Cement or Concrete?

Question

I am building a box in the ground and need it water-proof.
Whats the best mixure cement/sand, or should I use concrete?
What differs cement/concrete? And how do you make it strong from cracking without steel enforcement?

Answer 1

Technically, "cement" is what hold concrete together; concrete is an aggregate of sand, cement (usually "Portland" cement) and gravel. You can use pure cement as concrete if you want to, say, to fill cracks, same way you might use wood glue to seal up cracks where pieces of wood come together. Generally, fully cured concrete is stronger than cement by itself.

I need to know more about the backyard box to recommend a specific approach. How big, how deep, above ground/below ground...etc.

Answer 2

About the only suggestions I can give you is to put a descent amount of granite gravel in with the cement and to mix it a little on the dry side.

If you notice, old concrete from around the 1940's and earlier tends to hold up better than newer concrete. If you look at the old concrete in relation to new concrete it has larger gravel in it and it has more granite gravel in it.

You don't want to put gravel such as limestone in it. Limestone will cause the concrete to break up during winter.

A trick I learned off of a friend of mine who worked for a concrete company is to mix concrete on the dry side. A dryer concrete mix instead of a soupy one will tend to be stronger and last longer.

Answer 3

The origins of concrete can be traced back to the Babylonians, who used a clay-mix similar to concrete. However, the modern-day form of concrete was not invented till 1756, when British engineer John Smeaton pioneered the use of cement in 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.