Effect of Aggregate Gradation on Compressive Strength and Elastic Modulus of Cement Treated Aggregate Base Material for Highway Pavement


 Justina Stone
 3 months ago
 Views:
Transcription
1 IOSR Journal of Engineering (IOSRJEN) ISSN (e): , ISSN (p): Vol. 07, Issue 10 (Oober. 2017), V2 PP Effe of Aggregae Gradaion on Compressive Srengh and Elasi Modulus of Cemen Treaed Aggregae Base Maerial for Highway Pavemen Ekwulo E. O 1. and Eme D. B 2. 1 Deparmen of Civil Engineering, Rivers Sae Universiy, NkpoluOroworukwo, Por Harour, Nigeria 2 Deparmen of Civil Engineering, Universiy of Por Harour, Por Harour, Nigeria ABSTRACT: Pavemen failure is defined as he failure of he onsrued layer of durable maerial of speified hikness, usually oonree, asphal, or any maerial designed o arry wheeled vehiles. The defleion on highway pavemens an be as a resul of exess wheel load, poor maerial properies or inadequae aggregae gradaion of base maerial for onsruion. Aggregaes used should have he proper parile, shape, gradaion and parile srengh o onribue o a mehanially sable mixure. In his sudy, aggregaes of 19.00mm, 2.00mm, mm, 0.075mm and passing 200 s were ombined o produe normal gradaions ha mees he speifiaions limis for Cemen Treaed Aggregae Base (CTAB) mixures. Five oher gradaions were produed by removing eah aggregae from he normal gradaion. CTAB mixures were prepared using aggregaes from he differen gradaions a 3%, 4.5% and 6%, emen onen. The ompressive Srengh and elasi modulus of he mixures were deermined. Resul showed ha a all emen onen, he normal gradaion me he minimum srengh requiremen for base maerial bu removing individual aggregae s relaively redued or inreased ompressive srengh and elasi modulus depending on he aggregae removed. I was onluded ha aggregae gradaion affes ompressive srengh and elasi modulus of CTAB mixure. The sudy reommended ha aggregaes for CTAB mixures should be ombined o mee speifiaion limis and furher sudies should be arried ou for uniform aggregaes in order o furher invesigae heir effe on ompressive srengh and elasi modulus of CTAB mixures. Keywords: Aggregae Gradaion, Compressive Srengh, Elasi Modulus, CTAB Dae of Submission: Dae of aepane: I. INTRODUCTION Pavemen failure is defined as he failure of he onsrued layer of durable maerial of speified hikness, usually oonree, asphals, or any maerial designed o arry wheeled vehiles. Eah ime a load passes hrough a pavemen sruure, some defleion of he surfae and underlying layer ours. The defleion an be as a resul of exess load, poor maerial properies or inadequae aggregae gradaion of base maerial for onsruion. Aggregaes are granular mineral pariles used eiher in ombinaion wih various ype oemening maerial o form onrees, or alone as road bases, bakfill e. Aggregaes omprises he major porion of sabilized base, normally beween 80 o 95 peren by weigh of sabilized base mix may onsis of Aggregaes. Aggregae used should have he proper parile, shape, gradaion and parile srengh o onribue o a mehanially sable mixure. In order o ensure an eonomial and praial soluion, boh fine and oarse aggregaes are uilized o make up he bulk of he Aggregae mixures. Sand, naural gravel and Crushed sone are mainly used for he purpose. There are wo differen aggregae base maerials used urrenly in praie for road base onsruion in many ounries. One is he onvenional rushed based maerial and he oher is reyled onree maerial. This sudy is based on he onvenional rushed based maerials whih onain 1.5in (37.5mm), 3 / 4 in (19.00mm), No.10 (2.00mm), No.40 (0.425mm), No. 200(0.075mm), and passing 200 sieve in aordane wih he grading requiremens of he Amerian soiey of Tesing Maerials[1]. Speifiaions are generally lear and onise qualiaive desripion of he signifian haraerisis of a onsruion maerial. The speifiaion overs qualiy onrolled gradual aggregaes ha when handed o and properly spread and ompaed on a prepared grade o appropriae densiy sandard whih may be expeed o provide adequae sabiliy [2] and load suppor for use as highway bases. Coarse aggregae reained on he sieve shall onsis of durable pariles orushed sones, gravel, e whih may or are apable of wihsanding he 79 P a g e
2 effes of handling, spreading and ompaing. Fine aggregaes passing he various sieve s shall normally onsis of fines from he operaion orushing he oarse aggregae. Aggregae base maerials (bound or unbound) are used as pavemen maerials. Unbound aggregae base maerial is a mixure of aggregae maerial and filler suh as sone or emen dus. Bound aggregae base maerial suh as Cemen reaed aggregae base (CTAB) is a mixure of aggregae maerial and measured amoun of Porland emen and waer ha hardens afer ompaion and uring o form durable paving maerial [3]. As a sruural layer of pavemen, CTAB is widely used as a base ourse for eiher flexible or rigid pavemens. CTAB also shows elasi, slablike response o loading and is performane is influened by he srengh and modulus of he maerials. These properies are also ruial for design proedures ha onsider he sresssrain relaionship and faigue haraerisis of he CTAB layer [4, 5]. In CTAB onsruion, objeives are o obain a horough mixure of aggregae and granular maerial wih he orre quaniy oemen and waer o permi maximum ompaion whih hardens he emen aggregaes mixure during uring. By virue of he simpliiy of he es mehod, he unonfined ompressive srengh is mos ommonly referred o as he mix design rieria for he onsruion of CTAB. Many previous sudies proposed empirial relaionships beween he ompressive srengh and flexural or ensile srengh oemenreaed maerials ha are useful for he sruural design of he layer. The flexural and spli ensile srengh oemenreaed maerials were found o be abou 2025% and 1015% of he unonfined ompressive srengh, respeively (6). For he design and analysis purposes, 10% of he ompressive srengh is generally regarded as an aepable esimae of he ensile srengh of CTAB. I is noed ha hese relaions are no signifianly differen from he relaionships proposed for normal onree. Elasi modulus of CTAB is a neessary inpu for mehanisi design of highway pavemens. CTAB maerial for use as pavemen maerial mus mee speifiaions in erms of gradaion and ompressive srengh [1, 7]. The use of gapgraded aggregaes for pavemen base maerial resuls in unaepable voids in he pavemens and may affe pavemen maerial properies suh as elasi modulus. Tes for elasi modulus for CTAB is relaively expensive. AASHTO design guide for mehanisi design of pavemens reommends he use oorrelaion equaions for he deerminaion of elasi modulus of pavemen maerials. The ACI proedure adoped in his sudy is adequae in ha i an deermine he elasi modulus of CTAB maerials from is ompressive srengh[7]. The ASTM [1] sandards adoped also provide gradaion speifiaion for base maerials in order o ahieve adequae ompressive srengh and elasi modulus of CTAB ha an wihsand vehiular wheel loads. The researh will go a long way in insilling auion in he seleion of aggregaes for road pavemens. Mehods o deermine an appropriae elasi modulus of CTAB