Performance of Portland-Limestone Cements in ... - NRMCA.com

Decreasing the Clinker Component in Cementing Materials: Performance of Portland-Limestone Cements in Concrete in combination with Supplementary Cementing Materials R. D. Hooton1, A. Ramezanianpour1, and U. Schutz2 1 University of Toronto, Dept. of Civil Engineering, Toronto, Ontario, Canada, M5S1A4 PH 416-978-5912; FAX 416-978-6813; email: [email protected] and [email protected] 2 Holcim (Canada) Inc. 2300 Steeles Avenue West, 4th Floor, Concord, Ontario L4K5X6 email: [email protected] Abstract Portland-limestone cements have been used in Europe for decades and now meet EN 197 CEMIIA-L (6-20% limestone) or CEM IIB-L (1-35% limestone). In Canada, Portland-limestone cements (PLC) with up to 15% interground limestone were included in CSA A3001 in 2008, and adopted in the CSA A23.1 concrete standard in 2009 (except for sulfate exposures until further data is collected). In CSA A3001, these cements have the same setting time and strength development performance as Portland cements, and this is typically achieved through grinding to increased Blaine finenesses (but similar 45 Pm sieve residue) in order to get similar particle size distribution of the harder clinker fraction, and by optimizing the calcium sulfate addition to the cement. As well, part of the calcium carbonate will react with clinker aluminate phases to form calcium-carboaluminates, filling in porosity, and contributing to strength. One of the initial concerns was that concrete producers would not be able to use normal levels of fly ash or slag in combination with Portland-limestone cements. However, this concern appears to be unfounded and certainly with slag, PLC mixtures can actually develop better early strengths and lower permeabilities than when used with Portland cements. The additional aluminates from slag, and likely fly ash, appear to help form more carboaluminates. Therefore, when PLC with 15% limestone is used in combination with 25% slag, the clinker factor in the cementitious component of concrete will drop to less than 60%. This contribution provides data on the impact of PLC on both the physical and durability properties of concrete made with and without slag. Introduction In order to address pending caps on point-source green house gas emissions, the cement industry in Canada needed to make significant reductions in CO2 emissions by reducing the clinker content of cements. Plants had already improved their operational efficiencies and had been intergrinding up to 5% limestone since 1983. The use of blended cements, rather than separate additions of pozzolans or slag have not become popular. Therefore, in 2006 the concept of allowing higher levels of limestone in

2010 Concrete Sustainability Conference

1

© National Ready Mixed Concrete Association

cements, similar to the European CEM IIA-L cements having up to 20% limestone, was raised at the Canadian Standards Association (CSA) meeting. A comprehensive literature review was undertaken. The report indicated European countries and others had been using limestone cements since the 1960s, they are now the most commonly used cements in the European Union, and the technical data supported the addition of up to 15% limestone was feasible (Hooton, Thomas and Nokken, 2007). Therefore, the cement companies started trial grinds and testing for fresh, hardened, and durability properties in mortars and concretes was initiated. In 2008, a ballot was taken and a new class of Portland-Limestone Cements (PLC) with up to 15% interground limestone was approved by the CSA A3000 cements committee. However, the literature was found to be conflicting with respect to use of Portland-limestone cements in sulfate exposures due to possibilities of thaumasite sulfate attack. Therefore, it was decided for the time being to not allow the use of PLC in sulfate exposures until further research had been conducted. In 2009, the CSA A23.1 concrete committee also approved the use of PLC in concrete, and in 2010, it is being included in the National Building Code of Canada. This paper presents some of the laboratory and field data being developed in cooperation with one of the cement companies. Laboratory data on sulfate resistance is described, followed by properties of concrete, and finally results from a field trial. Portland-Limestone Cements A CSA GU (ASTM Type I) Portland cement clinker with 12% C3A was commercially interground with different levels of limestone. Cements were produced having 3.5, 10 and 15% limestone and labelled GU, PLC10, and PLC 15. CSA Portland cements are allowed to have up to 5% limestone and to stay below that limit; it is typically used at up to 3.5%. With PLC (designated as GUL in CSA 3001) the practical maximum limestone levels will be 12 to 13%, so the 15% level used in these tests is above what would be used in practice. The CSA A3001 standard requires PLC to meet the same setting time and strength development limits as Portland cement. Since limestone is softer than cement clinker, in order to get equal performance, the clinker has to be of the same fineness and this resulted in a higher cement Blaine fineness, by about 100 m2/kg, than with the reference Portland cement. These cements were used for most of the laboratory tests. Compositions of the materials used in most of the tests reported here are given in Table 1. Table 1. Composition of Cement Materials Used in Lab Tests

