GEOTECHNICAL STUDY OF AGGREGATES FOR CONCRETE PRODUCTION IN CONSTRUCTION INDUSTRY SINDH PAKISTAN
MUSHTAQUE A. PATHAN, RAFIQUE A. LASHARI, MARYAM MAIRA
C P & A GEOLOGY,
UNIVERSITY OF SINDH, JAMSHORO
[email protected], [email protected], [email protected]
concrete is one of the flexible and widely used buiding material in the world construction industry. fine and coarse aggregates make about 70% through volume of concrete manufacturing. it goes with out saying that concrete is thus strongly influenced by means of mixture.,in addition to chemical composition of the parent combination making mix. The identification and classification of aggregates so that they are used to satisfy the required targets.in this paper, the physical, mechanical, and chemical properties of aggregates are reviewed. the resources and modes of manufacturing of coarse and high-quality aggregates inside theJamshoro production agencies are assessed. Some random samples, which can be particularly quarried from around the countryside of Jamshoro, where the main share of construction works are taking place, are discussed. the check results are as compared with the usual requirements and urban demand.
Aggregates, los agles test, ACV, SP. GRAVITY, LIMESTONE CRUSH ETC.
concrete is a versatile and maximum famous construction material within the world. it’s far produced by mixing fine and coarse aggregates, cement, water and components in a sure prescribed percentage. aggregates are acknowledged to be particles of rock or equal which, when introduced together in a bound or unbound situation, form part or entire of an engineering or building shape. aggregates, each fine and coarse, take approximately seventy-seventy five% by volume of concrete and are essential elements in concrete production. the parent substances of aggregates are derived specially from sedimentary rocks. the dominant rock for coarse mixture manufacturing in SINDH PAKISTAN is normally LIMESTONE at the same time is most generally used for masonry stone. on the other hand most of the sand is accumulated from riverbeds.
it’s an established truth that the compressive strenghth of concrete is observed by, among other things, the best and proportion of fine and coarse aggregate, the cement paste and the paste-combination bond traits. those, in flip, depend upon the macro- and microscopic structural capabilities which include general porosity, pore size and form, pore length distribution and morphology of the hydration merchandise, and the bond among character strong additives. different traits of concrete including sturdiness and abrasion resistance also are tremendously dependant on the aggregate, which in turn relies upon the strenghth of determine rock, purity, surface texture, gradation and so on.
basically three classes of aggregates are identified relying on their weight: light weight, normal weight and heavy weight. light-weight aggregates are aggregates whose maximum dry & bulk density is about 880kg/m3 for course aggregates and 1040kg/m3 for all-in aggregates 1.
regular weight aggregate is usually produced in Jamshoro area with the aid of crushing determine rocks the use of mechanical crushers or traditional strategies. limestone rock is a superb example of available rock, that’s used in particular for coarse aggregate production in all over the Sindh province.
the principle recognition of this research paper is, therefore, to study sources and production of aggregates, examine the suitability of available rocks for concrete production, and propose higher approaches of aggregate manufacturing and utilization for maximum concrete production.
classification of aggregate
aggregates may be classified as natural oe artificial dpending on their sources. Natural aggregates are taken from quarries through processing beaten rocks or from riverbeds while artificial aggregates are acquired from crushing plants, the physical and mechanical properties of aggregates are inherited from parent materials, while fabric intern depend on its geological formation. geologically rocks are categorized into three most important divisions based totally on their foundation, namely igneous, sedimentary and metamorphic. igneous rocks are rocks fashioned from the solidification of molten depend (magma) both at or underneath the earth’s floor. igneous rocks are divided into : plutonic or intrusive, the ones having cooled slowly with within the earth (e.g. granite, diorite, gabro, and so on) and volcanic or extrusive, those which are formed from short cooled lava (eg. volcanic rock, volcanic glass, felsites, basalt, and many others). plutonic rocks normally have grain sizes larger than 1mm and categorised as route or medium grained at the same time as volcanic rocks have grain sizes less than 1mm and are classified as nice-grained. those grains are, however, now not seen to the bare eyes 2,3.
the most typically discovered common rocks in and round Jamshoro vicinity are limestone rock, the chemical composition is summarised in desk 1.
