Advances in Civil Engineering Materials...be applied to the modified mixture design method...

Advances in CivilEngineering Materials

Rodrigo Antunes1 and Mang Tia2

DOI: 10.1520/ACEM20180030

Effects of Aggregate Packing onConcrete Strength andConsistency

VOL. 7 / NO. 1 / 2018

Copyright by ASTM Int'l (all rights reserved); Thu Sep 6 16:29:02 EDT 2018Downloaded/printed byUniversity of Florida (University of Florida) pursuant to License Agreement. No further reproductions authorized.

REVIEW PAPER

Rodrigo Antunes1 and Mang Tia2

Effects of Aggregate Packing on ConcreteStrength and Consistency

Reference

Antunes, R. and Tia, M., “Effects of Aggregate Packing on Concrete Strength and Consistency,”

Advances in Civil Engineering Materials, Vol. 7, No. 1, 2018, pp. 479–495, https://doi.org/10.1520/

ACEM20180030. ISSN 2379-1357

ABSTRACT

Designing concrete based on aggregate packing and optimized gradations can

result in 25 % less cement content to reach a targeted compressive strength and less

water-reducing admixture to obtain a required consistency. In this research, two

studies were conducted: (1) an experimental analysis to determine the effects of

aggregate packing on concrete strength and consistency; and (2) an investigation

of the relationship between the traditional dry-rodded and the vibrated aggregate

packing. Excellent correlation was found between 240 packing results, which can

be applied to the modified mixture design method presented. Also, 40 slump and

120 compressive strength standard tests were performed to evaluate the effects

of reducing cement content by 7.5, 15, 20, and 25 % to slump and compressive

strength of concrete mixtures. The compressive strength of the optimized

mixture demonstrated less susceptibility to variations due to cement content

reductions when compared to nonoptimized mixtures. The Modified Coarse

Factor Chart can be used to design an optimized concrete mixture efficiently in

conjunction with aggregate gradation and packing, cement content, and concrete

consistency.

Keywords

limestone, silica sand, optimized gradation, aggregate, packing, portland cement, concrete,

mixture design, admixture

Manuscript received March 16,

2018; accepted for publication

July 20, 2018; published online

September 7, 2018.

1 Department of Civil and Coastal

Engineering, University of Florida,

PO Box 116580, Gainesville, FL

32611, USA (Corresponding

author), e-mail: rodrigo.antunes@

ufl.edu, https://orcid.org/

0000-0002-1878-382X

2 Department of Civil and Coastal

Engineering, University of Florida,

PO Box 116580, Gainesville, FL

32611, USA

Advances in Civil Engineering Materials

Copyright © 2018 by ASTM International, 100 Barr Harbor Drive, PO Box C700, West Conshohocken, PA 19428-2959 479

doi:10.1520/ACEM20180030 / Vol. 7 / No. 1 / 2018 / available online at www.astm.org


https://doi.org/10.1520/ACEM20180030


mailto:[email protected]

mailto:[email protected]

https://orcid.org/0000-0002-1878-382X

https://orcid.org/0000-0002-1878-382X


https://www.astm.org

Introduction

Optimized aggregate blends may improve the concrete performance and be used to de-

sign concretes with lower cementitious material content [1]. Usually, 70 to 80 % of

concrete is composed of aggregate, which significantly dominates the mechanical

and physical properties of this composite material, both by the quality and quantity

of the aggregates [2–4]. The characteristics of the aggregates, such as maximum size,

particle size distribution, and aggregate packing, besides proportioning, profoundly

affect the performance of concrete.

This study aims to evaluate the effects of aggregate packing on the concrete strength

and consistency as well as to investigate the relation between the traditional dry-rodded

and the vibrated aggregate packing by adopting the Vebe apparatus. The methodological

approach consists of relating optimized and nonoptimized aggregate gradation parameters

to the properties of fresh and hardened concrete mixtures under different aggregate pack-

ing and cement contents.

This investigation argues that designing concrete based on aggregate packing and

optimization can result in the reduction of water-reducing admixture contents in order

to reach a target workability of the fresh concrete, as well as in significant reduction of

cementitious material consumption to reach a desired compressive strength.

Background

AGGREGATE OPTIMIZATION

Traditional optimized aggregate gradations have been specified and endorsed to provide

concrete improvement. In contrast, very few, if any, comprehensive methods are readily

available at the disposal of engineers to perform aggregate optimization [5].

Theoretical and empirical approaches can be used to obtain a typically optimized

aggregate gradation [5,6], and the underlying premise behind each method is similar.

A well-graded aggregate, that is, one that covers all aggregate particle sizes, usually con-

tains a higher percentage of particles with intermediate sizes and smaller portions at the

extremes. Such gradation takes on what is often described as a haystack shape when plot-

ted on a percent retained chart.

Achieving a traditional optimized gradation usually requires the combination of at

least three differently sized aggregates. However, most concrete typically contains two ag-

gregates: (1) fine aggregate, with particles smaller than 4.75 mm; and (2) coarse aggregate,

with particles larger than 4.75 mm. The combination of two aggregates is usually not well

graded because of the absence of intermediate-sized particles, having a peak-valley-peak

distribution.

