The practice and effects of hot weather concreting

Item Type text; Thesis-Reproduction (electronic)

Authors Creager, William Bronson, 1948-

Publisher The University of Arizona.

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THE PRACTICE AND.EFFECTS OF HOT WEATHER CONCRETING

byWilliam Bronson Creager

A Thesis Submitted to the Faculty of theDEPARTMENT OF CIVIL ENGINEERING AND ENGINEERING MECHANICS

In Partial Fulfillment of the Requirements For the Degree ofMASTER OF SCIENCE.

WITH A MAJOR IN CIVIL ENGINEERINGIn the Graduate College

THE UNIVERSITY OF ARIZONA

1 9 7 2

STATEMENT BY AUTHOR

This thesis has been submitted in partial fulfill­ment of requirements for an advanced degree at The University of Arizona and is deposited in the University Library to be made available to borrowers under rules of the Library.

Brief quotations from this thesis are allowable without special permission, provided that accurate acknowl­edgment of source is made. Request for permission for extended quotation from or reproduction of this manuscript in whole or in part may be granted by the head of the major department or the Dean of the Graduate College when in his judgement the proposed use of material is in the interest of scholarship. In all other instances» however» permission must be obtained from the author.

SIGNED: id lL L L a rrh 5 . /CnM bqOl,

APPROVAL BY THESIS DIRECTOR This thesis has been approved on the date shown below:

— i j l — — I,.-- ■ jj~ Q try\. -— 1 ( i ./, £ Zfrr James D. Krregh 7/ DacePrVfessor of Civil Engineering

To my parents, for their continuing encouragement

throughout my college years, and

to my fiancee, Linda, for her patience and help

in writing and typing this manuscript.

ill

ACKNOWLEDGMENTS

The author wishes to express his graditude to Professor James D. Kriegh and Mr. Wilfred T. Hamlyn for their helpful guidance and suggestions during the course of this study. .

Appreciation is also extended to Mr. John Stoss, Tucson’s Portland Cement Association representative, for his help in coordinating the field work with local concrete producers and test laboratories.

Thanks is also given to the personnel of Engineering Testing Laboratories, especially Mr, Gene Pitts and Mr. Dal Wakefield, for their cheerful cooperation and assistance during the field work.

Finally, thanks is given to the owners of. the con­crete producing companies in the Tucson area for allowing this study to be carried out.

iv

TABLE OF CONTENTS

. PageLIST OF ILLUSTRATIONS . . . . . . . . . . . . . . . viABSTRACT . . . . . „■ . . . . . . . . . . . .. .. vii

1. INTRODUCTION— BASIC HOT WEATHER CONCRETINGPROBTAM8 .. . .. . . . . @ . . . * . . .. . * . I

2. RECOMMENDED PROCEDURES TO:FOLLOW DURING HOTWEAIHER O O O . O . O O O . O . . 0 0 . 0 0 . 0 . 0 ^

3. PURPOSE OF THESIS . . . . . . . . . . . . . . . . . ?4. FIELD AND LAB DATA COLLECTING. PROCEDURES y

3. RESULTS . . . . . . . . . . . . . . . . o . o . o 18Discussion of Field Work . . . . . . . . . . . 18Discussion of Laboratory Work . . . . . . . . . 2 8

6. CONCLUSIONS AND RECOMMENDATIONS . . . . . . . . . . 42Conclusions . . . . . . . . . . . . . . . . . . 42Recommendations . . . . . . . . . . . . . . . . 43

APPENDIX: DATA SHEETS . . . . . . . . . . . . . . . . 45REFERENCES . . .. . . . . . . . . . ... . . . . . 6l

v

LIST OP ILLUSTRATIONS

Figure Page1. Compressive Strength--6/29/71 292. Compressive Strength--7/9/71 . . . . . . . . o „ 303. Compressive Strength— 7/12/71 . . . . . . . . . . 304. Compressive Strength— 7/13/71 . . . . . . . . . . 315. Compressive Strength— 7/l^/71 . . . . . . . . . . 316. Compressive Strength— *7/15/71» A.M. . . . . . . . 327. Compressive Strength— 7/15/71 « P.M. . . . . . . . 328. Compressive Strength— 7/16/71 » A.M. . . . . . . . 339. Compressive Strength— 7/16/71 . P.M. . . . . . . . 33

10. Compressive Strength— 7/19/71 . . . . . . . . . . 3^11. Compressive Strength— 7/20/71 i A.M. . . . . . . . 3^12. Compressive Strength— *7/20/71, P.M. . . . . . . . 3513. Compressive Strength— 7/22/71 . . . . . . . . . . 3514. Compressive Strength— 7/23/71 «■ A.M. . . . . . . , 3615. Compressive Strength— 7/23/71 • P.M. . . . . . . . 3616. Concrete Temperature--Site versus Plant . . . . . 3917. Temperature of Concrete as Affected by

Temperature of Materials . . . . . . . . . . 3918. Water Temperature versus Concrete Temperature . . 4019. Aggregate Temperature versus Concrete

Temperature . . . . . . . . . . . . . . . . . 40vi

ABSTRACT

This study evaluated the hot weather concreting practices in the Tucson vicinity during the hot summer months. It consisted of two parts; field investigations and laboratory tests. Field investigations were carried out at batching plants and pour-sites. Laboratory compressive strength tests were run on field cured and laboratory cured concrete cylinders poured on the job-sites. The actual field observations were compared with the American Concrete Institute's recommended hot weather practices and an evaluation of current practices was presented. Laboratory test results were used to show relationships between the actual and the recommended practices.

The results of this study showed that high quality concrete was being produced consistently, even though many of the American Concrete Institute's recommended practices were not followed.

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CHAPTER 1

INTRODUCTION— BASIC HOT WEATHER CONCRETING PROBLEMS

Much.of Tucson’s concrete construction is done under Arizona’s hot summer sun. Moisture and temperature condi­tions are frequently unfavorable to produce good quality Concrete sr especially in the early summer months of June and July. Spring and fall provide more ideal conditions for the batching, placing and curing of concrete, at least as far as temperature and moisture effects are concerned. In these two seasons freshly placed concrete becomes neither too hot nor too cold.

Thus, hot weather» a phrase which encompasses any. i

combination of high temperatures, low humidity and winds„ presents special problems in the manufacturing, placementand curing of concrete. It should be noted that the effects

. ' 'of hot weather are most critical during periods of rising temperature, falling relative humidity, or both. Thus, precautionary measures on a calm, humid day will not be as strict as those on a windy, dry day, assuming the air temperature is the same each day.

1

In the absence of special guidelines and precau- . tions» undesirable hot weather effects may include s

1. accelerated set2 larger volume changes 3« reduced strengths4o rapid evaporation of mixing water5« rapid slump loss6. reduced bond of concrete to reinforcing steel7„ increased tendency to crack8. difficulty in controlling entrained air9» possible "cold joints"In addition to these problems, a number of new

factors have been complicating hot weather concreting opera tions. These non-climatic factors include:

1. greater use of finely ground and more rapidlyhardening cements

2„ handling of larger batches of concrete andlarger delivery truck size

3« use of thinner concrete sections with greateramounts of steel

ty* increased use of pumping and conveyor equip­ment

5« increased speeds in all construction operations

CHAPTER 2

RECOMMENDED PROCEDURES TO FOLLOW DURING HOT WEATHER

All of the foregoing problems have been studied very thoroughly by several organizations whose main interest lies in the field of concrete use. After many years of

Iresearch and development» the American Concrete Institute(hereafter referred to as the ACI)$ in their manual of

• • . * standards„ has included a special section concerning therecommended practice for hot weather concreting. This recommended practice provides information that is useful in reducing the detrimental effects of hot weather on concrete.

In summary of the ACI standards, the difficulties arising from hot weather concreting may usually be

' minimized (ACI Committee 60$, 1959) by:1, Using cool mixing water. The mixing water has a greater effect per unit of weight on final con­crete temperature than any of the other ingredients. This is due to its specific heat, which is four and one-half to five times that of cement or aggregate. Water should be obtained from a cool source, and every effort should be made to keep it cool by the use of insulated or underground pipes and storage

- 3

tanks„ If the pipes or tanks must be exposed, a coat of white paint on the outside will help keep the water cool.2. Keeping aggregates as cool as possible. The second largest source of heat on a weight basis is the aggregates. The aggregate's temperature can be kept low in several ways. Shading aggregate stock­piles from the direct rays of the sun is beneficial Sprinkling the stockpiles causes cooling through the evaporation of water.3. Reducing length of mixing time. To insure adequate quality mixing time should be minimized. Prolonged mixing results in increases in mixing water demand or reduction in slump. The easiest solution to this problem is the use of well organized work schedules and dispatching of trucks so as to avoid delays.4. Placing concrete as soon as possible after mixing and hauling. Delays in this category con­tribute to slump loss, which results in the use of additional mixing water to offset this reduction and increase the workability of the now stiff mix. Speeding up placement and finishing operations help minimize these problems.

