Curing plays a vital role in developing the dense microstructure and pore structure of concrete from the proper chemical reactions between cement compounds and water. It is crucial to prevent or control the moisture loss of concrete during cement hydration to ensure it attains the desired properties.
In general, the rate of curing is found to decrease with increased dilution rate, humidity, and lower temperature, particularly when factors are compounded (low temperature and high humidity).
Salt (sodium chloride) is the primary ingredient used in meat curing. Removal of water and addition of salt to meat creates a solute-rich environment where osmotic pressure draws water out of microorganisms, slowing down their growth. Doing this requires a concentration of salt of nearly 20%.
The curing period is 3 days for concrete containing Type III cement (ASTM C 150) and 7 days for other concrete. Temperature of air and forms in contact with concrete must be above 10 °C for the first 3 days and above 0 °C for the remainder of the curing period.
Water facilitates the curing and hardening processes. Without it, the chemical reactions needed to form the hard crystals that give the concrete its strength can't take place. Too little water leads to structurally weak concrete, and too much will disrupt effective curing and cause flaking, shrinking, divots or cracks.
Strength
Strength is the primary reason why concrete has been used by housing developers and construction companies for many decades. Concrete is a solid material that can easily withstand tensile and compressive stresses without getting affected.
Curing is the addition to meats of some combination of salt, sugar, nitrite and/or nitrate for the purposes of preservation, flavor and color.
Curing entails four essential steps: wilting, yellowing, colouring, and drying.
The single most important indicator of strength is the ratio of the water used compared to the amount of cement. Basically, the lower this ratio is, the higher the final concrete strength will be.
Cement hardens when it comes into contact with water. This hardening is a process of crystallization. Crystals form (after a certain length of time which is known as the initial set time) and interlock with each other. Concrete is completely fluid before the cement sets, then progressively hardens.
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.
Concrete surfaces can be coated, stained or acid treated. These techniques restore color and make old concrete look new again. The treatments are best applied after physical repairs are made.
Excess water is the biggest culprit but we also have to consider the following; poor or insufficient curing, too little cement, carbonation, incorrect proportion of trace ingredients such as pozzolans or shrinkage additives.
When concrete is not cured properly, its durability, strength and abrasive resistance are affected. Due to inadequate curing, concrete develops plastic shrinkage cracks, thermal cracks, along with a considerable loss in the strength of the surface layer.
Curing takes place immediately after concrete placing and finishing, and involves maintenance of desired moisture and temperature conditions, both at depth and near the surface, for extended periods of time.
The time to start the curing of concrete depends on the evaporation rate of moisture from the concrete. The evaporation rate is influenced by wind, radiant energy from sunshine, concrete temperature, climatic conditions, relative humidity.
It is also recommended that the curing duration should not be less than 10 days for concrete exposed to dry and hot conditions and 14 days for concrete with mineral admixture.
There are three main factors that affect concrete compression results: the specimen size, shape, and friction at its ends. These factors affect the observed phenomena, and they affect each other. This paper aims to review the current knowledge on concrete compression and the effect of size, shape and friction on it.
Concrete strength is affected by many factors, such as quality of raw materials, water/cement ratio, coarse/fine aggregate ratio, age of concrete, compaction of concrete, temperature, relative humidity and curing of concrete.