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25-429: The Suguta valley today is one of the driest parts of Kenya, with annual rainfall below 300 millimetres (12 in). Lake Logipi seasonally fills a small part of the northern end of the valley. The valley has a relatively flat floor about 300 metres (980 ft) above sea level. It is bordered by land to the east and west rising to 1,000 metres (3,300 ft) and dotted with volcanic cinder cones. The Barrier Volcano ,

50-458: A pH of 9.5-10.5 and salinity (total dissolved salts) that varies from less than 20 g/L to greater than 50 g/L. Efflorescent salt crusts ( trona ) are present around its margins. Flamingoes frequently inhabit the saline waters feeding on cyanobacteria ( Arthrospira spp. - formerly termed Spirulina ) and other plankton. Lake Turkana extended after extreme rainfalls in 2020 and overflowed Lake Logipi. This Kenya location article

75-529: A broad volcanic complex, separates the valley from Lake Turkana. Mount Ngiro rises to the east of the Suguta valley. The Losiolo Escarpment , rising 2,000 metres (6,600 ft) above the valley floor on the east side near Maralal provides one of the most dramatic views of the Kenyan rift valley. Namarunu , a volcano active in historic times, extends into the valley from the western wall. The Suguta Valley lies along

100-411: A cosmetic outer problem only (primary efflorescence causing staining), but can sometimes indicate internal structural weakness (migration/degradation of component materials). Efflorescence may clog the pores of porous materials, resulting in the destruction of those materials by internal water pressure, as seen in the spalling of brick. Primary efflorescence is named such, as it typically occurs during

125-446: A nanomolecular level, converting it into non-sodium chemicals and other harmless matter that will not leach out or migrate to the surface. In fact, the nanotechnology in these additives can be up to 100,000 times smaller than even the smallest cement particles, allowing their molecules to literally pass through cement minerals or sand particles and ultimately become part of the cement or sand with which they react. And since they require

150-477: Is a stub . You can help Misplaced Pages by expanding it . Efflorescence In chemistry , efflorescence (which roughly means "the flowering" in French) is the migration of a salt to the surface of a porous material, where it forms a coating. The essential process involves the dissolving of an internally held salt in water or occasionally, in another solvent. The water, with the salt now held in solution, migrates to

175-662: Is drained by a seasonal stream, the Suguta River , which in the rainy season forms the temporary Lake Alablad, a playa lake that combines with Lake Logipi at the northern end of the valley. In the dry season saline hot springs help maintain water levels in Lake Logipi, which is about 3 metres (9.8 ft) to 5 metres (16 ft) at its greatest depth, about 6 kilometres (3.7 mi) wide and 3 kilometres (1.9 mi) wide. The saline waters provide food for cyano-bacteria and other plankton, which in turn are food for flamingoes . Due to

200-431: Is first charged into the mixer, then the oil-based primary anti-efflorescence admixture is added with constant mixing to allow the oil to coat the sand. Then coarse aggregates, colorants, and cement are added, followed by water. If CSD is used, it is then introduced usually at this point during or after the addition of the mix water. CSD is an aqueous dispersion wherein fine solid particles of calcium stearate are suspended in

225-519: Is introduced into the batch mix at an early stage by coating onto the sand particles prior to the introduction of any mix water, so that the oily admixture is distributed uniformly throughout the concrete batch mix. Secondary efflorescence is named such as it does not occur as a result of the forming of the cement stone or its accompanying hydration products. Rather, it is usually due to the external influence of concrete poisons, such as chlorides. A very common example of where secondary efflorescence occurs

250-447: Is steel-reinforced concrete bridges as well as parking garages. Saline solutions are formed due to the presence of road salt in the winter. This saline solution is absorbed into the concrete, where it can begin to dissolve cement stone, which is of primary structural importance. Virtual stalactites can be formed in some cases as a result of dissolved cement stone, hanging off cracks in concrete structures. Where this process has taken hold,

275-413: Is the most stable polymorph of calcium carbonate (CaCO 3 ). The only way to completely and permanently prevent (both primary and secondary) efflorescence in cementitious materials is by using special admixtures that chemically react with and bind the salt-based impurities in the concrete when hydrogen (H) is present. The chemical reaction in these special additives fuses the sodium chloride on

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300-537: The Suguta Valley near Baragoi while on a mission to recover stolen cattle. Lake Logipi Lake Logipi is a saline, alkaline lake that lies at the northern end of the arid Suguta Valley in the northern Kenya Rift. It is separated from Lake Turkana by the Barrier volcanic complex , a group of young volcanoes that last erupted during the late 19th century or early 20th century. Saline hot springs discharge on