SiO2 (%) GU 19.59 PLC10 19.33 PLC15 18.6 Slag 38.14

Al2O3 Fe2O3 ( %) 5.36 5.22 5.09 7.18

(%) 2.36 2.3 2.23 0.74


CaO

MgO

SO3

LOI

(%) (%) 62.43 2.37 61.68 2.34 60.03 2.26 39.95 10.57

(%) 4.45 4.31 4.21 2.71

(%) 1.8 3.63 5.9 -

2

Limestone Alkali equiv. (%) 3.5 10 15 -

(%) 0.96 0.95 0.93 0.63

Blaine (m2/kg) 391 442 507 -


Sulfate Resistance Tests Even though CSA does not currently allow the use of PLC in sulfate exposures, laboratory testing is being undertaken. A series of cements was commercially interground with different levels of limestone. The sulfate resistance of the cements was evaluated in accordance with ASTM C1012. Mortar bars and cubes were cast and cured until they reached a compressive strength of 2850 psi (20 MPa). Then, the bars were immersed in a 50 g/L of sodium sulfate (Na2SO4) solution and their length change was measured periodically for 1 year. The tests included 3 sets of mixes: (1) using 100% Portland-limestone cement (no slag replacement); (2) replacing 30% of the cement with slag (70% Portland-limestone cement plus 30% slag), and (3) replacing 50% of the cement with slag (50% Portland-limestone cement plus 50% slag). According to the ASTM C1157 performance standard and the Canadian CSA A3001 standard for hydraulic cements, a cement is considered to be moderately sulfate-resistant if the expansion of the bars is less than 0.10% after 6 months and highly sulfate-resistant if the expansion of the bars is less than 0.05% after 6 months or 0.10% after 1 year. Table 2 and Figures 1 and 2 show the results for the change in the length of the mortar bars made from the 3 types of cement. It is clear that, as expected, when no slag was used, none of the cements used could be considered sulfate-resistant, since all of them had clinker C3A contents of 12% and all exceeded the 0.10% limit at 180 days. The average length change of the mortars increased as the limestone content of the cement increased. However, when 30% of the cements were replaced with slag, all the 3 sets exhibited expansions less than 0.10% after 1 year of immersion. Therefore, using 30% slag was effective in controlling the expansion due to sulfate attack. The same conclusion could be drawn for the 50% slag mixes. The expansion of the mortar bars containing slag was less than 0.10% even after 18 months exposure. According to the results, the PLC samples had a slightly higher expansion than that of the GU samples. The expansion of the PLC10 and PLC15 samples were almost identical after 6 months and 1 year of exposure. Table 2. ASTM C1012 Sulfate Resistance Expansions

Length Change (%) 180 Days 365 Days 540 Days

GU 100%

PLC10 100%

PLC15 100%

GU 70% SLAG 30%

0.062

0.328

0.777

0.016

0.021

0.022

0.033

0.025

0.024

0.426

1.177

1.630

0.030

0.037

0.037

0.044

0.033

0.032

1.121

1.812

2.087

0.028

0.030

0.036

0.036

0.031

0.030


PLC10 70% SLAG 30%

PLC15 70% SLAG 30%

GU 50% SLAG 50%

PLC10 50% SLAG 50%

PLC15 50% SLAG 50%

3


Length Change vs. Time 1.8000

1.6000 GU 100%

Average length change (%)

1.4000 GU 70% + SLAG 30%

1.2000

PLC10 100%

1.0000

0.8000

PLC10 70% + SLAG 30%

0.6000

PLC15 100%

0.4000 PLC15 70%+ SLAG 30% 0.2000

0.0000 0

50

100

150

200

250

300

350

400

Time (days)

Figure 1. ASTM C1012 Expansions of Cements and 30% slag mixes to 12 months Length Change vs Time 0.1200

0.1000

Average length change (%)

GU 70% + SLAG 30% PLC10 70% + SLAG 30%

0.0800

PLC15 70% + SLAG 30% 0.0600 GU 50% + SLAG 50% PLC10 50% + SLAG 50%

0.0400

PLC15 50% + SLAG 50% 0.0200

0.0000 0

100

200

300

400

500

600

700

800

900

1000

Time (days)