Sedimentary rocks are formed as strata as a result of sedimentation from disintegrated products. They are stratified rocks usually laid down under water although they can also be formed by wind and glacial action. The sediments are cemented together or compacted during geologic time with varying degree. Typical examples are sand stone, limestone, and shale.
Properties of Aggregate
The physical properties like specific gravity, porosity, thermal behaviour, and the chemical properties of an aggregate are attributed to the parent material. The shape, size and surface texture which are essential for concrete workability and bond characteristics between the aggregate and cement paste are, however, attributes of the mode of production. It is, therefore, essential to understand the mechanical, physical and chemical properties of aggregate and its modes of production in an effort to produce the required quality of concrete at a minimum price.
Aggregate Size, Shape and Surface Texture
The use of larger maximum size of aggregate affects the strength in several ways. First, since larger aggregates have less specific surface area and the aggregate–paste bond strength is less, aggregate fails along surfaces of aggregates resulting in reduced compressive strength of concrete. Secondly, for a given volume of concrete, using larger aggregate results in a smaller volume of paste, thereby providing more restraint to volume changes of the paste. This may induce additional stresses in the paste, creating microcracks prior to application of load, which may be a critical factor in very high strength concretes 5. Therefore, it is the general consensus that smaller size aggregates should be used to produce higher strength concrete.
Particle shape and surface texture influence the properties of freshly mixed concrete more than the properties of hardened concrete. Rough-textured, angular, and elongated particles require more water to produce workable concrete than smooth, rounded and compact aggregate. Consequently, the cement content must also be increased to maintain the water-cement ratio. Generally, flat and elongated particles are avoided or are limited to about 15 percent by weight of the total aggregate. The essential requirement of an aggregate for concrete production is such that it remains stable within the concrete and in the particular environment throughout the design life of the concrete without adversely affecting the performance of concrete in either the fresh or hardened state.
Both the shape and surface texture of aggregates influence the strength of concrete, especially so for high strength concrete. Generally, flexural strength is more affected than compressive strength. Rougher texture results in a greater adhesion or bond between the particles and cement matrix. Determination of the quality of bond is rather difficult. When bond is good, a crushed concrete specimen should contain some aggregate particles broken right through, in addition to the more numerous ones separated from the paste matrix. On the other hand, an excess of fractured particles suggest that the aggregate is too weak.
It is generally understood that the compressive strength of concrete cannot significantly exceed that of the major part of the aggregate contained therein, although it is not easy to determine the crushing strength of the aggregate itself. The required information about the aggregate particles has to be obtained from indirect tests, such as crushing strength of prepared rock samples, crushing value of bulk aggregate, and performance of aggregate in concrete. The aggregate crushing value (ACV) test is prescribed by different standards, and is a useful guide when dea1ing with aggregates of unknown performance.
Toughness can be defined as the resistance of aggregate to fai1ure by impact, and it is usual to determine the aggregate impact value of bu1k aggregate based on ASTM standard 1. Toughness determined in this manner is related to the crushing value, and can, in fact, be used as an alternative test.
Hardness, or resistance to wear, is an important property of concrete used in roads and in floor surfaces subjected to heavy traffic. The aggregate abrasion value of the bulk aggregate is assessed using Los Angeles abrasion machine. The Los Angeles Abrasion test combines the processes of attrition and abrasion, and gives results which show a good correlation not only with the actual wear of the aggregate in concrete but also with the compressive and flexural strength of concrete when made with the same aggregate.
The physical properties of aggregates include specific gravity, porosity, absorption capacity, moisture content, unsoundness due to volume changes and thermal properties and need a close scrutiny.
Chemical Properties: Alkali-Aggregate Reactions
Alkali-aggregate reactions are chemical reactions in concrete involving certain active mineral constituents often present in some aggregates and the sodium and potassium alkali hydroxides from portland cement paste. The reactions are potentially harmful only when they produce significant expansion and hence cracking of concrete, leading to loss of strength and elastic modulus.
