use of blast furnace slag in road construction. report

Use of Blast-Furnace Slag in road construction

A

SEMINAR REPORT

ON

“USE OF BLAST-FURNACE SLAG IN ROAD CONSTRUCTION”

Submitted

BY

Mr.Nagarjun

NIT,Raichur

DEPARTMENT OF CIVIL ENGINEERING

NAVODAYA INSTITUTE OF TECHNOLOGY

RAICHUR-584101

Civil department, NIT Raichur


CONTENTS

S.No TITLE Page No.

1 INTRODUCTION 1

2 STRENGTH DEVELOPMENT OF CONCRETES WITH SLAG 32.1 Research Significance 32.2 Experimental 32.3 Experimental Results and Discussion 52.4 Analysis of the Results 5

3DEVELOPMENT OF ENGINEERED CEMENTITIOUS COMPOSITES (ECC) WITH SLAG 83.1 Materials 83.2 Mixing and Curing 83.3 Four-point bending and compressive tests 83.4 Uniaxial tensile test 93.5 Loaded crack width measurement 113.6 Results and discussion 11

4 Stabilization Of Expansive Clay 124.1 Experimental Studies 124.2 Preparation of Samples 134.3 Sample Properties 134.4 Free Swell Testing Procedure 144.5 Test Results 154.6 Discussion of Test Results 17

5 Using Blast-Furnace Slag in Road Construction 19

6 SUMMARY 23

7 REFERENCES 24



List of Table

Table

No.Description

Page

No.

1 Cube compressive strength 4

2 The linear regression analysis results of the strength-time data 7

3 Sample properties 13

Fig

No.Description

Page

No.

1 Four-point bending test setup 9

2 Uniaxial tensile test set-up 10

3 Compaction of specimen into the consolidation ring 13

4 Variation of t50with stabilizers added 17



Chapter 1

Introduction

10 million tons of blast furnace slag is produced in India annually as a byproduct of Iron

and Steel Industry. Blast furnace slag is composed of silicates and alumino silicates of lime

and other bases. It is a latent hydraulic product which can be activated with anyone- lime,

alkalies or Portland cement.

Lime-GBFS mix as alternate binder to cement, and for its use in mortar, soil stabilization as

well as in concrete. Lime - granulated blast furnace slag (GBFS) binder in 1 : 2 ratio, with

and without 7.5 percent gypsum fulfils the IS requirements for soundness as required for

OPC. With 7.5 percent gypsum final setting time of lime granulated blast furnace slag binder

is reduced from 338 minutes to 270 minutes as compared to lime – GBFS mix without

gypsum. The compressive strength of lime – GBFS sand mortar is improved by 77.0 percent

and 40 percent at 28 and 180 days by the addition of 7.5 percent gypsum by weight of lime-

GBFS binder.

Lime – GBFS soil stabilized mixes (10-25 percent replacement of soil with lime-GBFS mix)

gave CBR values in the range of 48-92 percent and the unconfined compressive strength 15-

40 kg/cm2 in comparison to plain soil which gave CBR value of 7 percent and unconfined

strength 3 kg/cm2 at 28 days. Addition of 7.5 percent gypsum to Lime –GBFS (by weight of

binder) soil stabilized mixes further improved CBR and the unconfined compressive strength

and the values obtained were in the range of 112-266 percent and 29-58 percent respectively.

The hydration of granulated blast furnace slag is slower than that of the ordinary Portland

cement. When mixed with Portland cement, BFS accelerates the hydration of Portland

cement and reacts with the calcium hydroxide, and mixture of the two will retard the rate of



strength development. The degree of retardation depends upon the chemical composition of

the slag and OPC, percentage of slag, temperature and humidity of the environment.