The commonly used techniques to develop traditional optimized aggregate grada-

tions are: (1) the percent retained chart; (2) the power chart; and (3) the Modified

Coarseness Factor Chart (MCFC). All aim to determine a target gradation, and thus select

an optimized blend of the available aggregates [5].

To clarify the MCFC applications, first it is essential to define the Coarseness Factor

(CF), the adjusted Workability Factor (WFadj), and the parameters Q, ISA, and W, as

shown in Eqs 1 and 2.

CF = ½Q=ðQ + ISAÞ� × 100 % (1)

480 ANTUNES AND TIA ON AGGREGATE PACKING AND CONCRETE



where:

CF= coarseness factor,

Q= cumulative percent retained on the sieve 9.5 mm,

ISA= percent retained within sieves 2.36 and 9.5 mm.

WFadj =W + ð2.5% × ΔC=WTÞ (2)

where:

WFadj= adjusted workability factor,

W= cumulative percent passing the 2.36-mm sieve,

ΔC= cement content difference to 335 kg/m3,

WT=weight of cement bag, 42.6 kg.

The MCFC is an empirically developed chart that is widely used to plot CF andWFadjas a single point representing fine and coarse aggregate proportions by using two equa-

tions. Mixtures appearing near the center of Zone II consistently provide good workability

[7], so that many of the traditional optimized gradation concrete practitioners recommend

that gradations be plotted within the center of Zone II for slip-formed concrete [8]. In

contrast, for some, the MCFC is considered not helpful in comprehending slip-formed

consistency behavior [9].

AGGREGATE PACKING

Aggregate packing is relevant to concrete since it relates to the volume of cement paste

needed to fill the gaps in between the aggregates and to separate particles. Typically, dry-

rodded packing is used in current official mixture designs in the United States. However, in

Europe, vibrocompaction has been successfully used as a packing method [10].

Aggregate packing k is the ratio between the actual volume of the solid particles Pv and

the compacted bulk volume V. Packing depends on three main parameters: (1) size of the

grains, (2) shape of the grains, and (3) packing method. Usually, aggregate packing of

rounded aggregate blends appears to be about 12 % greater than the outcomes obtained

from crushed aggregate blends [11]. Most theoretical models consider monosized or random

spherical particle shapes to determine aggregate packing [10]. Consequently, theoretical sim-

ulations may generate fewer voids to fill with cement paste than experimental packings. As a

result, these spherical blends may lead to excessive optimistic results in which less cement

paste is required to fill the gaps between grains. Hence, most simulations may unrealistically

predict the use of 12 % less cement paste content in actual concrete mixtures.

On the other hand, some models have successfully adopted characteristic diameter

and packing to reduce error in outcomes when compared to the Toufar’s theoretical pack-

ing curve. It is thought that comparing actual packing test results to the Toufar’s curve can

increase adherence to actual results and reduce the need for experiments [12].

Some parameters need to be calculated to determine aggregate packing. The volume

of solid particles Pv is the actual aggregate particles volume [10] as shown in Eq 3.

Pv =W=ρ (3)

where:

Pv= volume of solid particles, m3,

W=mass of the aggregates, kg,

ρ= density of the aggregates, kg/m3.

Compacted bulk volume V is the volume occupied by the particles after the compac-

tion, as expressed in Eq 4.

ANTUNES AND TIA ON AGGREGATE PACKING AND CONCRETE 481



V =W=M (4)

where:

V= compacted bulk volume, m3,

W=mass of the aggregates, kg,

M= compacted unit weight of the aggregates, kg/m3.

Furthermore, aggregate packing k is defined as the ratio between the volume of solid

particles Pv and compacted bulk volume V [10], as seen in Eq 5.

k = Pv=V (5)

where:

k= aggregate packing,

Pv= volume of solid particles, m3,

V= compacted bulk volume, m3.

POWER CHART

Fundamentals on maximum density of aggregate gradations have been known for about

100 years [8]. Initially, the power curve index n was proposed as 0.50 [13] and was later

adjusted to 0.45 [14]. Since then, each sieve opening is raised to the 0.45 power on the

cumulative percent passing chart. It is typically a straight line representing the maximum

aggregate blend density, connecting the origin to the aggregates’ nominal maximum size

(NMS). Aggregate proportions can be obtained based on the best-fit curve of the straight

line [8]. It is recognized that concrete mixtures using very dense gradations produce harsh

concretes [14,15].

Although there are other types of ideal gradation references, such as Rissel, Graf, and

Boloney, this investigation was based on the Fuller and Thompson curve equation based

on the maximum size (MS) of aggregates as shown in Eq 6.

Pd = 100 × ðd=DmaxÞn (6)

where:

Pd= particles passing a sieve opening, %,

d= sieve opening, mm,

Dmax=maximum sieve opening, mm,

n= 0.45.

ENTRAPPED AIR IN CONCRETE

Entrapped air voids are typically spherical with diameters as large as 3 mm. Air bubbles are

usually trapped in cement paste during the mixing process. Often, for a given consistency,

the lower the cement paste volume, the lower the entrapped air content in concrete [16].