Alkali-aggregate reactions occur in two forms: alkali-silica reaction (ASR) and alkali-carbonate reaction (ACR). Alkali-silica reaction is the reaction between the alkali hydroxide in portland cement and certain siliceous rocks and minerals present in the aggregates, such as opal, chert and chalcedony. The products of this reaction often result in significant expansion and cracking of the concrete and ultimately, failure of the concrete structure. Alkali-carbonate reaction on the other hand is the reaction between the cement hydroxides and certain dolimitic limestone aggregates which can also result in deleterious expansion. Alkali-silica reaction is of more concern than alkali-carbonate reaction because the occurrence of aggregates containing reactive silica minerals is more common. Alkali reactive carbonate aggregates have a specific composition whose occurrence is relatively rare 6,7. Since the occurrence of dolomitic limestone is very rare in Ethiopia, more emphasis should be given to alkali-silica reactions.
Abebe et al in a recent study reviewed the mechanisms of alkali-silica reactions and discussed the potential of such reactions in Ethiopia by examining: i) the chemical and mineralogical composition of selected rocks, ii) the oxide concentration of silica sand obtained from different localities, iii) the alkali content of cements produced in Ethiopia and iv) the temperature and relative humidity of Ethiopian conditions 9. The study emphasized the need for laboratory analysis of aggregate samples with a particular focus to those aggregates susceptible to alkali silica reactions.
There are three broad categories of deleterious substances that may be found in aggregates: impurities which interfere with the processes of hydration of cement, coatings preventing the development of good bond between aggregate and cement paste, and certain individual particles which are weak or unsound in themselves. These harmful effects are distinct from those due to the development of chemical reactions between the aggregate and the cement paste. Aggregates may also contain sulphate or chloride salts that can be easily removed by washing in fresh water as otherwise it can have dangerous consequences in reinforced concrete structures resulting in corrosion of steel.
LOCALLY AVAILABLE AGGREGATES
The most commonly available local coarse aggregates are obtained from limes stone and sandstone.
limestone are light- dark colored, fine-grained surface rock. The mineral grains are so fine that they are impossible to distinguish with the naked eye or even with a magnifying glass. They are the most widespread of all the sedimentary rocks. Most limestones are fossiliferous in nature.
Sandstone is a sedimentary rock with dark yellow-brownish yellow in colour, partly ferrogenous, hard and strong in shape of large boulders at places, medium to highly weathred founf on surface.
GEOLOGICAL MAP OF JAMSHORO.District Jamshoro lies between the longitude 67o, 30′ E and68o, 30′ E and Latitude 250Nand260, 30′ N, and it is bordered in the east by Hyderabad, Matiari and ShaheedBenazeerabad and in the south by Thatta and Karachi, in the west by Dadu, Karachi andLasbela of Baluchistan and in the north by Dadu and Noshehro Feroz districts of Sindh. Thisarea lies in the east of Laki ranges.Geologically this area contains the exposed Cenozoic rocks from Paleocene to Recent Deposits. The Paleocene is exposed in Ranikot area in the form of Khadro, Bara and LakhraFormations with clastic and carbonate Lithology. The exposed formation of Eocene age isLaki Formation. Nari Formation of Oligocene age, Gaj Formation of Miocene and ManchharFormation of Miocene-Pliocene ages are exposed at various localities in the district. Thesurface is covered by Recent cover of unconsolidated surficial deposits of silt, sand andgravel.
The general topography of the area is that of alternate valleys and hills with their long axes in North- South direction. The geology of area is composed of sedimentary formations of marine origin, besides having some volcanics which are sills horizontally injected igneous bodies. Lithology sand, clay, silt, gravel, limestone, conglomerate, sandstone and shale are found having geological age from recent to cretaceous. Structurally the area is complex one as synclines, anticlines and thrust faulting is quite visible and beds exhibit steep dip and limbs of major structures.
The different quarries in Jamshoro produce crushed aggregates, stones, clay and selected materials. limestone is used for the production of aggregates on major quarries. The stone is crushed into different aggregate sizes. It is mainly mined around Jamshoro , Kotri ; Petaro area which are the areas producing the majority of the demand. Loose sand is mainly used for marter and block making. It is mainly mined around Bholari area. A reasonable amount of aggregate is also brought from the areas in the vicinity.
aggregate production in Jamshoronearly most ofl aggregates used for construction in Sindh are natural in origin. the general fabric of coarse aggregate resources in jamshoro are located round superhighway inside the town, with the exceptions of sources of sand. the huge riverbanks of bholari NAI (STREAM) and BARAAN NAI (STREAM) are the principle providers of FINE aggregates to the city of Jamshoro.