Figure 2. ASTM C1012 Expansions of 30% and 50% slag mixes to 2.5 years Later, another series of 5 cements was commercially ground using a similar 12% C3A cement clinker and containing 0, 2.4, 10.6, 12.7, and 21.8% limestone. These cements were also tested using ASTM C1012 at 0, 30, and 50% slag replacements. In addition, since one of the concerns with PLC in sulfate exposures is an increased potential for thaumasite sulfate attack, it was decided to store duplicate sets of C1012 mortar bars in 2010 Concrete Sustainability Conference

4


sulfate solution at 40oF (5oC). Thaumasite has a composition of 3CaO.Al2O3.3CaSO4.32H2O and preferentially forms at cooler temperatures in the presence of wet sulfate and carbonate-bearing environments. Thaumasite was first identified as occurring in deteriorating concrete by Erlin and Stark (1966), then much later by Bickley et al. (1995), and was extensively investigated by Matthews (1994), the Thaumasite Expert Group (1999) in the UK, and Crammond (2000, 2002). Thaumasite sulfate attack is not very common relative to conventional ettringite-type sulfate attack. The expansions to date are summarized in Table 3. Regardless of the limestone content, the 73oF (23oC) expansions were controlled by both 30 and 50% slag to less than 0.10% after 18 months (meeting ACI 318-08 requirements for the S3 Very Severe exposure class). For C1012 mortar bars in sulfate solution at 40oF (5oC), all of the Portland and PLC mixes failed and thaumasite was detected by XRD in the PLC mortars. While the tests are still in progress, 30% slag replacement appears to be insufficient to control expansion at 40oF (5oC), but 50% slag mixtures are performing well after 9 months. No evidence of thaumasite has been found in any of the slag mixes. Therefore, slag (and likely pozzolans, based on personal communications with other researchers) appear to be able to prevent the formation of thaumasite at cool temperatures. Table 3. Further ASTM C1012 Expansions Stored at 73oF and 40oF Average Expansion (%) Temperature o F (oC)

73 (23)

40 (5)

Time of Exposure (Days)

Plain Portland

Type GU

GUL 11

GUL13

GUL22

% Limestone

0.0

2.4

10.6

12.7

21.8

0

6 months 12 months 18 months

0.188 1.690 X

0.267 1.554 X

0.271 1.854 X

0.485 2.978 X

0.562 1.479 X

30


0.040 0.053 0.064

0.036 0.044 0.054

0.031 0.038 0.050

0.029 0.038 0.048

0.030 0.039 0.049

50


0.025 0.032 0.040

0.023 0.028 0.036

0.016 0.021 0.030

0.018 0.022 0.031

0.018 0.022 0.031

0

6 months 12 months

0.067 1.420

0.097 X

1.260 X

X X

X X

30

6 months 330 Days

0.028 0.041

0.031 0.042

0.031 0.043

0.032 0.058

0.036 0.142

50

6 months 272 Days

0.016 0.024

0.014 0.022

0.010 0.016

0.011 0.018

0.016 0.022

% Slag

Note: X indicates that bars had failed.


5


Alkali-Silica Reactivity Tests The ASTM C1567 accelerated mortar bar test and the ASTM C1293 concrete prism test were used to assess the effect of using Portland-limestone cements with and without partial replacements with slag to mitigate alkali-silica reactivity of aggregates. Three sets of mixes were evaluated: (1) using 100% of the various Portland-limestone cements (no slag replacement); (2) replacing 30% of the cement with slag (70% Portland-limestone cement plus 30% slag); and (3) replacing 50% of the cement with slag (50% Portland-limestone cement plus 50% slag). The reactive aggregate used in this study was from the Spratt quarry, a siliceous limestone from near Ottawa, Ontario which has been well documented. In the accelerated mortar bar test, the aggregate was crushed to sand size to meet the specified particle size distribution. Then, mortar bars 1 x 1 x 12 inch (25 x 25 x 285 mm) were cast with the desired combination of cement and supplementary cementitious materials. After the mortar bars have set, the forms were stripped and the bars are immersed in water and heated up in an 80°C oven for 1 day. Next, they were immersed in sodium hydroxide solution and stored at 80°C. The change in length of the bars was monitored periodically for 28 days in NaOH solution. According to the standard, expansions greater than 0.10% at 14 days are considered to be indicative of potentially deleterious expansion of the aggregate. Alternatively, where supplementary cementitious materials are used with a known alkali reactive aggregate, expansions less than 0.10% at 14 days indicate that the supplementary cementitious material was effective in controlling the deleterious effect of the aggregate. Table 4 and Figure 4 show the results for the change in the length of the mortar bars. According to the results, when no slag was used, none of the cements, as expected, could pass the test as the average length change of all sets of samples exceeded the 0.10% limit at 14 days. Replacing 30% of the cements with slag was also not effective in terms of controlling the effect of alkali-silica reactivity. However, when 50% of the cements were replaced with slag, all the 3 types of cements were able to pass the test as the average length change of all the sets was less than 0.10% at 14 days. As the results show, the PLC10 and PLC15 cements exhibited less expansion than the GU cement, both at 14 and 28 days. Table 4. ASTM C1567 ASR Mortar Bar Expansions