SLUMP OF FRESH CONCRETE

The slump is a direct measurement of fresh concrete consistency and is part of the work-

ability in conjunction with cohesiveness. Usually, the water content is directly proportional

to the slump. Also, the slump of concrete can increase with the addition of water-reducing

admixtures without increasing the water content. However, typically no more than 2 %




(by weight of cement) of water-reducing admixtures are added to concrete to increase

consistency while reducing water content by 5 % [16].

Concrete workability can also be enhanced by adding intermediate-sized aggregates,

which can fill major voids in the aggregate portion of portland cement concrete and reduce

internal friction. Mixtures deficient in aggregates retained between sieves 2.36 and 9.5 mm

are expected to require more mortar to provide needed mobility [7].

COMPRESSIVE STRENGTH OF CONCRETE

It is widely known that water-cement ratio (w/c) is the critical factor influencing the com-

pressive strength of concrete. This is usually true since the strength of aggregates is much

higher than that of the cement paste matrix and interfacial transition zone (ITZ). However,

for a given consistency and cement content of high- and moderate-strength concretes, the

compressive strength of the matrix tends to increase if the NMS of coarse aggregate in-

creases. Also, it is known that the ITZ dramatically influences the tensile strength. Then, if

the NMS of coarse aggregate increases, the ITZ tends to be weaker, decreasing the tensile-

compressive strength ratio [16].

Materials and Methods

AGGREGATES

The fine aggregate (FA) used was silica sand from the supplier GA397 according to the

Florida Department of Transportation (FDOT) producers list. Intermediate coarse aggre-

gate (IA) used was the Miami Oolite Limestone #89 from the mine 87,090 (supplier code

TM447). Coarse aggregate (CA) was the Miami Oolite Limestone #57 from the same IA

quarry. Tables 1–3 show the FA, IA, and CA properties, respectively.

For aggregate packing testing, all aggregates were oven-dried. For concrete mixing,

moisture content tests were performed with specimens taken simultaneously when ma-

terials were batched. Right before mixing, moisture content was determined. Thus, aggre-

gates and water contents were adjusted accordingly.

PORTLAND CEMENT

The portland cement Type I/II used in this experimental study was provided by Suwannee

American Cement Company (Branford, FL). Physical properties and chemical composi-

tion met current requirements of the ASTM C150/C150M-17 [17], Standard Specification

for Portland Cement.

TABLE 1Physical properties of fine aggregate.

Physical Properties Standard Value

Materials <75 μm ASTM C117-17 [28] 0.2 %

Fineness Modulus ASTM C136-14 [29] 2.34

SSD Specific Gravity ASTM C128-15 [30] 2.70

Apparent Specific Gravity ASTM C128-15 [30] 2.75

Bulk Specific Gravity ASTM C128-15 [30] 2.69

Absorption ASTM C128-15 [30] 0.3 %

Note: ASTM C136-14, Standard Test Method for Sieve Analysis of Fine and Coarse Aggregates; ASTM C128, StandardTest Method for Relative Density (Specific Gravity) and Absorption of Fine Aggregate; SSD, saturated-surface drycondition of aggregates.




https://www.astm.org/Standards/C150









AGGREGATE BLENDS

Proportions of aggregate blends required a broad range of combinations. The 14 combina-

tions shown in Table4 have the percent of IA varying from 0 to 20%, usually reducing half of

the percentage from the CA and the other half from the FA. Blends SD1 and SD2 are binary;

PK1 and PK2 are ternary with 10 % IA; PK3 and PK4 are also ternary, however with 20 % IA.

The combinations PK5, PK6, PK7, PK8, and PK9 have IA contents within 2.5 and 17.5 %.

TABLE 2Physical properties of intermediate aggregate.



NMS ASTM C33-16e1 [31] 3/8 in.





Note: ASTM C33/C33M-16e1, Standard Specification for Concrete Aggregates; ASTM C127-15, Standard Test Method forRelative Density (Specific Gravity) and Absorption of Coarse Aggregate; SSD, saturated-surface dry condition of aggregates.

TABLE 3Physical properties of coarse aggregate.



NMS ASTM C33-16e1 [31] 3/4 in.





Note: SSD, saturated-surface dry condition of aggregates.

TABLE 4Aggregate blend proportions.

Blend CA, % IA, % FA, % Total, %

OPT 56.700 10.300 33.000 100

OPT1 47.125 5.750 47.125 100

OPT2 41.000 18.000 41.000 100

SD1 60.000 0.000 40.000 100

SD2 57.450 0.000 42.550 100

PK1 55.000 10.000 35.000 100

PK2 45.000 10.000 45.000 100

PK3 50.000 20.000 30.000 100

PK4 40.000 20.000 40.000 100

PK5 58.200 11.200 30.600 100

PK6 47.500 5.000 47.500 100

PK7 42.500 15.000 42.500 100

PK8 48.750 2.500 48.750 100

PK9 41.250 17.500 41.250 100


















The acronym “SD” refers to standard mixes containing two aggregates, typically one

finer and one coarser. Also, the acronym “PK” identifies blends specifically developed for

packing tests, while “OPT” represents an optimized blend.

