20 Comments to "KUIKcrete"
1 | NASHWAN HAMID YAHAY AL-EMAD
24 de March de 2009 to ● 5:27 am
Concrete
Concrete is easily and readily prepared and fabricated in all sorts of conceivable shapes and structural systems. It is used in the realms of infrastructure, habitation, work and play. Its great simplicity lies in the fact that its constituents are ubiquitous and are readily available almost anywhere in the world 1. As a result of its ubiquity, functionality and flexibility it has become by far the most popular and widely used construction material in the world 2.
The material concrete is often confused with the material cement. Cement is one of the many constituents of concrete, part of the glue that holds the other materials together. Concrete is made by mixing cement, supplementary cementitious materials, water, fine aggregate (sand), coarse aggregate (gravel or crushed stone) with or without admixtures, reinforcement, fibres or pigments.
The ingredients are proportioned and engineered to produce a concrete of a specific strength and durability, so it is ‘fit for purpose’ for the job for which it is intended. It can be produced in the form of precast products or as ready-mixed concrete, which is delivered in the familiar rotating concrete lorry.
2 | NASHWAN HAMID YAHAY AL-EMAD
24 de March de 2009 to ● 5:28 am
What is Sustainability?
The most commonly used definition was established by the World Commission on Environment and Development and defines sustainable development as:
“Development that meets the needs of the present without compromising the ability of future generations to meet their own needs”. 1
The UK Government has set four priority areas in order to focus efforts in achieving sustainable development 2. These are:
Sustainable Consumption and Production.
Climate Change and Energy.
Natural Resource Protection and Environmental Enhancement.
Sustainable Communities.
Sustainable Development is also linked with the terms ‘triple bottom line’, ‘three pillars of development’ and in commercial organisations with ‘Corporate Social Responsibility’. In all cases organisations are expected to consider the economic, environmental and ethical implications of its actions.
The built environment is fundamental to a sustainable society. The effective management of existing and new buildings can deliver significant CO2 reductions and resource efficiency while providing a level of service which maintains quality of life and economic growth.
Designers, engineers, owners, contractors and manufacturers – everyone in the construction process – can make a difference in creating a more sustainable built environment. This website is intended to demonstrate how concrete can be used to meet the highest levels of sustainable construction.
3 | NASHWAN HAMID YAHYA AL-EMAD
25 de March de 2009 to ● 11:39 am
Determination Concrete Mix Design using ACI Method
Table 10.16 (a) &10.16 (b)
Consistence slump = 80-130
Maximum size of aggregate = 20mm(3/4in)
Water content = 200 x 1 = 200 kg/m3
Entrapped air content = 2%
Table 10.8 (a)
Margin = 8MPa
Compressive Strength at 28 days = 28MPa
Water/cement ratio(by weight)
Non-air-entrained concrete = 0.57
Cement content = 200 / 0.57
= 350 kg/m3
Table 10.17
fineness modulus of sand = 2.60
Maximum size of aggregate = 20mm(3/4in)
Bulk volume of rotted coarse
Aggregate per unit volume concrete = 0.64
The weight of coarse aggregate = 0.64 x 1600
= 1024 kg/m3
Ultimate volume concrete per cubic ;
Cement = 350/(3.15 x 1000) = 0.111 m3
Water = 200/1000 = 0.2 m3
Coarse aggregate = 1024/(2.64 x 1000) = 0.388m3
Entrapped air content = 0.02 m3
Total volume concrete = 0.719 m3
the volume of fine aggregate = 1 – 0.719 = 0.281m3
so, weight of fine aggregate = 0.281 x 2.58 x 1000 = 725 kg/m3
Concrete material content per cubic.
Cement = 350 kg
Water = 200 kg
Weight of fine aggregate = 725 kg
Weight of coarse aggregate = 1024 kg
Total = 2299 kg
Adjustment Water Content at Site Construction
Assume :
Fine aggregate = 5% non air entrained
Coarse aggregate = 1% air entrained
absorb water from fine aggregate = 5 x 725 / 100
= 36.25 kg
absorb water by Coarse aggregate = 1 x 1024 / 100
= 10.24 kg
Clean non air entrained water = 36.25 kg – 10.24 kg
= 26.01 kg
water capacity = 200 – 26.01
= 174 kg
Weight fine aggregate = 725 + 36.25
= 761 kg
Weight coarse aggregate = 1024 kg
Comparison mix concrete material;
Cement : Fine aggregate : Coarse aggregate(water)
350 : 761 : 1024 (174)
1 : 2.2 : 2.9 (w/c = 0.5)
4 | NASHWAN HAMID YAHYA AL-EMAD
25 de March de 2009 to ● 11:40 am
Determination Concrete Mix Design using C&CA Method
Margin = 2.33 x 4.2 = 10 MPa
Average Compressive Strength = 60 MPa
Fig 10.12 Reference Number = 17 for 14 days.
