Following two months of extensive upgrades, concrete block will now be made a lot faster
at Kirkpatrick Concrete’s Guntersville production facility.
Ricky Mead, general manager of Kirkpatrick’s northern division, says temporarily closing the company’s only block plant was somewhat painful for customers, but the resulting increase in efficiency will make the downtime worth it. “Here in our area, we're pretty strong with block,” says Mead. “A lot of schools go with block because they’re fire-resistant. Also, with us being in a storm area, you can also fill the cells in block and make them pretty resistant to tornado-type winds,” says Mead.
Manufacturer Columbia Machine, based in Vancouver, Washington assisted personnel with upgrades to the three-at-a-time block machine. “The machine is only about four or five years old, but these changes will really speed things up for us,” says Mead. Each cycle, the block machine can turn out three eight-inch concrete masonry units every six to eight seconds.
Tsali Burch, operations manager for the plant, says the modifications are already paying off. “Production is up,” says Burch. “We have the capacity now to produce four kiln a day, that’s about 10-thousand block in an eight to nine-hour day. For this plant, that is extraordinary,” he says.
The Guntersville operation is adjacent to the ready-mix plant and exclusively produces gray lightweight concrete masonry in a number of sizes. These units are lighter and easier for masons to handle. Block sales are made to residential and commercial customers in a 35-mile radius of the Marshall County facility.
“We value our block customers in Northeast Alabama,” says Mead. “It’s the cornerstone of building in this area because without a good foundation, you don’t have a good house. So, concrete and block, that’s what it’s all about,” he says. “I think over the next five to ten years this plant is going continue to do well.”
Hot weather defined: “Normal” masonry construction is generally thought of as having ambient temperatures between 40 and 90 degrees F. The American Concrete Institute, ACI 530.1, considers hot weather conditions when the ambient temperature exceeds 100 degrees F or 90 degrees F with a wind velocity greater than 8 mph. Of course, there may be building codes and specifications that vary.
The Brick Industry Association, in their Tech Note 1 states, “The primary concern during hot weather is rapid evaporation and absorption of water from the mortar. ……without sufficient water, cement hydration slows or stops, which reduces the bond strength and extent of bond between brick and mortar”. Naturally compressive strength suffers as well. And, remember, the purpose of mortar is to bond the masonry units together.
In hot temperatures the mortar actually requires more water than at cooler temperatures to achieve a given workability or plasticity. Despite this increased initial water demand, the mortar may be more difficult to use and the board life and stiffening time is shortened. This is due to the increased water loss brought on by the higher temperatures of the masonry units, their associated higher absorption rates, and naturally, the higher evaporation rate into the air.
Significant problems that are brought on by hot temperatures include:
Both scenarios can create non-durable and low quality mortar and can lead to reduced buckling strength of a wall that is concentrically loaded. It also reduces the wall strength under horizontal and wind loading.
Type M mortar is a high strength mix of at least 2500 psi that offers greater durability than other mortars. Use it for both reinforced and unreinforced masonry that may be subject to high compressive loads, severe frost action, or high lateral loads from earth pressures, hurricane winds, or earthquakes. Type M may be used in structures below grade and in contact with soil, such as in foundations, retaining walls, walks, sewers, and manholes. To produce Type M mortar, combine one bag of Coosa Portland Cement and one bag of Coosa Light Type N Masonry Cement (see Type N description below) along with 4 ½ to 6 cubic feet of damp, loose, masonry sand. *
Type O mortar is a high lime, low strength mortar, achieving 350 psi minimum. It is primarily recommended for tuck-pointing and similar repair work. Its’ exterior use is limited because of its’ low structural limitations. It is not recommended for areas of high winds.
When preparing Type O mortar, combine 1 bag of Coosa Portland Cement and 1 ¼ to 2 ½ cubic feet of Type S hydrated lime along with 2 1/4 to 3 times the sum of the separate volumes of cementitious materials of damp, loose, masonry sand.* Mix all of the solid materials and then add sufficient water to produce a damp mix that will retain its shape when pressed into a ball by hand. Mix time is 3 to 7 minutes, preferably with a mechanical mixer. Let the mortar stand for 1 to 1 ½ hours for pre-hydration. Add sufficient water to bring the mortar to the proper consistency for tuck-pointing, which is somewhat drier than for laying the units.
Type K mortar has not been a part of ASTM C270 for many years. Sometimes it may be specified for restoration of historic or “ancient” buildings or structures that require a mix that is not significantly stronger than the surrounding masonry work. Type K mortar compressive strength is about 75 psi. *Use masonry sand conforming to ASTM C144, Aggregates for Masonry Mortar. Add sufficient water to obtain desired mortar consistency. Mix 3-5 minutes after all of the ingredients are in the mixer. Workmanship, unit suction, mixing, curing and other variables affect the overall masonry quality.
