Survey of Mineral Admixtures and Blended Cements in Ready Mixed Concrete

Transcription

1 Survey of Mineral Admixtures and Blended Cements in Ready Mixed Concrete A survey of concrete producers to quantify the use of cement, admixtures and blended cements in ready mixed concrete. October 2000 The information contained herein is based on sources which we believe reliable but are not guaranteed by us. The Portland Cement Association assumes no legal responsibility for the outcomes of decisions or commitments made on the basis of this information. Copyright 2000 by the Portland Cement Association. All rights reserved.

2 Survey of Mineral Admixtures and Blended Cements in Ready Mixed Concrete The Portland Cement Association s (PCA s) Market Research Department analyzed the results of a questionnaire designed and administered by the National Ready Mixed Concrete Association (NRMCA). This survey was conducted to quantify the use of cement, admixtures and blended cements in ready-mixed concrete. The aggregate results will be shared with PCA and NRMCA members as well as with the Environmental Protection Agency (EPA) and other government agencies. The 1998 survey was the second follow-up to a benchmark survey conducted in 1983 and an initial follow-up conducted in Comparisons among these three surveys are presented in this analysis. Methodology Questionnaires were mailed to all 1,400 members of the NRMCA. A sample questionnaire is located in Appendix A. In exchange for returning a completed questionnaire, respondents were offered a complimentary copy of the videotape, Stockpile Recovery to Minimize Segregation. s were instructed to fill out a separate form for company production in each NRMCA region. The NRMCA regions are defined in Appendix B. In total, 125 surveys were returned, achieving a 9% response rate. This sample size allows for statistical analysis at the 95% confidence level with a margin of error of plus or minus 9%. Caution is advised when reviewing the results of subcategories of data since smaller bases yield higher margins of error. While the company production and regional break-outs contain important information, these results may be less reliable due to lower response rates. Executive Summary This summary highlights key information obtained from the survey; however, the 1998 aggregate results are located in data tables in Appendix C. The first section of this summary contains data reported by respondents for all types of concrete. The following five sections contain data for specific types of concrete mixes, including fly ash concrete, ground slag concrete, concrete with other pozzolans, portland cement only concrete, and blended cement concrete. Total Concrete Total concrete production was 38.7 million cubic yards in This represented approximately 11% of a 340 million cubic yard market. In 1989, respondent production was 35.7 million cubic yards, representing 15% of an estimated 240 million cubic yard market. Ninety-five percent of the production represented in this survey was manufactured by companies with an annual production over 100,000 cubic yards. This was a slight increase from the 1989 figure of 93%. In 1983, companies of this size accounted for only 74% of the total production. PCA Market Research September Survey of Admixtures and Blended Cements Page 1