Fig 10.15/10.16 w/c = 0.32 for degree of workability – Very Low(19.05mm)
Fig 10.13 2.6 Aggregate/cement ratio (by weight) OPC.
Fig 10.14
Comparison of the weight of cement per cubic :
Cement : Coarse aggregate : Fine aggregate : Water
1 : 75 x 2.6 / 100 : 25 x 2.6 / 100 : 0.32
1 : 1.95 : 0.65 : 0.32
Ultimate volume method : assume C = cement in kg.
C ( 0.317 + 0.252 + 0.739 + 0.32 )= 103
1.628 C = 103
C = 614.25 kg/m3
So ,
Cement = 614.25 kg/m3
Coarse aggregate = 1.95 x 614.25 = 1197.79 kg/m3
Fine aggregate = 0.65 x 614.25 = 399.26 kg/m3
Water = 0.32 x 614.25 = 196.56 kg/m3
Total intensity of concrete mix = 2407.86 kg/m3
2400 kg/m3 acceptable
5 | NASHWAN HAMID YAHYA AL-EMAD
25 de March de 2009 to ● 11:58 am
ACI Method
The American Concrete Institute (ACI) mix design method is but one of many basic concrete mix design methods available today. This section summarizes the ACI absolute volume method because it is widely accepted in the U.S. and continually updated by the ACI. Keep in mind that this summary and most methods designated as “mix design” methods are really just mixture proportioning methods. Mix design includes trial mixture proportioning (covered here) plus performance tests.
1 Slump
The choice of slump is actually a choice of mix workability. Workability can be described as a combination of several different, but related, PCC properties related to its rheology:
• Ease of mixing
• Ease of placing
• Ease of compaction
• Ease of finishing
Generally, mixes of the stiffest consistency that can still be placed adequately should be used (ACI, 2000). Typically slump is specified, but Table 5.14 shows general slump ranges for specific applications. Slump specifications are different for fixed form paving and slip form paving.
Type of Construction Slump
(mm) (inches)
Reinforced foundation walls and footings 25 – 75 1 – 3
Plain footings, caissons and substructure walls 25 – 75 1 – 3
Beams and reinforced walls 25 – 100 1 – 4
Building columns 25 – 100 1 – 4
Pavements and slabs 25 – 75 1 – 3
Mass concrete 25 – 50 1 – 2
Table 5.15: Typical State DOT Slump Specifications (data taken from ACPA, 2001)
Specifications Fixed Form Slip Form
(mm) (inches) (mm) (inches)
Typical 25 – 75 1 – 3 0 – 75 0 – 3
Extremes as low as 25
as high as 175 as low as 1
as high as 7 as low as 0
as high as 125 as low as 0
as high as 5
2 Maximum Aggregate Size
Maximum aggregate size will affect such PCC parameters as amount of cement paste, workability and strength. In general, ACI recommends that maximum aggregate size be limited to 1/3 of the slab depth and 3/4 of the minimum clear space between reinforcing bars. Aggregate larger than these dimensions may be difficult to consolidate and compact resulting in a honeycombed structure or large air pockets. Pavement PCC maximum aggregate sizes are on the order of 25 mm (1 inch) to 37.5 mm (1.5 inches) (ACPA, 2001).
Water-Cement Ratio
The water-cement ratio is a convenient measurement whose value is well correlated with PCC strength and durability. In general, lower water-cement ratios produce stronger, more durable PCC. If natural pozzolans are used in the mix (such as fly ash) then the ratio becomes a water-cementitious material ratio (cementitious material = portland cement + pozzolonic material). The ACI method bases the water-cement ratio selection on desired compressive strength and then calculates the required cement content based on the selected water-cement ratio. Table 5.17 is a general estimate of 28-day compressive strength vs. water-cement ratio (or water-cementitious ratio). Values in this table tend to be conservative (ACI, 2000). Most state DOTs tend to set a maximum water-cement ratio between 0.40 – 0.50 (based on data from ACPA, 2001).
Table 5.17: Water-Cement Ratio and Compressive Strength Relationship
(after ACI, 2000)
28-Day Compressive Strength in MPa (psi) Water-cement ratio by weight
Non-Air-Entrained Air-Entrained
41.4 (6000) 0.41 -
34.5 (5000) 0.48 0.40
27.6 (4000) 0.57 0.48
20.7 (3000) 0.68 0.59
13.8 (2000) 0.82 0.74
5 Cement Content
Cement content is determined by comparing the following two items:
• The calculated amount based on the selected mixing water content and water-cement ratio.
• The specified minimum cement content, if applicable. Most state DOTs specify minimum cement contents in the range of 300 – 360 kg/m3 (500 – 600 lbs/yd3).
