CHARGING A CON-E-CO CONCRETE TILT MIXER

Central Mix Plant Material Discharge and Sequencing

When operating a central mix plant the sequence of how the materials are introduced into the central mixer greatly affects the quality of product out of it and the time it takes to achieve a good mix.  When sequencing materials into a central mix drum CON-E-CO found the best results are achieved when introducing the water into the drum first, followed by the aggregate entering one to two seconds later and the cement entering one to two seconds after the aggregate. This is all based on when the materials enter the drum not when they leave the scale (batchers or meters).

With a batch control there is no indication on when the individual materials enter or finish discharging into the drum so the operator will physically have to look at when the materials are entering and their length of discharge. You can not solely rely on the batch control when sequencing material discharge for a central mix plant.

After the materials start entering the drum they should continue discharging together. The cement should be the first material to finish with the aggregate ending one to two seconds later and the water should end one to two seconds after the aggregate.

To achieve proper starting times it is usually a good idea to use time delays to start the material discharge. The use of percentage delays is not recommended when setting up a discharge sequence because regardless of the batch size the material takes the same amount of time to travel to the mixer from each batcher. With percentage delays the start timing will vary depending on the size of batch.

Since in most cases the aggregate batcher is located furthest away from the mixer compared to the other materials the aggregate will start discharging first and the time delays will be based on when the aggregate starts. For instance if the aggregate takes eight seconds to reach the drum you would have approximately a six to seven second delay on the water from when the aggregate starts, thus allowing water to enter the drum one to two seconds before the aggregate. With this example on cement you would delay the cement nine to ten seconds to allow the aggregate to enter the drum for one to seconds before the cement begins.

Aggregate Discharge – When controlling the speed of the material discharging or how it ends each material has to be looked at individually. With most central mix plants the speed of the material discharging is much faster than a dry batch plant. Due to this fact it may be difficult for the batch control to regulate the flow effectively enough to provide a good discharge sequence. By the time the control makes an adjustment to the discharge gate a large volume of material may have discharged and gotten ahead of all the other material.

Discharging of the aggregate batcher usually is the limiting factor (slowest material) when dealing with discharge. Discharge of the aggregate batcher will typically open the discharge gates fully or run the batcher conveyor at fully speed throughout discharge; this is dependent on the type of plant.

Cement Discharge – To regulate the flow out of the cement scale a physical gate stop will be used to allow the discharge valve to only open partially and regulate discharge. When doing this the batch control should be set up to hold an open signal on the valve throughout discharge, flow regulation should be turned off in the batch control. The gate stop will have to be manually adjusted to speed up or slow down the cement discharge so the cement ends properly in the discharge sequence, one-two seconds before the aggregate. The use of a gate stop provides an even discharge rate through the discharge sequence, when allowing the batch control to regulate the rate you may get an ever changing discharge rate.

Water Discharge – To regulate the flow out of the water scale a physical gate stop will be also used to allow the discharge valve to only open partially and regulate discharge.

When doing this the batch control should be set up to hold an open signal on the valve throughout discharge, flow regulation should be turned off in batch control. The gate stop will have to be manually adjusted to speed up or slow down the water discharge so the water ends properly in the discharge sequence, one to two seconds after the aggregate.

An improper discharge sequence can cause many different issues mainly: build up in drum or long mix time to achieve uniform material. If you are experiencing problems with these issues observe how the materials are entering the drum, these problems usually can be resolved with an adjustment to the discharge sequence.

REPLACING A 5 YARD PLANT WITH A 12 YARD CONCRETE BATCH PLANT INSIDE OF A BARN.

P&L Concrete in Northern California has been operating with a 5 yard Concrete Batch Plant for over 25 years.  As their business has grown, plant production become limited with a 5 yard plant.  In addition the plant was wearing thin from so many years of use.  DHE Inc. was hired to upgrade the old 5 yard plant with a new 12 Yard CON-E-CO Concrete Batch Plant with Command/Alkon automatic batch controls.  Applying new plant technology and automation controls, increased the end product quality control for P&L Concrete.