55° Beginning protection and curing procedures as soon as possible. Because hot weather promotes ,rapid drying of the concrete, protection and curing are critical. Therefore, all facilities should be ready to begin curing promptly.A maximum concrete temperature of 90° F should be

considered a reasonable and practical upper limit in hot weather. Difficulties in handling and placement may be encountered, however, with concrete temperatures approaching 90° P..

A maximum temperature of 170*F should be considered the upper limit for cement used in hot weather concrete.High cement temperature appears to have no detrimental effects other than slightly raising the temperature of the mix.

The quality of concrete depends directly on how meticulously the foregoing recommendations are followed.To'what extent these recommendations in reality are followed will be revealed, later in this thesis.

For a more thorough discussion of the methods and procedures which can be used to reduce concrete temperature, refer to ACI Manual 605=59«

In a recent issue of Journal of the American Concrete Institute, July 1971» a proposed revision to ACI’s

•'Recommended Practice for Hot Weather Concreting” was presented. This revision updated several sections of the old recommended practice and included several excellent graphs and charts showing the various relationships of several of the previously mentioned factors (ACI Committee305* 1971).

CHAPTER 3

■ PURPOSE OF THESIS

The purpose of this thesis was to evaluate the hot weather practices of concrete producers in the Tucson area and try to correlate laboratory and field compression test results with actual, prebatch and on-the-job preventive techniques. A comparison was made between the ACI's recom­mended practice and the actual, conditions under which the concrete is produced„ delivered and placed. Although the final strength of the concrete is dependent upon its curing conditions, which in.turn are dependent upon the contractor on the particular job-site, this study was only concerned with the concrete producer's responsibility. (It should be noted e however, that no particular concrete producer will be singled out or specifically named, whether or not it pro­duced good quality concrete.)

Full permission and cooperation was acquired from all concerned personnel before the study began. This included the owners of the various batch plants, contractors on the job-site and test lab personnel. . Several different concrete batch plants were evaluated in this study in order

7

8to provide a more generalized picture of hot weather practices»

This study encompassed all phases of the batching operation-™from the storage and handling of the aggregates to the actual batching» delivery and on-site placement of the: final mix. Data sheets of special form were used in order to present the raw data clearly and enable easier evaluation of the results.

In the interest of time and money„ this study was carried out in part in conjunction with a local engineering test laboratory (hereafter referred to as ETL) on several occasions. On the days when work was coordinated with ETL, the 7-day and 28-day lab cured compressive strength tests were run by ETL and all other tests were run by the writer. The test results from ETL are shown on the data sheets as starred Values

CHAPTER 4

FIELD AND LAB DATA COLLECTING PROCEDURES

Since this study evaluated both field and laboratory data« each raw data sheet (see Appendix) contains a con­siderable amount of recorded information, The data recorded was obtained from numerous sources and was acquired using several different methods, all of which are fully explained in this chapter..

This thesis was concerned with the evaluation of hot weather concreting practices. Therefore, the most logical place to begin the study was at the batching plant. Each day, after checking with ETL’s personnel about their respective daily schedule, initial field investigations were begun at the batching plant.

By knowing the location of that day’s job-site and when ETL's personnel would be there for sampling, enough time was allowed at the particular batching plant to gather some preliminary field data. Ten to twenty minutes before actual batching of the job-site’s concrete, the temperature of the raw ingredients— fine aggregate (sand), water and cement--were recorded„

9

10The temperature of the fine aggregate was recorded

using the following procedure. The surface layers of sand were shoveled off, leaving a small hole exposing the inner layers of the pile. This small hole was always located on- the shady side of the aggregate pile so as to protect the inner sand from the direct rays of the sun. A copper armored thermometer was used to record the temperature'of the sand in several locations. This was done by pushing the thermometer even deeper into the storage pile. This meant that the temperature being recorded was that of sand 1§ feet to 2 feet away from the outer surface of the.pile.

The temperature of the large aggregate (gravel) was extremely difficult to reliably record due to the number and large size of the voids in the storage pile. Therefore, its temperature was not recorded. Although the gravel's tempera­ture may vary from that of the sand, it would not be enough to significantly influence the final results of this study.

Water temperature was recorded directly from pipes or tanks where the batching water was stored. (The same thermometer was used in all phases of the study except for recording cement temperature.) From a faucet or outlet valve, the water was allowed to flow for several seconds. A small container was then filled with water and the temperature was taken. This was repeated two to three times until a stable reading was reached.

11The temperature of the*cement was not always avail­

able. The cement was stored underground» which made the recording of temperature a difficult task. From the under­ground storage bins, the cement was transported via conveyor to weighing bins high above ground level. Again there was no available means for acquiring a temperature reading.From the weighing bins, the cement was dropped into the delivery trucks, where it was immediately mixed with the other ingredients.

After conferring with several of the owners and . employees of the various batch plants, it was decided that the only feasible way to get the cement’s temperature was when the delivery truck from the cement plant arrived.Since these trucks came at various odd times during the day, the recording of cement temperature for every data sheet was impossible. When it was recorded, a special extended range thermometer had to be used since cement temperatures fall above the range of normal thermometers. When recorded, the temperature was acquired directly from the delivery trucks and immediately before being placed in the storage bins underground.

After this data was recorded, the writer conferred with the truck dispatcher in order to coordinate the work remaining that day with ETL and the particular batch plant. After speaking to the dispatcher, it was learned which truck

' " : 12 was to be followed to the job-site. Immediately before leaving the batch plant with the delivery truck, the con­crete temperature in the truck's rotating drum was. recorded» The truck was then followed to the job-slte. Time in transit, speed of rotating drum, and any delay after arrival to the job-site were all duly recorded.

While the concrete truck was waiting and/or being positioned for the pour, preparations were made to cast test cylinders and perform a slump test and air content test.

During the pour, usually after two to three cubic yards of mix had been poured, a wheelbarrow of concrete was taken from the truck. The concrete was taken in this manner to insure that a representative sample had been acquired. ASTM Standards Manual, Section C172, indicates that this is the proper procedure for sampling. If the sample had been taken at the beginning or near the end of the pour, the . probability of acquiring a non-uniform or non-representative sample would have been greater (ASTM, 1964),

After the wheelbarrow of concrete was transported to the working location, the temperature of the concrete was taken with a concrete thermometer, copper armored at the tip for protection.. After recording the concrete's on-site temperature, the same thermometer was used to take air

■ 13temperature at the .time of the pour. During both readings» the thermometer was placed in.the shade so as not to be affected by the direct rays of the sun.

During the time that the temperatures were stabi­lizing, slump tests and air content tests were run and con­crete cylinders were made. As little time as possible was lost in performing the various required functions, according to ASTM, in order to lessen the effects of the sun's heat.

The slump tests were run in accordance with the Method of Test for Slump of Portland Cement Concrete (ASTM C143, 1964). The slump cone was filled in three layers of approximate equal volume. . Each layer was rodded twenty-five times. The actual slump on the job-site was compared with the required slump for the mix. It should be noted that the required slump shown on the data sheets (see Appendix) is just a guideline and as such is not strictly adhered to,.

The air content of the mix was taken.next, using the Chase Air Indicator method. This method is only used to estimate the air content volumetrically; it is not a substitute for a full scale pressure or volumetric test.

In this procedure, a representative sample of mortar from the concrete mix was placed in a small container. A certain volume of isopropyl alcohol was also placed in the container and the container was shaken to remove the air from the mortar. The approximate air content was determined

14by comparing the drop in the level of the alcohol with a calibration chart.

. It should be noted that this was the writer's first experience using the Chase method» and as such the results from these tests might be of questionable value, Because of this fact* the writer will try not to relate too heavily to these results in further discussions.

Sufficient concrete cylinders had to be made for 3*7 and 28,day lab cured and field cured compressive strength tests. After consulting with Professor James D. Kriegh of the University of Arizona Civil Engineering Department and Mr. John Stoss» Tucson's Portland Cement Association (PCA) representative» it was decided that two cylinders for each test would be sufficient for the purpose of this study. Although ASTM (1964) recommends three test specimens per tests ACI, in their "Building Code Requirements for Reinforced Concrete (1971)." states that a minimum of two specimens shall be used for each compressive strength test. Since there were time, money and handling factors to consider, two specimens for each compressive strength test would be the only practical number to use.

Therefore, twelve cylinders were made on each pour; two each for 3 day lab and field cure, 7 day lab and field cure and 28 day lab and field cure. On the jobs when work was coordinated with ETL, only eight cylinders were made.

15since the ? and 28 day lab tests (4 cylinders) were taken by the test lab. It should be noted that when the writer and ETL worked together, all cylinders were made from the same wheelbarrow of concrete.

All cylinders were made in Standard 6 inch by 12 inch disposable molds conforming to ASTM 0^70. All speci­mens were made in accordance with ASTM €31, and since slumps were never less than one inch (meaning the use of vibratory compaction), all specimens were rodded in three equal layers (ASTM, 1964).