Coarse aggregate manufacturing in Jamshoro manufactured aggregates, limestone crush do have distinctive modes of productions normal weight aggregate is made from quarries by simple digging or bulldozing as it is a smooth shape and the unique sizes produced mainly depend upon digging or bull slumbering.
the ordinary weight coarse aggregates for the production area are produced by means of both, traditional and modern manner. traditionally coarse aggregate is produced by way of grinding a boulder and crushing it through a hammer the use of a guide exertions to the specified approximate sizes. aggregates produced the usage of such approach are typically flaky and donot fulfill the grading requirements set through general recommendations. however, such aggregates are used for construction in regions wherein aggregates crushing gadget(s) isn’t always available, and first-class control isn’t a criteria within the execution of the paintings.
alternatively, the current manner of aggregate production requires mixture crushing machines in order that the quarry is both drilled, blasted or dug with unique mechanisms, fed to crushers, beaten, sieved and separated in line with their sizes. the distinct sizes normally known as 01, 02, 03 and 04 are stockpiled one after the other. aggregates having a most aggregate length of 20mm, at the same time as 01, 03, 04 has a most aggregate size of 10, 30 and 40 mm resepectively. this approach enables to categorise aggregates primarily based on their maximum combination sizes and enable engineers to indicate specific blend share to reach at the required concrete satisfactory production. the dust content over the surface of the mixture, but, isn’t always given adequate emphasis via the producers even as growing critical problems at some point of concrete manufacturing. besides, no attempt has been made, thus far, to rehabilitate quarry sites after the mining operation is finished. not even the old mining sites are systematically recorded and marked nicely. common coarse aggregate manufacturing site round Jamshoro is shown in figure no. 1
plate 1 standard coarse aggregate production site around jamshoroFINE AGGREGATE production in JAMSHORO
FINE aggregates (sand), is unconsolidated and fairly variable combos of different elements. the construction industry utilizes sand especially from streambeds, which might be typically derived from quartz-feldspathic basement rocks, sandy marine sidements and alluvial deposits 14. the predominant sand deliver for the construction works in and around JAMSHORO is basin positioned about 7-10 km southeast of the town. the approach of quarring sand is normally very MODEREN and the manufacturers do not attempt to clean and grade the sand right from the source. a sand with a silt content material as excessive as 20% is usually purchased from those quarry sites. ordinary method of sand quarrying operations and transporting to the close to through loading station BY TRUCKS AND DUMPERS are shown in plates 2 and three, respectively.
SAND QUARRY FIGURES……………………………………..
studies made within the University of Sindh, jamshoro has indicated that a significant boom (about 50%) in compressive energy of concrete is acquired by means of converting the homes of aggregates preserving the grading limit, cement content material and silt content material the same 15,16. this calls for a concerted attempt by means of relevant government corporation, concrete producers and professional associations in standardizing of aggregate debris in terms of size, form, density, texture and different relevant parameters with the view of producing quality product at a reduced cost.
CONCLUSION and summary of laboratory TESTS
particle length distribution of aggregates is critical to get the maximum feasible near packing of aggregates, which reduces voids and therefore the required paste, and reap cost-effective mix. near packing additionally effects in more potent blend, as aggregates generally tend to hold more loads. thus ok care must be taken in proper type and grading of aggregates like minded with preferred requirements.
sample laboratory check effects acquired throughout nice checks for quarry establishment and for concrete mix design arrangements in addis ababa had been accrued from experienced laboratories, namely cdsco, and tcdsco, and are summarised in tables 2, 3 and four.
desk 2 laboratory take a look at results on direction combination obtained from exceptional crusher websites.
Table 2 Laboratory test results on course aggregate obtained from different crusher sites.
Crusher site Site Site Site Site Site Site Site Site Site Site
1 2 3 4 5 6 7 8 9 10
Sp.Gr. (SSD) – 2.86 – – – – – – – 3
Absorp. (%) – 1.2 2 – – 1.4 1.2 1.6 – 0.9
LAA (%) 15 18 16 19 12 16 16 16 14 12
Sound. (%) 1 1 1 1 10 2 1 1 6 1
ACV (%) – 15 14 15 – 18 17 14 – –
AIV (%) – – – 14 – 15 13 – – –
FI (%) 24 27 27 – 21 43 29 42 – –
Source: Transport Construction and Design Share Co. December 2004.