Length Change (%)

GU 100%

PLC10 100%

14 Days 28 Days

0.445 0.685

0.801 1.155

PLC15 100%

GU 70% SLAG 30%

PLC10 70% SLAG 30%

PLC15 70% SLAG 30%

GU 50% SLAG 50%

PLC10 50% SLAG 50%

PLC15 50% SLAG 50%

0.594 0.784

0.205 0.377

0.214 0.41

0.318 0.63

0.06 0.218

0.041 0.163

0.047 0.187


6


Length change vs Time 1.4000

1.2000 GU 100%

Length change ( % )

1.0000

GU 70% + SLAG 30% PLC10 100%

0.8000

PLC10 70% + SLAG 30% PLC15 100%

0.6000

PLC15 70% + SLAG 30% GU 50% + SLAG 50% PLC10 50% + SLAG 50% PLC15 50% + SLAG 50%

0.4000

0.2000

0.0000 0

5

10

15

20

25

30

Time ( days )

Figure 4. ASTM C1567 ASR Expansions As for the ASTM C1293 concrete prism tests (Table 5 and Figure 5), all the mixes without slag exceeded the 0.04% expansion limit at the early ages of the test. This was not unexpected since the cement had a high-alkali content of ~ 0.91% and in this test, alkalis are added to boost to 1.25% by mass of cement. However, when 30% of the cements were replaced with slag, the GU and PLC10 samples exceeded the 0.04% limit after 2 years while the PLC15 samples expanded less than the limit at that age. Nevertheless, the mixes with 50% slag all had expansions less than the 0.04% limit even after 2 years. The expansions were in increasing order with the limestone content. Table 5. ASTM C1293 Concrete Prism Expansions GU

PLC10 70% SLAG 30%

PLC15 70% SLAG 30%

GU 50% SLAG 50%

PLC10 50% SLAG 50%

PLC15 50% SLAG 50%

0.036 0.055

0.027 0.041

0.023 0.036

0.016 0.013

0.014 0.018

0.016 0.021

Length 70% Change GU PLC10 PLC15 SLAG (%) 100% 100% 100% 30% 1 year 2 years

0.182 0.201

0.218 0.228

0.241 0.248


7


Length Change vs. Time 0.3000 GU 100% 0.2500

GU 70% + SLAG 30% PLC10 100%

Average Expansion ( % )

0.2000

PLC10 70% + SLAG 30%

0.1500

PLC15 100% 0.1000

PLC15 70% + SLAG 30% GU 50% + SLAG 50%

0.0500

PLC10 50% + SLAG 50%

0.0000 0

100

200

300

400

500

600

700

800

PLC15 50% + SLAG 50%

-0.0500

Time (days)

Figure 5. ASTM C1293 ASR Concrete Prism Expansions Laboratory Concrete Tests A series of concretes were cast at w/cm = 0.40 and total cementitiouis materials content of 360 kg/m3, water-reduced, air-entrained, and using ¾ inch (20 mm) crushed limestone and natural sand. These mixes were designed to meet CSA A23.1 Exposure Class C-1 for exposure to de-icer salts and freezing and thawing cycles. Requirements are 35 MPa at 28 days, max. w/cm = 0.40, 5 to 8% air, and meeting a 1500 coulomb limit at 56 days. Results are as follows: Compressive Strength: The results for compressive strength of concrete cylinders made from the 3 types of cement at a water to cement ratio of 0.40, are presented in Table 6. Based on the results, when no slag was used, the compressive strength of PLC10 and PLC15 samples were slightly higher than that of GU at all ages, except at 91 days. When 30% of cement was replaced with slag, the samples made with PLC10 and PLC15 had significantly higher compressive strength at all ages. In almost all instances, the compressive strength of samples made with PLC10 and PLC15 were similar. The increased strength of PLC with 30% slag replacement is attributed to the beneficial role of carboaluminate hydrates formed due to additional aluminates contributed by the slag.


