Tag Archives: Concrete

Efflorescence on Exterior Concrete Wall

Efflorescence is a very common problem with poured concrete foundations. The white powdery substance you see along the outside of your basement wall is efflorescence and indicates moisture is in contact with the masonry. Don’t worry this unattractive build up isn’t hazardous; efflorescence is simply salt and can be easily removed with efflorescence removers or other cleaning techniques.

This does not necessarily mean that intrusion will occur. We recommend checking gutters, downspout drain lines for proper operation. Efflorescence is found on many homes without water intrusion occurring inside the home. But, it should alert you to the possibility that future steps may be needed.

What is happening, water infiltrates the block or the concrete wall and as water evaporates from the surface the mineral deposits are left behind in the form of white substance. Although efflorescence is generally a visual problem, if the efflorescence crystals grow inside and under the surface, it can cause spalling of the foundation wall, which is when the surface peels, pops out or flakes off. The salt pushes from the inside out and can eventually cause crumbling and deterioration.

Efflorescence, water-soluble salts come from many possible sources. First of all; there must be water present to dissolve and transport the salts. Groundwater is often a source of efflorescence. For water to carry or move the salts to the surface there must be channels through which to move and migrate. The more dense the material more difficult for the water to transport salts to the surface. On the other hand, the more porous the material, the greater the ease with which salts are transported and deposited. Salt-bearing water, on reaching the surface of a structure, air evaporates to deposit the salt.

When humidity is low, the water may evaporate before reaching the surface of the structure, leaving the salt deposit beneath the surface, and unseen. When the humidity is high, water evaporation is slower allowing more opportunity for salted to be deposited.

Since humidity has a definite effect on whether or not the salts appear, it can be assumed that efflores­cence is a seasonal problem. The intensity of efflorescence increases after rainy winter seasons, de­creases in spring, and by summer has practically disappeared. This cycle may repeat for months or years, but generally the intensity of the efflorescence decreases in all but very extreme cases, and by about the third year it should be practically eliminated.

Again I repeat, this does not necessarily mean that intrusion will occur. Checking the exterior for grade issues and low spots, ensuring the proper operation of downspouts and that water is being directed away from the foundation may help prevent efflorescence on the exterior of your foundation wall.

Working Safely with Concrete

Concrete is easy to work with, versatile, durable, and economical. While observing a few basic precautions, it is also safe-one of the safest building materials known. Over the years, relatively few people involved in mixing, handling, and finishing concrete have experienced injury. Outlined below are some simple suggestions-protection, prevention and common sense precautions-useful to anyone working with Portland cement and concrete.

The jobsite should be adequately marked to warn the public of construction activities. Fences, barricades, and warning signs can be used to restrict public access. The work area should be kept clean and uncluttered to minimize hazards to workers. Remember: safety is the job of everyone onsite.

Protect Your Head and Eyes

Construction equipment and tools represent constant potential hazards to busy construction personnel. It is therefore recommended that some sort of head protection, such as a hard hat or safety hat, be worn when working any construction project, large or small.

Proper eye protection is essential when working with cement or concrete. Eyes are particularly vulnerable to blowing dust, splattering concrete, and other foreign objects. On some jobs it may be advisable to wear full-cover goggles or safety glasses with side shields. Remember that sight is precious. Protect the head and eyes by using proper safety equipment and remaining alert.

Protect Your Back

All materials used to make concrete – Portland cement, coarse aggregate, sand, and water-can be quite heavy even in small quantities. When lifting heavy materials, your back should be straight, legs bent, and the weight between your legs as close to the body as possible. Do not twist at the waist while lifting or carrying these items. Rather than straining your back with a heavy load, get help. Remember to use your head, not your back.

Let mechanical equipment work to your advantage by placing concrete as close as possible to its final position. After the concrete is deposited in the desired area by chute, pump, or wheelbarrow, it should be pushed-not lifted-into final position with a shovel. A short-handled, square-end shovel is an effective tool for spreading concrete, but special concrete rakes or come-alongs also can be used. Excessive horizontal movement of the concrete not only requires extra effort, but may also lead to segregation of the concrete ingredients.

Avoid actions that cause dust to become airborne. Local or general ventilation can control exposures below applicable exposure limits; respirators may be used in poorly ventilated areas, where exposure limits are exceeded, or when dust causes discomfort or irritation. Avoid prolonged exposure to dust.

Protect Your Skin

When working with fresh concrete, care should be taken to avoid skin irritation or chemical burns. Prolonged contact between fresh concrete and skin surfaces, eyes, and clothing may result in burns that are quite severe, including third-degree burns. If irritation persists consult a physician. For deep burns or large affected skin areas, seek medical attention immediately.

The A-B-Cs of fresh concrete’s effect on skin are:

Abrasive Sand contained in fresh concrete is abrasive to bare skin. Basic & Portland cement is alkaline in nature, so wet Caustic concrete and other cement mixtures are strongly basic (pH of 12 to 13). Strong bases-like strong acids-are harmful, or caustic to skin. Drying Portland cement is hygroscopic-it absorbs water. In fact, Portland cement needs water to harden. It will draw water away from any material it contacts-including skin.

Clothing worn as protection from fresh concrete should not be allowed to become saturated with moisture from fresh concrete because saturated clothing can transmit alkaline or hygroscopic effects to the skin.

Waterproof gloves, a long-sleeved shirt, and long pants should be worn. If you must stand in fresh concrete while it is being placed, screeded, or floated, wear rubber boots high enough to prevent concrete from getting into them.

The best way to avoid skin irritation is to wash frequently with pH neutral soap and clean water.

Placing and Finishing

Waterproof pads should be used between fresh concrete surfaces and knees, elbows, hands, etc., to protect the body during finishing operations. Eyes and skin that come in contact with fresh concrete should be flushed thoroughly with clean water. Clothing that becomes saturated from contact with fresh concrete should be rinsed out promptly with clear water to prevent continued contact with skin surfaces. For persistent or severe discomfort, consult a physician.

When working with fresh concrete, begin each day by wearing clean clothing and conclude the day with a bath or shower.

Information Source: Portland Cement Association