Although all blends were used in the packing tests, a similar-shape gradation curve

procedure was used to select the blends to mix into concrete following Antunes and Tia

[18]. Aggregate blends with a similar shape of gradation plots were thus selected.

Gradation plots of blends PK6, PK7, PK9, and OPT, as shown in Fig. 1, are representative

samples of gradation plots of the aggregate blends used.

AGGREGATE PACKING TESTING PROCEDURE

Two methods were used to test aggregate packing: (1) the dry-rodding method according to

ASTM C29/C29M-17a [19], Test Method for Bulk Density (“Unit Weight”) and Voids in

Aggregate, and (2) the vibration method per ASTM C1170/C1170M-14e1 [20], Standard

Method for Determining Consistency and Density of Roller-Compacted Concrete Using a

Vibrating Table. Because of the experimental nature of this study, a relatively wide range

of combinations of the three aggregates was carefully selected. The sample size required by

the statistical model was 24, specifying a minimum of 12 determinations of dry-rodded and

12 trials of vibrated aggregate blends, resulting in a 5 % type 1 error (95 % confidence), and 1

% type 2 error. The twelve tests on each blend were divided into three independently pre-

pared specimens tested four times each. The weighed binary and ternary aggregate blends

had the same average dry weights: 12.8 kg for dry-rodded and 8.6 kg for vibrated packing.

Aggregate packing of each binary and ternary aggregate blend was systematically

determined to achieve accurate results. A total of 240 results were obtained: 120 for

dry-rodded and 120 for vibrated specimens.

Vibrated aggregate packing tests were conducted as follows: (1) specimens were

mixed thoroughly before horizontal layers of aggregate were poured into the measure

in three equal layers, which were vibrated for 30 seconds each; (2) distance between cyl-

inder rim and the top of the specimens was measured at four evenly distributed locations.

Fig. 2a and b shows the Vebe apparatus and specimen measurement, respectively.

FIG. 1

Gradation curves of selected

aggregate blends.






AGGREGATE OPTIMIZATION PROCEDURE

Gradation optimization technique provides the ability to employ multisource aggregates

to be blended and optimized. Optimizations were performed as follows: (1) all aggregate

gradations were determined using the standard sieve series; (2) aggregate blends were math-

ematically combined based on the initial trial proportions; (3) NMS of combined blends

were determined to identify eventual intermediate aggregate effect on aggregate system;

(4) the percent passing and percent retained charts were prepared; (5) desired gradations,

typically following the theoretical maximum density line, were determined based on the

Talbot and Richart [14] power curve equation (n= 0.45); (6) CF and WFadj of combined

gradations were calculated and plotted on the MCFC; (7) traditional optimized gradation

proportions were calculated by interaction of individual gradations to reach the Workability

Box (WB) surroundings of 33 %≤WFadj≤ 37 % and CF= 60 %, aiming the maximum

consistency for w/c= 0.50; and (8) the percent passing and percent retained charts of both

combined and optimized blends were plotted against the desired curve for final comparison.

MIXTURE DESIGN PROCEDURE

Twenty FDOT Class I (pavement) for slip-formed concrete mixtures were designed and

prepared in the laboratory to evaluate the possibility of reducing the cement content by

between 7.5 and 25 %. One of the goals was to obtain a mixture with sufficient cement

paste to consolidate the concrete while keeping the edge stiff. Following the FDOT

Section 346 [21], Portland Cement Concrete, and the FDOT Section 9.2 [22],

Structural Concrete Production Facilities Guide, all mixtures required a minimum com-

pressive strength of 29 MPa and minimum cement content of 279 kg/m3. The decision

to adopt a constant and maximum allowed w/c ratio of 0.50 aimed to (1) evidence con-

sistency behavior without water-reducing admixture aid, (2) analyze the lowest possible

FIG. 2 Aggregate packing test: (a) Vebe apparatus and (b) step two of the vibrated packing test on ternary aggregate blends,

measuring distance between the top vibrated specimen and measure rim.




compressive strength and highest consistency behaviors under different cement contents,

and (3) highlight the aggregate packing and optimization effects on concrete properties.

Table 5 shows the mixture designs summary.

The following tests were performed on fresh and hardened concrete: (1) air content as

per ASTM C173/C173M-16 [23], Air Content of Freshly Mixed Concrete by the Volumetric

Method; (2) slump according to ASTM C143/C143M-15a [24], Standard Test Method for

Slump of Hydraulic-Cement Concrete; and (3) compressive strength at 28 days following

ASTM C39/C39M-18 [25], Test Method for Compressive Strength of Cylindrical Concrete

Specimens. Fig. 3 presents the adjusted mixture design procedure adopted, based on ACI

211.1 [26], Standard Practice for Selecting Proportions for Normal, Heavyweight, and Mass

Concrete. Although the procedure is not new, for mixtures with predetermined aggregate

proportions, the ACI 211.1 [26] mix design procedure was followed for the cement and

water content determination. An adaptation was necessary because (1) the aggregate pro-

portions were given, and aggregate weights were known; (2) packing (k) was given, cement

paste (CP) to fill voids (CPv) and separate particles (CPs) were known; and (3) CP index

could be applied to reduce or increase CPs as demonstrated in Fig. 4.