An older practice used to be to specify the cement content in terms of the number of 94 lb. sacks of portland cement per cubic yard of PCC. This resulted in specifications such as a “6 sack mix” or a “5 sack mix”. While these specifications are quite logical to a small contractor or individual who buys portland cement in 94 lb. sacks, they do not have much meaning to the typical pavement contractor or batching plant who buys portland cement in bulk. As such, specifying cement content by the number of sacks should be avoided.
6 Coarse Aggregate Content
Selection of coarse aggregate content is empirically based on mixture workability. ACI recommends the percentage (by unit volume) of coarse aggregate based on nominal maximum aggregate size and fine aggregate fineness modulus. This recommendation is based on empirical relationships to produce PCC with a degree of workability suitable for usual reinforced construction (ACI, 2000). Since pavement PCC should, in general, be more stiff and less workable, ACI allows increasing their recommended values by up to about 10 percent. Table 5.18 shows ACI recommended values.
Table 5.18: Volume of Coarse Aggregate per Unit Volume of PCC
for Different Fine aggregate Fineness Moduli for Pavement PCC (after ACI, 2000)
Nominal Maximum Aggregate Size Fine Aggregate Fineness Modulus
2.40 2.60 2.80 3.00
9.5 mm (0.375 inches) 0.50 0.48 0.46 0.44
12.5 mm (0.5 inches) 0.59 0.57 0.55 0.53
19 mm (0.75 inches) 0.66 0.64 0.62 0.60
25 mm (1 inches) 0.71 0.69 0.67 0.65
37.5 mm (1.5 inches) 0.75 0.73 0.71 0.69
50 mm (2 inches) 0.78 0.76 0.74 0.72
Notes:
1. These values can be increased by up to about 10 percent for pavement applications.
2. Coarse aggregate volumes are based on oven-dry-rodded weights obtained in accordance with ASTM C 29.
Fine Aggregate Content
At this point, all other constituent volumes have been specified (water, portland cement, air and coarse aggregate). Thus, the fine aggregate volume is just the remaining volume:
Unit volume (1 m3 or yd3)
- Volume of mixing water
- Volume of air
- Volume of portland cement
- Volume of coarse aggregate
Volume of fine aggregate
8 Adjustments for Aggregate Moisture
Unlike HMA, PCC batching does not require dried aggregate. Therefore, aggr content egate moisture must be accounted for. Aggregate moisture affects the following parameters:
1. Aggregate weights. Aggregate volumes are calculated based on oven dry unit weights, but aggregate is typically batched based on actual weight. Therefore, any moisture in the aggregate will increase its weight and stockpiled aggregates almost always contain some moisture. Without correcting for this, the batched aggregate volumes will be incorrect.
2. Amount of mixing water. If the batched aggregate is anything but saturated surface dry it will absorb water (if oven dry or air dry) or give up water (if wet) to the cement paste. This causes a net change in the amount of water available in the mix and must be compensated for by adjusting the amount of mixing water added.
http://training.ce.washington.edu/WSDOT/Modules/05_mix_design/05-8_body.htm
6 | NASHWAN
29 de March de 2009 to ● 11:52 pm
High Workability Concrete
The workability of fresh concrete should be suitable for each specific application to ensure that the operations of handling, placing and compaction can be undertaken efficiently.
EN206 : BS8500 the European and UK standards for concretegives guidance on workabilitys for different uses.
The handling and placing properties of concrete mixes can be improved considerably by the use of cement replacement materials such as pulverised fuel ash or ground granulated blast-furnace slag. Further more, the use of admixtures such as water reducers and superplasticisers have beneficial effects on workability without compromising other concrete properties.
On site productivity can be greatly increased by utilising highly workable concretes. They are especially suitable in the following applications:
inaccessible locations
large flat areas
underwater applications
pumping concrete over long distances
7 | NASHWAN
29 de March de 2009 to ● 11:54 pm
Lightweight Concrete
Lightweight ConcreteLightweight concretes can either be Lightweight Aggregate concrete, Foamed concrete or Autoclaved Aerated concrete (AAC). Such lightweight concrete blocks are often used in house construction.
Lightweight Aggregate ConcreteLightweight aggregate concrete can be produced using a variety of lightweight aggregates. Lightweight aggregates originate from either:
Natural materials like volcanic pumice
The thermal treatment of natural raw materials like clay, slate or shale i.e. Leca
Manufacture from industrial by-products such as fly ash, i.e. Lytag
Processing of industrial by-products like FBA or slag
The required properties of the lightweight concrete will have a bearing on the best type of lightweight aggregate to use. If little structural requirement, but high thermal insulation properties are needed, then a light, weak aggregate can be used. This will result in relatively low strength concrete.
Lightweight aggregate concretes can however be used for structural applications, with strengths equivalent to normal weight concrete.
The benefits of using lightweight aggregate concrete include:
Reduction in dead loads making savings in foundations and reinforcement.