8


Table 6. Compressive Strengths of Concrete Cylinders Compressive Strength (MPa)

7 Days

28 Days

56 Days

91 Days

GU 100%

39.3

47.3

50.2

58.5

PLC10 100%

42.6

50.7

56.8

60.2

PLC15 100% GU 70% SLAG 30% PLC10 70% SLAG 30% PLC15 70% SLAG 30%

40.4

49.4

55.9

56.1

19.4

30.0

33.0

33.6

30.0

42.6

46.2

53.4

31.4

43.0

46.8

54.0

De-Icer Salt Scaling: The salt scaling resistance of the concrete samples made with the 3 types of cements was investigated based on the Ontario Ministry of Transport (MTO) provincial standard OPS LS-412. This test is similar to ASTM C672 except that 3% NaCl solutions are used and the mass loss due to scaling is also measured in addition to visual damage ratings. The samples used were 12 x 12 x 3 inch (300 mm × 300 mm × 75 mm) concrete specimens. At 24 h after casting, the specimens were demoulded and placed into moist storage conditions of 73°F (23°C) and 100% RH for 13 days. Then, the specimens were air cured for 14 days at 73°F (23°C) and 50% RH. When the samples were 28 days old, their surface was covered with a 3% NaCl solution and the samples were then subjected to freeze-thaw cycling. The specimens were placed in a freezer for 16 to 18 h and then manually removed to a thawing environment for 6 to 8 h. This procedure was repeated for 28 days and the dry mass of the flaked off concrete is measured every five cycles at which time the salt solution was washed off and replaced. Compliance with the test requirement of MTO is based upon a cumulative surface mass loss of not more than 2.64 lb/yd2 (0.8 kg/m2) after 50 cycles of freezing and thawing. Figure 5 shows the results for de-icer salt scaling test of concrete samples made with the 3 types of cement and with 0 and 30% slag replacement. The results indicated that all the mixes passed the MTO 0.8 kg/m2 limit except for the one made with PLC15 and 30% slag even though PLC15 without slag showed the lowest mass loss.


9


Scaling Test 1.00 GU 100%

0.90

Cumulative Mass/ Area (kg/m2)

0.80 GU 70% + SLAG 30%

0.70 PLC10 100%

0.60 0.50

PLC10 70% + SLAG 30%

0.40 0.30

PLC15 100%

0.20 PLC15 70% + SLAG 30%

0.10 0.00 0

5

10

15

20

25

30

35

40

45

50

Number of cycles

Figure 5. De-icer Salt Scaling Mass Loss Drying Shrinkage: Table 7 and Figure 6 show the drying shrinkage of concrete prisms according to ASTM C157, using 7 days wet curing prior to drying at 50% RH. Shrinkage was either not affected or reduced slightly with increasing limestone contents. The replacement of cement with 30% slag reduced drying shrinkage by about 0.1% in all mixes. Table 7. ASTM C157 Drying Shrinkage

Length Change (%)

GU 100%

PLC10 100%

28 days 1 year 2 years

0.036 0.069 0.067

0.037 0.061 0.068


PLC15 100%

GU 70% SLAG 30%

PLC10 70% SLAG 30%

PLC15 70% SLAG 30%

0.037 0.062 0.065

0.026 0.058 0.062

0.027 0.052 0.060

0.025 0.053 0.067

10


ASTM C 157 Shrinkage 0.01

0 0

100

200

300

400

500

600

700

800

GU 100%

Average Length Change (%)

-0.01 PLC10 100% -0.02 PLC15 100%

-0.03

-0.04

GU 70% + SLAG 30%

-0.05

PLC10 70% + SLAG 30%

-0.06 PLC15 70% + SLAG 30% -0.07

-0.08

Age (Days)

Figure 6. Drying Shrinkage to 2 Years RCPT: ASTM C1202 coulomb ratings were obtained on 2 inch (50 mm) thick slices from the top (after discarding the top inch) and middle of 4 x 8 inch (100 x 200 mm) concrete cylinders after 28 and 85 days of moist curing. Results, shown in Table 8, indicate that the PLC10 had no effect on coulomb values at either age both with and without 30% slag replacement. As expected, slag had a strong beneficial effect in reducing coulomb ratings. Table 8. ASTM C1202 Resistance to Chloride Penetration