maerial are ompliaed beause of he diffiulies assoiaed wih esing and inerpreing he es resuls. Beause of hese diffiulies, i was reommended for design purposes o use a relaionship beween he srengh and modulus of elasiiy of he maerial in lieu of esing. Many previous sudies have proposed relaionships beween he unonfined ompressive srengh and modulus of elasiiy oemenreaed maerials [810]. These sudies sugges ha differen relaionships exis for differen ypes oemenreaed maerials depending on he qualiy of aggregaes used. For lean onree and CTAB maerials, Thompson [6] reommended use of he relaionship of normal onree provided by he Amerian Conree Insiue (ACI). The ACI ommiee 209 [7] proposed he esimaion oompressive srengh wih ime for normal onree using he model in equaion 1. ( ) f ( 28 ) a b. (1) Where ( ) = Compressive srengh a ime () ( 28 ) = referenes 28days ompressive srengh a,b = Experimen oeffiien. Where a = 0.4, b = 0.85 Calibraion of he ACI model wih he CTAB es daa [11] resuled in a new se ooeffiien as shown in equaion 2 ( ) f ( 28 ) a b. (2) Where ( ) = Compressive srengh a ime () ( 28 ) = referenes 28days ompressive srengh a,b = Experimen oeffiien. 80 P a g e
3 Where a = 2.5, b = 0.9. This new se ooeffiiens is expeed o be appliable o any CTAB mixure regardless of aggregae ype and mixure proporioning. The relaionship beween he ompressive srengh and elasi modulus or modulus of elasiiy as proposed for CTAB maerials [11] is as shown in equaion W. f ( ) (3] E ( ) Where, E() = Elasi modulus a ime in psi w = mixure densiy in pf ( () = ompressive srengh in psi a ime The relaionships is expeed o over any ype of CTAB maerials having 7day srengh in he range of 200 o 2000psi (1.4 o 13.8 MPa) [11]. The waeremen raio of CTAB also affes ompressive srengh an elasi modulus of CTAB maerial. The use unbound aggregaes base maerials (ommonly alled sone base or 0/50) and CTAB maerials as highway pavemen maerial wihou onsidering he effe of aggregae gradaion on he elasi modulus have onribued o he frequen road failures in Nigeria (Ajayi, 1987). Compressive srengh and elasi modulus of CTAB may be affeed if he mixed aggregae gradaion of he maerial is alered or no properly mixed aording o speifiaion. This will also affe he parile disribuion (PSD) by forming a wis a ha pariular poin where he aggregaes is removed hereby ausing a sligh shif of he PSD urve from he envelop leading o an unsaisfaory gradaion ha will no mee speifiaion. This sudy is aimed a invesigaing he effe of gapgraded aggregaes on he ompressive srengh and elasi modulus oemen reaed aggregae base maerial for highway pavemen. II. MATERIALS AND METHODS 2.1 Maerial The maerials used in his sudy whih are loally available pavemen maerials in Nigeria inlude: i. Ordinary Por Land Cemen ii. Porable waer iii. Coarse aggregae (rushed sone) iv. Sone dus v. Fine sand The rushed sone, sone dus and fine aggregaes were soured from a onsruion firm in Rivers Sae, Nigeria and wellgraded o mee sandard speifiaion. 