CONCRETE MIXING AND TESTING

Cement and aggregates were stored in laboratory conditions at room temperature between

20°C and 30°C. A total of 20 mixtures were designed and batched twice. Thus, a total of 40

samples of fresh concrete were tested for a slump to investigate the consistency and uni-

formity of the fresh concrete. Also, 40 samples were tested for unit weight of fresh concrete

to ensure the yield volume and for air content. Also, 120 specimens were tested for com-

pressive strength (3 specimens per mixture) at the age of 28 days to evaluate whether the

material reached the expected strength. Single compression results were occasionally

TABLE 5Concrete mixture designs.

Blend ID PC. Red., % w/c Cement, kg/m3 Water, kg/m3 CA, kg/m3 IA, kg/m3 FA, kg/m3

OPT#1 0 0.50 374 187 952 173 554

OPT#2 7.5 0.50 346 173 984 179 573

OPT#3 15 0.50 318 159 1,016 185 591

OPT#4 20 0.50 299 150 1,037 188 604

OPT#5 25 0.50 280 140 1,058 192 616

PK7#1 0 0.50 374 187 714 252 714

PK7#2 7.5 0.50 346 173 737 260 737

PK7#3 15 0.50 318 159 761 269 761

PK7#4 20 0.50 299 150 777 274 777

PK7#5 25 0.50 280 140 793 280 793

PK6#1 0 0.50 374 187 798 84 798

PK6#2 7.5 0.50 346 173 824 87 824

PK6#3 15 0.50 318 159 851 90 851

PK6#4 20 0.50 299 150 869 91 869

PK6#5 25 0.50 280 140 887 93 887

PK9#1 0 0.50 374 187 693 294 693

PK9#2 7.5 0.50 346 173 716 304 716

PK9#3 15 0.50 318 159 739 314 739

PK9#4 20 0.50 299 150 754 320 754

PK9#5 25 0.50 280 140 770 327 770







FIG. 3 Fluxogram of the adapted concrete mixture design.




rejected because of excessive strength deviation from the group. The results were calcu-

lated from the average of the remaining specimens.

The procedure adopted during each concrete batching and mixing followed ASTM

C192/C192M-16a [27], Standard Practice for Making and Curing Concrete Test Specimens

in the Laboratory. Materials were batched 24 hours before mixing and stored in buckets

with lids. Aggregate specimens for moisture content were simultaneously taken, and the

aggregate and mixing water contents were adjusted right before mixing. Concrete spec-

imens were placed into water curing tanks within 30 minutes after removal from the cylin-

drical molds. The curing water was lime water kept at an average temperature of 23°C.

Fig. 5a and b shows the slump test and the cylindrical specimen being tested for com-

pressive strength, respectively.

FIG. 5 Fresh and hardened concrete testing: (a) slump test and (b) the cylindrical specimen being tested for compressive strength.

FIG. 4 Increase of aggregate proportion in concrete that is due to the reduction in cement paste volume.





Results and Discussion

In this study, the objectives were to (1) evaluate the effects of aggregate packing on slip-

formed concrete strength and consistency and (2) evaluate the relationship between dry-

rodded and vibrated packing methods. To reach the first objective, standard tests were

performed on fresh and hardened concrete to investigate the relationship between the

concrete properties and the gradation parameters, such as MCFC factors and aggregate

packing. For the second objective, comparisons were made between the two packing meth-

ods: the traditional dry-rodded, kr, and the vibrated, kv, using a Vebe apparatus.

Since concrete is a composite material, the methodological approach was to evaluate

the fresh and hardened behaviors of concrete using different aggregate blends and cement

contents. Each selected mixture had its cement content reduced by 7.5, 15, 20, and 25 %.

The compressive strength of each mixture was plotted against the cement reductions to

evaluate the strength of concrete under different cement contents. Slump outcomes were also

plotted against the cement reductions to evaluate workability. The possibility of using slump,

packing, gradation, and cement content to design concrete mixtures more efficiently was also

investigated.

Lastly, dry-rodded and vibrated aggregate packing tests were performed with the same

selected aggregate blends, and the results were plotted to seek the best-fit trend line. Table 6

displays the testing outcomes. Fresh concrete air content data ranged from 0.7 to 3.7 %.

COMPRESSIVE STRENGTH AND CEMENT CONTENT

Since each of the 4 aggregate-blend mixtures was tested twice with 5 different cement

contents, a total of 40 mixes were prepared. Every mixture had the same w/c ratio of

TABLE 6

Test results.

