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Mixers, Pumps and Delivery Systems
Core Filling With a Masonry Grout Pump
Mason contractors can accomplish structural reinforcement core filling requirements by pumping grout or mortar with a masonry grout pump. Using a masonry grout pump can be beneficial to the mason contractor in several instances, such as:
Grout pumps used in the masonry field typically are powered by a gas engine (although electric or LP gas power have been used successfully for indoor jobs). The engine powers a hydraulic pump, which extends and retracts a material cylinder. Material is fed into the receiving hopper and forced or “pumped” out of the material cylinder into the material hose connected to the pump. The extend/retract motion of the cylinder is referred to as a “stroke.” The material hose may include various types of fittings and couplings that connect to the pump or any line reducers at the pump discharge. Sections of grouting hose are typically 25 or 50 feet long. A pipe bend otherwise known as a “wall hook” is connected at the end of the hose and is inserted into the block when pumping.
When using a grout pump, some keys to success are worth keeping in mind, namely material mix design, pump priming and taking full advantage of the grout pump’s capabilities.
Material mix design
Masonry grout pumps are compatible with the specification for fine grout as stated in ASTM C476 Standard Specification for Grout for Masonry. This specification classifies fine grout as either “conventional grout (requiring mechanical consolidation by puddling or vibration when placed) or self-consolidating grout (not requiring mechanical consolidation when placed).” The self-consolidating grout owes its automatic consolidation characteristics and high-flow rates to the water-reducing agent included in the mix. High-range water reducers are preferred. ASTM C476 states, “Polycarboxylate-based high-range water-reducing admixtures are best suited to achieve the water reduction and slump flow values required for self-consolidating grout.
The related specification ASTM C404 Standard Specification for Aggregates for masonry grout further clarifies the actual dimensions of aggregates in a fine grout mixture by stating that all aggregate must pass a sieve test at 9.5mm/3/8-inch minus for the grout to be classified as fine grout.
Proper mix design should be specified when ordering material from ready-mix if using a grout pump. Masonry grout pumps are designed to pump Portland cement, blended cements, sand and fine grout aggregates, non-shrinking grouts, pre-bagged mortar, pulverized lime/hydrated lime, quicklime, fly ash, pozzolan and slag – provided all materials are proportioned in the proper amounts with adequate water content. The inclusion of any admixtures, such as water reducing or air entraining, may be determined by the building code or contractor. These admixtures may be useful in ensuring overall “pumpability” of the material used with the grout pump. Some all-in-one admixtures claim to offer “water reduction, plasticizing, air entraining and gelling” in addition to featuring “higher flexural psi, workability, excellent bonding, freeze-thaw protection, easier pumping, high-range water retention and maximum ASTM C-494 and C-260 requirements” (Kel-Crete Admixture).
When batching onsite using a high-strength grout or mortar, be sure to evaluate the aggregate size, first and foremost, to ensure that the mix does not include aggregates more than 3/8-inch minus. Also, test the material by squeezing a small amount of material in your hand; it should all squeeze out between your fingers and leave no aggregates or clumps. All mixtures must be slick to pump through the grout pump, material line and hose. If not slick, the material could clog the hose.
Large clumps caused by dried materials could also clog the pump or material hose. The addition of more fines (sand) to suspend aggregates, cement, plasticizer or lime also could improve the material mixture. Pay close attention to water content in the mixture, and ensure it does not separate out from the other materials. Too much water can, depending on the material, cause sand to separate from cement, preventing the material from performing its function as structural reinforcement in the core filling process.
Mason contractors interested in using a grout pump for grouting walls should be aware of all recommended procedures for setting up the grout pump on a job. Most of these procedures are fairly basic. One procedure – priming the pump – is especially worth mentioning. For masonry grouting and mortar pumping (especially when using 3/8-inch minus pea gravel in the mix), it is crucial to prime the pump and hose before starting the job.
Priming involves the following simple steps:
After successful priming of the pump, connect any remaining lengths of hose, and add the material for core filling to the grout pump’s material hopper. Circulating the material through the hose and back into the hopper is recommended, until you are sure the material is correct.
Making full use of the grout pump: hoisting
For more information, call 513-321-2950 or visit www.airplaco.com.
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|Last Updated on Wednesday, 16 March 2011 11:17|