2.2 Apparaus The equipmen ha were used in he sudy were: 100mm x 115mm ylindrial seel moulds, ags sieves, reainers, brush, weighing insrumen, rowel, spanners, eleri able vibraor, eleri onree mixer, slump es one, uring ank and onree load esing mahine. III. METHODOLOGY 3.1 Experimenal Design The sudy adoped he ACI and ASTM sandards and proedures [1, 7]. The experimenal mehodology of he sudy involved laboraory es on eigheen (18) ses of 100mm x 115mm ylindrial speimens of hree (3) speimens per se, prepared using wellgraded aggregaes (onrol speimen) and gapgraded aggregaes o evaluae he effe of aggregae gradaion on ompressive srengh and elasi modulus. The wellgraded aggregaes were obained by ombinaion of various aggregae s and sieved o ahieve aepable sandard gradaion speifiaion while he gapgraded aggregaes were obained by removing he amoun of aggregaes passing erain sieve s from he wellgraded aggregaes o obain ouofspeifiaion gradaion, he amoun removed is spread aross he oher s o make up for he los quaniy of aggregaes. The new ses of aggregaes were sieved o obain ouofspeifiaion gradaion. Six (6) gradaion were obained by his proess. The sieve analysis and he gradaion envelopes for normal gradaion and ouofspeifiaion gradaion are as presened in Tables 1a o 6a and Figures 1b o 6b respeively. A oal of fify four (54) CTAB speimens were prepared a 3%, 4.5% and 6% emen. 81 P a g e
4 Table 1a: Normal (Conrol) Aggregae Gradaion Weigh of Sample aken for sieving 1000g Weigh Reained Perenage reained Peren passing Graduaion requiremen (mm) (gm) (%) (%) / No No No Passing Figure 1b: Gradaion Envelop for Normal Gradaion Table 2a: Minus() 19.00mm Aggregae Gradaion Weigh of Sample aken for sieving 1000g Weigh Reained Peren reained Perenpa ssing (%) Gradaion requiremen (mm) (gm) (%) / No No No Passing Figure 2b: Gradaion Envelop for Minus 19.00mm Size Aggregaes Table 3a: Minus() 2.00mm Aggregae Gradaion 82 P a g e
5 Weigh of Sample aken for sieving 1000g Weigh Reained Peren reained Peren passing (%) Gradaion requiremen (mm) (gm) (%) / No No No Passing Figure 3b: Gradaion Envelop for Minus 2.00mm Size Aggregaes Table 4a: Minus() Aggregae Gradaion Weigh of Sample aken for sieving 1000g Weigh Reained Peren reained Peren passing Gradaion requiremen (mm) (gm) (%) (%) / No No No Passing Figure 4b: Gradaion Envelop for Minus 0.425mm Size Aggregaes 83 P a g e
6 Table 5a: Minus() 0.075mm Aggregae Gradaion Weigh of Sample aken for sieving 1000g Weigh Reained Peren reained Peren passing (%) Gradaion requiremen (mm) (gm) (%) / No No No Passing Figure 5a: Gradaion Envelop for Minus 0.075mm Size Aggregaes Table 6a: Minus() Passing 200m Aggregae Gradaion Weigh of Sample aken for sieving 1000g Weigh Reained Peren reained Peren passing Gradaion requiremen (mm) (gm) (%) (%) / No No No Passing Figure 6b: Gradaion Envelop for Passing minus 200 Size Aggregaes 84 P a g e
7 3.2 Speimen Preparaion and Curing Speimens were prepared in aordane wih ASTM 39 [12] a differen emen perenages of 3%, 4.5% and 6% by weigh. The wellgraded (normal) aggregae were used o prepare CTAB speimens o serve as a onrol o he ouofspeifiaion aggregae gradaions CTAB speimens. Three (3) ses of speimen samples were prepared for eah emen perenage using aggregaes of eah gradaion and ured for 28 days. A oal of fify four (54) speimens were prepared for he sudy. 3.3 Compressive Srengh Tes The speimen were esed a 28 days for ompressive srengh using he universal esing mahine in aordane wih BS 1881, par 166 [13]. The value of he load a whih he es speimen failed was reorded and used o alulae he ompressive srengh of eah speimen for differen emen perenages. The ompressive srengh a 7days was predied using he ompressive srengh a 28days adoping he model in equaion 4. ( ) f ( 28 ) a b. (4) Where ( ) = Compressive srengh a ime () ( 28 ) = referenes 28days ompressive srengh a,b = Experimen oeffiien. Where a = 2.5, b = Elasi Modulus The elasi modulus of CTAB was deermined using he relaionship beween he ompressive srengh and elasi