325-724: The axis of the Gregory Rift , which has been faulting in this area since the Pliocene along a belt 35 kilometres (22 mi) wide. The belt lies between the Ngiro basement uplift to the east and the Loriu Plateau to the west and is thicker in the eastern part. Exposed volcanic rocks include basalts , tuffs and ash formed between 4.2 and 3.8 million years ago, the products of trachytic volcanism from 3,8 to 2.6 million years ago and basaltic and alkali basaltic rocks created from that period until

350-448: The concrete's reaction to chlorides. Today's water repellents help create a vapor permeable barrier; liquid water, especially from wind driven rains, will stay out of the brick and masonry. Water vapor from the interior of the building, or from the underside of pavers can escape. This will reduce efflorescence, spalling and scaling that can occur from water being trapped inside the brick substrate and freezing during cold weather. Years ago,

375-413: The inaccessibility and harsh climate, with high temperatures, only the most determined tourists visit the site. The valley is used as a hide-out by Pokot and Turkana cattle rustlers. It is considered a "no go" region by the police due to the extremely harsh environment and familiarity of the rustlers with the terrain. In November 2012 over 40 Kenya Police officers and reservists were killed in

400-413: The initial cure of a cementitious product. It often occurs on masonry construction, particularly brick , as well as some firestop mortars , when water moving through a wall or other structure, or water being driven out as a result of the heat of hydration as cement stone is being formed, brings salts to the surface that are not commonly bound as part of the cement stone. As the water evaporates, it leaves

425-547: The northern shoreline of Lake Logipi and at Cathedral Rocks near its southern limit, and help to maintain water at times of extreme aridity. During the rainy season, the lake is also recharged from the Suguta River which flows northward along the Suguta Valley , periodically forming a temporary lake (Lake Alablab) that unites with Logipi. Lake Logipi has a maximum depth of 3 to 5 m, and is about 6 km wide by 3 km long. Its waters are of sodium bicarbonate composition with

450-455: The presence of hydrogen they stop reacting as the concrete dries out and begin reacting again when the concrete is exposed to moisture. It is also possible to protect porous building materials such as brick, tiles, and concrete against efflorescence by treating the material with an impregnating, hydro-phobic sealer. This is a sealer that repels water and will penetrate deeply enough into the material to keep water and dissolved salts well away from

475-536: The present. In the early Pliocene the least horizontal stress direction - the direction of rift expansion - was NW-SE. Lake Suguta once filled the valley, at times overflowing into Lake Turkana. The lake level rose and fell several times in the last 18,000 years due to changes in rainfall during the African Humid Period that lasted from 14,800 to 5,500 years ago. The lake level began to drop about 8,000 years ago, falling by 250 metres (820 ft). The valley

500-578: The salt behind, which forms a white, fluffy deposit, that can normally be brushed off. The resulting white deposits are referred to as "efflorescence" in this instance. In this context efflorescence is sometimes referred to as "saltpetering." Since primary efflorescence brings out salts that are not ordinarily part of the cement stone, it is not a structural, but, rather, an aesthetic concern. For controlling primary efflorescence, formulations containing liquid fatty acid mixtures (e.g., oleic acid and linoleic acid) have commonly been used. The oily liquid admixture

525-399: The source of the water penetration is not addressed efflorescence may reappear. Common rebar protective measures include the use of epoxy coating as well as the use of a slight electrical charge, both of which prevent rusting. One may also use stainless steel rebar. Certain cement types are less resistant to chlorides than others. The choice of cement, therefore, can have a large effect upon

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550-429: The structural integrity of a concrete element is at risk. This is a common traffic infrastructure and building maintenance concern. Secondary efflorescence is akin to osteoporosis of the concrete. For controlling secondary efflorescence, admixtures containing aqueous-based calcium stearate dispersion (CSD) are often added at a later stage of the batching process with the mix water. In a typical batching process, sand

575-453: The surface, then evaporates, leaving a coating of the salt. In what has been described as "primary efflorescence", the water is the invader and the salt was already present internally, and a reverse process, where the salt is originally present externally and is then carried inside in solution, is referred to as "secondary efflorescence". Efflorescences can occur in natural and built environments. On porous construction materials it may present

600-419: The surface. However, in climates where freezing is a concern, such a sealer may lead to damage from freeze/thaw cycles. And while it will help to protect against efflorescence, it cannot permanently prevent the problem. Efflorescence can often be removed from concrete using phosphoric acid. After application the acid dilution is neutralised with mild diluted detergent, and then well rinsed with water. However, if

625-516: The water uniformly. Commercially available CSD has an average particle size of about 1 to 10 micrometres. The uniform distribution of CSD in the mix may render the resulting concrete masonry unit water repellent, as CSD particles are well distributed in the pores of the unit to interfere with the capillary movement of water. Calthemite is also a secondary deposit derived from concrete, mortar or lime, which can be mistakenly assumed to be efflorescence. Calthemites are usually deposited as calcite which

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