All cylinders were left in the molds for approxi­mately twenty-four hours at the job-site before being . removed from the mold. For the first twenty-four hours, the fresh cylinders were placed in a specially insulated box specifically made for concrete specimens or under a pile of damp sand. In some instances, when neither a box nor a sand pile was readily available, the cylinders were placed in a tool shed, under a trailer or in some other shady location.

• After the cylinders were removed from the molds, half were allowed to cure, in the field under job-site condi­tions and half were taken to the laboratory to cure. The field cure cylinders were placed so as to simulate the actual curing conditions of the main pour. If the main pour cured directly in the sun, then the field cure cylinders were placed accordingly. If the main pour was shaded or

16partially shaded during cure» the field cure cylinders were also shadedo

Lab cylinders were cured under conditions of 100$ humidity and 78*P.

The aforementioned procedure was followed every week-day» sometimes twice a day, for as long as temperatures were high and humidity was low. When the rainy season finally began in late July and early August, field work was terminated and lab work was pursued full time. (During the field work phase of the study, numerous 3 and 7 day compres­sive strength tests also had to be run.)

Lab cured cylinders were surface dried before cap­ping. This was done to reduce the probability of steam pockets forming, under the sulfur cap. They were then placed back into the curing rooms for approximately one hour to . allow the caps to harden.

Field cured cylinders were allowed to cool off for approximately one to two hours before capping. This was done to reduce the probability of an inferior cap due to a rubbery sulfur, which would result if the cylinder’s faces were hot. After capping, each cap was allowed to harden for approximately one hour before testing.

The cylinders were capped with a standard sulfur compound supplied by the University concrete laboratory.

17All of the writer's compressive strength tests were

run on a Forney compression testing machine in the concrete lab at the University of .Arizona Civil Engineering Building = Strength test results from E’TL were run on a Tinius Olson Universal testing machine at their Tucson office.

Loading the cylinders to failure was continuous and without shock, as recommended by ASTM Designation C39..

Compressive strength was recorded for each cylindertested.

The water-cement (w/c) ratio was calculated later directly from the weights of the ingredients for each mix. All calculations were done on an electronic calculator in the Math Building on the University of Arizona campus.

CHAPTER 5

RESULTS

The main objective of this study was to evaluate the procedures used when pouring concrete under adverse condi­tions » in this case„ hot weather» and try to correlate com­pressive test results with the actual precautionary measures used by the various responsible parties.

Discussion of Field Work Since the most direct approach to keeping concrete

temperature down is by controlling the temperature of its ingredientse the first concern of this study was an evalua­tion of batching methods.

Generally, when predications indicated a high daily temperature, all of the batching plants involved in this study used a water spray evaporation technique for reducing aggregate temperatures in the storage piles. Two companies in particular used a layered cooling procedure, where the sand was cooled in layers as the storage pile Increased in size. Not one of the batching plants had covered aggregate piles, although in some cases conveyors or other batching, equipment above the piles afforded some protection from the sun,

18

19The temperature of the aggregates ranged from 76°F

to 85°F» with the exception of one particularly hot day(108* P) when the aggregate temperature soared to 92*F (see7/13/71 in Appendix). It has been shown by Lerch (1955)„

©that for an average mix design, an increase of 1.6 F in aggregate temperature results in a 1.0*F increase in final concrete temperature. This was verified in this study.With due consideration for air and water temperatures, a high aggregate temperature usually resulted in a high con­crete temperature.

For example, compare the data sheets for July 9 and July 13 (see Appendix). In both cases, the air temperature was 108* P. On July 9» the aggregate temperature was recorded at 88*F (aggregates were cooled by a water spray). On July 13, however, the aggregate temperature was 92*F (aggregates were not cooled by a water spray). As a result, the final concrete temperature on the job-site was 9̂ ° F on July 9 and an intolerable 100*F on July 13» These results also reinforce the statement that a water spray on aggre­gates can significantly reduce the concrete temperature on hot days.

The second most important ingredient in the concrete mix, as far as temperature effects are concerned, is water. It was pointed out in Chapter 1 that the water temperature has a greater effect on concrete temperature than do the

20aggregate temperatures, due to a higher specific heat value. In the actual batched mix, however, the weight of the aggregates far exceeds that of the water. Therefore, in the final mix, the aggregate temperature has a greater effect on concrete temperature than does water temperature.

All of the batch plants had water lines and storage tanks exposed to the direct rays of the sun. In some cases, portions of the water Tines from pumps, or larger tanks were buried or painted a light color, but unless this practice is followed along the entire system, the effects are minimal.In all Cases, however, the main water storage tank was painted silver or white. In one or two instances, an elevated water tank was partially shaded by other batching equipment, but this is a rather Ineffectual solution to the high temperature problem.

The temperature of the Water ranged from 80° F to 9?eF, with an average of 88.1°F. Lerch (1955) has shown that for an average mix, a change of 3.6*F in water temperature changes the final concrete mix temperature by 1.0°F. In comparing Lerch*s values for water and aggre­gates , it is apparent that aggregate temperature does have a greater effect on the final concrete temperature than does water temperature.

Generally, when the water temperature remained in the low or middle 80*s, resulting concrete temperature was

21In the low 90 * s„ When the water temperature approached or passed 90° F, the resulting concrete temperature was in the middle and high 90’s.. Again the interaction of aggregate temperature exerts a large influence on final concrete temperature„

In PCA's "Design and Control of Concrete Mixes" (1968) , Figure 6l on page 74, there is a plot of aggregate temperature versus water temperature, with a resulting predicted concrete temperature based on these values, In comparing the water, aggregate and concrete temperatures from this study with PCA's graph of predicted final concrete temperatures, it was noted that the recorded temperatures were slightly higher than the predicted values. This indicated that there was another temperature-influencing factor that was hot considered in PCA’s plot. This factor appears to be air temperature.

During the course of field work, air temperatures during the pour ranged from a low of 88*F to a high of 108°F in the shade. During all pours but one, the air temperature exceeded 90° F. The average air temperature during the field work was 99«8*F.

Comparing PCA's predicted concrete temperatures with the final concrete temperatures recorded in this study results in the observation that the actual on-the-job temperatures generally were from 1° F to 3° F higher than the

22predicted values„ This indicated that the air temperature at the time of the pour does have an influence on the final

^concrete temperature„ Also, by comparison with predicted values, the higher the air temperature, the more the con­crete temperature appeared to increase, (The word appeared is emphasized because more field tests and Comparisons should be run in order to conclusively prove this hypothesis,) Other effects of high air temperature will be discussed later in this section.

The temperature of the final Ingredient of concrete, cement, was recorded on the data sheets when available (see Chapter 4 for explanation). A high reading of 170*F was recorded, while a low reading of 158°F was recorded. Insufficient data in this category implied that an average temperature for the cement is negligible. But, in convers­ing with the cement truck drivers, it was found that the cement from the batch plant usually varies in temperature from 155°F to l6^*P. This fact was adequately substantiated by the few available cement temperatures recorded. It was also pointed out to the writer by the cement truck drivers that occasionally, during busy times, the cement may reach a temperature of 180*F or 185°F. This information was acquired only by conversing with various truck drivers and was not verified by any field work. ACIfs Standard places

23a maximum limit of 170° F on cement as it enters the con­crete „ Because of portland cement’s relatively small quantity in the usual mix and its low specific heat, the temperature of the portland cement appears to exert only a minor influence On the concrete’s final temperature. For the most part, the cement temperatures recorded were within ACI’s recommended range.

The storage bins for the cement were underground at the batching plants. Therefore, the contribution of the sun’s heat to cement temperature was negligible.

Since problems of production and delivery overlap those of materials, this will be the next topic of discus­sion.

As noted in Chapter 2, care must be exercised to keep mixing at a minimum in order to obtain a lower concrete temperature and insure adequate quality. In association with the batching plants, it was quite obvious that the individual concrete producers were quite concerned with this particular aspect of their operation. Each batching plant had a planned schedule for each day, and this schedule was followed exactly. On this schedule were recorded time of delivery, required strength of the mix, location of the pour and much more information. With this information at hand, the radio dispatcher could have the trucks loaded and sent to the jobs with a minimum of mixing.

When done this way, mixing time in transit and on-the-job waiting time are reduced considerably. One particular con­crete firm had three or four plants located around the city. In this case, there were not any long mixing times in tran­sit because a truck could be sent from the plant which was nearest to the job-site.

All of the concrete delivery trucks in this study had rotating drums that were painted white. This light color reflected the sun’s rays and helped to reduce the Interior drum temperature. In conversing with several of the truck drivers, it was learned that one particular company had used darker colored drums in the past, but their own quality control department suggested the drums be painted a lighter color, which in turn resulted in a con­crete temperature reduction of 3° F to 4-0 F on the job-site.

Another practice which helped to reduce final con­crete temperature was the wetting of the outside of the rotating drums before, during and after mixing. Under a hot summer sun, even a light colored drum can generate consider­able heat. By continually washing down the drum, cooling was effected by evaporation.