3 An average of 311,800 cubic yards of concrete were produced per respondent in For total concrete, on average 460 pounds of cement were used per cubic yard of concrete. Following a 9% decline in the amount of cement in concrete used between 1983 (499 pounds) and 1989 (453 pounds), there was only a slight increase in the amount of cement used between 1989 (499 pounds) and 1998 (460 pounds). Ten percent of the concrete produced by respondents was used in highway infrastructure (i.e. bridges, pavements). In 1998, an average of 11,234 employees worked at 738 plants resulting in an average of 15 employees per plant. Companies produced an average of 3,441 cubic yards of concrete per employee in This was up from 3,237 cubic yards per employee in The majority of concrete reported by 1998 respondents was produced by companies who used fly ash in their mixes (53.6%), and more than one-third of the concrete was produced by companies that produce portland cement only concrete (36.9%). The remaining 10% of concrete was produced by companies that used ground slag (8.9%), blended cement (0.3%) and other pozzolans (0.4%) in their concrete mixes. Fly Ash Concrete Companies who used fly ash in their mixes accounted for 94% of the total concrete production in While this was not significantly different from the 92% recorded in 1989, it was three times the 1983 figure of 31%. In both 1998 and 1989, approximately 54% of all concrete contained fly ash. This was up from 46% percent in An average of 209,100 cubic yards of fly ash concrete were produced per respondent in In 1998, fly ash concrete contained a calculated average of 119 pounds of fly ash and 442 pounds of cement per cubic yard. This level of fly ash concrete was up from both the 1989 and 1983 calculations of approximately 107 pounds. The amount of cement per cubic yard in 1998 wasjust slightly more than the amount reported in 1989 (436 pounds), but significantly less than the 1983 average of 497 pounds of cement per cubic yard. The amount of cementitious materials actually used by respondents differed from the amount typically used by respondents. For example, when 1998 survey participants were asked how many pounds of cement and fly ash were in a typical cubic yard of fly ash concrete, respondents reported that a typical mixture consisted of 101 pounds of fly ash and 432 pounds of cement. Yet, when participants were asked to provide the quantity of each ingredient in fly ash concrete, the quantities of fly ash and cement found in fly ash concrete averaged 18 pounds per cubic yard more of the fly ash (resulting in a total of 119 pounds per cubic yard) and 10 pounds per cubic yard more of the cement (resulting in a total of 442 pounds per cubic yard). These differences were even more evident when examining the regional and company size sub-categories of data. The average amount of fly ash per cubic yard of concrete was estimated at 65 pounds. Although this figure remained relatively constant between 1983 and 1989, at approximately 40 pounds per cubic yard, this figure jumped 25 pounds between 1989 and When asked which type of ASTM C 618 fly ash they use, 51% of the respondents reported using Class C and 49% reported using Class F. s used an average of 466 tons of fly ash in flowable fill and produced an average of 3,091 cubic yards of flowable fill. PCA Market Research September Survey of Admixtures and Blended Cements Page 2

4 Ground Slag Concrete In 1998, respondents reported producing a total of 3,423,000 cubic yards of ground slag concrete, averaging 131,700 cubic yards per respondent. In the case of ground slag concrete, like fly ash concrete, the quantities of cementitious materials actually used differed from the amounts typically used. When respondents were asked how much cement and ground slag were in a typical cubic yard of ground slag concrete, the quantities varied significantly from the values calculated by their responses. For example, in 1998, ground slag concrete contained a calculated average of 236 pounds of ground slag and 324 pounds of cement per cubic yard. Yet, respondents reported that a typical ground slag mixture contained 179 pounds of ground slag and 364 pounds of cement. Concrete With Other Pozzolans s reported producing a total of 140,800 cubic yards of concrete made with other pozzolans, averaging 17,600 cubic yards per respondent. Once again, respondents reported differences in quantities of cement and pozzolans used versus the quantities found in a typical cubic yard of concrete. When calculated from respondent values, an average of 76 pounds per cubic yard of other pozzolans and 416 pounds of cement are used to manufacture concrete. However, the respondents then reported that a typical cubic yard of concrete with other pozzolans contains 60 pounds per cubic yard of other pozzolans and 579 pounds per cubic yard of cement. Note that the response rates for concrete with other pozzolans were low. Portland Cement Only Concrete s in 1998 reported producing 14,269,900 cubic yards of portland cement only concrete. Portland cement only users indicated that an average cubic yard of concrete contained 531 pounds of cement per cubic yard. Blended Cement Concrete s reported producing a total of 123,300 cubic yards of blended cement, averaging 20,500 cubic yards per respondent in Blended cement concrete contained a calculated average of 459 pounds of blended cement per cubic yard of concrete according to the five respondents who responded to this question on the survey. PCA Market Research September Survey of Admixtures and Blended Cements Page 3