Improved thermal properties.
Improved fire resistance.
Savings in transporting and handling precast units on site.
Reduction in formwork and propping
8 | NASHWAN
31 de March de 2009 to ● 1:41 am
The History of Concrete and Cement
Concrete is a material used in building construction, consisting of a hard, chemically inert particulate substance, known as an aggregate (usually made from different types of sand and gravel), that is bonded together by cement and water.
The Assyrians and Babylonians used clay as the bonding substance or cement. The Egyptians used lime and gypsum cement. In 1756, British engineer, John Smeaton made the first modern concrete (hydraulic cement) by adding pebbles as a coarse aggregate and mixing powered brick into the cement. In 1824, English inventor, Joseph Aspdin invented Portland Cement, which has remained the dominant cement used in concrete production. Joseph Aspdin created the first true artificial cement by burning ground limestone and clay together. The burning process changed the chemical properties of the materials and Joseph Aspdin created a stronger cement than what using plain crushed limestone would produce.
The other major part of concrete besides the cement is the aggregate. Aggregates include sand, crushed stone, gravel, slag, ashes, burned shale, and burned clay. Fine aggregate (fine refers to the size of aggregate) is used in making concrete slabs and smooth surfaces. Coarse aggregate is used for massive structures or sections of cement.
Concrete that includes imbedded metal (usually steel) is called reinforced concrete or ferroconcrete. Reinforced concrete was invented (1849) by Joseph Monier, who received a patent in 1867. Joseph Monier was a Parisian gardener who made garden pots and tubs of concrete reinforced with an iron mesh. Reinforced concrete combines the tensile or bendable strength of metal and the compressional strength of concrete to withstand heavy loads. Joseph Monier exhibited his invention at the Paris Exposition of 1867. Besides his pots and tubs, Joseph Monier promoted reinforced concrete for use in railway ties, pipes, floors, arches, and bridges
9 | NASHWAN
31 de March de 2009 to ● 1:47 am
BATCHING CONCRETE
Batching is the process of weighing or volumetricall y measuring and introducing into a mixer the ingredients for a batch of concrete. To produce a uniform quality concrete mix, measure the ingredients accurately for each batch. Most concrete specifications require that the batching be performed by weight, rathcr than by volume, because of inaccuracies in measuring aggregate, especially damp aggregate. Water and liquid air-entraining admixtures can be measured accurate]y by either weight or volume. Batching by using weight provides greater accuracy and avoids problems created by bulking of damp sand. Volumetric batching is used for concrete mixed in a continuous mixer, and the mobile concrete mixer (crete mobile) where weighing facilities are not at hand. Specifications generally require that materials be measured in individual batches within the following percentages of accuracy: cement 1%, aggregate 2%, water 1%, and air-entraining admixtures 3%. Equipment within the plant should be capable of measuring quantities within these tolerances for the smallest to the largest batch of concrete produced. The accuracy of the batching equipment must be checked and adjusted when neccessary
10 | NASHWAN
31 de March de 2009 to ● 1:49 am
Mixing Concrete
Concrete should be mixed until it is uniform in appearance and all the ingredients are evenly distributed. Mixers should not be loaded above their rated capacities and should be operated at approximately the speeds for which they were designed. If the blades of the mixer become worn or coated with hardened concrete, the mixing action will be less efficient. Worn blades should be replaced and the hardened concrete removed periodically, preferably after each production of concrete. When a transit mixer (TM) (fig. 7-1) is used for mixing concrete, 70 to 100 revolutions of the drum at the rate of rotation designated by the manufacturer as mixing speed are usually required to produce the specified uniformity. No more than 100 revolutions at mixing speed should be used. All revolutions after 100 should be at a rate of rotation designated by the manufacturer as agitating speed. Agitating speed is usually about 2 to 6 revolutions per minute, and mixing speed is generally about 6 to 18 revolutions per minute. Mixing for long periods of time at high speeds, about 1 or more hours, can result in concrete strength loss, temperature rise, excessive loss of entrained air, and accelerated slump loss. Concrete mixed in a transit mixer should be delivered and discharged within 1 1/2 hours or before the drum has revolved 300 times after the introduction of water to cement and aggregates or the cement to the aggregates. Mixers and agitators should always be operated within the limits of the volume and speed of rotation designated by the equipment manufacturer.
http://www.tpub.com/content/engine/14080/css/14080_160.htm
11 | ashmann
31 de March de 2009 to ● 10:48 am
Discarded electronic hardware, including bits and pieces that built the information superhighway, can be recycled into an additive that makes super-strong asphalt paving material for real highways, researchers in China are reporting in a new study. They describe development of a new recycling process that can convert discarded electronic circuit boards into an asphalt “modifier.”
The material makes high-performance paving material asphalt that is cheaper, longer lasting, and more environmentally friendly than conventional asphalt, the scientists report.