In all instances, after primary mixing at the plant, the trucks used a very slow mixing speed during transit.The slow speed of the drum helped to keep concrete

25temperature down, A fast speed produces more friction between the concrete mix and the sides of the drum, generating more heat,

Up to this point, the writer had been following the practices of the concrete producers in hot weather, which was the main purpose of this study. However, on the job­site » the writer was in.a position to observe some of the hot weather practices of various local contractors who. usedthe concrete. Since the writer believes that the discus­sion of some of these practices may help explain or amplify various other topics in this and the next chapter, they will be included in the discussion that follows.

Generally, after the trucks reached the pour-site, waiting time was minimized due to good planning by the contractors. In some instances, though, a long waiting time was recorded, On June 29 (see Appendix), a waiting time of 25 minutes were recorded. On this specific occasion, the writer was with the first truck of the day on that particular job. The contractor thought that the concrete had been ordered for one-half hour later that it actually arrived (a later record check revealed that the contractor was wrong). Thus, the laborers were not ready to pour whenthe concrete arrived. .

On another occasion, July 23, a delay of 45 minutes was recorded on the data sheet. In this particular case.

; 26the concrete was being pumped by a subcontractor. The pump­ing equipment was quite old, and it continually failed mechanically. Thus, each truck waited before pouring for 20 to 25 minutes rather than about 5minutes. This caused a build-up of trucks around the job-site and longer waiting times. In neither of these cases was the waiting time the fault of the concrete producer.

On some occasions, the formwork was-dampened immediately before the pour to lessen moisture absorption by wood and soil and to cool off the reinforcing steel. At other times, the concrete was poured into hot, dry forms without any preparation. This practice seemed to follow an irregular pattern, depending upon the attitude of the con- . tractor.

These two previously mentioned practices initially indicated to the writer that most contractors are concerned about the quality of the concrete they use. But the following flagrant practice, which positively reduces final concrete strength, shattered the writer's newly formed opinion of some of the contractors.

On several occasions, while working alone (without ETL) a wheelbarrow of concrete was acquired by an employee of the particular contractor at the beginning of the pour over voiced objections by the writer. This was done so that water could be added to the concrete, after samples were

2?taken6 to Increase the workability of the mix and ease the placement of the mix in difficult situations„ This practice was carried out with full cooperation and knowledge of the laborers, the truck drivers„ and the supervisor on the job­site. The writer had no way of estimating just how much water was added, but enough was added so as to change the w/c ratio considerably. This resulted in a mix at the job­site which was entirely different than the specified mix batched at the plant. Needless to say, strength loss can be considerable in this situation.

Just how frequently this practice is carried out is unknown. The writer would like to point out, though, that it occurred only on small jobs involving some of the smaller contractors. Whether or not it occurs on larger jobs, where concrete strength is more critical, is not known. Since this study is concerned only with the practices of the con­crete producers, further investigation into these practices . was not pursued. It should be noted that this was only an observation made by the writer to help justify some of the conclusions presented in the next chapter.

Occasionally, during pours when,air temperatures were extremely high, the concrete would "flash-set" in the delivery trough. This was sure to occur when a truck had to be repositioned before it had dumped its entire load. After

28emptying their load„ the concrete trucks were washed down. Inside and outside, and returned to the batch plant.

Discussion of Laboratory Work Figure 1 through 15 contain graphs showing the

results of the laboratory compressive strength tests. The dark horizontal line indicates the required strength of the concrete for that particular pour. The solid thin line shows the compressive strength of the lab cured 3, 7 and 28 day samples. The dashed line denotes the compressive strength of the field cured 3» 7 and 28 day. samples. Below each graph is given the date of the pour and.the percent reduction in strength of the field cured samples from the laboratory cured samples and the required strength.

As can easily be seen on the graphs contained in the following pages, the field cured strength falls far below the required strength in every case but.one. The field cured strength varies from 62% to 91^ of the required strength. In the only exception (July 23), the field strength was only 3.2% below required strength or 96*7% of required strength. Although this approaches the required strength, it still does not equal or exceed it.

Also, from the graphs, it can be seen that the lab cured strength exceeds the required strength in every case but one. In the one exception, the lab strength fell only 36 psi short of the required strength (see Appendix,

29

COMPRESSIVE STRENGTH (psi)600050004000

30002000

1000

DAYS% REDUCTION IN STRENGTH: 45.6# from Lab Strength

34.5/6 from Required Strength

Figure 1 Compressive Strength— 6/29/71

30COMPRESSIVESTRENGTH (psi)

6000 --

40003000

2000• 1000

28 DAYS% REDUCTION IN STRENGTH: 20.9# from. Lab Strength

21.7# from Required StrengthFigure 2 Compressive Strength— 7/9/71

COMPRESSIVESTRENGTH (psi) 6000 -------5000

40003000

2000

1000

28 DAYS# REDUCTION IN STRENGTH: 26.3# from Lab Strength

4.5# from Required StrengthFigure 3 Compressive Strength— 7/12/71

31COMPRESSIVESTRENGTH (psi)

6000 ------------------------

4000

3000-6-

20001000

28 DAYS% REDUCTION IN STRENGTH: ]4.0^ from Lab Strength

22.2# from Required StrengthFigure 4 Compressive Strength— 7/13/71

COMPRESSIVESTRENGTH (psi)

6000 — 1—

4000

3000

20001000

28 DAYS% REDUCTION IN STRENGTH: 33-8# from Lab Strength

27.4# from Required StrengthFigure 5 Compressive Strength— 7/14/71

32COMPRESSIVESTRENGTH (psi 6000 ------

500040003000

2000

1000

2B DAYS% REDUCTION IN STRENGTH: 51.4% from Lab Strength

38.7% from Required StrengthFigure 6 Compressive Strength— 7/15/71, A.M.COMPRESSIVESTRENGTH (psi) 6000 -------

40003000

2000

1000

28 DAYS% REDUCTION IN STRENGTH: 33.0% from Lab Strength

24.8% from Required StrengthFigure 7 Compressive Strength— 7/15/71» P.M.

33COMPRESSIVESTRENGTH (psl 6000 ------

4000

30002000

1000

28 DAYS% REDUCTION IN STRENGTH: 33.?% from Lab Strength

29.7% from Required StrengthFigure 8 Compressive Strength— 7 / 1 6 / 7 1 , A.M. COMPRESSIVESTRENGTH (psl) 6000 --------

5000

40003000

20001000

28 DAYS% REDUCTION IN STRENGTH: ' 55*3% from Lab Strength

33.9% from Required StrengthFigure 9 Compressive Strength— 7/16/71, P.M.

34COMPRESSIVESTRENGTH (psi)6000-------500040003000

2000

1000

DAYS% REDUCTION IN STRENGTH: 29.9# from Lab Strength

10.8# from Required StrengthFigure 10 Compressive Strength— 7/19/71 COMPRESSIVESTRENGTH (psi) 6000 -------

5000

40003000

20001000

28 DAYS# REDUCTION IN STRENGTH: 24.6# from Lab Strength

11.9# from Required StrengthFigure 11 Compressive Strength--7/20/71, A.M.

35COMPRESSIVESTRENGTH (psi)6000 --- U

40003000

20001000

7 28 DAYSREDUCTION IN STRENGTH: 32.5# from Lab Strength32 from Lab

9•3# from Required StrengthFigure 12 Compressive Strength— 7/20/71, P.M.

COMPRESSIVESTRENGTH (psi 6000 — --

40003000

20001000

28 DAYS% REDUCTION IN STRENGTH: 32.5# from Lab Strength

19.8# from Required StrengthFigure 13 Compressive Strength— 7/22/71

36COMPRESSIVESTRENGTH (psi)

6000 ------5000

4000

3000

2000

1000

28 DAYS% REDUCTION IN STRENGTH: 25.5/S from Lab Strength

3,2% from Required StrengthFigure 14 Compressive Strength— 7/23/71,A.M.

COMPRESSIVESTRENGTH (psi)

6000 \ --

40003000

2000

1000

DAYS% REDUCTION IN STRENGTH: 34.2# from Lab Strength

2?.9% from Required StrengthFigure 15 Compressive Strength— 7/23/71» P.M.

37data sheet for July 9)» It Is quite possible that a small error in the testing procedure, machine operation or some other phase of the laboratory or field work may have caused this difference. Therefore, generally speaking, the lab compressive strength equalled or exceeded the required strength in every case.

