any special provision for the average person or the common man. Interests charged on financial loans are not encouraging. You can go on and on; but complaining is obviously not the solution. They say if life gives you lemons, make lemonades out of it. Here we are; we need to reinforce concrete to maximize its potential and we have got an option –bamboo.

Tested, tried and trusted, bamboo has appreciable tensile and compressive strengths making it suitable for use as reinforcement in concrete. With ultimate tensile strength reaching 124N/sqMM, it only takes a combination of bamboo strands to equal the 250N/sqMM ultimate tensile strength of mild steel and 460N/sqMM  tensile strength of high-yield steel rebars in common use today. More so, provision for bamboo reinforcement in concrete is structurally designed in the same way as steel rebars; the mix ratios and construction processes for bamboo in concrete are not different from the norm, making it not necessarily a change in technology but a change in the material used. It’s that simple!  

There are around 15,000 species of bamboos around the world; the suitable variants are abundant and wasting away in our mangrove forests and elsewhere while we simply look away. There is need to put on a thinking cap and intensify research on the use of the naturally-occurring bamboo which is bio-degradable and eco-friendly than the carbonized steel rods. However just like every other construction material, bamboo has its own limitations; perhaps that is why it has not been approved for use in fully load-bearing members. Does this mean it can’t be used for concrete at all? No!

Bamboos, like several other plants when placed in water tend to absorb it and swell. As it expands in the concrete, it makes the concrete to crack. Water is needed to work concrete and there lies an issue. Researchers have provided solution to curing bamboo to be used in concrete so that it does not absorb water as much as it would normally do.  This treatment can be done right on the site or through other industrial processes before taking the bamboo strands to site. You have to be sure to select healthy brown ones with sizable culms to reduce the cost of treatment. Another worrisome issue was the bonding potential. Naturally bamboo has a smooth surface so it may not bond properly with cement, sand and granite or other aggregates in the mix therefore the strands are often chopped in various sections along its length before they are used in concrete. 

Beyond these two prevailing limitations, what bothers users is the durability of the material in concrete; that’s why it’s not yet broadly applicable for use in fully load-bearing members. As it stands now, the improved variety can be comfortably used for concrete piers, coping and panel of fence walls, lintel beams, ground floor slabs (or ‘German’ floors) in areas with low water table, construction of concrete kerbs, dividers, entrance pavements, wholly in concrete in temporary structures, roof parapets, ground decks, in the construction of low traffic concrete roads and as composite placed side by side with iron rods. Using bamboo as reinforcement slashes the cumulative cost of producing reinforced concrete by almost half. There are no known producers of the improved variety of this material in the country and this also poses an investment opportunity to investors interested in alternative building materials and technology. 

Wednesday, 12 July 2017

Bad Rendering or Plastering of Your Walls: Here is what to do - Engr. Osaz' Enobakhare

‘Perfection’ is the word. ‘Smoothness’ is the feeling. ‘Mortar’ is the item. The wall is the receiver and we are the admirers. Everybody wants a perfectly smooth wall for their interiors but we sometimes get more than what we bargained for. Rough, uneven and not properly detailed wall plastering or rendering are some end results that stares us in the face because we somehow engaged the wrong hands. But that’s not the end of the road. 

Rendering (or plastering) action on wall usually precede painting. It is the process of applying mortar made from a mix of cement, fine aggregates (or smooth sand) or Plaster of Paris and water to cover the surfaces of block, brick or concrete walls. This process if not properly handled can lead to a bad output. 
For instance there is often the problem of unevenness in the texture of the finish, flaking-off, breaking edges, cracking, etc. which hitherto affect overall aesthetics and durability. But not all cracks on walls are as a result of poor mortar or rendering work; sometimes it is a consequence of structural defects in the building. Sometimes when this happens, there is a temptation to simply cover it with paints or other finishing material; but that really doesn’t work. The effect of a bad plastering will still resurface with time. Talking about getting the job done properly; it is important that the mason team understands the mix ratio for mortar in order to get the right output. They must also know how to use the trowel (or application device) and smoothing devices well. A cement-sand mix ratio of 1:6 -12mm thick is generally acceptable for walls; corresponding to about 3 wheelbarrows of smooth sand to 1 bag of cement. 12mm specified here represents the thickness of the layer on the wall after application.