This would of been a typical project had it not been for the new plant to remain inside of the old concrete batch plant steel shed. The original plant was removed by the customer and the new plant was installed with the assistance by DHE Inc.  A new plant concrete foundation was installed tying the new pad to the existing building pad.  In addition 2 material feed conveyors were added with 10 yard loader hoppers to increase material capacity.  The 3 belts automatically start & stop based on the plant aggregate high bin indicator.  The larger volume aggregate weigh batcher allows P&L to meet the growing demand of specialty mix designs for new residential and housing construction.  A new Mixer Truck dust collector or vacuum system was also added to reduce the amount of time drivers needed to clean the trucks prior to leaving for the construction job site.  By cutting the batch cycle time in half, P&L should also see a reduction in their electrical and fuel bill.

 

New ASTM Standard Supports Recycling Fresh Concrete, Boosts Sustainable Construction

New ASTM Standard Supports Recycling Fresh Concrete, Boosts Sustainable Construction
Source: ASTM International Jan 13, 2017
A new ASTM International standard will help manufacturing plants better recycle returned fresh concrete, supporting the growth in sustainable construction practices. The new standard (C1798, Specification for Returned Fresh Concrete for Use in a New Batch of Ready-Mixed Concrete), developed by ASTM’s committee on concrete (C09), covers process, verification, and record-keeping procedures for such recycling.
“Quite simply, this standard recognizes unused concrete in a fresh state as a potential ingredient for a new concrete batch,” says ASTM member Rich Szecsy, president, Texas Aggregates and Concrete Association. “In other words, recycled fresh concrete can be treated as a raw-material component just like water, aggregates, and cement.”
According to Szecsy, prior to this, manufacturers had some options for re-purposing or recycling fresh concrete but such material was most often disposed of in a landfill. Owners and end users will benefit from the new standard, since it will help lower the environmental impacts of construction.
“Because of this new standard, the industry can participate in a more sustainable construction practice in which millions of cubic yards of concrete can now be recycled in a way that is safe for end users and provides a more conscious approach to environmental stewardship,” says Szecsy.
To purchase standards, visit www.astm.org and search by the standard designation, or contact ASTM Customer Relations (tel (877) 909-ASTM; sales@astm.org).

WHAT TO CHECK FOR IF YOUR PLANT IS “LOOSING” CEMENT.

Call DHE Inc. Equipment 1.800.434.3462

Call DHE Inc. Equipment 1.800.434.3462

At some point most Concrete Producers will have a inventory problem of not being able to balance the amount of cement delivered Vs. the Automatic Batch Controller inventory.  The problem can be a few tons to several truck loads over a short time period.

FIRST STEP – Confirm the Automatic Batch Controller is not capturing a lighter or heavier weight then the actual batch weight. Settle time of 3-4 seconds is common for most plants.

To check this:
Start a batch in automatic mode.  When the feed light on the manual panel turns off, press the HOLD button on the panel and watch the actual scale weight (not the feed amount) for about 10 seconds.  The scale should settle after about 3 seconds without any change in weight.  Compare the scale weight to the “Feed Weight” displayed on the screen.  If the number continues to fluctuate then try the following;

1.  Check the calibration of the scale with a certified scale company.  Inspect the scale system, including levers, load cells, bearing points and hoppers. Correct any  damaged parts or altered factory adjusted settings and re-calibrate the scale.
2.  Perform a scale build-up with certified test weights.  Each build up increment should be no more than 20% of full scale capacity. At each scale build up point, add a test weight equivalent to 1 grad to a scale corner.  Record the added weight before checking the 1 grad weight at the next corner.  Any required adjustments can be completed with a summing box.  A scale build-up confirmation will confirm the accuracy of the scale in a full range of batch sizes.
3. Confirm the plant foundation is level and not settling.  A batch plant scale must be level in order to be accurate.  Scales can be “unloading” on one corner with a false average into the actual amount.
4.  Make sure the Bag House cartridge or bags are clean.  Plugged bags will pressurize the silo pushing cement past a 3 psi butterfly valve seal.  Also confirm the “cleaning sequence” time for the bag house is adequate for the amount of cement being offloaded.
5.  Last but not least, confirm the bulk truck driver is actual offloading the complete load of cement.  It is difficult to confirm a full load has been offloaded with out running the truck back across a set of truck scales.  It is rare but it does happen that drivers leave the plant site with some cement still inside the bulk truck.

HOW TO REDUCE THE TIME IT TAKES TO FILL A CEMENT SILO.