BFS improves the properties of fresh and hardened concrete, such as workability and

durability, for instance, enhancing sulfate attack resistance and decelerating chloride ion

penetration. Besides, the addition of BFS results in a more homogeneous fiber distribution,

because BFS particles provide a driving force for fiber dispersion. Therefore, the use of

limestone powder and BFS in concrete not only reduces the cost and increases the greenness,

but also improves the workability, the mechanical properties and the durability of concrete.

Research on the use of granulated blast-furnace slag in road construction shows that the

strength of the reinforced bed depends on the activity and granule size of the slag, the

quantity and quantity of lime (the activator), the composition of the bed and the relative

content of binder, and also the setting conditions. On the basis of the results, blast-furnace

slag may be recommended as a hydraulic binder for the reinforcement of road materials, with

the addition of lime and other activators



Chapter 2

Strength Development of Concretes with Slag

2.1 RESEARCH SIGNIFICANCE

The compressive strength development of OPC, fly ash, and slag concretes at early ages

subjected to different temperature is greatly affected by the curing temperature. In order to

predict time-strength development, this effect should be taken into consideration.

Compressive strength results of the concretes subjected to different constant curing

temperatures until the age of testing were analyzed according to the hyperbolic strength-age

function.

2.2 EXPERIMENTAL

Throughout this investigation, ordinary Portland cement, ground granulated-blast

furnace slag, and fly ash were used as cementing materials. Composition of OPC, fly ash, and

slag are given in Table 1. The coarse aggregate used was a 10 mm maximum size quartzite

crushed gravel which complied with the grading limits of the BS 882 [8]. The fine aggregate

was 3 mm maximum size and it was obtained from the same source of the coarse aggregate.

During this study five mixes were used.

i) The first one, made by using OPC without any replacement, was used as the mix

control.

ii) The second and third mixes had 30%and 50% of the cement replaced by fly ash.

iii) The fourth and fifth mixes had 30% and 50% of cement replacement with slag.

For all the five mixes the total aggregate/cementitious materials ratio was 6.0 with 33% of

fine aggregates, and the water/cementitious ratio was 0.55. Prior to mixing, the mix

ingredients were stored at the temperatures of 6, 20, 35, 60, and 80ºC for at least 24 hours.



For each temperature 10 standard test cubes (100xl00xl00 ram) were cast for each of the five

mixes. The specimens were kept in their moulds for 24 hours in predetermined constant

temperature curing tanks and then they were & mounded and put back in their curing tanks

until the testing age.The compressive strength was obtained at ages of 1, 3, 7, 28, and 90 days

for water-cured specimens at 6, 20, 35, 60, and 80ºC the test was carried out in accordance

with the requirements.

Table 1-Cube compressive strength

2.3 EXPERIMENTAL RESUUS AND DISCUSSION

The results of the compressive strength tests for five mixes are given in Table 1. At 6 and

20 ºC curing temperature, OPC concrete shows greater strength than other concretes up to the

age of 90 days. They also found that concretes containing slag initially gained strength at a



slower rate than 100% OPC mix. However, at later ages (56 days) the slag mixes did tend

towards achieving their equivalent OPC mix strength. It can be seen from the results of this

research that with a 50% slag replacement level at the 20ºC curing temperature, the slag

concrete did not achieve the equivalent OPC mix strength up to the age 90 days.

From the result we proved that the curing temperature has marked effect on the strength

development of the OPC concrete. Concrete cured at 20 ºC temperature has a higher strength

at 28 days than similar concrete cured at temperatures between 40 and 60ºC Same trend can

be seen from these research results.

2.4. ANALYSIS OF THE RESULTS

It can be seen from the compressive strength of concretes subjected to different

temperature is affected by the curing temperature greatly. In order to predict time-strength

development, this effect should be taken into consideration. Carino [12] suggested a

hyperbolic strength age function that can account for temperature and time effects on strength

development of concretes cured under isothermal conditions.

where

fc = Strength at age t;

to = Age when strength development begins;

fu= Ultimate strength;

k = Initial slope of the relative strength (fc /fu) versus t curve.