Blend ID kr kv CF WFadj MCFC Zone

Comp. Strength

(28 days), MPa SD, MPa Slump, mm

OPT#1 0.727 0.759 60 37 II 45.4 0.2 229

PK9#1 0.733 0.823 51 45 IV 44.7 1.4 133

PK7#1 0.729 0.798 52 46 IV 45.3 1.1 178

PK6#1 0.722 0.791 63 50 IV 44.8 0.7 95

OPT#2 0.727 0.759 60 36 II 45.1 1.5 133

PK9#2 0.733 0.823 51 44 IV 45.0 2.0 64

PK7#2 0.729 0.798 52 45 IV 43.3 1.1 89

PK6#2 0.722 0.791 63 49 IV 43.0 0.8 51

OPT#3 0.727 0.759 60 34 II 46.2 1.1 76

PK9#3 0.733 0.823 51 42 II 45.1 0.9 13

PK7#3 0.729 0.798 52 43 IV 41.8 0.2 25

PK6#3 0.722 0.791 63 47 IV 41.4 0.7 19

OPT#4 0.727 0.759 60 33 II 45.3 0.5 32

PK9#4 0.733 0.823 51 41 II 43.9 0.2 6

PK7#4 0.729 0.798 52 42 II 43.0 1.5 13

PK6#4 0.722 0.791 63 46 IV 41.4 0.1 6

OPT#5 0.727 0.759 60 33 II 43.6 0.5 25

PK9#5 0.733 0.823 51 41 II 39.9 0.6 6

PK7#5 0.729 0.798 52 42 II 39.8 0.0 6

PK6#5 0.722 0.791 63 46 IV 39.3 0.0 0

Note: SD, standard deviation.




0.50 and five different cement contents. However, aggregate proportions remained the

same regardless of the cement content. At least three 100 by 200-mm cylindrical specimens

were cast for each mixture to be evaluated for compressive strength at 28 days, with a total

of 6 specimens per mix design, or a grand total of 120 specimens. Fig. 6 shows the average

compressive strengths plotted against the cement content reductions, featuring a low aver-

age standard deviation of 0.8 MPa.

When no cement content was reduced, all mixes presented a similar compressive

strength around 45 MPa. At 25 % cement reduction, nonoptimized mixtures (PK7,

PK9, and PK6) presented a similar compressive strength of about 39.6 MPa, while the

traditional optimized mixture (OPT) had a compressive strength of 43.6 MPa. Also,

the compressive strength of OPT mixtures remained constant and higher than the non-

optimized mixes for all cement content levels.

Changes in strength were not significant since optimized mixes gave fairly constant

strength at a greater extent, while nonoptimized mixes gave approximately 12 % reduction

in strength where cement content was reduced by 25 %. All mixtures presented a com-

pressive strength higher than the target design value (29 MPa), even with 25 % less cement

in their compositions.

CONSISTENCY AND CEMENT CONTENT

The objective was to test the concrete slump within a wide range of cement contents to

identify a trend. Some of the mixes would not be of practical use in concrete pavements

considering their slump results.

The slump of each mixture was the average of at least two determinations, with a total

of 40 tests (Fig. 7). Optimized mixtures presented 229-mm slump at no cement content

reduction, compared to the lowest 95 mm displayed among the nonoptimized mixtures.

With no water-reducing admixtures added, outcomes indicate that nonoptimized

mixtures reached the designed slump of 50 mm at 10 % cement reduction.

Meanwhile, optimized mixtures reached 50 mm slump at 18 % cement reduction.

DRY-RODDED AND VIBRATED AGGREGATE PACKING

The relationship between dry-rodded packing, well known as dry-rodded unit weight as

stated in ASTM C29/C29M-17a [19], and vibrated aggregate packing was investigated.

Past publications have documented the low reliability of theoretical models, suggesting

that experimental results would compare well to the Toufar model if the aggregate

FIG. 6

Compressive strength behavior

of optimized and nonoptimized

mixtures under different

cement contents.





diameter and experimental packing were used to calibrate results. Thus, an experimental

approach was used in this study to address the effects of aggregate packing on compressive

strength and slump, and the outcomes can add to the existing academic literature, with a

focus on southern U.S, limestone and silica sand.

The results of 240 tests (Fig. 8) indicated a strong linear relationship (R2= 0.98)

between dry-rodded and vibrated aggregate packing, which is thought to be due to con-

stant and steady higher energy applied to the vibrated specimens. Aggregate and concrete

producers can benefit from this outcome given the higher accuracy of absolute volumes of

aggregates transported and concrete produced.

An experimental approach was performed by Antunes and Tia [18] to investigate how

k of silica sand and limestone correlates to ISA contents in aggregate blends. Overall, the

lowest packing (k) variation (1.7 %) occurred when ISA was between 25 and 27 % by weight,

indicating that blends containing 25 to 27 % of particles within sieves 2.36 and 9.5 mm (ISA)

might be considered optimal. In other words, a lower variation in packing can increase the

predictability of the concrete consistency since concrete is typically designed based on

dry-rodded unit weight (dry-rodded packing) and vibrated during placement.

FIG. 7

Slump behavior of optimized

and nonoptimized mixtures

under different cement

contents.

FIG. 8

A linear relationship between

dry-rodded and vibrated

aggregate packing.