Cement silo’s can come in many different sizes but are typically filled by a 4″ or 5″ fill pipe.  Some high production concrete batch plants can have multiple cement fill pipes feeding the same silo.  The cement is transferred by a pneumatic blower, and depending on the blower size will determine the amount of cement that will be transferred per minute.  Although you might have the largest blower available, the transfer speed will remain slow if the dust collector is not sized to handle the C.F.M.  If the collector is to small, then the air cannot move efficiently into the silo and thus will slow down the transfer speed.  A good reference is the following chart;

Fill Pipe C.F.M.
850 CFM – Truck mounted blower
1,250 CFM – 60 H.P. blower
1,800 CFM – 75 H.P. blower

You can download the Cement Silo Collector specs from the manufacture to confirm the proper sizing of the collector to confirm the CFM.

Under sizing the silo collector can lead to the collector or cement silo roof being blown off.  Cement silo’s are typically designed to 3 PSI, and if the pop-off valve is not properly functioning, the silo can become over pressured and damage your equipment.
IMG_1300

 

 

NEW NOBLE VERTICAL GUPPY (5 Loads of Cement)

DHE Inc. now provides Vertical Cement Guppy’s or Pigs.  Compared to typical horizontal guppy’s, vertical guppy’s can be easily automated and simultaneously loaded from a pneumatic bulk truck while feeding a batch plant silo.  The guppy’s hold approximately 5 loads of cement (128 tons) and can be used for cement, fly-ash or slag storage. The unique NOBLE design includes seismic design legs for most West Coast applications. The base plate foot print is approximately 12ft x 12ft allowing for greater placement opportunity in a existing Concrete Batch Plant operations. The vertical guppy’s include a portable transportation system and can be easily relocated between concrete plants as needed. For pricing on guppy and optional equipment as well as a layout drawing please visit http://dhenoble.com/concrete-equipment/cement-silo/

NOBLE 1000MV Vertical Guppy

NOBLE 1000MV Vertical Guppy in Travel Position.

STATE OF CALIFORNIA BOARD OF EQUALIZATION PARTIAL EXEMPTION CERTIFICATE FOR MANUFACTURING, RESEARCH AND DEVELOPMENT EQUIPMENT

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6377.1. Manufacturing and Research & Development Equipment. (a) Except as provided in subdivision (e), on or after July 1, 2014, and before July 1, 2022, there are exempted from the taxes imposed by this part the gross receipts from the sale of, and the storage, use, or other consumption in this state of, any of the following:

(1) Qualified tangible personal property purchased for use by a qualified person to be used primarily in any stage of the manufacturing, processing, refining, fabricating, or recycling of tangible personal property, beginning at the point any raw materials are received by the qualified person and introduced into the process and ending at the point at which the manufacturing, processing, refining, fabricating, or recycling has altered tangible personal property to its completed form, including packaging, if required.

(2) Qualified tangible personal property purchased for use by a qualified person to be used primarily in research and development.

(3) Qualified tangible personal property purchased for use by a qualified person to be used primarily to maintain, repair, measure, or test any qualified tangible personal property described in paragraph (1) or (2).

(4) Qualified tangible personal property purchased for use by a contractor purchasing that property for use in the performance of a construction contract for the qualified person, that will use that property as an integral part of the manufacturing, processing, refining, fabricating, or recycling process, or as a research or storage facility for use in connection with those processes.

(b) For purposes of this section:

(1) “Fabricating” means to make, build, create, produce, or assemble components or tangible personal property to work in a new or different manner.

(2) “Manufacturing” means the activity of converting or conditioning tangible personal property by changing the form, composition, quality, or character of the property for ultimate sale at retail or use in the manufacturing of a product to be ultimately sold at retail. Manufacturing includes any improvements to tangible personal property that result in a greater service life or greater functionality than that of the original property.

(3) “Primarily” means 50 percent or more of the time.

(4) “Process” means the period beginning at the point at which any raw materials are received by the qualified person and introduced into the manufacturing, processing, refining, fabricating, or recycling activity of the qualified person and ending at the point at which the manufacturing, processing, refining, fabricating, or recycling activity of the qualified person has altered tangible personal property to its completed form, including packaging, if required. Raw materials shall be considered to have been introduced into the process when the raw materials are stored on the same premises where the qualified person’s manufacturing, processing, refining, fabricating, or recycling activity is conducted. Raw materials that are stored on premises other than where the qualified person’s manufacturing, processing, refining, fabricating, or recycling activity is conducted shall not be considered to have been introduced into the manufacturing, processing, refining, fabricating, or recycling process.