In comparing the compressive strength results with the field data, several interesting observations can be made. For example,.on July 231 the air temperature was 88° F at the time of the pour and the concrete temperature was 90*F, the maximum allowed by ACI. The compressive strength graph indicated that lab cured strength exceeded the required strength and the field cured strength almost reached the required strength.(3-2^ short). On July 13, however, the air temperature at the time of pour was 97*P, with the concrete temperature again recorded as -90° F. In this case, both the lab cured and field cured strengths were reduced considerably from the strengths on July 23•The required strength was the same on both days. Waiting times on the job-site and mixing times were nearly the same. The only factor that could have possibly caused the. strength reduction was the increase in air temperature on July 15«

Looking at another example, on July 22, the air temperature was 98°F at the time of the pour. Concrete temperature was recorded at 9^°F. The lab cured strength

I

38exceeded the required strength by about 15^» while the field cured strength was about 20% short. On July 9» however, air temperature rose up to 108*F and the concrete remained at 9^°F. Although the required strength was somewhat higher, both the lab cured strength and field cured strength fell below the required strength. The lab cured strength was , about 1% short and the field cured strength was about 22%

short. These results futher reinforce the fact that lower, strengths can be expected as air temperature increases, with all other temperature Influencing factors being held con­stant. '

On the following pages, graphs are plotted using the data from the Appendix. The first plot, figure 16 on page 39; shows the relationship between plant concrete tempera­ture and. job-site temperature. As indicated on the graph, the job-site temperature can be expected to be 2°F to 3°F higher than the temperature at the batch plant* The resulting points were resolved into a band of values rather than a straight line. One extraneous point was evident, but this was due to a long waiting time on the job-site before the pour (July 23). These results were plotted for slow mixing times in transit (usually 15 minutes or less), slow drum rotations, and minimal delay on the job-site.

On the bottom of page 39r figure 1? shows water temperature versus aggregate temperature, with a resulting

SITETEMPERATURE(°F)110

100

. PLANT TEMPERATURE

(°F)11100

Figure 16 Concrete Temperature— Site versus Plant

WATER TEMPERATURE

(°F)100

90

80

70170

*>• »/•_ o' © 66‘

O?300*9--093-

80 90 100

HIGH 90 ’s

LOW 90 's

HIGH 80 'sPLANT

TEMPERATURE(°F)

Figure 1? Temperature of Concrete as Affected byTemperature of Materials

WATERTEMPERATURE

40

(°F)100-

90

80

80 100CONCRETE

TEMPERATURE(°F)

Figure 18 Concrete Temperature versus Water Temperature

AGGREGATETEMPERATURE(° F)100

80

TooCONCRETE

TEMPERATURE(°F)

Figure 19 Aggregate Temperature versus Concrete Temperature

41

concrete temperature indicated near each point. /This plot is similar to Figure 6l on page ?4 of iCA1s "Design and Control of Concrete Mixtures" (1968)/. Three distinct bands are indicated on the graph showing expected concrete temperatures for particular water and aggregate temperature. These bands are only approximate, and as such will only help to approximate final concrete temperatures under the condi­tions similar to those for which this study was carried out.

Figure 18, on the top of page 40, shows the relationship between water temperature and final concrete temperature at the plant. The "banded" area shows that increased water temperature results in higher concrete temperature.

Figure 19» on the bottom of page 40, shows the relationship between aggregate temperature and final con­crete temperature at the plant. Again it is shown that increasing aggregate temperature results in a higher con­crete temperature.

It should be noted that the points discussed in this chapter were the result of a field study, where many variables, both expected and unexpected, entered into the work. Therefore, several plotted points on the graphs are not representative. These graphs should be referred to with this in mind.

CHAPTER 6

CONCLUSIONS AND RECOMMENDATIONS

An evaluation of hot weather concreting practices has been presented. It is felt that a sufficient amount of data was acquired and an ample number of tests run to make the following conclusions and recommendations.

Conclusions1. The parties responsible for producing concrete are

producing high quality concrete during hot weather.This situation exists even though many recommended temperature restrictions are exceeded and severalACI hot weather procedures are not heeded. This state­ment is based on the fact that all lab cured strengths (with the exception of one) exceeded the required strength for the particular job in question.

2. The method of curing the concrete in hot weather seems to have a greater and more damaging effect on ultimate strength than does the actual concrete temperature at the time of the pour. The basis for this statement is that in almost every case in this study, concrete temperature exceeded ACI* s recommended maximum of 90° F,

42

sometimes excessively. Even under these adverse conditions, lab cured concrete strength exceeded the required strength, while field cured concrete strength fell below required strength. This was further verified by Lerch (1955)» who said: "There appears to be littleeffect on strength until the temperature of the freshly mixed concrete is well above 100* F (p. 4)."Strength loss in concrete during curing is more likely attributed to factors other than concrete temperature at the time of the pour.Air temperature during the pour and during the curing seems to exert a major influence on ultimate concrete strength.

Recommendations Since specimens cured in the same manner as the struc­ture they represent give a more accurate interpretation of the actual strength of the structure, many of the job-sites worked on have structures made of concrete that is of lower strength than required. With this fact in mind, it is suggested that two modes of testing should be employed. One mode of tests should be run on the concrete as delivered (using lab cured specimens), to Insure that high quality mixes are being used. The other mode of testing should be run on the concrete as cured (using field cured specimens), to

insure that proper curing procedures are being followed. This would also result in less arbitration between con­tractor and concrete producer, should unacceptable test results develop.The concrete producer, for his own legal protection, should require that an employee of said firm be present at the pour-site to observe and record pouring proce­dures. Thus, if any malpractice was witnessed (such as adding water to the mix to increase workability as discussed in Chapter 5)» it would be duly recorded if at a later time it was of use as evidence.The use of a shed or tin roof over aggregate piles would do much to decrease aggregate temperature, thereby reducing concrete temperature.Water storage tanks should be placed in a shady location since just painting them a light color does not seem to be sufficient for keeping temperatures low on hot days.

APPENDIX

DATA SHEETS

45

DATE POURED CYLINDERS

46

TEMPERATURE:A IR ...........................................AGGREGATE........................... _ _ Z ZCEMENT................................../ 5 &WATER......................................CONCRETE;

AT P L A N T ...................—AT S IT E ........................ __88 ]

AGGREGATES COOLED . .HOW W A TB R . SPRAY__________

WATER C O O LE D ................ - V 0- -h o w — zzr_________________

PHYSICAL DATA:CEMENT BRAND.............. P ogru^PCEMENT T Y P E ................... -------------28 DAY DESIGN S T R E N G T H -2 0 0 0 p s i

.............. 3 ^ -DESIRED SLUMP.................._=L% _ACTUAL SLUMP................... —W /C...........................................—= ------TIME MIXING IN TRANSIT.I.Q-M.^-MIXING SPEED......................DELAY ON JOB SITE. . . 25 M JKf. ADMIXTURES -Z ! ------------------

COMPRESSIVE STRENGTH TESTS

• LAB CURE_____________________, FIELD CURE

3 D A Y -

NUMBER LOAD STRESS

3 DAY —

n u m b er l o a d s t r e s s

AVG. STRESS tL A i

7 DAY—

NUMBER LOAD STRESS3 8 , 0 0 0 1 3 4 -63 5 , 0 0 0 1 2 3 8

AVG. STRESS / 2 9 2

28 DAY-

n u m b e r LOAD STRESS69, O oo 2 4 -4 -26 7 , 0 0 0 2 3 7 1

AVG. STRESS -ZfLQk

AVG. STRESS

7 DAY —

NUMBER LOAD STRESS3 4 - ,o o o / 2 0 33 3 , 0 0 0 1 / 6 8

AVG. STRESS / / 8 6

28 D A Y -

NUMBER LOAD STRESS3 6 ,0 0 0 / Z 7 4 -3 8 , 0 0 0 / 3 4 5

AVG. STRESS

DATE POURED 7 / 9 / 7/

47

CYLINDERS l-IZ

TEMPERATURE:A IR ............................................. 19 .8 ° ,AGGREGATE __88 .CEMENT................................. t ~70°V/ATER........................................—CONCRETE;

AT P L A N T .................... 9 5 * .AT S IT E .........................■■-9-41

AGGREGATES COOLED . .HOW WATER SPRAT- EVAPORATiON

WATER C O O LE D ................HOW J Z ------------------------------------------

PHYSICAL DATA:CEMENT BRAND................PoqlauoCEMENT T Y P E .................. — I 28 DAY DESIGN STRENGTH_4.QQP.ps/ % A IR ........................................ j—DESIRED SLUMP................. — TTTACTUAL SLUMP...................Y //C ........................................ ■TIME MIXING IN TRANSIT. ^ M W.MIXING SPEED......................DELAY ON JOB SITE. . . 1P..M1.M- ADMIXTURES ............................

COMPRESSIVE STRENGTH TESTS

• LAB CURE____________________ , FIELD CURE

3 DAY 3 DAY

NUMBER LOAD STRESS/ 7 L O o o 2 5 / Z

2 71 >000 2 5 / 2

AVG. STRESS 2 5 / 2

7 D A Y -

NUMBER LOAD

AVG. STRESS

28 DAY-

AVG. STRESS 3 9 6 4

STRESS

IV VrnUt- 1 \9 l o 8yo o o 3 8 2 2lo 11 6,000 4 1 0 5

AVG. STRESS 3 1 3 2 .

