ACI 305R PDF

R Hot Weather Concreting. ACI R Concrete mixed, transported, and placed under conditions of high ambient temperature, low humidity, solar. Temperature, volume changes, and cracking problems associated with mass concrete are treated more thoroughly in ACI R, R, and R. ACI Committee defines hot weather as any combination of high ambient temperature, high concrete temperature, low relative humidity, wind speed and.

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The method requires concrete materials to be at room temperature [in the range of 305f to 86 F 20 to 30 C ]. The added refinement of using chilled air instead of air at ambient temperature can reduce the coarse aggregate temperature to as low as 45 F 7 C. A more exact approach would be to use Eq.

Plastic sheeting or sprayable compounds for applying temporary aco films should be available to reduce evaporation from flatwork between finishing passes. In relatively massive placements, revibration before floating can sometimes close this type of cracking.

This interval may be extended by the judicious use of set-retarding admixtures.

R Guide to Hot Weather Concreting

Committee activities include the development of building codes and specification standards; analysis of research and development results; presentation of construction and repair techniques; and education. Box Farmington Hills, Mich. Compared with concrete without aco, a concrete mixture that uses a water-reducing and retarding admixture may have a higher rate of slump loss. In addition, the following should recorded identified be and with the work progress in so that conditions relating to any part of the concrete conbe identified at a later date: Qci, impermeability, dimensional stability, and resistance of the concrete to weathering, wear, and chemical attack all depend on the following factors: Thebenefits may include lower mixing water demand, extended periods of use,and strengths comparable with,orhigher than, concrete without admixtures placed at lower temperatures.

High temperature, low relative humidity, and drying winds are particularly detrimental to the sample of fresh concrete used for making tests and molding specimens.

Delays increase offset it. Concrete pumps, if used, must be capable of pumping thespecified class of concrete through the length of line and elevation at required rates per h. The total water initial water plus the remixing water can be adi to equal that required at the batch plant to give the required site slump; and job 5.

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An alternative to using block ice is to set up an ice plant near the concrete plant. Most 30r5 these problems relate to the increased rate of cement hydration at higher temperature and increased evaporation rate of moisture from the freshly mixed concrete. If thecylinders are allowed to dry at early ages, strengths will bereducedeven further Cebeci Harmful effects are minimized by control procedures outlined in this report.

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These will be of particular benefit in the event of delayed placements or deliveries over greater distances. Trial batches of concrete for the job should be made at the limiting temperature selected, or at the expected job site high temperature, rather than the68 to 86 F 20 to 30 C range given in ASTMC Generally, centrally mixed concrete can be inspected visually as it is being discharged the into transportation unit.

Unless the amount of cementitious material is increased proportionately, the extra water increases the water-cementitious material ratio and will decrease the strength, durability, watertightness, and otherrelated properties of the concrete. Trial batches, however, should also be performed at the expected maximum placing temperature with consideration of using a mixing and agitating period longer than that required in ASTM C to help define the performance to be expected.

305R-10 Guide to Hot Weather Concreting

After form removal, form tie holes can be filled and any necessary repairs made by uncovering a small portion axi the concrete at a time to carry on this work. For example, anundetectedchange of only1. Anyone interested in the activities of the Institute is encouraged to seek membership. Methods for the cooling of mass concrete are explained in AC1 The work of the Institute is done by individual members andby volunteer committees. This afi not unusual for newly manufactured cement that has not had an opportunity to cool after grinding of the component materials.

Concrete should not be allowed to rest exposed to the sun and high temperature before placing it into the form.

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Download Aci R Guide To Hot Weather Concreting

Embedding i n dampsand. Users who have suggestions for the improvement of AC1 documents are requested to contact the AC1 Engineering Department in writing, with the following information: Erosion of Concrete in Hydraulic Structures Reapproved I’d like to read this book on Kindle Don’t have a Kindle? Testing of concrete must be diligent and accurate so that results represent the true condition of the concrete.

If items found in this document are desired by the ArchitectEngineerto bea part of the contract documents, they shallbe restated in mandatory language for incorporation by the ArchitectEnaineer. If possible, the work should be kept in a uniformly moderate temperature condition to allow theconcrete to develop its full strength potential.

These admixtures,together with the cementitious materials and other ingredients proposed for the ac, should be evaluated in the field for 305g properties. Laboratory Investigation, 92 2 The probability for plastic-shrinkage cracks to occurmay be increased if the setting time of the concrete is delayed due to the use of slow-setting cement, an excessive dosage of retarding admixture, fly ash as a cement replacement, or cooled concrete. In spite of these efforts, the users of AC1 documents occasionally find ai or requirements that may be subject to more than one interpretation or may be incomplete or incorrect.

This method is most effective when adequate amounts of coarse material are contained in a silo or bin so that cooling can be accomplished in a short period of time. The use of various typesof water-reducing admixtures can offset increased water demand and strength loss that could otherwise be caused by higher concrete temperatures.

Sprinkling of coarse aggregates with cool water can reduce aggregate temperature evaporation and direct coolby ing Lee Arrangements should be made for readily available backup equipment. The most commonlyquoted value is 0. With the limitations on accurately predicting slump, as explained in Section 3.