(5) “Processing” means the physical application of the materials and labor necessary to modify or change the characteristics of tangible personal property.

(6) (A) “Qualified person” means a person that is primarily engaged in those lines of business described in Codes 3111 to 3399, inclusive, 541711, or 541712 of the North American Industry Classification System (NAICS) published by the United States Office of Management and Budget (OMB), 2012 edition.

(B) Notwithstanding subparagraph (A), “qualified person” shall not include either of the following:

(i) An apportioning trade or business that is required to apportion its business income pursuant to subdivision (b) of Section 25128.

(ii) A trade or business conducted wholly within this state that would be required to apportion its business income pursuant to subdivision (b) of Section 25128 if it were subject to apportionment pursuant to Section 25101.

(7) (A) “Qualified tangible personal property” includes, but is not limited to, all of the following:

(i) Machinery and equipment, including component parts and contrivances such as belts, shafts, moving parts, and operating structures.

(ii) Equipment or devices used or required to operate, control, regulate, or maintain the machinery, including, but not limited to, computers, data-processing equipment, and computer software, together with all repair and replacement parts with a useful life of one or more years therefor, whether purchased separately or in conjunction with a complete machine and regardless of whether the machine or component parts are assembled by the qualified person or another party.

(iii) Tangible personal property used in pollution control that meets standards established by this state or any local or regional governmental agency within this state.

(iv) Special purpose buildings and foundations used as an integral part of the manufacturing, processing, refining, fabricating, or recycling process, or that constitute a research or storage facility used during those processes. Buildings used solely for warehousing purposes after completion of those processes are not included.

(B) “Qualified tangible personal property” shall not include any of the following:

(i) Consumables with a useful life of less than one year.

(ii) Furniture, inventory, and equipment used in the extraction process, or equipment used to store finished products that have completed the manufacturing, processing, refining, fabricating, or recycling process.

(iii) Tangible personal property used primarily in administration, general management, or marketing.

(8) “Refining” means the process of converting a natural resource to an intermediate or finished product.

(9) “Research and development” means those activities that are described in Section 174 of the Internal Revenue Code or in any regulations thereunder.

(10) “Useful life” for tangible personal property that is treated as having a useful life of one or more years for state income or franchise tax purposes shall be deemed to have a useful life of one or more years for purposes of this section. “Useful life” for tangible personal property that is treated as having a useful life of less than one year for state income or franchise tax purposes shall be deemed to have a useful life of less than one year for purposes of this section.

(c) An exemption shall not be allowed under this section unless the purchaser furnishes the retailer with an exemption certificate, completed in accordance with any instructions or regulations as the board may prescribe, and the retailer retains the exemption certificate in its records and furnishes it to the board upon request.

(d) (1) Notwithstanding the Bradley-Burns Uniform Local Sales and Use Tax Law (Part 1.5 (commencing with Section 7200)) and the Transactions and Use Tax Law (Part 1.6 (commencing with Section 7251)), the exemption established by this section shall not apply with respect to any tax levied by a county, city, or district pursuant to, or in accordance with, either of those laws.

(2) Notwithstanding subdivision (a), the exemption established by this section shall not apply with respect to any tax levied pursuant to Section 6051.2, 6051.5, 6201.2, or 6201.5, pursuant to Section 35 of Article XIII of the California Constitution, or any tax levied pursuant to Section 6051 or 6201 that is deposited in the State Treasury to the credit of the Local Revenue Fund 2011 pursuant to Section 6051.15 or 6201.15.

(e) (1) The exemption provided by this section shall not apply to either of the following:

(A) Any tangible personal property purchased during any calendar year that exceeds two hundred million dollars ($200,000,000) of purchases of qualified tangible personal property for which an exemption is claimed by a qualified person under this section. For purposes of this subparagraph, in the case of a qualified person that is required to be included in a combined report under Section 25101 or authorized to be included in a combined report under Section 25101.15, the aggregate of all purchases of qualified personal property for which an exemption is claimed pursuant to this section by all persons that are required or authorized to be included in a combined report shall not exceed two hundred million dollars ($200,000,000) in any calendar year.

