effect of limestone and inorganic processing addition on the ...

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EFFECT OF LIMESTONE AND INORGANIC PROCESSING ADDITION ON THE PERFORMANCE OF CONCRETE FOR PAVEMENT AND BRIDGE DECKS Mustapha A. Ibrahim Research Assistant Phone: 313-231-5069 [email protected] Mohsen A. Issa (Corresponding Author) Professor 2095 Engineering Research Facility 842 West Taylor Street, Chicago, IL 60607, Phone:(312) 996-3432 Mobile: (312) 375-8186 Fax:(312) 996-2426 [email protected] Mustafa Al-Obaidi Former UIC Research Assistant Staff Structural Engineer HBM Engineering Group, LLC Phone: 312-863-1755 [email protected] John Huang IDOT, District 1 Area Construction Supervisor Phone: 847-846-7261 [email protected] Abdul Dahhan IDOT, District 1 Bureau Chief of Materials Phone: 847-705-4361 [email protected] Carmen Lopez IDOT, District 1 [email protected] Civil and Materials Department University of Illinois at Chicago 842 W. Taylor St Chicago, Illinois 60607

A Paper Submitted for Presentation at the 2014 Annual Meeting of the Transportation Research Board

TRB 2014 Annual Meeting

Total words = 5,487 + 250*8 (5 Tables and 3 Figures) = 7,487

Paper revised from original submittal.

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ABSTRACT The Illinois Department of Transportation (IDOT) is making several changes to concrete mix designs, using revisions to cement specification ASTM C150/AASHTO M 85 and ASTM C465/AASHTO M 327. These proposed revisions will enable use of more sustainable materials for concrete pavements, overlays, and bridge decks. Accordingly, a study was conducted by the University of Illinois at Chicago (UIC) to test the performance of concrete batched with cement comprising less (conventional) and more (modified) than 5% by weight of limestone and inorganic processing additions (IPA) specified in ASTM C465/AASHTO M 327, and/or insoluble residue (IR) content above the specified limit by ASTM C150. Twenty-four concrete mixes with different cementitious combinations and aggregates were developed for this study. Each cement source was batched in a concrete mixture by replacing 30% of the total cement content with fly ash or slag. Also, each cementitious combination was batched with fine aggregates (natural or combined sand) and coarse aggregate (crushed limestone). The study included measuring fresh properties such as slump, air content, unit weight, and setting time. The hardened properties included measuring the strength and durability for each concrete mix combination. The strength results were measured in terms of compressive and flexural strength, and the durability results were measured in terms of rapid chloride penetration resistance (coulombs) and water permeability (DIN 1048). The study found similar performance in terms of strength and durability of concrete between the conventional and modified cements and demonstrated their performance with fly ash or slag replacements and fine aggregate types. KEYWORDS: Air content, chemical admixtures, chloride penetration, compressive strength, durability, flexural strength, fly ash, hardened entrained air, inorganic processing addition, insoluble residue, permeability, limestone, setting time, slag, workability



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INTRODUCTION The addition of limestone and alternative raw materials to cement to reduce CO2 emissions in the cement production and concrete industries has been used in Europe for decades, with quantities up to 35% replacement of cement by weight. The Canadian Standards Association (CSA A3000) recently approved the addition of limestone in cement up to 15% by weight. The success in modifying cement production in both Europe and Canada prompted the United States to move toward a more sustainable approach in the cement production and concrete industries. The current ASTM C150/AASHTO M 85 and ASTM C465/AASHTO M 327 specifications state that maximum limestone and IPA of cement is limited to 5% by weight. IDOT is pushing forward in its efforts to modify the ASTM specifications to approve the use of limestone and IPA with more than 5% replacement of cement by weight. If this modification is approved, it will have both an environmental and economic impact on the concrete industry in the United States. From a sustainability standpoint, cement production is energy intensive and harmful to the environment because of the high temperatures required to burn the raw materials and also because of the emission of gaseous by-products in that process. On average, each ton of cement produced from a cement plant accounts for 0.92 tons of CO2 emissions (1). The emission of CO2 and other gases from cement production is attributed primarily to the calcination process of limestone and fuel combustion. Calcination is necessary in the process of cement production and now it accounts for more than 60% of total CO2 emissions (1). The addition of more than 5% limestone and IPA to cement, as proposed by IDOT, will mitigate some environmental problems by reducing the amount of raw materials burned to produce cement and to reduce the carbon footprint by at least 3% to 4% of total CO2 emissions. The modification will also help reduce the depletion of natural resources and will offer a lowcost, efficient method to secure waste materials. BACKGROUND Most studies were conducted in Europe and Canada to document the performance of Portland cement when replaced by alternative materials with different quantities and properties. Studies conducted on adding IPA to cement were very limited for this research. Therefore, the literature focused on studies investigated adding limestone to cement by blending or intergrinding. Studies that were conducted in Canada were initiated after the Canadian Cementitious Materials Compendium CAN/CSA A 3000 adopted the use of up to 15% Portland-limestone cement. For Portland cement with limestone, it is noted the following: “the appropriate choice of clinker quality, limestone quality, % limestone content and cement fineness can lead to the production of a limestone cement with the desired properties”(2). Accordingly, the effect of adding limestone to cement in concrete has been attributed through many studies to the quality and quantity of limestone, production method whether it was blended or interground with cement, cement particle size distribution and shape, Blaine fineness, and adding other cementitious and pozzolanic materials. Tsivilis et al. (2) observed that cement with up to 10% limestone with fineness up to a limit value, showed insignificant strength reduction compared to pure cement. Most recently, three major studies were published in Canada on the effect of limestone addition on the strength and durability properties of concrete. These studies were conducted by Thomas et al (3), Thomas et al (4), and Hooton et al. (5). Their results strongly supported the validation to increase the limestone content up to 15% replacement to cement by weight in Canada.