Table 3 Tests for Trachitic stone on Addis Ababa – Ambo road for crusher sites on course aggregate.
Site Site Site Site Site Site Site Site Site Crusher site 1 2 3 4 5 6 7 8 9 1.3- 7.6- 3.5- 1.85- 4.9- 2.4- Depth (m) 15 15 15 15 15 4-15 0-15 15 0-15 Mean
Sp Gr. 2.85 2.84 2.85 2.84 2.87 2.84 2.84 2.85 2.87 2.9
Absorp. (%) 1.7 1.7 1.8 1.9 0.8 1.4 1.5 1.5 1.4 1.5
LAA (%) 13 15 15 15 15 17 17 16 15 15.3
Sound. (%) 28 25 40 10 2 2 11 2 2 13.6
ACV (%) 15 17 16 16 18 18 18 17 17 16.9
FI (%) 22 37 30 36 38 42 44 44 47 37.8
Source: Transport Construction and Design Share Co. December 2004.
Table 4 Tests for concrete mixes on coarse aggregate. Contractor A B C D E F Crusher 1 2 3 4 5 6 site Specific gr. 2.74 2.88 2.68 2.79 2.49 2.67 (SSD) Absor. (%) 1.07 3.31 1.79 1.97 2.53 1.2 LAV (%) 12 13 19 1.54 13 21 Gradation Well Coarser Finer Finer Finer Good graded Source: Construction Design Share Co. December 2004 considering the fact that, lightweight aggregates aren’t normally used for structural functions, it become no longer feasible to get enough wide variety of test outcomes. the purpose for constrained application of lightweight aggregates for structural concrete might be because of loss of self assurance in the usage of the cloth for structural purposes. in this regard, researchers should try to justify using lightweight aggregates for structural concrete and ahead hints on precise application of light-weight concrete in creation undertakings.
comparison of take a look at outcomes with standards recommendation
the following standard developments had been determined from the analysis of pattern laboratory check effects.
i)los angel’s abrasion fee specified in astm c 33 is 50%, that’s lots higer than the imply value obtained from the pattern test effects indicating that the basaltic stone of addisababa is of exceptional sturdiness. supplied, the important gradation and bodily identity are made, it ought to be viable to produce higher energy first-class concrete with the to be had combination materials.
ii)soundness is one of the pleasant indicators of direction aggregates. a most of 18% for magnesium sulfate and 12% for sodium sulfate mixture supply is authorized for concrete in keeping with astm 33. the basaltic stone of addis ababa has considerable great in this admire. but, the variation in soundness acquired from trachitic stone requires similarly scrutiny. it may be because of intrusion of water and viable weathering that may affect part of the rock, which could convey the combination to a kingdom of unfit.
iii)unfortunately, it has been observed that no attention is given to test parameters including friable debris, cherts, and fabric finer than no. two hundred sieve.
conclusionsthe subsequent conclusions are drawn based at the research paintings:
1.the general fine of addis ababa basaltic stone for aggregate manufacturing is excellent.
2.the quarry web sites around addis ababa are not systematically selected and now not well rehabilitated after mining. this calls for ok attention by using concerned our bodies.
3.combination manufacturers must supply right interest in generating consistent and quality products to the customers, that are compatible with the same old
requirements. the producers ought to additionally be able to guarantee the nice in their products pleasurable the specified applicable requirements.
4.designers have to be brave to specify higher electricity high-quality concrete, to be able to have a high-quality saving in area, and improved concrete properties rather than restricting concrete class specifically to c-25.
five.the abilities of fabric laboratories in managing the desired preferred investigations ought to be progressed, and laboratory test results must be compiled indicating the supply, fabric houses and client’s identification.
6.aggregate, each high-quality and coarse, identification, quarring, garage and handling have to be executed professionally. in addition, a country wide wide effort must be made in making ready mix layout procedure, which could allow to reach at the desired satisfactory concrete manufacturing without tons problem.
7.it’s been confirmed that in-intensity investigation of combination residences is highly critical to assure quality against reactivity of aggregates. on this regard, near investigation of geological houses would be clean if engineers and geologists paintings together.
8.quarry web sites ought to be checked periodically, without giving be aware, with the aid of impartial frame for pleasurable preferred requirements.