modulus equaion W. f ( ) (5] E ( ) Where, E() = Elasi modulus a ime in psi w = mixure densiy in pf ( () = ompressive srengh in psi a ime IV. RESULTS AND ANALYSIS The resul of he ompressive srengh and elasi modulus of CTAB for he differen gradaions and varying emen perenages are presened in Tables 7 and 8 respeively. Cemen Conen (%) Table 7: Compressive srengh of CTAB maerial for various gradaions 7 days Compressive Srengh for Various Gradaions 28days Compressive Srengh for Various Gradaions (N/mm 2 ) (N/mm 2 ) Normal Passing 200 Normal Passing Cemen Conen (%) Table 8: Elasi modulus of CTAB maerial for various gradaions 7 days Elasi Modulus for Various Gradaions 28days Elasi Modulus for Various Gradaions (MPa) (MPa) Normal Passing 200 Normal Passing P a g e
8 4.1 Compressive Srengh The variaion oompressive srengh wih of aggregae gradaion of CTAB are shown in Figures 7a o 7. From Figure 7a (3% emen onen), he normal gradaion resuled in ompressive srengh of 1.59N/mm 2 and 1.99N/mm 2 a 7 and 28days respeively. This implies ha he normal gradaion me he minimum srengh requiremen of 1.4PMa a 7days for base maerials [11]. Removing he 19mm aggregae (19) resuled in a reduion of srengh o 0.89N/mm 2 and 1.08N/mm 2 for 7 and 28days respeively. Also, removing he 2mm, 0.425mm, 0.075mm or passing 200 aggregaes resuled in srenghs of 1.85N/mm 2 and 2.33N/mm 2, 1.36N/mm 2 and 1.71 N/mm 2, 2.15N/mm 2 and 2.7N/mm 2, and 0.99N/mm 2 and 1.25N/mm 2 for 7 and 28days respeively. The relaive reduion in srengh (less han minimum srengh requiremen) on removal of he 19mm aggregae ould be aribuable o reduion in he load arrying apaiy of he CTAB mixure when ompared o ha of he normal gradaion. Also, he relaive reduion in srengh (less han minimum srengh requiremen) for and passing 200 aggregaes ould be due o he absene of fine aggregaes ha would produe a good sandemen mixure wih less voids for he CTAB mixure. For 4.5% emen onen, removing he 19mm ( 19) aggregaes resuled in ompressive srengh of 1.02N/mm 2 and 1.29N/mm 2 a 7 and 28 days respeively. These values are less han he7 days minimum ompressive srengh requiremen for CTAB maerial. Similarly a 6% emen onen, he normal gradaion resuled in ompressive srengh of 1.99N/mm 2 and 2.38N/mm 2 a 7 and 28days respeively. Removing he 19mm, 2mm, 0.425mm, 0.075mm or passing 200 aggregaes resuled in srenghs of 1.69N/mm 2 and 2.12N/mm 2, 1.99N/mm 2 and 2.50N/mm 2, 2.08 N/mm 2 and 2.62N/mm 2, 3.82N/mm 2 and 4.80N/mm 2, and 1.98N/mm 2 and 2.49N/mm 2 a 7 and 28days respeively. This resul shows ha a 6% emen, he CTAB mixures me minimum srengh requiremen for base maerial for all gradaions. This ould be due o he high emen onen of he mixures. The relaive inrease in ompressive srengh a 2, and gradaions ould be due o high emen onen in he CTAB mixure, while he relaive reduion a passing 200 gradaion ould be aribuable o absene of fine aggregaes for good sandemen mixures and voids reduion. 86 P a g e
9 4.2 Elasi Modulus The variaion of elasi modulus of CTAB mixure wih gradaion is shown in Figures 8a o 8. From Figure 8a a 3% emen onen, resul shows ha he elasi modulus of he CTAB mixure for he normal gradaion were 3372MPa and 4004MPa a 7 and 28days respeively. On removal of he 19mm aggregaes, he elasi modulus redued o 2110MPa and 2506MPa a 7 and 28days respeively. Also, removing he 2mm, 0.425mm, 0.075mm or passing 200 aggregae s resuled in elasi modulus of 3746MPa and 4456MPa, 2955MPa and 3508MPa, 4123MPa and 4894MPa, and 2357MPa and 2800MPa a 7 and 