The parameters k, to, and fu are all functions of the temperature. Brooks and A1-Kaisi [13]

introduced a power index n, for the (t-to) term to get better fits at high temperatures (40-

60ºC).

Therefore the function becomes:

For each curing temperature, k and fc values were determined by linear regression of

Equation (3) with various combinations of n, until the sum of errors squared were minimized.

It was found that the parameter did not vary consistently with temperature or replacement

level of slag and fly ash, k increases with an increase in temperature up to 60 ºC the

parameter n decreased generally with an increased temperature. The other parameter, which

is the setting time to, decreased with an increase in temperature. The trends of to , decreased

with an increase in temperature.

The prediction of compressive strengths for varying temperatures was done by first

considering the zero strength as either the time at which the initial or final

Setting times occurred (see Table 2). Regression analysis was carried out by considering the

effective age starting from initial and final setting times. It was found that, the final setting

time gave the smaller squared sum of errors for all the temperatures and therefore the

effective age is taken as the time measured from the final set.

Table 2 gives the results of the linear regression analysis according to Equation (3).

Calculated and experimental analysis strength results are compared in Figs. 1 to 5 and it can

be seen that the regression analysis gives good fit to the experimental results.



Table 2-The linear regression analysis results of the strength-time data



Chapter 3

Development of engineered cementitious composites(ECC) with slag

3. Experimental program

3.1 Materials

Two groups of matrix materials were used to produce ECC. The first group included

Portland cement 42.5 N, limestone powder and BFS. The mix proportion of a standard ECC

mixture M45 is used as a reference in the ECC mix design. The second group included BFS

cement and limestone powder.

3.2 Mixing and curing

The matrix materials were first mixed with a HOBART_ mixer for 1 min at low speed.

Then water and super plasticizer were added at low speed mixing. Mixing continued at low

speed for 1 min and then at high speed for 2 min. After fibers were added, the sample was

mixed at high speed for another 2 min.

The fresh ECC was cast into six coupon specimens with the dimension of 240 mm 9 60 mm 9

10 mm and a prism with the dimension of 160 mm 9 40 mm 9 40 mm. After 1 day curing in

moulds covered with plastic paper, the specimens were demoulded and cured under sealed

condition at a temperature of 20_C for another 27 days.

3.3 Four-point bending and compressive tests

After 28-day curing, the coupon specimens were sawn into four pieces with the dimension of

120 mm x9 30 mm x9 10 mm. These specimens were used in fourpoint bending test. The

support span of the four-point bending test set-up was 110 mm, and the load span was 30 mm

as shown in Fig. 4. Two LVDTs were fixed on both sides of the test set-up to measure the

flexural deflection of the specimen. The test was conducted under deformation control at the



speed of 0.01 mm/s. Three measurements were done for each mixture. After 28 days of

curing, the prism specimens were sawn into three cubes with the dimension of 40 x 40 x 40

mm3. These cubes were used for compressive tests. Three measurements were done for each

mixture.

Fig 1 Four-point bending test setup

3.4 Uniaxial tensile test

A uniaxial tensile test set-up was developed for ultra ductile fiber reinforced concrete, such

as ECC, as shown in Fig. 2. The specimen is clamped by four steel plates, one pair at each

end. Each pair of steel plates is tightened with four bolts. Two pairs of steel plates are fixed

on the loading device with four steel bars, two for each pair. Between the pairs of steel plates

and the loading device, there is a ± 3 mm allowance. It is used to diminish the eccentricity in

the direction perpendicular to the plate of the specimen by moving the steel plates along the

steel bar. The tensile force is transferred to the specimen by the friction force between the

steel plates and the specimen. Four aluminum plates, 1 mm thick each, are glued on both

sides of the ends of specimen in order to improve the friction force, to ensure the clamped

area work together and to prevent the local damage on the specimen caused by high clamping

force.



