Homes and Property
A powder to stop cracking buildings
Posted Wednesday, March 6 2013 at 02:00
Plasticisers are a powdered building material that stops a building from developing cracks.
Mahad Ssenyomo is putting up a multi-million facility of rented suites at Post Office ward in Entebbe town. When he took me to his constrution site of eight months, I was struck with the strength and pace at which the project is going up.
He attributes the workmanship to the powder building material his masons mix in the cement.
“That powder is called Powdered Mortar Plasticiser. It makes the building strong and the mortar or plaster plastic-like. But many people don’t use it, and that is why their constructions develop cracks, and at times, collapse,” Charles Kamya Kayanja, an engineer with Bulicon Engineering Services that is constructing the site, offered to explain to me. It was the first time I had come across such a material.
Powdered Mortar Plasticiser is a powder form mixture packed in sachets for easy and accurate dosing. It is designed for modifying cement mortar used in brick-laying and pointing mortars, back coats, renderings and block work.
It also improves manipulability without the addition of lime and increases resistance to freeze thaw cycles in the set mortar.
Mr Ssenyomo says, he was told about the plasticisers by his brother, who lives in UK. His brother told him, it is mandatory to add plasticisers when setting up a building in the UK and some European countries. That explains why some of their houses are covered by ice during severe seasons like winter but the mortar never gives way or collapses because of absorbing water.
Ssenyomo explains that when applied, the plasticisers make the building not only strong and durable but provide a plastic-like linen meaning it will never grow algae and mortar will never wear out even after 100 years because of the plastic-like layer.
Mr Fred Waligo, a mason at one of the big constructions firms in Uganda adds, “Plasticisers not only improve workability of mortar and concrete mixes but also minimises cracking and crazing, reduces water content of mortar and also enables accurate dosing.”
Many people have different names for the plasticisers with many calling it concrete fibres, retarders, or even water reducers.
Mr Waligo says the plasticisers are very good when constructing swimming pool beams, plastering walls or ceilings and flooring a house.
According to Eng Kayanja of Construction Services Limited, plasticisers are not so common in Uganda because people think the materials are not common on the market and are too expensive.
They instead use other cheap methods like binding where people apply water and sand or cement paper in some incidences to make concrete set properly.
He says concrete drying so fast under high temperatures is not good just as concrete taking long to dry under cool temperatures like in the septic tank and under shades.
“If it dries so fast under sun, it is likely to develop cracks while taking long to dry may create water voids that plasticisers can address,” Mr Kayanja notes.
He says, however, there needs to sensitiwe builders on the importance of plasticisers because many people are ignorant about these great importance of these powders.
How to mix it
Mr Kayanja says each sachet gives best results when mixed in the concrete with a ratio of 1:1:2:4 meaning, one bag of cement added to one wheel barrow of plaster sand to two wheel barrows of lakeside sand, with four wheel barrows of stone.
Plasticisers contain components like those in cement that stimulate some compounds to work faster depending on what the builder intends but also adding some plastic-like linen to a constructed wall.
Eng Joseph Mukiibi, Entebbe Municipal Council says they mostly read about them while in school but are not so commonly used in Uganda’s construction industry.
“Plasticisers are highly recommended when putting up structures but are mostly used by big companies like Roko,” he says
Although plasticisers are not so common in Uganda, they are slowly penetrating the Ugandan market especially Powdered Mortar plasticisers manufactured by Build Chemical Research in the United Kingdom and are found at Roko technical services on Nasser Road Kampala, Viva General Hardware in Ndeeba and various other shops in Uganda at very relatively low prices.
A packet of plasticisers cost between Shs5,000 and Shs10,000 on the market.