3 Terms and Definitions

Concrete mixers equipping the large-and medium-scaled hydraulic concrete mixing plants are mainly used for mixing large aggregate and high density hydraulic concrete (including roller compacted concrete),and also used for concrete mixing in civil works.

The working condition is defined as the standardized test condition when the concrete mixers satisfy the following require ments:

a)Raw materials of concrete can be timely,completely and exactly delivered to concrete mixers after being weighted,and then can be mixed continuously,smoothly and uniformly.The finished concrete shall be discharged timely and smoothly.

b)The mixed raw materials shall meet the requirements of DL/T 5112—2009 and DL/T 5144.

c)For batch type concrete mixers,the concrete volume per batch (measured after being rammed)shall be 100%to 110%of the nominal capacity of the concrete mixer.

d)During mixing,admixture(or additive)which would influence the mixing time is not allowed to be added nor slice ice and without dry mixing.The concrete aggregate gradation shall meet the requirements of allowable maximum particle size of concrete mixers.

e)The slump of the ready–mixed concrete shall be 30 mm to 70 mm for tilting type concrete mixers,and 10 mm to 70 mm for forced type concrete mixers.

f)The rammed density of the ready–mixed concrete shall be 2.4 kg/L to 2.65 kg/L.

g)The voltage and air pressure supplied to mixers shall be kept stable.The voltage shall be 95%to 105%of the rated design value,and air pressure shall be 0.5 MPa to 0.7 MPa.

h)Hydraulic oil and lubricants required for operation of mixers shall be supplied adequately.

i)The product concrete quality shall be kept stable and satisfy the preset indexes.

It refers to a type of mixer that takes three processes of charging,mixing and discharging as one working cycle and mixes concrete in sequence.The three processes are governed according to a certain time interval,namely,mixing batch by batch.

A mixer by which the three processes of charging,mixing and discharging are carried out simultaneously and continuously.

A mixer which operates in such a way that the mixing materials are brought to a higher elevation by its rotating drum and paddle fixed inside the drum,and then fall down by gravity for mixing.

A mixer conducting forced mixing of materials by means of the relative movement between the fixed drum and the revolving paddle inside the drum.

A mixer with both functions of the tilting type and the forced type concrete mixers,also called as vortex type concrete mixer.

The aggregate with a particle size of no less than 5 mm.

The concrete with relative deviation of mortar density in concrete not greater than 0.8%and the relative deviation of coarse aggregate mass per unit volume of concrete not greater than 5%.

It refers to the volume of the discharged rammed homogenous concrete of a batch which is normally mixed by a batch type concrete mixer in specified time based on design capacity and under the standardized test condition(L).It is also called discharging capacity.

It refers to the effective mixing space in the batch type concrete mixer(L).

For batch type concrete mixers,mixing time refers to the time required for mixing a batch of concrete as per nominal capacity,from the moment all the materials were put into the mixer until the materials stirred into homogeneous concretes(s).For continuous type concrete mixers,mixing time refers to the time required from a certain material (such as a kind of aggregate)put into the mixer to discharged(s).

For batch type concrete mixers,discharging time refers to the time required from the moment of 0%discharging until not less than 95%of the nominal capacity after mixing a batch of homogeneous concrete as per nominal capacity(s).For tilting type concrete mixers,discharging time refers to the time from the beginning of the discharging to resetting of mixing drum(s).For forced type concrete mixers,discharging time refers to the time from opening of the discharging door to closing of the door(s).

For batch type concrete mixers,operating cycle refers to the time for mixing a batch of concrete as per nominal capacity from starting of charging to completion of discharging (for tilting type concrete mixers,it refers to the time of resetting the mixing drum;for forced type concrete mixers,it refers to the time of closing the discharging door),(s).It includes charging time,mixing time and discharging time.