The experimental procedure is described in details hereafter. The coupon specimens were

sanded to obtain a flat surface with a larger bond strength with the aluminum plates. After

cleaning the specimen surface and the aluminum plate with Acetone, the aluminum plates

were glued on the specimen. The glue was cured for 1 day before testing. Before placing the

specimen in the test set-up, two pairs of steel plates were connected to the bottom and the top

parts of loading device, respectively. The lower end of the specimen was first clamped with

the steel plates by tightening four bolts. Then the upper end of the specimen was clamped

with the other pair of steel plates. Finally, two LVDTs were mounted on both sides of the

specimen. The testing gauge length was 70 mm. The tests were conducted under

deformationvcontrol with a loading speed of 0.005 mm/s. More than four specimens were

tested for each mixture.

Fig. 2 Uniaxial tensile test set-up

How to alleviate eccentricity is of most concern in uniaxial tensile testing. The eccentricity

can lead to a bending moment in the cross-section of the testing specimen and therefore an

uneven stress distribution. The larger the eccentricity is, the larger the bending moment is.

With large bending moment imposed on the specimen, cracking starts on the side of the

specimen with high tensile stress, even when the average stress in this cross-section is lower

than the tensile strength. The crack can quickly propagate into



the specimen, due to the stress localization at the crack front and the loss of cross sectional

area. As a result, the measured tensile strength and strain capacity appears far from true

uniaxial tensile properties.

3.5 Loaded crack width measurement

The crack width was measured on the coupon\ specimens after the uniaxial tensile test.

Three lines parallel to the loading direction were drawn on the specimen. These lines were

uniformly spaced on the width of specimen . Under microscope, the number of cracks

crossing each line was counted. The average crack number of each specimen was calculated

by averaging the number of cracks crossing these three lines. Since ECC deforms several

hundred times larger than the matrix, the tensile deformation of the matrix contributes little to

the overall tensile deformation of ECC. Therefore, the overall tensile deformation of ECC

can be related only to the crack opening. Accordingly, the average crack width w can be

calculated by dividing the measured tensile deformation at the peak load Dl by the average

crack number N.

(4)

The calculated crack width is the loaded crack width. This is different from the residual crack

width in the previous studies , in which the crack width is measured after partial crack closure

due to the relaxation after unloading. The loaded crack width is roughly twice of the

residual crack width.

3.6 Results and discussion

3.6.1Compressive strength

The compressive strength of the ECCs at 28 days is summarized . The increasing limestone

powder content results in a decrease in the compressive strength in M1-4. Comparing the



compressive strength of mixtures M5 and M6, the high cement replacement by BFS causes

little decrease in the compressive strength. The mixtures M3, M5 and M6 with good tensile

property all show compressive strengths higher than 38 MPa. This value can fulfill

engineering requirements in most projects.

Chapter 4

Stabilization of Expansive Clays

4.1 Experimental Studies

The scope of this experimental study was: (a) to determine the effects of GBFS and

GBFSC on grain size distribution, Atterberg limits, swelling potential, and rate of swell of an

expansive soil sample with and without curing, and (b) to investigate the possible

contamination effects from using GBFS and GBFSC in expansive soil stabilization by

leachate analysis.

4.2 Preparation of Samples

An artificial, potentially expansive soil, sample A, was prepared by mixing 85% Kaolinite

(Gs = 2.69) and15% Na-Bentonite (Gs = 2.39) by dry mass. After weighing the constituents,

Na-Bentonite and Kaolinitewere mixed using a trowel. Then the mixture was sieved together

through No. 30 (0.600 mm) sieve to obtain a more homogeneous blend. A preliminary swell

test on sample a resulted in 32.90% vertical swell, indicating a highly expansive soil. To

overcome the swelling potential, ground GBFS (Gs = 2.88), was first added in amounts

ranging from 5, 10, 15, 20 and 25% in dry mass to sample A,

And GBFSC (Gs = 2.89) was manufactured by blending ground GBFS (80%) and ordinary

Portland cement (20%) by mass). GBFSC was added in amounts ranging from 5, 10, 15, 20

and25% in dry mass to sample A.