MCFC AND CONCRETE MIXTURE DESIGN

Aggregate blend gradations are displayed in Fig. 1, providing parameters for CF andWFadjcalculations. Fig. 9 shows the MCFC with aggregate factors related to each concrete mix-

ture and varied cement contents.

Results show that optimized mixtures plotted near the center of the WB and had the

highest slumps in comparison to mixtures with the same cement content. Nonoptimized

mixes plotted away from the WB and presented slumps inversely proportional to their

distance to the WB. On the other hand, the slump results of each blend showed a direct

relationship to cement content. The slump of the optimized mixture was 229 mm at 0 %

reduction and 25 mm at 25 % reduction. In comparison, the average slump of the non-

optimized mixtures was 135 mm at 0 % reduction and 4 mm at 25 % reduction. The

cement content variation provides a local alteration on the location of the WFadj plotted

on the MCFC, in which the higher the cement content, the higher theWFadj. This may be

explained by the proportionally higher water content associated with the higher cement

content since all mixes had a fixed w/c of 0.50.

Results also indicate a nonlinearity in aggregate packing outcomes when plotted on

the MCFC. At the WB, the optimized blend had packing of 0.727 and 0.759 for the

dry-rodded and vibrated specimens, respectively, increasing to the average 0.731 and

0.811 between Zones II and IV (PK7 and PK9), and decreasing to 0.722 and 0.791 in

Zone IV (PK6).

Conclusions

This study provided a theoretical and experimental analysis of the effects of aggregate

packing on concrete strength and consistency. Also, an investigation of the relationship

between the traditional dry-rodded and the vibrated aggregate packing was performed.

The results can contribute to filling the gap in the literature addressing southern U.S. lime-

stone and silica sand. The main findings are as follows:

(1) Slump and compressive strength of optimized concrete mixtures are less sensitiveto cement content reductions (0 to 25 %) than nonoptimized mixtures. This can be

FIG. 9

MCFC with aggregate packing

and slump for all cement

contents tested, adapted from

Ref. [7].




explained by the fact that the greater content of limestone particles in the optimizedmix reduces the fine-coarse aggregate friction, as well as the influence of theaggregate-cement paste interfacial zone on the concrete strength.

(2) Optimized mixtures require less water-reducing admixture to reach the desiredconsistency because of less friction between aggregate particles, which can requireboth less cement paste and admixtures to reach the desired workability.

(3) Dry-rodded and vibrated aggregate packing present a robust linear relationship(R2= 0.98) since the energy applied to the vibrated specimens was steady andhigher than the energy applied by rodding.

(4) Aggregate packing cannot be used alone to optimize gradations and should be usedin conjunction with aggregate gradation, slump, and cement content because pack-ing results indicate nonlinearity with aggregate proportions. Conversely, the linearrelationship between aggregate proportions and concrete slump is one of thetheoretical bases of the ACI 211.1 mix design procedure.

Finally, designing concrete based on packing, consistency, and aggregate gradation

can result in 25 % less cement content to reach an expected compressive strength and less

water-reducing admixture to obtain a required consistency.

ACKNOWLEDGMENTS

We thank the Brazilian Coordination for the Improvement of Higher Education Personnel

for the financial support. We acknowledge the support from the State Materials Office of

the FDOT for aggregate donation and Vebe apparatus usage.

References

[1] Moini, M., Flores-Vivian, I., Amirjanov, A., and Sobolev, K., “The Optimization ofAggregate Blends for Sustainable Low Cement Concrete,” Constr. Build. Mater.,Vol. 93, 2015, pp. 627–634, https://doi.org/10.1016/j.conbuildmat.2015.06.019

[2] Ley, T. and Cook, D., “Aggregate Gradations for Concrete Pavement Mixtures,” CPRoadmap, Ames, IA, 2014.

[3] Tasi, C. T., Li, L. S., and Hwang, C. L., “The Effect of Aggregate Gradation onEngineering Properties of High Performance Concrete,” J. ASTM Int., Vol. 3,No. 3, 2005, pp. 1–12, https://doi.org/10.1520/JAI13410

[4] Tia, M., Liu, Y., Haranki, B., and Su, Y.-M., “Modulus of Elasticity, Creep and Shrinkageof Concrete,” RPWO 67, Florida Department of Transportation, Gainesville, FL, 2009.

[5] Lindquist, W., Darwin, D., Browning, J. A. K., McLeod, H. A. K., Yuan, J., andReynolds, D., “Implementation of Concrete Aggregate Optimization,” Constr. Build.Mater., Vol. 74, 2015, pp. 49–56, https://doi.org/10.1016/j.conbuildmat.2014.10.027

[6] Anson-Cartwright, M., “Optimization of Aggregate Gradation Combinations toImprove Concrete Sustainability,” M.A.Sc. thesis, University of Toronto, Toronto,Canada, 2011–unpublished.

[7] Shilstone, J. M., Sr., “Concrete Mixture Optimization,” Concr. Int., Vol. 12, No. 6,1990, pp. 33–39.

[8] Richardson, D., “Aggregate Gradation Optimization: Literature Search,” RDT 05–001,Missouri Department of Transportation, Jefferson City, MO, 2005, 113p.