(B) The sale or storage, use, or other consumption of property that, within one year from the date of purchase, is removed from California, converted from an exempt use under subdivision (a) to some other use not qualifying for exemption, or used in a manner not qualifying for exemption.

(2) If a purchaser certifies in writing to the seller that the tangible personal property purchased without payment of the tax will be used in a manner entitling the seller to regard the gross receipts from the sale as exempt from the sales tax, and the purchase exceeds the two-hundred-million-dollar ($200,000,000) limitation described in subparagraph (A) of paragraph (1), or within one year from the date of purchase, the purchaser removes that property from California, converts that property for use in a manner not qualifying for the exemption, or uses that property in a manner not qualifying for the exemption, the purchaser shall be liable for payment of sales tax, with applicable interest, as if the purchaser were a retailer making a retail sale of the tangible personal property at the time the tangible personal property is so purchased, removed, converted, or used, and the cost of the tangible personal property to the purchaser shall be deemed the gross receipts from that retail sale.

(f) This section shall apply to leases of qualified tangible personal property classified as “continuing sales” and “continuing purchases” in accordance with Sections 6006.1 and 6010.1. The exemption established by this section shall apply to the rentals payable pursuant to the lease, provided the lessee is a qualified person and the tangible personal property is used in an activity described in subdivision (a).

(g) (1) Upon the effective date of this section, the Department of Finance shall estimate the total dollar amount of exemptions that will be taken for each calendar year, or any portion thereof, for which this section provides an exemption.

(2) No later than each March 1 next following a calendar year for which this section provides an exemption, the board shall provide to the Joint Legislative Budget Committee a report of the total dollar amount of exemptions taken under this section for the immediately preceding calendar year. The report shall compare the total dollar amount of exemptions taken under this section for that calendar year with the department’s estimate for that same calendar year. If that total dollar amount taken is less than the estimate for that calendar year, the report shall identify options for increasing exemptions taken so as to meet estimated amounts.

(h) This section is repealed on January 1, 2023

http://www.boe.ca.gov/sutax/manufacturing_exemptions.htm

CALTRANS ALLOWS THE RE-USE OF RETURN PLASTIC CONCRETE INTO FRESH CONCRETE FOR STATE PROJECTS.

Through the Materials & QA Subtask Group of the Concrete Task Group of the Rock Products Committee (RPC), Caltrans and Industry partnered to create a specification that would allow the use of recycled concrete for certain applications.  Section 90-7 includes specifications for incorporating returned plastic concrete (RPC) into concrete.  RPC must be used only where the specifications allow its use. Do not use RPC in pavement or structural concrete.

Background:
RPC “provides leadership and commitment to develop and improve Caltrans material specifications, test methods, and construction procedures used in the construction of transportation facilities that improve mobility across California, working with the Industry and the Federal Highway Administration.” http://www.dot.ca.gov/hq/esc/Translab/OSM/rpc_concrete_task_group/index.htm
* Between 2-­8% of all concrete produced in California is returned to the batch plant.
* CalEPA’s Climate Action Team estimates that this corresponds to 2,200,000 lb of CO2 excess per year.
* At the request of the RPC Materials & QA STG, Climate Earth provided an in depth analysis on the potential carbon footprint reduction that would be realized if Caltrans were to pursue the use of recycled plastic concrete.

Precedence Considered:
Other transportation agencies have adopted the use of recycled aggregates for certain applications.
The Greenbook Standard Specifications were taken into consideration during the specification development.
California Public Resources Code and the US Environmental Protection Agency’s CISTIC protocol were also referenced for the development of the specifications.

Specifications:
Contractors are now allowed to use returned plastic concrete for certain applications provided that certain criteria are met.
Some of the criteria that must now be met include the following:
The weighmaster certificate must be submitted along with:
* Quantity of returned plastic concrete.
* Time, type, brand and dosage of the hydration stabilizing admixture (HSA).
* Copy of the original weighmaster certificate of the returned plastic concrete.
* Batch plant must have an endorsement complying with the Department’s MPQP.

Other Requirements:
Concrete may contain a maximum of 15 percent returned plastic concrete.
Returned plastic concrete must not exceed 100° F at any time.
Must be proportioned within 4 hours after original batching if HSA is not used.
If HSA is used, HSA must be added within 4 hours of original batching and returned plastic concrete must be proportioned within 4 hours after adding HSA.

