Another option is for the individual dry ingredients to be shipped to the job site in compartments and then mixed with water on site using continuous proportioning equipment and auger mixing to the desired consistency.
Grout also may arrive at the job site in a wet-mixed condition. Ready-mixed grout may have the slump adjusted at the site to bring it to the desired consistency. If water is added, the grout must be remixed for at least 1 minute before discharging. When approved by the specifier, grout may be mixed by hand instead of a mechanical mixer when only small volumes are required.
Grout quantities required on a job can vary depending on the specific circumstances of the project. The unit properties, such as absorption and configuration, can have a significant impact. The delivery method pumping versus bucketing can also introduce different amounts of waste. Although the absolute volume of grout waste seen on a large project may be larger than on a comparable small project, smaller projects may experience a larger percentage of grout waste.
Table 2 provides guidance for estimating grout quantities. A variety of admixtures is available to enhance certain grout properties. However, ASTM C requires admixtures to be included in the project documents or to be approved by the purchaser. Likewise, Specification for Masonry Structures ref. Admixtures containing chlorides should also not be used in grout, because chlorides may corrode steel reinforcement and can contribute to efflorescence in the wall.
Several admixtures are available that provide a combination of desirable characteristics, such as shrinkage compensating, plasticizing and retarding.
Note that individual admixture results can vary from one cement supplier to another. Superplasticizing admixtures are used to reduce the water content of a plastic cementitious mix while maintaining high flow consistency.
They are not normally used in conventional grout except self-consolidating grout since the excess water is absorbed into the masonry units. In some areas, however, this absorption of excess water has resulted in efflorescence problems. Superplasticizers have been found effective in reducing this problem by reducing the amount of water available for absorption.
It should be noted however, that special formulation skills are required to ensure that the grout remains fluid long enough to completely fill all the voids. In grout, accelerating admixtures increase both the rate of hydration and the amount of heat generated during hydration.
They are used in cold weather to decrease grout setting time and increase the rate of strength gain. The increased heat of hydration does not eliminate the need for cold weather protection requirements. Accelerators should be free of chloride materials and not perpetuate the corrosion of embedded metals. Shrinkage compensating admixtures cause a slow, controlled grout expansion that is intended to offset grout shrinkage due to the initial water loss.
These admixtures may be especially useful for high-lift grouting, where a large volume of grout is placed and consolidated at one time. Retarding admixtures are used in hot weather to keep the grout workable long enough for placement, consolidation and reconsolidation. They may also be used when the grout cannot be placed right away, as may be the case when the plastic grout will travel a long distance to the job site. Fly ash is a by-product of coal combustion, and is not usually thought of as an admixture in the same sense as the chemical admixtures discussed above.
Fly ash can be used in grout as a pumping aid or to provide a greater slump with less water. Fly ash can also replace some of the portland cement in the grout mix, which has an economic advantage since the unit cost of fly ash is less than that of portland cement.
Addition rates of fly ash and raw natural pozzolans ref. These products can produce grout mixes with a slower initial strength gain, which may need to be considered in cold weather to achieve the minimum compressive strength previously discussed. C damage resistance is quantified in terms of the resulting size and type of damage in the specimen. Thus, results are generally not scalable to other configurations, and are particular to the combination of geometric and physical conditions tested.
The values stated in each system may not be exact equivalents; therefore, each system shall be used independently of the other.
Combining values from the two systems may result in non-conformance with the standard. It sstm the responsibility of the awtm of this standard to establish appropriate safety and health practices and determine the applicability of regulatory limitations prior to use.
Referenced Documents purchase separately The documents listed below are referenced within the subject standard but are not provided as part of the standard. Friends of PDF all our visitors are our friends. Log In. Thank you for helping keep Eng-Tips Forums free from inappropriate posts. The Eng-Tips staff will check this out and take appropriate action.
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