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IDOT is making several changes to concrete mix designs, using revisions to cement specification ASTM C150/AASHTO M 85 and ASTM C465/AASHTO M 327 for the new IDOT Standard Specifications book. Current specifications allow addition of limestone and IPA content up to 5% and IR content up to 0.75% of cement weight. The addition of more than 5% limestone and IPA and the increase in IR content above 0.75% require strength and durability testing. Because of the lack of experimental test data, an experimental investigation was conducted at UIC to assess the strength gain, ultimate strength, and durability characteristics of concrete mixes containing Portland cements with more than 5% limestone and IPA, and/or with IR exceeding 0.75% in combination with fly ash or slag. MATERIAL SELECTION AND MIX DESIGN The sources of materials procured for the study are: (a) two sources of cement, (b) one source of coarse aggregate, (c) two sources of fine aggregate, and (d) one source of class C fly ash and one source of Grade 100 slag. Each cement source (Cem1 and Cem3) provided cement with limestone and IPA less than and exceeding 5% in accordance with ASTM C465. Ground, granulated blast furnace slag was used as IPA for cement with more than 5% limestone and IPA. The cement properties are shown in Table 1. Cem1 source was prepared by intergrinding limestone and partially intergrinding IPA at CTL laboratory in Skokie, Illinois. Cem3 was produced by intergrinding limestone and homogeneously blending IPA. Because of a shortage of Cem3, the producer delivered a new shipment labeled Cem3R because it has 0.8% limestone more than the original Cem3. The IR content of ASTM C150 and AASHTO M 85 Portland cements is limited per the specifications to a maximum of 0.75% by weight. Cem2 is made by blending Cem1 with fly ash that has 0.49% and 32.41% IR, respectively, to give Cem2 with 0.75% IR and Cem2 with 1.5% IR. As a result, Cem1 and Cem3 were produced to test the performance of concrete mixes with cement exceeding 5% of limestone and IPA, and Cem2 was prepared to test the performance of cement in concrete with higher amount of IR. The designations for cements with less than 5% limestone and IPA, or with 0.75% IR is Cem5%. TABLE 1 Amount of Limestone and IPA to Cement and their Blaine Fineness Cement Source Cem15% Cem25% Cem35% Cem3R5% Note:

157 158 159 160 161

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% of Limestone and Inorganic Processing Additions Limestone Inorganic Process Total

4.2 3.8 4.2 4.2

0 4.5

2.6 2.5 3.4 3.1

0 3 0 3

380 407

Insoluble Residue (%)

Blaine Fineness (m2/Kg)

1 Day

Compressive Strength, psi 3 Day 7 Day 28 Day

0.49 0.50

380 407

2070 2010

3800 3940

5020 4650

6130 6400

385 383 378 386

2960 2920 2910 3183

4340 4160 4043 4413

5070 5020 4648 5220

5973 6390

0.75 1.5 385 383 378 386

0.20 0.18 0.21 0.15

1 Mpa = 145.037 psi

Note: Cem25% were prepared by blending Cem15% required less amount of admixtures to achieve a slump equivalent to mixes made with Cem5% gave slightly higher slump, except for Mix 4R which required more admixture to retain a slump equivalent to Mix 3R. The same figure, showing mixes batched with combined sand, indicates inconsistent variation between the slump and admixture dosage for mixes with Cem5%. Effect of Fly Ash or Slag The use of slag or fly ash affected the workability of concrete as shown in Figure 1. Concrete mixes batched with fly ash had 0.02 w/cm less than concrete mixes batched with slag. Moreover, mixes with fly ash required fewer admixtures to maintain the desired slump in comparison to mixes batched with slag. The improved workability of using fly ash in comparison with slag is attributed to their different physical characteristics (specific surface area and surface texture). The specific surface area for fly ash is typically lower than



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slag, and d the surface texture for fly f ash is sph herical in shaape in compparison with slag, which has rough, an ngular-shapeed grains (6). Effect off Fine Aggreegate Sourcce Combined d sand requirred a high doosage of highh-range wateer reducer and a air entraiining agent to t maintain workability. w Consequenttly, the w/cm m ratio increeased from 0.42 2 to 0.44 forr all mixes made m with slaag and batchhed with com mbined sand.. On the otheer hand, mix xes made wiith fly ash an nd natural saand experiennced higher sslump than ddesired and tthe w/cm ratio was, thereefore, reduceed from 0.42 2 to 0.40.