In the new study, Zhenming Xu and colleagues note that millions of tons of electronic waste (e-waste) pile up each year. The printed circuit boards used in personal computers, cell phones, and other electronic gear, contain toxic metals such as lead and mercury and pose a difficult disposal problem. The boards also are difficult to recycle. Xu’s group, however, realized that the boards, which provide mechanical support and connections for transistors and other electronic components, contain glass fibers and plastic resins that could strengthen asphalt paving.
The scientists describe a new recycling method that quickly separates toxic metals from circuit boards, yielding a fine, metal-free powder. When mixed into asphalt in laboratory tests, the powder produced a stronger paving material less apt to soften at high temperatures, the researchers say.
SOURCE: http://www.sciencedaily.com
12 | ashmann
7 de April de 2009 to ● 4:45 am
Eastern Concrete Materials Announces Expansion of the U.S. Concrete Commitment to Environmentally-Friendly Production Technologies Through Licensing Agreement with iCrete.
Licensing agreement will offer advanced concrete technology for high rise structures, industrial buildings, residential complexes and public works projects in New York City and New Jersey.
New York City’s recent shift to performance-based construction standard in concrete motivates the joint marketing effort.
(HOUSTON, TEXAS) — Eastern Concrete Materials, Inc., a subsidiary of U.S. Concrete, Inc. (NASDAQ: RMIX) and iCrete, LLC, have announced a licensing agreement, whereby Eastern will offer iCrete’s advanced technology for concrete mix designs for infrastructure and major construction projects in the New York City and New Jersey markets, including high rise structures, industrial buildings, residential complexes and various agency (NYDEC, PANYNJ, NYDOT etc.) infrastructure projects.
Eastern and the entire U.S. Concrete family of companies are committed to environmentally friendly technologies that reduce potential carbon dioxide (CO2) emissions through their EF Technology product line. Utilization of the iCrete mix designs will allow Eastern to further reduce greenhouse gases while continuing to deliver superior quality products to our customers.
Juan Carlos Terroba, Chief Executive Officer of iCrete said, “Eastern and U.S. Concrete are leaders in sustainable technology in the building products industry. We are delighted to be associated with them, as they continue to expand their EF Technology product line.”
The companies will work together on major construction and infrastructure projects, where federal, state and local governments increasingly require stronger, safer, more durable and more sustainable materials with a smaller carbon footprint.
“There have been significant advancements in concrete technology over the past quarter century, but they have not been fully utilized in traditional construction projects, which are often encumbered by the current prescriptive-based construction standards,” said Michael L. Gentoso, U.S. Concrete’s Vice President – Atlantic Region. “New York City, however, is now leading the nation in shifting to these newer performance based construction standards in concrete that will allow us to deliver improved quality and durability through our high performance environmentally designed mixes.”
About U.S. Concrete
U.S. Concrete (NASDAQ: RMIX) services the construction industry in several major markets in the United States through its two business segments: ready-mixed concrete and concrete-related products; and precast concrete. The Company has 132 fixed and 12 portable ready-mixed concrete plants, eight precast concrete plants, one concrete block plant and seven producing aggregates facilities.
During 2008 (including acquired volumes), these plant facilities produced approximately 6.5 million cubic yards of ready-mixed concrete, 0.9 million eight-inch equivalent block units and 3.5 million tons of aggregates. For more information on U.S. Concrete, visit http://www.us-concrete.com.
About iCrete
iCrete is a clean-technology provider of advanced concrete production systems to the construction industry. iCrete’s mission is to elevate the construction and concrete industries to a new standard of profitability, standardization and environmental stewardship.
iCrete’s core business is licensing the iCrete System, a mix design and quality solution for concrete producers, which is transforming the way ready mixed and precast concrete is designed, produced and used worldwide. For more details, visit us at http://www.icrete.com on the Web
13 | ashmann
10 de April de 2009 to ● 4:10 pm
Alabama road contractors are upset that the state’s largest single stimulus project so far — as much as $61 million to rebuild 11 miles of the washboard surface on Interstate 59 in Etowah County — is likely go to an out-of-state company.
The contractors say the Alabama Department of Transportation is being unfair to them on the project — on which bids are to be opened Friday — because ALDOT is requiring that the resurfacing be done in concrete. And there are no contractors based in Alabama capable of handling the job, industry and state officials agree.
Billy Norrell, executive director of the Alabama Road Builders Association, said state road contractors could bring concrete equipment in from out-of-state but doubts that is feasible.
While the state’s road builders can do smaller-scale concrete projects, such as culverts and barrier walls, Norrell said, “I’m not certain if any of our folks are geared up to do this on a large scale.”
Most of Alabama’s road builders rely on asphalt as their method of paving. The last major concrete-paving project was I-459, which was built in the mid-1980s.