NUMBER LOAD STRESS3 7 f , O o o 2 5 / 24 7 8,000 2 7 f o o

AVG. STRESS

7 DAY —

2 6 3 6

NUMBER LOAD STRESS7 8 i) 000 2 8 6 68 8 5 ,000 3 0 0 8

AVG. STRESS 2 9 3 7

28 D A Y -

NUMBER LOAD STRESS// 8 8 , 000 31 14-/2 8 9 ,000 3 1 4 9

!

DATE POURED J h ^ H l CYLINDERS / ~ / Z

TEMPERATURE:A IR ...........................................-L°- L 4AGGREGATE...........................—2 .8CEMENT..................................WATER.....................................CONCRETE;

AT P L A N T ..................—AT S IT E ......................._2§1

AGGREGATES COOLED . .H O W -T r----------------------------------------WATER C O O LED ..............._ N O _HOW — ---------------------------------------

PHYSICAL DATA:CEMENT BRAND.................. PortlandCEMENT T Y P E ................... -------------28 DAY DESIGN S T R E N G T H l2 £ 2 ^ f% A IR ......................................— j—-—DESIRED SLUMP.................ACTUAL SLUMP...................A - l —W /C...........................................P.: 4 ? .TIME MIXING IN T R A N S IT . " ' H -MIXING SPEED........................ .^ LP.V-.DELAY ON JOB SITE. . . ADMIXTURES ............................

COMPRESSIVE STRENGTH TESTS

• LAB CURE_____________________i

3 DAY —

NUMBER LOAD STRESS/ £ L o o o 2f682 63,000 2 Z 2 9

AVG. STRESS 2 1 9 4 -

7 D A Y -

NUMBER LOAD STRESS5 79.000 2 7 96

6 79,000 2 7 9 6

AVG. STRESS 2.7 9 fe

28 DAY-

n u m b e r LOAD STRESS9IC> ------

FIELD CURE

3 DAY —

NUMBER LOAD STRESS3 6 /, OOO 2(584- 6 0 , 0 0 0 2 /2 5

AVG.

7 DAY —

NUMBER

STRESS 2 / 4 /

LOAD STRESS7 IX 0 0 0 2 5 8 58 7 5 , 0 0 0 2 6 5 4 -

AVG. STRESS 2 6 / 8

28 D A Y -

NUMBER LOAD STRESS/ / 85.000 2 9 5 7/2 79,000 2 7 9 6

AVG. STRESS AVG. STRESS 2 8 6 6

DATE POURED

49

TEMPERATURE:A IR .........................................AGGREGATE.........................

10 8 ° 9 2 *

CEMENT............................... 1 6 3 °

WATER................................... 9 7 °

CONCRETE;AT PLANT ................ 99°AT S IT E ...................... /o o °

AGGREGATES COOLED . NoHOW —

WATER COOLED ............. NOHOW —

CYLINDERS / - IZ

PHYSICAL DATA:CEMENT BRAND..............CEMENT T Y P E ................... -------------28 DAY DESIGN STRENGTH 3 0 0 0 p s i% A IR .....................................................DESIRED SLUMP.......................... V 'ACTUAL SLUMP...................W /C......................: .................... ^ 6 G_TIME MIXING IN TRAN SIT J.P-^.1-1-MIXING SPEED......................DELAY ON JOB SITE. . . -N OME ADMIXTURES ............................

COMPRESSIVE STRENGTH TESTS

• LAB CURE____________________, FIELD CURE

3 D A Y -

NUMBER LOAD STRESS/ 4 8 \O O o / 6 9 82 60^000 / 7 6 9

AVG. STRESS / 7 3 4

7 DAY—

NUMBER LOAD STRESS5 66,000 2 3 3 5 "6 6 9 , 000 2 4 4 2

AVG. STRESS 2 3 S 8

28 DAY-

n u m b e r LOAD STRESS9 /O 0,000 3 5 3 9tc> 100,000 3 5 3 9

3 DAY —

NUMBER LOAD STRESS3 000is / 5 9 34 47 .000 / 6 6 3

AVG. STRESS

7 DAY —

/ 6 2 8

NUMBER LOAD STRESS7 5 Z .O O O ! 8 4 - o8 Lh 8 0 1 8 0 5

AVG. STRESS /82228 D A Y -

NUMBER LOAD STRESS// 6 6 , 0 0 0 2 3 3 5/Z 6 6,000 2 3 3 5 '

AVG. STRESS AVG. STRESS

DATE POURED ______

TEMPERATURE:A IR ............................................. - 2 £ LAGGREGATE.............................—121.CEMENT.................................WATER........................................— § 2 1CONCRETE;

AT P L A N T —S L ­AT S IT E ........................._ S H

AGGREGATES COOLED . . ^ 0HOW—= :-----------------------------------------WATER C O O LED ...............-M 2—HOW-EH-------------------------------------------

50CYLINDERS __ ________________

PHYSICAL DATA:CEMENT BRAND................. / ^ tlAwdCEMENT T Y P E ................... -------------28 DAY DESIGN STRENGTH! ?.5 0 . PSI

% AIR.............. — — „DESIRED SLUMP................. — - f -ACTUAL SLUMP...................— & —vyb............ .P:5LTIME MIXING IN TRANSlTLMJLbLMIXING SPEED.........................5.1..9.L.DELAY ON JOB SITE. . . - ~ ~ I— ADMIXTURES ............................

COMPRESSIVE STRENGTH TESTS

D A Y -

NUMBER LOAD STRESS

— .... « ■ ■ — —

3 DAY —

NUMBER LOAD STRESS7 5 2 ,0 0 0 /84o 5 45, o o o /6988 5/^000 l & O S (o 49, ooo 1734-AVG. STRESS

7 D A Y -

/ 8 2 2

AVG. STRESS L 4 0 5

20 DAY-

NUMBER LOAD STRESS

*

AVG. STRESS . . 4 ( 2 Q.

AVG. STRESS

7 DAY —

/ 7 / 6

AVG. STRESS

28 D A Y -

2 2 2 9

AVG. STRESS 2 7 2 4

NUMBER LOAD STRESS NUMBER LOAD STRESSI 6 3 , 0 0 0 2 2 2 9Z

000[ftsS 22 2 9

h vmuuix3 8o, ooo 2 8 3 14 74,000 2 <b 1 3

DATE POURED j/tslll

TEMPERATURE:A IR ............................................- 2 Z 1AGGREGATE........................... —fLQ.!-CEMENT................................. ........WATER...................................... - .- f f .y ..CONCRETE:

AT P L A N T .................. ....89AT S IT E ........................ - 2 0 1

AGGREGATES COOLED . . -MP-—H O W -H I-----------------------------------------WATER C O O LED ................ .± 1 2 —H O W - H -----------------------

51CYLINDERS Li-8__________

PHYSICAL DATA:CEMENT BRAND................ Po«tla>±d

CEMENT T Y P E ..................._______28 DAY DESIGN STRENGTHJSOOO f>st

% A IR .............................................. .......DESIRED SLUMP.................ACTUAL SLUMP................... —1! w /c ....................................TIME MIXING IN T R A N S I T . M,KI-MIXING SPEED......................DELAY ON JOB SITE. . . 12J1±L* ADMIXTURES ............................

COMPRESSIVE STRENGTH TESTS

. LAB CURE_____________________, FIELD CURE

3 DAY —

NUMBER LOAD STRESS/ 3 1 , 0 0 0 1 0 9 72 3 > 2 ,o o o 1 1 3 2

AVG. STRESS

7 DAY—-

NUMBER

AVG. STRESS

AVG. STRESS

1 1 ( 4

LOAD STRESS

2476

28 DAY-

NUMBER LOAD STRESS

37 84

3 DAY —

AVG. STRESS

28 D A Y -

/433

AVG. STRESS ( 8 4 o

NUMBER LOAD STRESS3 3 1 , OOo ( 0 9 74 51 O O O 1 o 97

AVG.

7 DAY —

NUMBER

STRESS 1097

LOAD STRESS5 41, OOO 1 4 5 /6 40,000 14 I'd

7 5 5 , 0 0 0 1 8 1 58 5 1 , 0 0 0 I 8 0 S

DATE POURED 7 / / 5 / 7 /

52

CYLINDERS /— 8

TEMPERATURE:A IR ...........................................AGGREGATE............................. — fi?CEMENT.................................. 164-°-WATER........................................— 9 .3 LCONCRETE;

AT P L A N T .....................— 2 1 1AT S IT E ...........................— 3 2 1

AGGREGATES COOLED . .HOW — ------------------------------------------WATER C O O LE D .................. — 14°—HOW— -------------------------------------------

PHYSICAL DATA:CEMENT BRAND..................PortlandCEMENT T Y P E ..................— I -------28 DAY DESIGN STRENGTHi2Pc!i?s/

% AIR.............-izir-DESIRED SLUMP..................^ 2 _ _ _ACTUAL SLUMP...................J A Lv/c....... JZi£L.TIME MIXING IN T R A N S IT i£ M LMIXING SPEED......................DELAY ON JOB SITE. . . ADMIXTURES ............................