The nature of sand is also important. The suitable grade of smooth sand for wall rendering is one that contains a good proportion of clay which gives it a tacky or gummy feel. This does not imply the use of pure laterite. The use of sharp sand for rendering should be avoided because overtime pores are generated within the layer that affects the surface texture of the wall. The moisture content in your mortar should be adequate; just enough to make the mix workable. There are special cements used to achieve quality rendering; they were produced with the required functional requirements of good mortar/plaster in mind. It is good to make use of them rather than the general purpose cement so as to obtain great results. It is wrong to use mortar made for setting blocks or bricks to also render your walls because the composition are naturally different. Naturally if you make a bad mortar, you can only expect a bad rendering.

 Building Contractor in Nigeria

Once there is a noticeable defect on a rendered wall, even if it has been painted; it is better to simply chip-off, prepare the surface and reapply properly so that it cures without cracks. Although it may cost more to chip-off old rendered layers before re-applying mortar or P.O.P, the durability potential often override the cost burden, hence making it a cost-effective approach to the alternatives. The use of filling materials to close-up voids in walls to create even texture without chipping off in walls is a welcome development but it is not often the best option; especially if the defect is on a large scale. If you must use filling materials some Experts advice that you drill tiny holes into sections of the wall (using a simple drilling device) to allow for a good grip to the wall; the hole is such as extends beyond the plastering layer well into the wall fabric. Special gums are sometimes used to fill the hole to enhance firmer grip; thereby improving stability in the face of shocks.

Saturday, 8 July 2017

Flooding: Turning Your Perimeter Fence into a Retaining Wall - Engr. Osaz' Enobakhare

Security and privacy are common reasons for constructing perimeter fences around a building. Some fences are simply symbolic while others are basically for defense. They also help to prevent land encroachment from neighbors which is not uncommon in this clime. However, fences can be designed to perform yet another critical function of flood control especially for buildings constructed in areas prone to flash floods, run-off waters from faulty drains, erosion, etc. This is the core functions of embankments and retaining walls including the ability to stay earth. Retaining walls hold back or fend off flood waters from entering into your compound. There are a number of designs and technologies suited for this purpose and they can be incorporated into your fence wall and not necessarily constructed separately; saving cost and space in the end.

Generally, aesthetics is valued from outside in, not necessarily inside out. Therefore the perimeter fence and gate of our houses becomes a very vital point for aesthetic reference for the buildings as a whole, being mostly the first point of contact. 

This places a burden on the designer (or architect) to allow for aesthetic considerations for perimeter fences intended to serve as retaining walls or embankments; understanding that these fence types will be under intense water pressure when the weather goes wild compared to ordinary fences. Only suitable color, texture and styles should be used for the finishes of such fence walls. Stone-based finishes are often recommended while some others prefer to use special moisture-resistant paints and coverings. There is also the structural engineering consideration which factors in the strength, stability and durability components. If the fence is beautiful but cannot stand strong against flood pressure adequately, then it may be considered good for nothing. The method of building them is slightly different from the normal ones. One striking difference is that the base for retaining walls are normally higher than those of other fence types usually extending beyond the level of projected flood heights before block walls are introduced. Some are even designed to be trapezoidal rather than rectangular in section.

Perimeter fences are normally designed either as non-load-bearing or partially-load-bearing walls but those intended for retaining walls are essentially load-bearing walls. They do not support their weights alone or small loads from security furniture but also sizable pressure forces from external flood. There are various types of materials that can be used for building special fences of this nature; the most common type is concrete. Other types include a composite of reinforced stabilized earth with bricks or blocks as well as other poly-based substitutes for concrete. Whichever material is used, there is need for it to possess sufficient strength to withstand the pressure forces of water as well as be stable enough not to deflect, crack, fail or over-settle in the process. It should also be able to perform this function throughout the life span of the building or space it was designed to serve.

In areas susceptible to flood, the sub-surface soil conditions are often poor because of the long overbearing effect of stayed water on them, so there is always a need to take cognizance of the nature of the soil during the design of the fence. Well-built solid raft base or a combination of short-bored piles and reinforced concrete strip are good options for the foundation of such walls. Reinforced stabilized earth has also been successfully used for this purpose and is said to be a cheaper option to both polymer-based fences and concrete. 

Flood control is serious business especially in rainy seasons. There is no better way to imagine the devastating effect of flood than to watch a house go partially or completely under water; destroying the building fabric and other valuable properties in the process. Although fencing alone cannot completely take care of flood on a large scale however it is known fact that the retaining wall fence type surely minimizes the effect by helping to redirect water from a property.