Figurre 1. Total admixture a dosage d vs. sllump for con ncrete mixees.



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Initial and Final Setting Times of Concrete The setting time were measured in accordance to ASTM C403 (Time of Setting of Concrete Mixtures by Penetration). Initial and final setting results indicated ±5% difference for most concrete mixes having the same mix proportioning and cement source with Cem5%. However, Cem2 mixes with combined sand and fly ash showed a decrease in the initial set by 13% and final set by 8% for Mix 18 (Cem2>5%) with respect to Mix 17 (Cem25% than concrete mixes with Cem5% experienced slight increase in initial and final setting times. This increase is attributed to a slowdown in the hydration process between cement and water because of the addition of more limestone and IPA, and/or IR. These materials are considered inert and had negligible effect on the chemical reaction of cement paste. Effect of Fly Ash or Slag The addition of fly ash or slag to concrete mixes showed a significant difference in setting times. Fly ash prolonged initial and final set times in comparison with slag. As shown in Table 4, the average time needed to reach the initial and final set times for concrete mixes batched with fly ash and natural sand was, respectively, 37% and 31% longer than the set times for concrete mixes batched with slag and natural sand. In addition, the average time needed to reach the initial and final set times for concrete mixes batched with fly ash and combined sand was, respectively, 70% and 63% longer than the set times for mixes batched with slag and combined sand. Effect of Fine Aggregate Source Natural sand resulted in quicker set time in concrete in comparison with combined sand. The initial and final set times for mixes made with Cem1 were significantly longer in the mixes batched with combined sand (Mix 13–Mix 16) than mixes batched with natural sand (Mix 1–Mix 4). In addition, the performance of mixes made with Cem2 and Cem3 was similar to Cem1 mixes. As shown in Table 4, the average time needed to reach the initial and final set for concrete mixes batched with fly ash and combined sand was, respectively, 34% and 39% higher than the set times for concrete mixes batched with fly ash and natural sand. Moreover, the average time needed to reach the initial and final set times for concrete mixes batched with slag and combined sand was, respectively, 8% and 11% higher than the set times for concrete mixes batched with slag and natural sand.



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TABLE 4 Avg Setting Times for Different Mix Combinations and their Difference in % Average Set Times, hrs:min Initial 7:15 7:28 5:20 5:24 10:08 (9:21) 9:40 (9:24) 5:39 5:59

Final 9:01 9:16 6:52 7:04 12:45 (11:47) 12:35 (12:06) 7:41 7:50

Difference in the Average Set Time, % Cem>5% vs. Fly Ash vs. CS vs. NS Cem5% in comparison to Cem5% experienced slightly lower compressive strength at early curing age in comparison with mixes with Cem5% demonstrated better strength gain over a 56 day curing period compared with Cem5% was less than the compressive strength of mixes made with Cem2 and Cem35% in comparison with mixes made with Cem15% was less at all ages than the strength for mixes made with Cem25% demonstrated a slight strength gain compared with mixes made with Cem25% resulted in



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365 366

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higher co ompressive strength s and strength gaiin at all agess in comparisson with mixxes with Cem35%_sllag) which ggave lower 3 day compreessive strenggth than Mix x 23 (Cem3< >5% resultedd in lower compresssive strength h at all ages than t mixes with w Cem25% C exxperienced sllightly lowerr strength at early curring age (3–7 7 day) and beetter strength h gain at lonng-term curinng age (28–556 day) in comparisson with Cem m5% or Cem5% _fly ashh) at 56 days but lower at 180 days; whereas, w the depth d of perm meability in Mix 3 (Cem m1 >5%_slag) att 56 days. Foor Cem3 mixxes, the perm meability deppth for Mix 9 (Cem35%_fly ash). This inconsistency is also apparent in the permeability results for concrete mixes batched with combined sand (Mix 13–Mix 24) at 56 and 180 days for a The RCPT results shown in Table 5, which slightly contradict with DIN 1048 results, indicate that most concrete mixes made with Cem>5% had slightly higher rapid chloride coulomb charge compared with concrete mixes made with Cem5% were greater or equivalent to those made with Cem5% had slightly higher charge than those made with Cem5% is summarized as follows:  Improved workability in concrete but slightly prolonged its initial and final setting times  Had comparable compressive and flexural strength properties to concrete mixes with Cem