Prior to mixing, all the constituents were oven dried for 24 h, and ground to pass through a

No. 40 (0.425 mm) sieve. GBFS was ground to 4,000 cm²/g fineness by a crusher. Stabilized

specimens of sample A were prepared by mixing a pre-calculated amount of GBFS or

GBFSC and sample A at a moisture content of 10%. The sample A—GBFS or sample A—

GBFSC blends were compacted directly into consolidation ring at 10% moisture content (Fig.

1) and sealed with stretch film to prevent loss of moisture. Samples were left to cure at 22_C

and 70% relative humidity for 7or 28 days.

4.3 Sample Properties

Hydrometer tests were performed to determine particle size distribution. The LL, PL, PI,

SL (Mercury Method), and specific gravity (Gs) of the samples were determined. The LL, PL

and PI of the untreated and treated samples are given in Table 2.1. All the samples were

classified according to the Unified Soil Classification System (USCS) by plotting test results

on a plasticity chart, and the sample properties are given in Table 2.1

Fig. 3 Compaction of specimen into the consolidation ring

Table 3Sample properties

Samples

Clay (%) Silt (%) G LL (%) PL (%) PI(%) SL(%)

Soil classification

Samples A 49 51 2.65 104.5 29.1 75.4 18 CH

95% A+ 5% GBFS 42 58 2.68 81.8 28.8 53 20 CH

90% A+ 10% GBFS 38 62 2.69 81 28.6 52.4 21 CH



85% A+ 15% GBFS 39 61 2.7 78.5 26.9 51.6 21.5 CH

80% A+ 20% GBFS 35 65 2.72 77.4 26.1 51.3 22 CH

75% A+ 25% GBFS 35 65 2.73 75.6 25.1 50.5 23 CH

95% A+ 5% GBFSC 45 55 2.7 106.7 34.6 72.1 34 CH

90% A+ 10% GBFSC 47 53 2.71 83.4 36.8 46.6 36 CH

85% A+1 5% GBFSC 46 54 2.73 69.1 39.1 30 38 MH

80% A+ 20% GBFSC 43 57 2.75 68.8 39.3 29.5 38.5 MH

75% A+2 5% GBFSC 43 58 2.77 65.5 40.3 25.2 39 MH

4.4 Free Swell Testing Procedure

In this experimental study, the ‘‘Free Swell Method’' was used to determine the amount

of swell. Each specimen was prepared to 60 g dry mass. To ease compaction into the

consolidation ring of the oedometer apparatus, 6 ml of water was added to the sample to

obtain 10% water content. The diameter of the consolidation ring was 50.8 mm. To obtain 1.8

g/cm³ bulk density in 34.5 cm³ of specimen volume, 62.1 g of the prepared sample was

weighed and compacted directly into the consolidation ring to a thickness of 17 mm, using a

manual compaction piston. In this way, disturbance caused by using guide rings while

preparing the specimen and then transferring it to the consolidation ring was avoided.

The consolidation ring containing the specimen was placed in the oedometer after placing

filter papers on the top and bottom of the specimen not to clog the porous stones. An air-dry

porous stone was placed on top of the specimen. After the oedometer was mounted on the

loading device, the dial gauge measuring the vertical deflection was set to zero. The specimen

was inundated with water to the upper surface directly, and to the lower surface through

standpipes. A seating pressure of at least 1 kPa applied by the weight of top porous stone and

load plate until primary swell is complete. As soon as the specimen was inundated, swelling

began. The specimen was allowed to swell freely. Dial gauge readings showing the vertical

swell of the specimen were recorded until the swell stopped. These data were used to

calculate the time-swell relations and final swell of each specimen upon inundation. After the



specimen stopped swelling, the final water content was determined in accordance with

ASTM Test Method with designation number D2435-90. Free swell percent was calculated

from Eq 1

Free Swell(%)= 100 dH/H (5)

Where dH is the change in the initial height of the specimen after it is inundated.