5 Appendix A: Questionnaire

6 NRMCA Survey October 1999 Use of Mineral Admixtures and Blended Cements in Ready Mixed Concrete This survey seeks to quantify the use of mineral admixtures like fly ash, ground slag, or other separately batched cementitious material in ready mixed concrete. We also request your input to estimate the amount of blended cement used and flowable fill production. This survey is intended to provide data to EPA and other governmental agencies regarding the use of these by-product materials. A frequently quoted statistic is that blended cement used by the concrete industry is only 1.5% of the total cement shipped and the information on mineral admixture usage is not readily available. Individual company information on production will be kept confidential. Previous surveys were conducted in 1983 and Fill out separate form for company production in each NRMCA region (see map at back) INFORMATION REGARDING TOTAL USAGE IN 1998 IS REQUESTED. COMPLETE ALL THAT APPLY. Fly Ash Ground Slag Other Pozzolans, -? Tons of Mineral Admixtures used tons 1 tons 2 tons 3 Tons of Cement Portland Cement, Types I, II, III, V Blended Cement, Type IP, IS Used tons 4 tons 5 Cubic Yards of Fly Ash Ground Slag Other Pozzolans Concrete with cy. 6 cy. 7 cy. 8 Cubic Yards of Portland Cement only Blended Cement only Concrete with cy. 9 cy. 10 Total Cubic Yards Concrete Produced cy. 11 Cubic Yards in Highway Infrastructure (bridges, pavements) cy 12 Please indicate the average amount of cementitious materials used in a typical cubic yard of concrete Type of concrete mixture Portland cement, lb./cu. yd. Mineral admixture, lb./cu. yd. 13 Containing only portland cement Containing fly ash Containing ground slag Containing other pozzolans Which Class (ASTM C 618) of Fly Ash do you use Flowable Fill (CLSM)! Class C 21 %Class C Flowable fill produced, cubic yards! Class F 20 If Both % Class F 22 Fly ash used in flowable fill, tons Company/Division Address City, State, Zip This information is to test the adequacy of the sample. Number of employees in ready mixed operations 25 Number of plants represented by production Please Circle the NRMCA Region of production (refer to map on the back). Eastern Southeastern Great Lakes Midwest N. Central 27 S. Central Rocky Mountain Pacific NW Pacific SW Free video offer (see back). Send the video Contact Phone! Yes! No Additional tapes (at $5 each + S&H) Respond by November 15, Thank you for your participation ATTN. COLIN LOBO PLEASE FAX BACK TO: NRMCA (301) Or mail to: NRMCA, 900 Spring Street, Silver Spring, MD

7 Appendix B: NRMCA Census Region Definitions

8 NRMCA Census Region Definitions Pacific Northwest Idaho Montana Oregon Washington Pacific Southwest Arizona California Nevada North Central Iowa Minnesota Nebraska North Dakota South Dakota Rocky Mountain Colorado New Mexico Utah Wyoming Great Lakes Midwest Illinois Indiana Michigan Ohio Wisconsin South Central Arkansas Kansas Louisiana Missouri Oklahoma Texas Eastern Connecticut Delaware Maine Maryland Massachusetts New Hampshire Rhode Island Vermont New Jersey New York Pennsylvania Virginia West Virginia Southeastern Alabama Florida Georgia Kentucky Mississippi North Carolina South Carolina Tennessee

9 Appendix C: The Data Tables

10 1998 Distribution of Concrete Production by Company Size Production (000 yd 3 ) , , , , , > , , , Total , , , Production Mix (%) % 54.4% 0.0% 0.0% 36.2% 9.4% % 42.3% 0.0% 0.0% 57.6% 0.1% % 42.1% 6.2% 0.2% 50.8% 0.7% % 40.5% 5.6% 5.5% 48.3% 0.0% % 48.4% 10.8% 0.0% 38.8% 2.0% % 50.7% 8.9% 0.7% 39.7% 0.0% > % 58.2% 8.7% 0.0% 33.1% 0.0% Total 100.0% 53.6% 8.9% 0.4% 36.9% 0.3% % of Total Production % 0.1% 0.0% 0.0% 0.1% 2.3% % 0.7% 0.0% 0.0% 1.4% 0.4% % 1.4% 1.2% 0.8% 2.4% 4.1% % 1.9% 1.6% 38.8% 3.3% 0.0% % 13.5% 18.1% 0.7% 15.6% 92.5% % 29.0% 30.7% 58.7% 32.9% 0.8% > % 53.4% 48.3% 1.1% 44.2% 0.0% Total 100.0% 100.0% 100.0% 100.0% 100.0% 100.0%