Asphalt contractors say money from the $787 billion federal economic stimulus bill earmarked for Alabama should be spent with Alabama companies. ALDOT says concrete is the better way to repair the interstate.
State transportation officials have violated their own engineering policies by limiting the repairs to concrete, said Mel Monk, executive director of the Alabama Asphalt Paving Association.
Monk said ALDOT’s bid restrictions could make the job significantly more expensive, require the closing of half the interstate for months while work is under way, and limit the work to out-of-state contractors.
“There are no concrete pavers in Alabama, and this I-59 work will go to an out-of-state crew,” Monk said. “The stimulus money is to create jobs for Alabamians. This won’t do it.”
He said his association asked ALDOT officials not to stipulate that the driving surface must be concrete or to at least allow an asphalt surface as an alternative on the bid.
“They said no. We were disappointed, because we knew we could do the work cheaper with asphalt,” he said. “There is no alternate on the bid; that closes the door on Alabama companies.”
The state allowed bidders on the Corridor X projects to submit proposals for either concrete or asphalt. With just one segment left to bid, the entire stretch from Birmingham to the Mississippi line has been paved with asphalt. Only two out-of-state companies submitted bids for concrete on one section; their bids were far higher than the asphalt contractors’ bids.
Monk said using asphalt on I-59 would be 22 to 23 percent cheaper.
State Transportation Director Joe McInnes said it was his decision to require a concrete driving surface on the rebuilt I-59, and said one travel lane in each direction will remain open while repairs are under way.
“The decision was made 45 to 50 years ago to construct our interstates with concrete,” he said. “We are just replacing a concrete highway with concrete.”
ALDOT made the decision to do the segment in concrete because of the long-term durability of concrete.
“We can pave with concrete, and it will have a service life of from 40 to 50 years; or we can pave with asphalt and within 10 to 15 years, it will likely need to be replaced,” McInnes said. We are making the initial investment now for a long life for this roadway.”
He noted that all previous ALDOT resurfacing job during his tenure have allowed asphalt surfacing.
McInnes said the I-59 project will include subsurfaces of asphalt. “This project also will have 81,000 tons of asphalt in it,” he said. “That’s almost $5 million worth of asphalt” likely to come from Alabama contractors.
McInnes said seven of ALDOT’s 15 sets of plans for the I-59 work were sold to Alabama contractors.
The director acknowledged that the contractor submitting the winning bid for the repairs is likely to be from out of state, but said he thinks the materials will come from Alabama.
“Alabama is the fifth-largest producer of cement. While there’s no guarantee that the contractor will use Alabama cement, I would think because of shipping and delivery costs that it will come from Alabama,” McInnes said.
But Monk said there is no guarantee that the contractor will buy Alabama cement. “It could come from Mexico,” he said.
The use of concrete to make the I-59 repairs, while new to Alabama, is not an experiment. McInnes said numerous states, including South Carolina, North Carolina, Florida and Georgia, are using concrete overlays on interstates. “Around Greenville, (S.C.), the interstate rides like a sheet of glass,” he said.
Georgia is repairing I-85 using concrete, he added.
The director said he feels concrete repairs will stand up better to increased truck traffic.
McInnes said gasoline was almost $4 a gallon when the decision was made to do the I-59 work with concrete. “Asphalt prices were very close to concrete prices then,” he said. “And that helped make the decision.”
In the long run, he said, allowing concrete paving could cultivate competition that could lower the cost of paving.
14 | ashmann
10 de April de 2009 to ● 4:33 pm
The World Bank Carbon Finance Unit convened a workshop on April 2 focused on reducing emissions from road projects. The event brought together representatives from the private sector, government officials, and staff from the Carbon Finance Unit. Following the workshop, attendees were given a tour of the Aggregate Industries’ Bladensburg asphalt plant, which produces warm mix asphalt. The plant tour was a part of the World Bank’s Transport Week Workshop on “reducing greenhouse gas (GHG) emissions from road construction projects through the use of green pavement technologies.”
Aggregate Industries, which hosted the tour, is a Rockville-based producer of aggregate and construction materials and was selected to participate in the event because of the Company’s commitment to developing and deploying sustainable products and solutions in the building materials market.
Along with organizers from the Carbon Finance Unit at the World Bank, members from the National Asphalt Pavement Association and representatives from the World Bank’s client country transport agencies, representing more than ten countries from around the world, attended the asphalt plant tour hosted by the plant manager, David Jones. During the tour, Jones explained the history, vision, products, and other significant facts about the plant to the visitors.
Aggregate Industries’ Bladensburg asphalt plant was commissioned on April 9, 2008. When the decision to go forward with the project was made in 2006, the DC market presented a unique opportunity, whereby market growth and a consolidated competitive market provided favorable conditions for an investment of this nature. This strongly competitive location and materials advantage, raw materials supplied direct from the quarry by rail, allow Aggregate Industries to capture market growth and market share from its competitors. Currently, the Bladensburg asphalt plant possesses a warm mix asphalt capability for all base and surface pavements as specified by surrounding jurisdictions and the private sector, while approval for the public sector is pending.