H is the original height of the specimen just before the inundation.

4.5 Test Results

4.5.1 Effects of GBFS and GBFSC Addition on the Atterberg Limits of Expansive Soil

The samples treated with GBFS showed a reduction in LL GBFSC caused a slight

increase in LL of sample A with the addition of 5% GBFSC, further additions of GBFSC

caused a decrease in LL of sample A

The PI for samples treated with GBFS and GBFSC showed a similar behavior of a decrease

in PI (Table 2) with an increase in % stabilizer.

Shrinkage limit of the samples decreased with the increased amounts of additives (Table 2).

4.5.2 Effects of GBFS and GBFSC Addition on the Specific Gravity of Expansive Soil

All GBFS (GS = 2.88) and GBFSC (GS = 2.89) additions caused increases in the specific

gravity of samples (Table 2) when compared to the specific gravity of sample A (GS = 2.65).

4.5.3 Effects of GBFS and GBFSC Addition on the Swelling of Expansive Soil

Swell percentage of specimens were decreased by all types and amounts of additives.

Granulated blast furnace slag (5%) addition caused a decrease of 31.1% in the swell when

compared to the swell of sample A. The decrease in swell continued with the increasing



amounts of GBFS in the samples. GBFS (25%) addition caused a decrease of 61.7% in the

swell percentage.

Granulated blast furnace slag cement added samples had the most powerful effect on the

swell amount. Only 5% GBFSC addition caused a decrease of 69.8% in the swell amount.

The decrease in the swell in the specimen containing 15% GBFSC was 80.5%. Specimens

having more than 15% GBFSC content also resulted in decrease of swell up to 81.6%.

4.5.4 Effects of GBFS and GBFSC Addition on the Rate of Swell of Expansive Soil

Rate of Swell is best described by t50. As defined earlier, t50 is the time required to reach

50% of the total swell of the specimen after inundation. Thus, if t50 is larger, rate of swell is

slower. t50 values of specimens were decreased by all types and amounts of additives.

Granulated blast furnace slag added specimens decreased the t50 by amounts ranging from 60

to 90% depending on the amount of GBFS. Decrease in the t50 was gradually increased with

the increased amounts of GBFS.

Granulated blast furnace slag cement added specimens also had a similar effect on t50.

GBFSC (5%) added specimen caused 92.3% decrease while 25% GBFSC added specimen

caused a 98.5% decrease in t50. Decrease in t50 was weakly related to the amount of GBFSC

in the specimens.

4.5.5 Effects of curing on rate the Swell

The results for rate of swell (inversely related to t50) of specimens with and without

curing are shown in (Fig.2). As a result of curing, rate of swell of the samples was generally

increased slightly, the t50 values being decreased.

(t50) without cure > (t50)7dayscuring > (t50)28dayscuring

This order was generally followed by each sample (Fig. 2). Curing shortens the time

necessary for the completion of the 50% swell.



Fig. 4 Variation of t50with stabilizers added

4.6 Discussion of Test Results

The LL, PI, SL and clay content (CC) results can be used to explain the swell results as

follows:

The addition of GBFS (or GBFSC) to the expansive clay:

i) Reduces the CC and a corresponding increase in the percentage of coarse particles

ii) Reduces the LL

iii) Raises the SL and

iv) Reduces the PL of the soil



Additions of GBFS and GBFSC resulted in the formation of aggregations which reduced the

swelling potential of the soil.