COMPRESSIVE STRENGTH TESTS

. LAB CURE_____________________, FIELD CURE

3 D A Y -

NUMBER LOAD STRESS/ 000 2 / 9 42 S S .o a o 2 0 5 2

AVG. STRESS 2 . /Z 3

7 DAY—

NUMBER LOAD

AVG. STRESS 3 0 9 5

28 DAY-

NUMBER LOAD

STRESS

STRESS

3 DAY —

INUiVIDC.n3

U V M U5 4 .000

0 1 IVC.OD1911

4 5 3 , 000 I S I S ’

AVG. STRESS

7 DAY —

/ 8 9 3

5 7 0 , 0 0 0 2 4 7 76 6 8 ,000 2 4 0 6

AVG. STRESS

28 DAY—

2 4 4 2 .

7 8 5 , o o o 3 0 0 88 85,000 3 o o 8

AVG. STRESS 449 AVG. STRESS

DATE POURED

53CYLINDERS / — 8

TEMPERATURE:A IR ...........................................4 2 LAGGREGATE........................... - h i ____CEMENT.................................WATER..................................... __82L_CONCRETE;

AT P L A N T ...................—2 3 1 .AT S IT E ........................ —2 A L

AGGREGATES COOLED . . —WATER SPRAT- E.VAPOKAT\DKi

V/ATER_COOLED................ -------------HOW------------------------------------------------

PHYSICAL DATA:CEMENT BRAND................CEMENT T Y P E ...................—1 -------28 DAY DESIGN STRENGTH.^ P .00/ ^ 7

% AIR.............. —DESIRED SLUMP.................ACTUAL SLUMP...................— 31-------w/c............ P-.41-TIME MIXING IN TRANSIT.1̂..,Mi.KLMIXING SPEED......................SLQlY~DELAY ON JOB SITE. . . tW b U L ADMIXTURES ............................

COMPRESSIVE STRENGTH TESTS

• LAB CURE_____________________, FIELD CURE

3 DAY

NUMBER LOAD STRESS/ 5") y

i 0 0 0 23 002 6 5,000 2300

AVG. STRESS

7 DAY—

NUMBER LOAD STRESS

AVG. STRESS

AVG. STRESS

o c 3 2 8 9

28 DAY—

n u m b e r l o a d s tr e s s

4244 *

3 DAY

AVG. STRESS 28 13

NUMBER LOAD STRESS3 60, ooo 2 / 2 34 63, Ooo 22 2 9

AVG.

7 DAY —

NUMBER

STRESS

LOAD

2 1 7 6

STRESS5 70 , ooo 2 4 7 76 6 9 , OoO 2 4 4 2 -

AVG. STRESS 2460

28 D A Y -

NUMBER LOAD STRESS' 7 85,Ooo 300 8

<5 78,OOo 2 6 ( 8

5̂DATE POURED , 7 / / £ / ? / CYLINDERS __________________

TEMPERATURE:A IR ...........................................AGGREGATE............................. .....? ? !-CEMENT.................................. — _WATER........................................__8Z1_CONCRETE;

AT P L A N T ....................—2 ^ 1 .AT S IT E ....................... 9 / -°_

AGGREGATES COOLED . .HOW WATER- SPRAY - E.V/APQRAT>° M '

WATER C O O LE D ................ -------------HOW ---------------------------------------------------

PHYSICAL DATA:CEMENT BRAND..................Pszgn^tlbCEMENT T Y P E ..................—L -------28 DAY DESIGN STRENGTH P s l

% AIR.............. ^

DESIRED SLUMP................—ACTUAL SLUMP................ — £ —W /C..................... : .................. ................TIME MIXING IN T R A N S IT J ^ M 'MIXING SPEED......................DELAY ON JOB SITE. . . /.$ > ? '*£ ADMIXTURES ............................

COMPRESSIVE STRENGTH TESTS

• LAB CURE_____________________, FIELD CURE

3 DAY —V IV M 1

NUMBER LOAD STRESS/ 4 2 , 0 0 0 I 4 8 62 4 2 , o o o I 4 8 6

3 DAY —

NUMBER LOAD STRESS3 3 8 , O oo 1 3 4 54 3 9 , o o o 1 3 8 0

AVG. STRESS J * 86

7 D A Y -

NUMBER LOAD STRESS

AVG. STRESS . 1 3

7 DAY —

NUMBER LOAD5 5 Z , o o o I 8 4 o6 5 0 , 0 0 0 1 7 6 9

STRESS

AVG. STRESS ..23 11 &

28 D AY-

NUMBER LOAD STRESS

AVG. STRESS 4 4 3 9 *

AVG. STRESS 8 0 4

28 D A Y -

NUMBER LOAD7 57,000 2 0 n8 5 5 , 0 0 0 1946

STRESS

AVG. STRESS 1 9 8 2

i

DATE POURED if 19 hi55

CYLINDERS /- 8

TEMPERATURE:A IR .............................................2 0 4 :AGGREGATE...........................CEMENT..................................._J=Z_WATER......................................... -8 .8- lCONCRETE:

AT P L A N T ..................... , -33.!-AT S IT E ...........................- 251-

AGGREGATES COOLED . . —MOW _=--------------------------------------------WATER C O O LED .......................... —HO W -Z--------------------------------------------

PHYSICAL DATA:CEMENT BRAND.................PoktlaupCEMENT T Y P E ................... —Z -------28 DAY DESIGN STRENGTH-5222P s/% A IR .................DESIRED SLUMP..................— f —ACTUAL SLUMP................... -S 4 ■w/c............ 0-5P-_TIME MIXING IN T R A N S I T

MIXING SPEED.....................5-L-2-V5-DELAY ON JOB SITE. . . A/P.N^.. ADMIXTURES ............................

COMPRESSIVE STRENGTH TESTS

• LAB CURE_____________________, FIELD CURE

3 DAY

NUMBER LOAD STRESSi l o ( ? o o o 3 5 7 4 -

Z 99,000 3 5 0 3

AVG. STRESS

7 DAY—

NUMBER LOAD

AVG. STRESS

28 DAY-

NUMBER LOAD

AVG. STRESS

3 5 3 8

STRESS

4 8 6 3 *

STRESS

63 G 6*

3 DAY

AVG. STRESS

28 D A Y -

33 8

AVG. STRESS 445$

NUMBER LOAD STRESS3 000r-''

O' 3 4 3 2

4 / O Z , OOO 3 6 0 9

AVG. STRESS 3 5 2 0

7 DAY —

NUMBER LOAD STRESS5 f 12>000 3 9 6 36 / / 3 , o o o y m

7 /2 9 , o o o 4 5 6 5a / 2 .3 , o o o 4 3 5 2 .

56DATE POURED _ l / z o / " ? / CYLINDERS L 8

TEMPERATURE:A IR ............................................. - M l .AGGREGATE..........................._______CEMENT.................................WATER........................................ . 9 / 0 ..CONCRETE;

AT P L A N T —SH­AT S IT E ...................... —.9 H -

AGGREGATES COOLED . .HOW WATER. SPRAY-E.VAPQ RATI OKI

WATER C O O LED .............. N P ..„H0W -T2------------------------------------------

PHYSICAL DATA:CEMENT BRAND.................Pq̂ tm m pCEMENT T Y P E ..................—I -------28 DAY DESIGN STRENGTHi 00Q />s '% A IR ......................................— _DESIRED SLUMP.................ACTUAL SLUMP.................................. .v/c............ .JhJ.P—TIME MIXING IN TRANS\T.L9JHL(i: MIXING SPEED......................S_LO_W_DELAY ON JOB SITE. . . .4 ^ :ADMIXTURES ............................

COMPRESSIVE STRENGTH TESTS

• LAB CURE_____________________, FIELD CURE

3 D A Y - 3 DAY —

NUMBER LOAD STRESS/ ^ 8 , OOO 2 4 0 6

2 7 0 , OOO 2 4 7 7

AVG. STRESS

7 DAY—

NUMBER , LOAD

AVG. STRESS

28 DAY-

n u m b e r LOAD

2 4 4 2

STRESS

3 5 3 7

STRESS

NUMBER LOAD STRESS3 £ 8,000 2 4 o a4 6 7 , O OO 2 3 7 /

AVG. STRESS 2 3 8 8

7 DAY —

NUMBER LOAD STRESS5 8L OOO 28666 80, o o o 2 8 3 /

AVG. STRESS 2 8 4 8

20 DAY—

NUMBER LOAD STRESS7 7 0 2 ,0 0 0 3 6 0 98 9 7 , o o o 3 4 3 2

AVG. STRESS AVG. STRESS - -?-5 -2-/-

DATE POURED 7 / 2 0 / 7 157

CYLINDERS /- 8

TEMPERATURE:A I R ........................................... - ? ,4AGGREGATE............................. _ 85 __CEMENT................................................WATER........................................_ J 9 2 LCONCRETE;

AT P L A N T ....................., - ^ 5 ...AT S IT E ........................... S § 1

AGGREGATES COOLED . ............ ...HOW -H I------------------------------------------V/ATER C O O LE D .......................... —H O W -IT ------------------------------------------

PHYSICAL DATA;CEMENT BRAND................n>KTk*bJQCEMENT T Y P E ...................— 5 28 DAY DESIGN S T R E N G T H A 200 ^ s /

% A IR ............................................... rn r-DESIRED.....SLUMP............... - f -ACTUAL....... SLUMP..............- A _ —w/c....... '.....-Qi£L-TIME MIXING IN TRANSIT.10MIXING SPEED...................... SLQ\V_DELAY ON JOB SITE. . . NONE... ADMIXTURES ............................