28days respeively. Similarly, a 4.5% emen, resul shows ha he elasi modulus of he CTAB mixure for he normal gradaion were 3680MPa and 4368MPa a 7 and 28days respeively. Removing he 19mm, 2mm, 0.425mm, 0.075mm or passing 200 aggregae s resuled in elasi modulus of 2398MPa and 2847MPa, 3844MPa and 4546MPa, 3227MPa and 3830MPa, 5009MPa and 5946MPa, and 3076MPa and 3650MPa a 7 and 28days respeively. Same rend ourred a 6% emen onen as shown in Table 7 and Figure 8. Generally, he elasi modulus of CTAB mixures inreased wih inrease in ompressive srengh. For 3% emen, he relaive reduion of elasi modulus of he CTAB mixure on removal of he 19mm aggregae is a resul of he relaive derease in ompressive srengh. This also applies o he elasi modulus a mm and passing 200. A 6% emen onen, he emen provided exra srengh for he mixure hene he variaion in elasi modulus is no as he ase wih he 3% and 4.5% emen onen. 87 P a g e
10 V. CONCLUSION AND RECOMMENDATION 5.1 Conlusion From he resuls of he sudy, he following onlusions are hereby made: 1. Compressive srengh of CTAB mixures inreases wih inrease in emen onen. 2. Elasi modulus of CTAB inreases wih inrease in ompressive srengh 3. Aggregae gradaion affes ompressive srengh and elasi modulus of CTAB maerials espeially for gapgraded aggregaes. 4. Absene of larger oarse aggregaes and fines in CTAB mixures redues he ompressive srengh and elasi modulus, hene is load arrying apaiy. 5.2 Reommendaion 1. CTAB mixures should be prepared from mixures ha mee he graduaion requiremen for base maerial 2. Gapgraded aggregaes should be avoided in he use of CTAB for pavemen bases maerials beause is gradaions does no mee minimum srengh requiremen for base maerials 3. Furher sudies should be arried ou o invesigae he effe of uniform aggregaes on he ompressive srengh and elasi modulus of CTAB maerials. 88 P a g e
11 REFERENCE [1]. ASTM D. 1241, Sandard Speifiaion for maerial for SoilAggregae sub base, Base and Surfae Course, [2]. Lilley, A.A, and R.I.T. Williams. CemenSabilized Maerials in Grea Briain, In Highway Researh Reord, HRB, Naional Researh Counil, Washingon, D.C; 1973, pp [3]. PCA. CemenTreaed Aggregae Base. Repor SR221.01S. Porland Cemen Assoiaion, [4]. PCA. Thikness Design for SoilCemen Pavemens. Bullein EB068.01S, Porland Cemen Assoiaion, [5]. George, K. P. Charaerizaion and Sruural Design of Cemen Treaed Base. In Transporaion Researh Reord 1288, TRB, Naional Researh Counil, Washingon, D.C., 1990, pp [6]. Thompson, M.R. Mehanisi Design Conep for Sabilized Base Pavemens. Civil Engineering Sudies, Transporaion Engineering Series No.46, Universiy of Illinois, Urbana, IL, [7]. ACI Commiee 230. Sae of he Ar Repor on Soil Cemen. Commiee Repor ACI 230. IR90, ACL Manual of Conree Praie, Par I, [8]. Lilley, A. A., and R. I. T. Williams. CemenSabilized Maerials in Grea Briain. In Highway Researh Reord, HRB, Naional Researh Counil, Washingon, D.C., 1973, pp [9]. Larsen, T. J., and P. J. Nassbaum. Faigue of SoilCemen. Bullein D119, Porland Cemen Assoiaion, [10]. Williams, R. I. T. Cemen Treaed Pavemens: Maerials, Design and Consruion. Elsevier Publishers, London, UK, [11]. Seungwook, L and Dan G. Z. Esimaion of The Compressive Srengh And Modulus of Elasiiy Of CemenTreaed Aggregae Base Maerials, Paper for Presenaion and publiaion a he 2003 Meeing of Transporaion Researh Board Washingon, D.C [12]. ASTM C 39 Tes Mehod of Cylindrial Conree Speimens.( ) [13]. BS , Tesing onree. Mehod for deerminaion oompressive srengh oonree ubes, P a g e