11 1998 Average Production by Company Size Number of s > Total Mix (%) % 60.0% 40.0% 20.0% % 61.1% 88.9% 5.6% % 72.2% 5.6% 16.7% 88.9% 5.6% % 64.3% 14.3% 7.1% 100.0% % 88.9% 30.6% 2.8% 97.2% 5.6% % 92.3% 30.8% 7.7% 96.2% 3.8% > % 100.0% 57.1% 14.3% 100.0% Total 100.0% 79.8% 21.0% 6.5% 92.7% 4.8% Average Production Levels (000 yds 3 ) > 750 2, , Total

12 Calculated (lbs/yd 3 ) Calculated (lbs/yd 3 ) Reported (lbs/yd 3 ) Percent of Average Cement Use Average Fly Ash Use Typical Cementitious Material % of Total Total Concrete Production Total Portland Fly Ash Total Fly Ash Portland Fly Ash Concrete Used in Highway (000 yd 3 ) Concrete Cement Only Concrete Concrete Concrete Cement Only Cement Fly Ash with Fly Ash Infrastructure % 0.0% % 7.3% % 1.7% % 2.9% % 8.8% % 6.8% > % 13.2% Total % 10.1% # of Responses Min N/A N/A Max N/A N/A Std. Deviation % 20.9% 95% C. I. (±) % 6.0% Calculated (lbs/yd 3 ) Calculated (lbs/yd 3 ) Reported (lbs/yd 3 ) Percent of Average Cement Use Average Fly Ash Use Typical Cementitious Material % of Total Total Concrete NRMCA Total Portland Fly Ash Total Fly Ash Portland Fly Ash Concrete Used in Highway Regions Concrete Cement Only Concrete Concrete Concrete Cement Only Cement Fly Ash w/fly Ash Infrastructure Eastern % 5.6% South Central % 20.2% Southeastern % 5.0% Great Lakes Midwest % 18.8% Pacific Northwest % 3.6% North Central % 2.4% Rocky Mountian* Pacific Southwest* Total % 10.1% # of Responses Min N/A N/A Max N/A N/A Std. Deviation % 20.9% 95% C. I. (±) % 6.0% * = Too few responses to report 1998 Cement and Fly Ash Usage/Yd 3 by Company Size 1998 Cement and Fly Ash Usage/Yd 3 by Region

13 1998 Admixtures and Blended Cements/Yd 3 by Size of Company Calculated (lbs/yd 3 ) Average (Avg.) Cement Use Production Portland Cement Fly Ash Ground Slag Other Pozzolan (000 yd 3 ) Only Concrete Concrete Concrete* Concrete* Total # of Responses Min Max Std. Deviation % C. I. () Calculated (lbs/yd 3 ) Avg. Gound Slag Use Avg. Other Pozzolan Use Avg. Blended Cement Use Production Total Ground Slag Total Other Pozzolan Total Blended Cement (000 yd 3 ) Concrete Concrete Concrete* Concrete* Concrete* Concrete* Total # of Responses Min Max Std. Deviation % C. I. () Reported (lbs/yd 3 ) Typical Cementitious Material Production Ground Slag Other Pozzolans (000 yd 3 ) Cement Ground Slag Cement* Pozzolans* Total # of Responses Min Max Std. Deviation % C. I. () * Note low response rates

14 1998 Distribution of Employment Data by Company Size Total Number of Employees ,814 1, , ,091 2, , > 750 5,430 5,430 4, ,430 0 Total 11,234 10,493 5, , Total Number of Plants > Total Average Number of Employees per Plant > Total

15 1998 Employee Based Productivity of Ready-Mixed Plants Production (000 yds 3 ) , , , , , , , > , , , , Total 38, , , , Production per Employee (yds 3 /Employee) , , , , , , , , , , , , , , , , , , , , , , > 750 3, , , Total 3, , ,

16 1998 Fly Ash Class (ASTM C 618) Company Average Use of: Average Fly Ash Use Average Amount of Production Class C Class F in Flowable Fill Flowable Fill produced (000 yd 3 ) Fly Ash (%) Fly Ash (%) Tons Cubic Yards % 100% % 27% % 46% % 56% % 46% % 52% > % 74% Total 51% 49%