Finally, and perhaps needless to say, this article merely touches on the highlights of mortar type selection, proportioning, and mixing. For additional information, and to name only a few, I’ll offer additional reference sources:
On so many complaints of leaking walls it is so apparent that the mortar is, in fact, the culprit. But it is the fact that not enough mortar has been put into the joints.
Bed joints for brick walls: these joints must be spread uniformly thick. Furrowing must be kept to a minimum, if performed at all, as some building codes prohibit furrowing. As the bricks are put/shoved into place, their weight and the weight of the coursed above will help to compact the mortar and help promote a water resistant joint. These efforts will provide a “void free” joint, not allowing collection areas for water that could cause areas of freeze damage or embedment corrosion.
Head Joints for brick walls: These joints seem to be more susceptible to water leakage than bed joints. Needless to say, if they are not filled full, (full head joint) there will be mortar void areas which provide channels for water to run to the inside face of the wall / building.
During one of my early on, leaking wall inspections, I was led to the attic space of a new house. The builder had already torn off the styrofoam sheething exposing the interior face of the brick. The wall certainly was leaking, as there were kitchen baking pans on the attic floor to catch the water. Interestingly enough, I could see daylight coming through several head-joint areas. I figured if the light could come through, so could the rainwater. Again, it was a mortar problem…not enough of it.
A classic, typical example of a non-full brick head joint can be seen below. Figure 1 shows the mason applying mortar to the head of the brick. Figure 2 shows the “as-installed” brick and joint. I call this a “clip-joint” where only the outer ½” - ¾” or so of the brick receives mortar. The cosmetic appearance of the finished wall looks good. But there are hidden problems. When it comes time for the mason to run his jointing tool on the joint, instead of the compacting and densifying action that is supposed to be accomplished, the mortar in the clip-joint can actually be pushed back, breaking the initial bond that had formed between the brick and mortar….a perfect beginning for a leak. Remember, the function of mortar is to bond all of the bricks together for strength and water tightness.
The Portland Cement association discusses two types of mortar bedding: full and face shell.
Full bed mortar bedding: the webs, ends and face shells are bedded in mortar. This is usually used for the first or starter course on a footing. As a side note it can also be used for work where the wall is to be partially grouted.
Face shell bedding: it is common practice to use this type of bedding for all other hollow concrete masonry unit construction, where a full bed of mortar is applied onto the top of the face shell
Head joints for block: a full width of mortar is applied to the ends of the face shell. Some masons apply the mortar to the ends already in place while others stand the block vertically and apply the mortar to the end. Regardless of the procedure, a full width of mortar is required.
To conclude: use plenty of mortar in the joints and avoid mortar void areas. And remember, an important purpose of the jointing tool is to compact and densify the mortar joint, making it as water tight as possible.
Efflorescence can be seen on mortar joints, concrete block faces, brick faces. A combination of conditions must be present for efflorescence to form: 1, there must be soluble salts in the masonry and 2, there must be moisture migration through the masonry, carrying the salts to the surface.
On a more technical note; in masonry work, Portland cement is generally used in the manufacture of concrete block, mortar, and stucco. The cement, in the hydration process contains calcium hydroxide. Naturally, water is used to make mortar or block-fill. Moisture, migrating through the body of the feature carries this calcium hydroxide to the surface where it combines with the carbon dioxide in the air forming a new substance….the white powdery material, now calcium carbonate.
Actually, at this point this material is water soluble, so it is usually easily cleaned off during the masonry cleaning effort. If left alone, though, and if there is a continual problem with water migration or leakage from external sources, the efflorescence becomes carbonate deposits or lime runs. These can be quite stubborn to remove, requiring more aggressive cleaning efforts.
The PCA further states that “All masonry and concrete materials are susceptible to efflorescence or staining. Interestingly enough, during periods of slow drying, and cool, damp conditions, such as in the winter, efflorescence can be more prevalent than in the summer.
Most efflorescence, especially on new construction, is temporary, very often called “new construction bloom”. It is most often removed during the masonry cleaning portion of the work. Recurring efflorescence indicates a chronic moisture or water flow problem such as from ground water in retaining walls, around un-caulked window openings, non-full mortar joints. Another source of “salts” can be where the masonry contacts the soil, such as basement and retaining walls. Also, some raw materials found in brick, for example, manganese, can cause brown stains.