RCPT (Coulombs)

56 Days

85 Days

Top Middle Average Top Middle Average

GU 100%

PLC10 100%

PLC15 100%

GU 70% SLAG 30%

3220 3050 3135 2500 2230 2365

3220 2910 3065 2510 2510 2510

3130 3130 3130 2850 2750 2800

1050 1090 1070 900 920 910

PLC10 70% SLAG 30%

PLC15 70% SLAG 30%

980 1140 1060 970 970 970

1270 1340 1305 900 990 945

Chloride Penetration: ASTM C1556 chloride bulk diffusion measurements were made on concretes moist cured for 28 days. Results for fitted surface chloride concentrations (Cs) and apparent diffusion values (Da) are given in Table 9. Again the


11


PLC had no negative effect in fact the value for the PLC15 concrete was much lower. As well, 30% slag had a strong beneficial influence on reducing chloride diffusion rates of all cements and PLC had no negative impact. Table 9. ASTM C1556 Chloride Bulk Diffusion Test Results

Cs (% mass) Da (m2/s * 1012)

GU 100%

PLC10 100%

PLC15 100%

GU 70% SLAG 30%

PLC10 70% SLAG 30%

PLC15 70% SLAG 30%

0.73

0.84

0.8

1.1

1.07

0.98

15.9

15.6

8.25

8.07

6.11

8.25

Field Trial on Highway Barrier Walls To help build a database and to increase construction experience, a number of the cement and concreter companies have initiated field trials with PLC. Another one was recently described in Thomas et al, 2010. In November 2009, in cooperation with the Ontario Ministry of Transportation (MTO) and the University of Toronto, Holcim (Canada) and Dufferin Construction performed field trials as a modification to an existing MTO contract. A 33 foot (10 m) long concrete barrier wall test section at a formed light standard transition section was constructed on a major expressway west of Toronto in Burlington, Ontario, using Portland-limestone cement. This was the first PLC trial on a public road in Canada and will be monitored over a period of 3 years. This section was placed adjacent to an identical control section constructed using the normal Portland GU cement. Both the PLC (10% limestone) and the Type GU cement control mix also contained 25% slag. Each pour was 30 cy (23 m3) and required 3 truck loads of concrete. Concrete was required to attain 4350 psi (30 MPa) at 28 days, have a slump from 2.5 to 4 inches (60100 mm) and be air entrained. Slump and air contents were measured on site (all pours were completed within 90 minutes) and test samples were cast after the placement when the trucks moved to a nearby test laboratory (at approximately 2 hours). Forms were covered in plastic and insulated blankets for 7 days as required by the MTO, then were covered with a white pigmented membrane forming curing compound after form removal. The properties of concrete for the two sections were evaluated based on cast samples and on cores removed prior to 28 days. Fresh concrete properties are shown in Table 10 and hardened properties in Tables 11 and 12. Temperatures in the barrier walls were monitored for the first 7 days and differences between the two concretes were minimal. Ambient temperatures ranged from 40 to 60oF (5 to 15oC) during the first 7 days.


12


Table 10. Fresh Concrete Properties from Field Trials Site Measurements (at ~30 minutes) Temp. Slump °C mm 18 75 15 100 13 95

Concrete

GU plus Slag

PLC10 plus Slag

13 17 16

Air % 7.2 8.2 6.4

70 100 100

7 7.8 6.6

At Laboratory (at ~2 hours) Temp. Slump °C mm

Air %

17 -

95 -

7.8 -

17

100

6.4

60

Temperature (C)

50 40 (GU - Surface) (GU - Center) (GUL - Surface) (GUL - Center) Air Temperature

30 20 10

97 10 6. 5 12 2 13 0 14 5

85

50 .5 74 .5

51

24 .5 25 .5

12

0

Ti m e

in

H ou rs

0

Time (hours)

Figure 7. Temperature profiles in Barrier wall Trials The 1-day strength of the PLC mix was slightly higher than the control mix but then strengths at later ages were very similar. ASTM C666 freeze-thaw durability factors were identical as were the de-icer salt scaling results. Drying shrinkages at 28-days were identical when calculated from the onset of drying, and would meet the Canadian Standards Association requirement for low shrinkage (