The issues are summarized as follows:-

i) At low, normal and elevated curing temperatures, fly ash and slag concretes

developed strength more slowly than OPC concretes.

ii) Slag concretes behaved similarly to OPC concretes after 28 days of age and gave

higher strength at 20ºCthan other curing temperatures.

iii) The increasing limestone powder and BFS contentslead to a smaller average loaded

crack width.

iv) Addition of GBFS and GBFSC to the soils altered the grain size distribution of

expansive soil sample Clay fractions decreased and silt fractions increased upon

adding GBFS and GBFSC.

v) Plasticity index is decreased for all GBFS and GBFSC additions



Chapter 5

Using Blast-Furnace Slag in Road Construction

Road construction has different requirements in terms of both production and operation,

calling for different properties of the Portland cement. In particular, relatively fast setting(2 −

4 h), for example, impairs the technological expediency of the material, especially in the case

of extensive construction work for monolithic cement–concrete road surfaces. The fast setting

of concrete with considerable heat liberation tends to create an internal stress state, which

reduces the crack resistance of the concrete plate; to reduce the stress, temperature seams

must be introduced in the plate. Temperature seams are usually introduced at intervals of 4–6

m; this, in turn, reduces the resistance of the coating to dynamic loads due to the moving

vehicles. As is evident, the fast setting of commercial Portland cement may be attributed to

the high content in the clinker of fast-setting highly basic silicates C3S, aluminates, C3A, and

alum ferrites C4AF, whose total contentis 75–85%. The C2S reaches 50% hydration after180

days; this indicates slow setting. However, on account of its low content (5–25%), this

component has practically no influence on the setting of the Portland cements.

By contrast, slag binders (cements) composed mainly of granulated slag and activators

consist of slow-setting low-basicity silicates C2S (75–85%), which results in slow setting.

Therefore, these are classified as slow-setting binders. Unroasted slow-setting binder largely

meets the requirements of road construction. Slow setting of the binder (2–3 days in normal

conditions) is convenient here. Hence, materials with slow-setting binder will retain their

thixotropic properties for a long period. This means that material may be applied and worked

over more than 2–3 km at a time, without loss of quality. The persistence of the thixotropic

properties will depend on many factors, such as the temperature, the moisture content, the

granular composition of the fillerthe weather, and the operating conditions of the machinery

employed.



The use of sand, gravel, and powder from blast-furnace slag is promising in various asphalt

concretes— for example, in porous asphalt concrete and in gravel– mastic coatings. French

scientists have established that, when using porous asphalt concrete, the noise from vehicles

is reduced by 3 dB. Therefore, the expanded use of this material is recommended, since it

improves both highway safety and environmental conditions. Moreover, this important

innovation improves driver comfort in any weather.

Such coatings ensure

i) Rapid drainage of water from the surface and hence increase road safety during

rainstorms,

ii) By reducing aquaplaning and increasing wheel adhesion to the road.

iii) At night, when the headlights are turned on, there is less reflective glare from the road

surface, with improvement in visibility for the driver.

iv) In many developed nations, the trend is to build highways hat ensure reliable and safe

motion, with minimum ecological impact.

In obtaining porous asphalt concrete with specified properties, the key factor is the interaction

between the bitumen and mineral fillers. A whole set of processes occurring with prolonged

contact of these materials in roadway operation must be taken into account: physical

processes at the bitumen–mineral interface; chemisorption; and filtration of the bitumen and

its components within the mineral grains. In comparison with minerals, blast-furnace slag

contains considerably less SiO2 (34–36%) and more CaO (38–41%).

The distinguishing feature of asphalt concretes based on blast-furnace slag, relative to

traditional rock, is rapid filtration of the binder and its components within the porous slag

material, since the slag is relatively hydrophobic. Bitumen filters through macro- and micro

pores within the asphalt concrete. The presence of micropores at the surface of the slag grains

leads to selective diffusion of the bitumen components. Oil penetrates deep into the

capillaries within the grains; on account of their lower mobility and greater activity, tars

reach smaller depths. Therefore, the surface layer of the bitumen at the slag grains is enriched

with asphaltenets. As a result of the interaction of porous slag’s with bitumen, the bitumen



films rapidly become harder and less lastic, which may accelerate aging of the asphalt

concrete. Therefore, the viscosity of the bitumen should be reduced to some limit. The ease of

deformation of the asphalt concrete may increase here, without loss of strength, and its aging

may be slowed.