As a committed provider of “green” building materials, Aggregate Industries manufactures warm mix asphalt. Manufacturing warm mix asphalt consumes less energy and results in lower carbon emissions. Warm mix also uses RAP (recycled asphalt product) to produce new product.
The Company leads the way in warm mix application in several markets, including the Mid-Atlantic and Northeast regions of the country. In Massachusetts, the Company successfully introduced warm mix asphalt for a paving commission at Logan Airport, completing the first runway to use the material. Since then, the use of warm mix has been added to the specifications for runway paving in the state. Aggregate Industries has been awarded a second paving contract to begin next month. In addition, the Company also successfully introduced the product to Mass Highway for the paving of I-93.
Aggregate Industries is actively promoting the use of the product in a number of major markets, as evidenced by its plant tour for World Bank officials. The Company is committed to greenhouse gas reduction and to minimizing emissions produced by the building materials industry. Aggregate Industries is a member of the EPA’s Climate Leaders program and is the only national partner of the Cool Climate Concrete program. This program focuses on reducing emissions by providing offset payments to concrete companies that use higher percentages of recycled products, like fly ash and slag, in lieu of Portland cement in their mix designs. To learn more about Aggregate Industries and its green building products, please visit http://www.aggregate-us.com.
15 | ashmann
10 de April de 2009 to ● 4:55 pm
The punishing work of filling sandbags has been made quick and efficient by an energetic 79-year-old Manitoban who was driven ‘to improve the process’.
(ELIE, MANITOBA, Canada) — At 79 years of age, late-blooming inventor and former gravel-pit operator Guy Bergeron is likely responsible for filling more sandbags than any other person alive.
“Twelve bags every 7.5 seconds,” the Manitoban says proudly.
He’s talking about his invention, The Sandbagger, a tarantula-like machine that automates the backbreaking work of stuffing sandbags.
Over the past 19 years, his Sandbaggers have pumped out millions of bags and stopped millions of litres of floodwater from inundating towns all over North America.
Volunteers in Grand Forks, N.D., use The Sandbagger, invented by Guy Bergeron of Elie, Man. He drew the plans for the invention in 1990 while he was convalescing from open-heart surgery. ‘If you’re really moving, it can fill 5,700 bags an hour,’ Mr. Bergeron says.
Volunteers in Grand Forks, N.D., use The Sandbagger, invented by Guy Bergeron of Elie, Man. He drew the plans for the invention in 1990 while he was convalescing from open-heart surgery. ‘If you’re really moving, it can fill 5,700 bags an hour,’ Mr. Bergeron says.
The Globe and Mail
But millions of bags don’t necessarily translate to millions of dollars. Mr. Bergeron was about to retire the business this year until he got a call from North Dakota last month.
“It was Fargo,” Mr. Bergeron recalls. “They wanted one, maybe two machines. And they wanted them right away.”
With that call, the Bergerons quickly hauled two Sandbaggers to Fargo, where they played a pivotal role in helping avert a catastrophic flood last month.
“I’m not sure we could have done it without them,” says Terry Ludlum, an official who looked after sandbagging efforts in Fargo, where a second Red River crest is expected later this month. “And with this next rise coming, we’ll be cranking them up again quite soon.”
The idea for The Sandbagger first sprouted in Mr. Bergeron’s restive brain three decades ago. In the spring of 1976, the gravel-pit operator lent his hand to a sandbagging operation near Elie, 45 kilometres west of Winnipeg. The military was running a gravel conveyor belt that funnelled sand down a single stovepipe and into a bag.
“They were filling one at a time, barely faster than hand-filling,” Mr. Bergeron remembers. “I knew right then there was something that could be done to improve the process.”
To understand this inventive compulsion, one must understand Mr. Bergeron. He is a precise man who abhors inefficiency. He walks 6.4 kilometres every day. When poor weather cuts his strolls short, he paces around his basement, along a measured-out figure-eight, until he hits his 6.4-km goal. His current house, a grey rancher, took two years to build because “the builders kept getting it wrong.”
He bubbles with ideas. During a two-hour interview earlier this week, he conceived several new inventions and fashioned a long metal tool for opening locked car doors.
For 14 years, he harboured his idea for an improved sandbagging machine. In 1990, while he was convalescing from open-heart surgery, he finally found time to draft plans.
At first, his wife was worried. “After his surgery, the doctors took me into a room and warned that the drugs he would be taking could cause him to get emotional or angry,” Ria Bergeron says. “So when we get home and he tells me about this machine, I just assumed the medication had made him crazy.”
