الفهرس 
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Abstract
The Eastern Desert has several drainages pattern toward the Red Sea represented by numerous independent dry Wadies. They are showered by annual rains, leading to accumulation of a large quantity of Wadi deposits, which comprise natural aggregates (Wadi wash aggregate). Accordingly, they could be used for a construction purposes.
Sedimentologically, Wadi wash deposits are developed from the weathered overburden and fractured bed rock of crystalline rocks of extrusive, uplifted intrusive and/ or metamorphic origin. Also, volcanic rocks mainly in upland areas are contributed where any weathering products tend to be rapidly eroded. Wadi Wash bed is considered the most upper layer in the Wadi filling, non-fossiliferous, with varied thickness and aggregates embedded usually in a sandy matrix, therefore it is easy to quarry and used for aggregate production.
Texturally, these deposits are poorly sorted, consisting of varying proportions of silt, sand, and gravel. The component particles are usually densely packed but lack orientation, so that the washed bed has a massive rather than a bedded nature.
Depositionally, all Wadi wash deposits sequences in Esh El-Mellaha range are similar to some extent. Differences were observed in the thickness of the washing layers also the size and type of sediments. Thickness of the studied sections varies between 2 and 9 m. The Wadi deposits in these areas are composed of sand and gravel of different sizes embedded in a poorly sorted matrix.
Wadi wash deposits in Wadi Asala are characterized by varied fragment sizes with irregular shapes and angular surfaces where large sizes of sediment are present. Most of clastics derived from Dokhan volcanics as andesite, porphyrite, and imperial porphyry.
Wadi El Ambagi could be distinguished as, homogeneous layers from rock deposits resulting from the disintegration of weathered meta-volcanics and younger granites rocks. These fragments mixed with clay, silt and rich with sand matrix. It is noted a scarcity in boulder size and commonly in medium and fine particles.
In Wadi Abu Dabbab, the deposits are formed of large massive layer of coarse fragments mixed with sand and silt matrix. It covered by friable sand and intercalated with thin gravel lenses. In that Wadi carbonate fragments are present in sites downstream but with minor percentage.
Wadi Ambaut doesn’t differ from the rest similar deposits of the Red Sea valleys, but its aggregate is characterized by abundance of felsic to mafic nature of gravelly size. They are derived from Older Granite, Metavolcanics and gneisses contaminated with small portion of carbonate fragments from the surrounding area.
Mineralogically, the most abundant minerals in the studied Wadi wash aggregates are quartz, albite with minor amounts of clay minerals as kaolinite, illite, chlorite and montmorillonite. Quartz reaches its maximum percentage at Wadi Asala, whereas Wadi Abu Dabbab and Esh El-Mellaha Range aggregates have the least values. Feldspar (albite) is the second abundant mineral in Wadi wash aggregates. The kaolinite mineral is the most highly distributed clay mineral. Also, actinolite mineral is abundant only in some areas as Wadi Ambagi, Wadi Abu Dabbab and Wadi Ambaut. Petrographical analysis showed the composition of aggregates and
helped in representing the extent of aggregate reactivity. Wadi wash aggregate is deposited during weathering process so many thin sections show micro fractures, pits, suture and undefined boundaries between minerals. Also, alteration and distortions of feldspars and cracked quartz grains shown by petrographical analysis explain the increase of aggregate reactivity. Amorphous form of groundmass in volcanic clasts indicated low crystallinity and gave the aggregate a reactive nature, causing ASR.
Chemically, the Wadi wash aggregates of the Red Sea drainage patterns show variation in oxide content percentage among the studied aggregates. This is related to the diversity of rocks that drive these aggregates.
The averages of soluble salts are accepted for all aggregate to be applied in concrete industry where the amount of sulfates did not exceeds the limit of Egyptian specification. The studied aggregate show low total chloride content, therefore minimized the risk of embedded steel reinforcement corrosion. Except one sample from Wadi Ambagi and Wadi Ambaut, they are relatively higher than the permissible limits, but such aggregates can be acceptable if the overall chlorides in the concrete mix are less than the maximum allowable limit.
The physical and physicomechanical properties of the studied aggregates are varied among Wadies, due to the changes of their sources. There is a gap in the grading of Wadi wash aggregate samples, which didn’t make a well graded aggregate. Particles size distribution of the aggregates is mixed and uneven. The closer distribution of the studied aggregates sizes are lined with 20 mm size limits. It is not entirely located in the permissible limits, but there is a deviation for large sizes in Km 35 north of Hurghada City, Wadi Asala, Wadi Ambagi, Wadi Abu Dabbab and Wadi Ambaut samples. This deviation may due to the diversity of rock type and shape constituent the aggregates in each area. Therefore, a suitable redistribution for grading should be done before using the natural Wadi wash aggregate in concrete mixtures. Wadi Ambagi has the highest elongation index value among all studied aggregates, relate to contribution of aggregate particles with a metamorphic origin. This value considered acceptable property according to the British Standard (BS 812 Section 105.2) and the Egyptian Code (ECP 203-2009). It should be concluded that, this source of aggregate needs a higher volume of cement paste that will influence the workability and cost of concrete.