[9] Cook, D., Ghaeezadeh, A., Ley, T., and Russell, B., Investigation of Optimized GradedConcrete for Oklahoma, Oklahoma Department of Transportation, Oklahoma City,OK, 2013, 156p.

[10] De Larrard, F., Concrete Mixture Proportioning: A Scientific Approach, CRC Press,Boca Raton, FL, 1999, 448p.

[11] De Larrard, F., “Concrete Optimisation with Regard to Packing Density andRheology,” presented at the Third RILEM International Symposium on Rheology




https://doi.org/10.1016/j.conbuildmat.2015.06.019


https://doi.org/10.1520/JAI13410

https://doi.org/10.1520/JAI13410




of Cement Suspensions Such as Fresh Concrete, Reykjavik, Iceland, Aug. 19, 2009,RILEM, Paris, France.

[12] Goltermann, P., Johansen, V., and Palbøl, L., “Packing of Aggregates: An AlternativeTool to Determine the Optimal Aggregate Mix,” ACI Mater. J., No. 94, Vol. 5, 1997,pp. 435–442.

[13] Fuller, W. and Thompson, S., “The Laws of Proportioning Concrete,” Trans. Am. Soc.Civ. Eng., Vol. LIX, No. 2, 1907, pp. 67–143.

[14] Talbot, A. and Richart, F., “The Strength of Concrete, its Relation to the CementAggregates and Water,” Univ. Illinois Eng. Exp. Station, Bull. 137, Vol. XXI,No. 7, 1923, pp. 1–122.

[15] Cook, M. D., Ghaeezadah, A., and Ley, M. T., “Impacts of Coarse-AggregateGradation on the Workability of Slip-Formed Concrete,” J. Mater. Civ. Eng.,Vol. 30, No. 2, 2017, pp. 1–8.

[16] Mehta, P. K. and Monteiro, P. J. M., Concrete: Microstructure, Properties, andMaterials, McGraw Hill, New York, NY, 2014, 704p.

[17] ASTM C150/C150M-17, Standard Specification for Portland Cement, ASTMInternational, West Conshohocken, PA, 2017, www.astm.org

[18] Antunes, R. and Tia, M., “Influence of Intermediate-Sized Particle Content onTraditional Dry-Rodded and Vibrated Aggregate Packing,” Int. J. Eng. Res. Appl.,Vol. 8, No. 4, 2018, pp. 21–27.

[19] ASTM C29/C29M-17a, Standard Test Method for Bulk Density (“Unit Weight”) andVoids in Aggregate, ASTM International, West Conshohocken, PA, 2017, www.astm.org

[20] ASTM C1170/C1170M-14e1, Standard Test Method for Determining Consistency andDensity of Roller-Compacted Concrete Using a Vibrating Table, ASTM International,West Conshohocken, PA, 2014, www.astm.org

[21] FDOT Section 346, Portland Cement Concrete, Florida Department ofTransportation, Tallahassee, FL, 2013, 21p.

[22] FDOT Section 9.2 Volume II, Structural Concrete Production Facilities Guide, FloridaDepartment of Transportation, Tallahassee, FL, 2011, 23p.

[23] ASTM C173/C173M-16, Standard Test Method for Air Content of Freshly MixedConcrete by the Volumetric Method, ASTM International, West Conshohocken,PA, 2016, www.astm.org

[24] ASTM C143/C143M-15a, Standard Test Method for Slump of Hydraulic-CementConcrete, ASTM International, West Conshohocken, PA, 2015, www.astm.org

[25] ASTM C39/C39M-18, Standard Test Method for Compressive Strength of CylindricalConcrete Specimens, ASTM International, West Conshohocken, PA, 2018, www.astm.org

[26] ACI 211.1, Standard Practice for Selecting Proportions for Normal, Heavyweight, andMass Concrete, American Concrete Institute, Farmington Hills, MI, 1991, www.concrete.org

[27] ASTM C192/C192M-16a, Standard Practice for Making and Curing Concrete TestSpecimens in the Laboratory, ASTM International, West Conshohocken, PA,2016, www.astm.org

[28] ASTM C117-17, Standard Test Method for Materials Finer than 75-μm (No. 200) Sievein Mineral Aggregates by Washing, ASTM International, West Conshohocken, PA,2017, www.astm.org

[29] ASTM C136 / C136M-14, Standard Test Method for Sieve Analysis of Fine and CoarseAggregates, ASTM International, West Conshohocken, PA, 2014, www.astm.org

[30] ASTM C128-15, Standard Test Method for Relative Density (Specific Gravity) andAbsorption of Fine Aggregate, ASTM International, West Conshohocken, PA,2015, www.astm.org

[31] ASTM C33 / C33M-16e1, Standard Specification for Concrete Aggregates, ASTMInternational, West Conshohocken, PA, 2016, www.astm.org

[32] ASTM C127-15, Standard Test Method for Relative Density (Specific Gravity) andAbsorption of Coarse Aggregate, ASTM International, West Conshohocken, PA,2015, www.astm.org
















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