COMPRESSIVE STRENGTH TESTS

• LAB CURE_____________________, FIELD CURE

3 DAY

NUMBER LOAD STRESS/ 7 7 , O o o 2 7 2 5 "2 79,000 2 7 9 6

AVG. STRESS

7 DAY—

NUMBER

AVG. STRESS

2.7 (a I

LOAD STRESS

3820 *

28 DAY-

NUMBER LOAD STRESS

AVG. STRESS

3 DAY

AVG. STRESS 5C27

NUMBER LOAD STRESS3 7 9 , 000 2 7 9 64 7 1,0 0 0 2 5 1 2

AVG. STRESS

7 DAY —

2 6 54-

NUMBER LOAD STRESS5 87, 0 0 0 3 0 7 96 CD 0 0 0 3 0 4 -5

AVG. STRESS 3 0 & 1

28 D A Y -

NUMBER LOAD STRESS"7 /02,000 5 fo 0 98 1 03,000 3 f o 4 5

DATE POURED 7/2 2/7/ CYLINDERS / - 8

TEMPERATURE:A IR ...........................................AGGREGATE..........................._______CEMENT.................................WATER......................................... 8 Q °.CONCRETE:

AT P L A N T ..................... - — 3-AT S IT E .......................... _ M L

AGGREGATES COOLED . .HOW WATER SPRAY - LVAPQ [ o kJ

WATER C O O LED ...................- H Q „HOW - = -----------------------------------------

PHYSICAL DATA:CEMENT BRAND.................. pQKTlAUPCEMENT T Y P E ................... - 1 -------28 DAY DESIGN STRENGTH.gl5.9 . j05% A IR ..............................................-j—77—DESIRED SLUMP.................ACTUAL SLUMP...................- 4 Z. ' .V //C...................TtME MIXING IN TRANSIT.!Pr.lg.M<KJMIXING SPEED......................5LO VJDELAY ON JOB SITE. . . MOKjE . ADMIXTURES ............................

COMPRESSIVE STRENGTH TESTS

• LAB CURE____________________ , FIELD CURE

3 DAY 3 D A Y -

28 DAY-

NUMBER LOAD

NUMBER LOAD STRESS/ 6 0 , 0 0 0 21 2 5

2 6 0 , 0 0 0 2 / 2 5

AVR STRFSS 2 / 2 3

7 D A Y -

NUMBER LOAD STRESS

AVG. STRESS .302.4*

STRESS

NUMBER LOAD STRESS3

00000in 2 0 5 24

000Kin 2 0 / 7

AVG.

7 DAY —

NUMBER

STRESS 2 0 3 4

LOAD STRESS7 6 6 ,0 0 0 2 3 3 58 7 / , O O O 2 5 T / 2

AVG. STRESS 2 4 2 4

28 D A Y -

NUMBER LOAD STRESS5 86,000 3 0 4 36 8 4 ,0 0 0 2 9 7 2

AVG. STRESS — AVG. STRESS

DATE POURED 7 / 2 3 / 7 /

59

CYLINDERS / - 8

TEMPERATURE:A IR ...........................................AGGREGATE............................. J U __CEMENT................................................WATER........................................ . 85

CONCRETE;AT P L A N T .................. & TAT S IT E ......................... - M L

AGGREGATES COOLED . . ----------HOW-----------------------------------------------WATER C O O LE D ................ ..............HOW------------------------------------------------

PHYSICAL DATA:CEMENT BRAND................CEMENT T Y P E ................... - J i 28 DAY DESIGN S lR Z m i\\4 0 Q Q _ f> s t

% A IR ..........................................DESIRED SLUMP.................. j y "ACTUAL SLUMP..................... - L A _W /C..................... : .................. ..TIME MIXING IN T R A N S I T ^OMiA/.MIXING SPEED......................S LO L/DELAY ON JOB SITE. . . 4$..!*!.*!- ADMIXTURES ............................

COMPRESSIVE STRENGTH TESTS

AVG. STRESS ^ 7 4 /*

28 DAY—

NUMBER LOAD STRESS

3 D A Y -

NUMBER LOAD STRESS

------- 1 • ~

3 DAY —

NUMBER LOAD STRESS/ 5 3 , 0 0 0 ( 6 7 5 3 Vt UJ |§ 0 1 8 7 52 5 2 . 0 0 0 1 4 Ut OJ 0 0 0 1875

AVfi STRFSS 1 8 5 % AVG STRESS 1 8 7 5

7 DAY— 7 DAY —

NUMBER LOAD STRESS NUMBER LOAD STRESS5 1 7 , 0 0 0 2 7 2 56 7 5 , 0 0 0 2 6 5 4

AVG. STRESS

28 D A Y -

ZGJO

7 7 7 , 0 0 0 2 7 2 58 86,000 3 0 4 - 3

AVG. STRESS — AVG. STRESS

DATE POURED 7/23/7/60

CYLINDERS I - <3

TEMPERATURE:88*

V/ATER COOLED HOW--------------------

I5Q'8 3 '

A IR ......................................AGGREGATE..........................._ 1 £CEMENT.................................WATER.....................................CONCRETE;

AT PLANT ..................AT S IT E ........................

AGGREGATES COOLED . .HOW-----------------------------------

8 9 '9 0 ‘

PHYSICAL DATA:CEMENT BRAND.................PognAUbCEMENT T Y P E ...................—L ------28 DAY DESIGN S lR Z m iW .lQ00 .? 51% A IR ........................................ —DESIRED SLUMP.................■■~ 4 „ACTUAL SLUMP..................— -W/C...........................................TIME MIXING IN T R A N S I T h\LL1MIXING SPEED......................DELAY ON JOB SITE. . . J L -M iU . ADMIXTURES ........................

COMPRESSIVE STRENGTH TESTS

. LAB CURE_____________________, FIELD CURE

3 D A Y - 3 DAY —

NUMBER LOAD STRESS/ 69,000 244-22 6 7 , 0 0 0 2371AVG. STRESS 2 4 C < b

7 DAY*—

NUMBER LOAD STRESS

AVG. STRESS

28 DAY-

NUMDER LOAD STRESS

AVG. STRESS -5.1 9-3.*

AVG. STRESS 3 6 1

NUMBER LOAD STRESS3 68,000 2 4 0 64 7 0 , 0 0 0 2 4 7 7

AVG. STRESS

7 DAY —

2 4 4 2

NUMBER LOAD STRESS5 94,000 3 3 2 66 9 4 , 0 0 0 3 3 2 6

AVG. STRESS 3 3 2 6

28 D A Y -

NUMBER LOAD STRESS7 1 0 7 ,0 0 0 3 S S 68 1 0 9 ,0 0 0 3 8 5 7

REFERENCES

ACI Committee 605» "Recommended Practice for Hot Weather Concreting . (ACI 605-59)»’' ACI Standards, 1959»

ACI Committee 318, "Building Code Requirements for Rein­forced Concrete (ACI 318-?1)," ACI Standards,1971.

ACI Committee 305* "Proposed Revision of ACI 605-59:Recommended Practice for Hot Weather Concreting," Journal of the American Concrete Institute,Volume 68, July 1971 * pp. 489-502.

American Society for Testing Materials, "Concrete andMineral Aggregates," Part 10, ASTM Standards, 1964,

"Control Tests for Quality Concrete," Concrete Information • Sheet ST104, Portland Cement Association,Chicago, 1966, 7PP»

"Design and Control of Concrete Mixes," EngineeringBulletin No. 3, Portland Cement Association,Chicago ̂ 19&8T

Lerch, William, "Hot Cement and Hot Weather Concrete," paper presented at the 30th Annual Meeting of the New Jersey, New York, and New England States Testing Engineers Association, Boston, Mass., 1955-

Robinson, LCDR G . S., and Engle» CDR R. M., "Strength of Concrete," Navy Civil Engineer, Spring 1971 $pp. 26-28.

"Sampling and Testing Ready Mixed Concrete," PublicationNo. 66, National Ready Mixed Concrete Association, August 1964, 32pp.

Timms, Albert G ., "Concreting Under Hot Weather Conditions," Modern Concrete, April 1965» pp. 38-41.

"Tips on Control Tests for Quality Concrete," PublicationNo. 828, Portland Cement Association! 1965,39”pp.

61