At about 0.65 to 0.70 w/c the permeability of concrete increases exponentially, so it is usually best to limit the w/c to 0.60 if that is tolerable with respect to other concrete properties.
Water can penetrate concrete slab-on-grade and basement walls due to hydrostatic pressure, capillary action, and vapor pressure.
Traditional concrete walls and columns tend to range from 3,000 to 5,000 psi, while 4,000 to 5,000 psi is needed for pavement. Concrete structures in colder climates require a higher psi in order to withstand more freeze/thaw cycles.
As a guide, use around 2 litres of water per 20kg bag. Do not over water unless you need to achieve a sloppy mix. The less water the stronger the concrete.
Adding one gallon of water per cubic yard increases the slump by one inch, decreases compressive strength 150 to 200 psi, wastes about ¼ bag of cement, and increases shrinkage by 10%. Measure and record all water added on the jobsite.
Strength Reduction
The excess water will not participate in the hydration process and retains in concrete even after hardening. This water will evaporate when exposed to atmosphere and form voids in the concrete. These voids formed are therefore responsible for the reduction of compressive strength of concrete.
Water damage in a foundation is often gradual, starting with small cracks allowing in small amounts of water. This weakens the foundation and lets in more water. This process can take months or even years to destroy your foundation.
Add approximately 2.7 L (2.85 qts) of clean water per 30 KG (66 lb) bag or enough to achieve a workable mix. Avoid a soupy mix.
Typically, 1m3 of concrete is made up of 350Kg of cement, 700Kg of sand, 1,200Kg of chippings and 150 Litres of water.
Concrete hardens as a result of the chemical reaction between cement and water (known as hydration and producing heat). For every mass (kilogram, pound, or any unit of weight) of cement (c), about 0.35 mass of water (w) is needed to fully complete the hydration reactions.
The concrete should be 4 to 6 inches thick. Once the dimensions are established and an outline laid out, dig out the soil for the entire pond. Forms must be built in place to hold the concrete while it dries and cures. Concrete reinforcing bars must be cut to size and fitted into the construction.
For a concrete slab, it is recommended that that they be at least 25 MPa and 4 inches thick with F62 mesh halfway through. It should be level and flat with no bumps or indents and the finished surface should have a trowelled finish.
Concrete slabs are very porous. This means standing water can easily fill in pores on the surface and eventually break down the concrete. As a result, the concrete may crack, move, or even settle.
Concrete is already a porous material. This means that water could find its way through your concrete by itself. But, if you have cracks or cove joints that aren't sealed properly, water will use those openings to enter your foundation.
High-quality, newly poured concrete foundation walls (8-10″ in thickness) are impermeable to water (0.4-0.3 perms).
Rain on freshly finished concrete can damage the surface, and in extreme cases, wash the surface off the concrete exposing the aggregate. To prevent this, covering the concrete with hessian will protect the surface from running water, reducing the risk of erosion.
Amount of water required for 1㎥ of Concrete = 102 kgs = 102 litres. Hence 180 Litres of Water is required for 1㎥ of M10 Concrete.
A cubic metre equals 1,000 litres of water.
Measure enough water for the concrete job. As a guide, use around 2.5 litre of water for 20kg concrete bag.
Water = 22.5 kg or litres.
If we need to calculate Water quantity for concrete, first find the cement content for the volume. Therefore, Required amount of water = 0.5 X 50 kg = 25 litres / 50 kg cement bag. For Design mix, the W/C Ratio will depend upon the workability, strength requirements.
Easy to Mix Concrete – 40kg Bag
The addition of 4 litres of water to a 40kg bag of EASY TO MIX will produce around 18½ litres of concrete.
A 'slump test' involves filling a cone of freshly mixed concrete on a hard, non-absorbent surface and testing how it subsides or slumps. An expert can check if the mix is too wet by measuring the slump and identifying the shape the concrete settles into once the cone is removed.
If the rain begins after 2-4 hours from concrete placement, the surface needs to be covered; otherwise, the concrete surface will suffer damages. If rains pound on concrete 12 hours after placement, the likeliness of any damage is negligible.
Moist curing is a common method of concrete curing. It involves wetting the concrete slab often with water (5-7 times per day) for the first 7 days. This method ensures your concrete slab will be extremely strong and durable, because it allows the moisture to evaporate slowly, preventing cracks and shrinks.