Masonry Magazine April 2000 Page. 30
Masonry Grout
Continued from page 19
ASTM C 476, TABLE 1- PROPORTIONS BY VOLUME
| TYPE | PARTS BY VOLUME OF PORTLAND CEMENT OR BLENDED HYDRAULIC CEMENT | PARTS BY VOLUME OF HYDRATED LIME OR PUTTY | AGGREGATE MEASURED IN A DAMP LOOSE CONDITION |
| --- | --- | --- | --- |
| | | | FINE | COURSE |
| Fine Grout | 1 | 0-1/10 | 21/4 to 3 times the sum of the volumes of the cementtitious materials | |
| Course Grout | 1 | 0-1/10 | 21/4 to 3 times the sum of the volumes of the cementitious materials | 1 to 2 times the sum of the volumes of the cementitious materials |
One of the first steps in considering the performance of grout is the implementation of a quality assurance program. These quality assurance provisions may include certificates of compliance or verification of material conformance by testing. When the grout is ready-mix dispatched or factory blended dry mix, the quality assurance program is relatively simple. The ready-mix grout is controlled by proportions at the batch plant and is typically regulated by a design mix, either generic or specific for the project. With pre-blended dry mix, once again, the mix is regulated by proportion at the plant, normally to a generic conformance with ASTM C 476.
In the case of field mixed grout, the volumes of the materials deserve closer regulation, and should be measured so that the constituents fall within the range of ASTM C 476, Table 1.
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Contrary to popular belief, grout is not required to be proportioned according to ASTM C 476, Table 1. Section 5.2 of ASTM C 476 states "The grout shall be either proportioned in accordance with the requirements of Table 1 or the compressive strength of grout shall be specified.". This means that a grout design of proportions outside the parameters of ASTM C 476, Table 1 may be submitted and reviewed by the appropriate parties, and there should be no reservation about approving the design mix, provided it meets the project requirements.
After it is determined that the materials are in conformance with the project requirements, proper methods of placement must be considered for an effective grouted system.
When grout is used for non-structural purposes, that is, to add weigh or mass to the system, the method of solid grout placement is less critical than with masonry of a deformed reinforcement structural steel nature. Precautions should, however, be taken to see that the intended cores are solidly filled, but small voids and incidental debris such as mortar droppings at the bottoms of cells may be acceptable.
Most of the time careful attention must be given to grout placement. The dichotomy of grout is that it must be fluid enough to flow vertically and horizontally in the masonry cavity, and at the same time it must provide adequate strength to meet the high compressive strength generally associated with masonry.
Section 2.6 B.2 of Specification for Masonry Structures (ACI 530.1-99/ASCE 6-99/TMS 602-99) states that the slump of masonry grout should be between 8 and 11 inches (203 and 279 mm). The slump cone test as shown gives a sense of how much grout should flow. When thinking on terms of concrete, one should ask how could grout possibly achieve the compressive strength requirements with such high water content. Since masonry units immediately draw excess water from the grout, the hydration process is normalized; therefore, the compressive strength requirements are met.
Once the required consistency of grout is met, the method of delivery to the wall is typically the choice of the contractor. For a small amount of grout, it may be desirable to use tubs and buckets. As the need for more widespread and faster placement develops, the grout pump, similar to the concrete pump, is normally used. One big advantage of using a mechanical grout pump is that if adequate water (contributing to the high slump) and cement content (contributing to the flow) are not met, then the grout hose usually plugs up. In a sense, this is a self-inspecting check process verifying the proportions of materials.
Before the actual grouting of masonry, the method of grouting must be determined. Will the contractor limit the grout lifts to 5 feet and circumvent the need to provide for, and subsequently seal, the cleanouts, or will the contractor elect to construct the wall full height, up to 24 feet (7.3 m) and provide cleanouts? Historically, this has been the contractor's option since both methods are acceptable, and this issue falls into the category of means of construction. Most of the time, the grouting method suggested by the
Slump of grout
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