All studied Wadi wash aggregates don’t pass the maximum limits of clay lumps and fine materials, given by the Egyptian Code and ASTM
C 142. On the other hand, samples show average of water absorption within the limits of the Egyptian standards of aggregates.
Wadi Abu Dabbab aggregates are characterized by the highest values of bulk density. Wadi wash aggregates values of the bulk density are acceptable for normal weight concrete. Apparent specific gravity values of Wadi wash aggregates are within the acceptable limits which range between 2.50 and 2.75 gm/cm3 for the natural aggregate. Mechanical properties of Wadi wash aggregates reflect low abrasion resistance by L.A test according to the Egyptian standard and ASTM limits. Their ACV didn’t exceed limits according to the Egyptian Code and BS 812. Most of the studied Wadi wash aggregates have a good strength and suitable to be used for normal concrete.
According to the Egyptian standard limits, all the studied Wadi wash aggregates are sounded when treated with magnesium sulfate salt through five cycles. Aggregates of Wadi Ambaut are considered the most durable.
According to ASTM C1260, all studied Wadi wash aggregates showed expansion less than 0.1% after soaking in sodium hydroxide solution for 14 days, and don’t pass 0.2% after 30 days, therefore studied samples are considered inconclusive. On the other hand, they may show more evidences of ASR products and expansion after long time. Clay content which formed due to alteration helped in increase the expansion by moisture uptake.
Microscope analyses showed more evidence of ASR. It was noticed as a zone darker than the rest of the cement paste appeared in most of the studied mortar polished sections. Alkali silica product found as white color inside voids, also between aggregates and surrounded their periphery. Detection of alkali reaction products was aided by using chemical stains like sodium cobalt nitrite (Lane, 2001). Accumulations of stained zone indicate cement paste with high potassium content. These zones may be the beginning of a reaction product.
When additives such as EPP, GGBF slag and Li2CO3 were used with the high reactive aggregate of Wadi El-Ambagi, they showed reduction in expansion and less evidence of AAR. This reduction in expansion was due to the pozzolanic effect in suppressing the ASR. There was a decreasing trend in the linear expansion with increasing EPP content from 6 till 15% replacement. Replacement by 15% EPP showed the lowest linear expansion with a value 0.04 after 14 days and 0.07 after 30 days. Replacement of cement by 10 and 20% slag reduces the expansion of the studied aggregate sample but didn’t prevent it. Other slag replacement percents as 25, 30 and 50% of cement resulted in the expansion into the 0.1% limit after 16 days soaking in the alkali solution. Lithium carbonate reduced the alkali-silica expansion of the studied Wadi wash aggregates. Li2CO3 was found to be more effective than the others, because it involved little amounts (1, 1.5, 2.5, 5 and 7.5%) of cement replacement.
Properties of the produced concrete were influenced by the content of its aggregates. The heavy Wadi wash aggregate gave to the concrete its high density. Density of concrte additives like EPP reach to 2529 kg/m3 and it lowered with increasing of replacement. Concrete made with aggregates from Wadi Abu Dabbab and Wadi Ambagi source showed highest water absorption. This is due to the higher percent of clay content in these aggregates which influence on concrete absorption. Water absorption increased when additives like EPP and Lithium carbonate salt were used. Also, it increased with increasing the replacement.
To some extent, there is a variation in strength among all studied concrete samples. This may relate to the difference in shape and some minerals content of all used aggregate. The strength ranges between 145 and 196 Kg/cm2 in the early age (3 days). But it increased to range between 301 and 413 Kg/cm2 in the later age (90 days). But these values achieve only low and normal strength purposes.
In Conclusion, the Wadi wash deposits in the Red Sea region represent another resource for natural wealth, as the natural Wadi wash construction aggregates. Such deposits will be studied carefully, for applying as coarse and fine aggregates in concrete industry along the new Red Sea construction region. Therefore, the present study recommends that:
1. Wadi Wash aggregate should be examined carefully for applying as coarse aggregates in concrete industry. A suitable grading should be done before making concrete with Wadi wash aggregate, also avoiding elongated aggregates will make a good influence on workability and reduce coast of concrete.
2. ASTM C1260 is not recommended to be used by themselves alone to confirm an aggregate as being reactive, more microscopic analysis should be done on mortar and concrete made by Wadi wash aggregate to confirm reactivity.
3. Researchers should be focus on the behavior of clay content of Wadi wash aggregate with cement paste.
4. Egyptian reactive Wadi wash aggregate will deal with additives like lithium salts, EPP or GGBF slag for inhabiting AAR. Such admixtures should be added with minor amounts to improve mechanical properties and give good compressive strength to concrete.