Overall, the interaction of bitumen with blast-furnace slag is intense, on account of physical,

mechanical, chemical, electrostatic, and diffusional processes. Therefore, the adhesive

binders at the boundary of the bitumen–mineral material are strong and stable under the

action of atmospheric factors. In addition, the hydraulic activity of the blast-furnace slag

facilitates prolonged setting of the material and the acquisition of additional strength, which

compensates the increased porosity of the asphalt concrete. In additional tests of asphalt

concrete at 75°C, the heating of the road surface in summer is taken into account. It is found

that slag based asphalt concrete is basically free of the deficiencies of traditional asphalt

concrete. With a dense water impermeable supporting layer, no additional layers are required

to compensate for the low carrying capacity of porous asphalt concrete, since it meets and

even exceeds all the physicomechanical requirements on traditional asphalt concrete.

The shear stability or gravel-mastic asphalt concretes with different additives is 10-15%

higher than for traditional asphalt concrete; this indicates high resistance to deformation. And

no special measures are required to clean coatings made of porous and gravel–mastic asphalt

concretes with slag fillers. Over time, the porosity of the asphalt concrete remains practically

constant, on account of the gradual uncovering of surfaces of

Considerable porosity, which is typical of slag materials. Given all the benefits of draining

asphalt concrete based on slag materials, it is recommended for the construction

of all roads in residential areas, so as to increase road safety, reduce noise, and improve the

comfort and visibility of drivers. This recommendation may also be extended to road sections

with sharp horizontal curves.



Chapter 6

Conclusions

• At low, normal and elevated curing temperatures, fly ash and slag concretes

developed strength more slowly than OPC concretes

• Slag concretes behaved similarly to OPC concrete after 28 days of age. \

• The strength age relationship is described more accurately by using the hyperbolic

power function

• Slag cement can enhance concrete pavement by improving workability in the plastic

state.

• Increasing strengths and reducing permeability in the harde ned state.

• The increasing limestone powder and BFS contents lead to a smaller average loaded

crack width

• blast-furnace slag is a long-acting binder, which facilitates the solidification of

materials used for road construction, thereby increasing the carrying capacity and

durability of road and runway coatings



References

• O.Eren, (2002). “Strength development of concretes with ordinary Portland cement,

slag or fly ash cured at different temperatures”, Department of Civil Engineering,

Eastern Mediterranean University, Gazimagusa, Kibris, Mersin 10, Turkey, vol

35,page no.536-540

• J. Zhou , S. Qian , M. G. Sierra Beltran G. K. van Breugel “Development of

engineered cementitious composites with limestone powder and blast furnace slag”

Microlab, Faculty of Civil Engineering and Geosciences,Delft University of

Technology, Delft, The Netherlands

• S V Srinivasan,” Use of blast furnace slag and fly-ash in road construction”Indian

highways. Vol. 21, no. 11 (Nov. 1993)

• Erdal Cokca , Veysel Yazici , Vehbi Ozaydin” Stabilization of Expansive Clays Using

Granulated Blast Furnace Slag (GBFS) and GBFS-Cement”, Department of Civil

Engineering, Middle East Technical University, 06531 Ankara, Turkey

• B.A.Asmatulaev.R.B.Asmatulaev,A.S.Abdrasulova,”Use Of Blast-Furnace Slag in

Road construction”, Dortrans Kazakh Scientific-Research and Design Institute,

Almaty, Kazakhstan,AK Kazzhol, Kazakhstan,Vol 37 p.no 722-725

•