Benefits:
Study found that 15% recycling returned plastic concrete would result in a 15.3% reduction in carbon footprint (in kgCO2e/cyd) and a 16.2% reduction in embodied energy for 1 CYD concrete mix.
Study located at: http://www.dot.ca.gov/hq/esc/Translab/OSM/rpc_concrete_task_group/documents/Environmental_Impacts_of_Recycled_Plastic_Concrete.pdf
* Reduced waste materials sent to landfills.
* Conservation of natural resources such as water, aggregate and cement.
* Decreased transportation impacts associated with shipping waste material and replacement material.
* Decreased overall project costs.

Applications:
Cement slurry
Curb, gutter and sidewalks.

Caltrans Projects:
2015 Caltrans projects: 07-3X7114, 05-1C0904, 03-0F4004, 05-1F5704, 03-1F4004

2016 Caltrans projects: 10-0T8104, 05-330784, 07-300604, 03-1F9904, 05-330784

As Reported by: Charley Rea of CalCIMA www.calcima.org

CALIFORNIA HIGH SPEED RAIL CONCRETE BATCH PLANT

DHE Inc. Concrete Equipment provided a CON-E-CO AllPro 12CM concrete batch plant for the first phase of the new California High Speed rail project.

CON-E-CO AllPro 12CM

CON-E-CO AllPro 12CM

IMG_8306

AllPro 12CM Aggregate Module

The plant will supply concrete for the numerous over-passes and bridges as the rail is placed in Fresno and Madera county’s.  The plant is configured to charge both Concrete Mixer Trucks and End-Dump transfers for delivery of concrete to the project sites.  The CON-E-CO AllPro 12CM is modular built Central Mix Concrete Batch Plant based around the aggregate and cement core module.  The overhead aggregate bin, cement silo’s and water weigh batcher bolt onto the core section of the plant.  The mixer legs bolt into the front of the plant reducing the seismic design loads.  The AllPro12CM flexible configuration allowed the producer to layout the central mix plant and drive over grizzly in a area 14′-0 X 150′-0″.  The plant is owned and operated by Outback Materials, and expands their current Ready-mixed concrete market area to the west of Fresno. By incorporating the CON-E-CO 12 yard tilt mixer, Outback can provide increase quality control and production for the High Speed Rail concrete mixes.

5 WAYS CENTRAL MIX CONTRIBUTES TO HIGHER PROFIT

1 Quality Concrete Every Load

Central Mix Plant

Central Mix Plant

In this age of multiple additives, highly sophisticated specifications and tremendous liability, the industry still predominantly relies on the mixer driver to manufacture the finished product. In contrast, a central mix concrete plant allows the batch plant operator to batch, mix and check, with a mixer ampere gauge, the product being manufactured.

2 Higher Compressive and Flexural Strength

A transit mixer is designed for multiple purposes: auger the mix into the mixing section of the drum, mix the ingredients to specifications, transport the load on streets, highways, and job sites without spillage, and auger mix out of the drum into the chutes for placement. Because of the multiple functions of a transit mixer, the manufacturer has to compromise on the design of its individual components. The stationary tilt mixer is designed for one purpose only; to mix concrete. It does this one job extremely well.

3 Faster Loading and Turnaround of Trucks

A dry batch plant loads a transit mixer in 3 to 3-1/2 minutes. A central mix plant loads a transit mixer in 1-1/2 to 2 minutes. The traditional school of thought is that a dry batch plant can regularly handle 20 mixer trucks in the time a central mix plant turns around 30.

4 Less Transit Mixer Maintenance

A transit mixer that seldom leaves the 1 to 2 rotations per minute drum speed for agitation requires considerably less maintenance than a mixer turning 16 or 20 rpm for 5 minute durations 4 to 5 times each working day. A truck whose drum is turning at the slower agitation uses less fuel and has less wear on the drum mechanism.

5 Cleaner Trucks-Cleaner Environment

With central mix plants there is almost total containment of dust and a significant reduction of water runoff. Ready Mix trucks stay cleaner. This dramatically reduces the use of cleaners and acids, which are expensive and dangerous. Cleaner trucks present a better image to the public. Further, the rear drum section of a transit mixer being loaded wet remains much cleaner than a mixer being loaded with dry materials. Annual jackhammer labor to clean out drums is dramatically reduced with central mix.