Concrete grinding 
1.Why do we need to do concrete polishing and hardening? 
Answer:The concrete floor is easy to be weathered, dusting and sanding without doing hardening and polishing.
Conversely, the concrete floor can extend the life-spam with good vision and more durability after being polished. It can prevent dusting and sanding. It is easy to be cleaned.

2.How to distinguish the concrete hardness? How to do it without instruments? Do I have to select a lighter machine when it is soft concrete floor? Answer:
Way 1 :With Concrete Floor Hardness Tester
Under 30 PSI  soft concrete
30-50 PSI   medium concrete
Up to 50 PSI  hard concrete

Way 2: With a hard material to do a simple test(like a coin). Commonly used in China.
Coin Test Method
 A, With a coin to scrape the floor and get a result of marked but can not go deep, that means the density of the floor is good. Generally, this kind of floor is C30 label with good maintenance of industrial concrete floors and carborundum wearable floor. The grinding curing construction effect is obvious. It has good brightness and the cost can be controlled.
B, With a coin to scrape the floor and there are obvious signs of grooves, then the label of this kind of floor is usually low and it is bad maintenance concrete floor. For this kind of floor, we can choose concrete hardening technology, it can also have an obvious effect after construction, but the construction costs are significantly higher..
C, With a coin to scrape the floor and you can draw a deep groove easily. And even the groove can bury the coins. Then we shall give up this kind of floor and do not need to think about any construction process. We can just communicate with the Party B directly to shatter the existing terrestrial re-paving concrete. To do good maintenance and polished concrete after that. \
D.Test the floor with your own eyes.--It is not scientific.
3 Whats the differences between dry polishing and wet polishing? When shall we choose wet polishing?
Answer:
A. The advantages of concrete dry polishing:
①It can reduce the moisture content of the floor, which will help the densifier penetration.
②The powder is filled into the holes and reacted with hardener to form a crystal which improves the compactness of the floor.
③It is good for checking the level of all steps of grinding and if the surface scratches are well-distributed. It is better for timely remedial rework. The quality of construction is higher.
④This polishing system is equipped with industrial vacuum. The waste generated by dry polishing is easy to be handle and recycled. Environmental protection is required by most countries.
⑤The main composition of concrete is silicates which is suitable for physical polishing. It can improve the floor smoothness and keep it more longer. Wet polishing can not reach such high temperatures, which is not good for polishing and the brightness will not last long. Higher costs need for maintenance.When we do wet polishing, the mud is mixed with water. There are water stains left and get a hazy feeling.

Disadvantages:It needs to be equipped with vacuum equipment to achieve dust-free working. The cost of abrasives are relatively higher than wet polishing.
2 The advantages of concrete wet polishing:
① The grinding effect of wet polishing is better than the dry polishing as it can better moisturize the abrasive.
② The grinding media generated from wet polishing can reduce scratches.
③ The costs of abrasives are lower than dry polishing relatively and it is suitable for a wide range.
Disadvantages:
Non-environmentally friendly. The security coefficient is lower than dry polishing. The wasted mud is hard to deal with and it is very prone to clogging drains.

Polishing process is depend on the customer’s and operators choice.
4.How to account the cost of polished concrete floor ? how to quote ?
Answer: The main costs of polishing concrete include:hardener costs, abrasive costs, labor costs, waste disposal costs, travel expenses, depreciation of machinery and management costs.
A,Hardener Costs: hardener in different brands have different prices.
B,Abrasive Cost: First depend on what system you choose: wet or dry polishing systems. And different condition floors get different hardnesses, so abrasive consumes are not the same. The hardest of floor, the less of the abrasive consumes. The better quality of the floor,the less of the abrasive consume,
According to the requirements of the result, product costs are not the same. For example, high degree final result needs at least to polishing till 3000 #. 400# just get hone final floor. Metal diamond pads 30 # or 60 # used for leveling floor. Of course, if you use more grits, then grind cost, labor costs will increase accordingly
C. Labor costs: different places have different labor costs standard. The higher efficiency machinery you used,the less labor costs you can get.
Therefore, the cost of polishing concrete depends on the material chosen by customers, polishing process, machine efficiency, customer requirements, technical workers and other factors. Cost is approximately $ 1 -$10/ m2.
Price: Do demo on a 50 sq.m job for clients, then calculate the cost.