Within months, he had a working prototype that appears identical to his latest models. The whole steel mechanism looks like a massive 12-legged octopus. A conveyor belt transports sand to a rotating head four metres off the ground. Turning a full rotation every 7.5 seconds, the head funnels sand down 12 spouts, which trail off like tentacles toward someone holding an empty bag.
“If you’re really moving, it can fill 5,700 bags an hour,” Mr. Bergeron says. “In Fargo, we had them putting out 5,000 bags in the first hour alone.”
The Bergerons have sold The Sandbagger as far west as Abbotsford, B.C., and as far south as Minnesota. Winnipeg flood authorities own four and the province has several more.
They won’t say how many of the $30,000 machines they’ve sold in all. “You save one basement and it’s paid for itself,” says Mr. Bergeron, who has no engineering experience and dropped out of high school at age 14. “But I’m not a great salesman. Nobody really wants to think about buying one of these things until the water is up to their eyeballs. By then, it can be too late.”
That could change. Fargo officials have been singing The Sandbagger’s praises to an international audience. The Army Corps of Engineers has recently been in touch, as have flood experts as far away as Britain and Australia.
That interest may be too late. The restless Mr. Bergeron is already onto his next invention. “It has to do with truck tires,” he says coyly. “The application is already at the patent office.”
PATRICK WHITE
16 | ATEF MOHAMMED AHMED
11 de April de 2009 to ● 8:02 am
Firstly, I want to highly thank ashman for building this website that give us chance to share our knowledge and I vote this website as one of the most useful website in concrete. Finally I wish you (AHSMAN) a happy life and full of a great achievements.
Gravels, crushed stones and other materials which are mixed with cement and water to make concrete.
•Aggregate is the component of a composite material used to resist compressive stress. For efficient filling, aggregate should be much smaller than the finished item, but have a wide variety of sizes.
•For example, the particles of stone used to make concrete typically include both sand and gravel.
TYPES OF AGGREGATE
Aggregates are used for a variety of purposes. Each purpose requires a specific aggregate type, and specific properties of the aggregate. In general, aggregates are naturally occurring relatively inert materials formed by various geologic processes. The geologic process of formation imparts some of the properties to the aggregate that make it more or less useful.
The aggregates fall into two broad categories, based on their size distribution: Coarse Aggregates and Fine Aggregates. They may be used separately or in combination, depending on their purpose. Natural coarse aggregates are obtained by crushing stone or gravel into desired size distribution. Some coarse aggregates are obtained from recycled material such as slag or old concrete. Fine aggregates fall into two broad categories: natural and manufactured sands. The former are obtained from water-deposited sources, either fluvial or glacial. The latter are screened from the finer fraction of the rock crushing process.
The purpose to which the aggregate is produced determines both the grain size and quality requirements. The quality requirements, from the highest to lowest, are for use in: concrete, filter stone, bituminous mix, base, and sub base. There are, of course, myriad of other uses, but the above mentioned require greatest volumes
The aggregates normally used for concrete are natural deposits of sand and gravel, where available. In some localities, the deposits are hard to obtain and large rocks must be crushed to form the aggregate. Crushed aggregate usually costs more to produce and will require more cement paste because of its shape. More care must be used in handling crushed aggregate to prevent poor mixtures and improper dispersion of the sizes through the finished concrete. At times, artificial aggregates, such as blast-furnace slag or specially burned clay, are used.
FINE AGGREGATE
Fine aggregate is defined as material that will pass a No. 4 sieve and will, for the most part, be retained on a No. 200 sieve. For increased workability and for economy as reflected by use of less cement, the fine aggregate should have a rounded shape. The purpose of the fine aggregate is to fill the voids in the coarse aggregate and to act as a workability agent.
COARSE AGGREGATE
Coarse aggregate is a material that will pass the 3-inch screen and will be retained on the No. 4 sieve. As with fine aggregate, for increased workability and economy as reflected by the use of less cement, the coarse aggregate should have a rounded shape. Even though the definition seems to limit the size of coarse aggregate, other considerations must be accounted for. When properly proportioned and mixed with cement, these two groups yield an almost void less stone that is strong and durable.
In strength and durability, aggregate must be equal to or better than the hardened cement to withstand the designed loads and the effects of weathering. It can be readily seen that the coarser the aggregate, the more economical the mix. Larger pieces offer less surface area of the particles than an equivalent volume of small pieces. Use of the largest permissible maximum size of coarse aggregate permits a reduction in cement and water requirements. One restriction usually assigned to coarse aggregate is its maximum size. Larger pieces can interlock and form arches or obstructions within a concrete form. That allows the area below to become a void, or at best, to become filled with finer particles of sand and cement only.
17 | ashmann
7 de June de 2009 to ● 10:25 am
(Gaza City, Palestinian) — In the face of the ongoing Israeli ban on imports of building materials Palestinians in the Gaza Strip are looking at new building methods, and one project is using clay and rubble.
Local Palestinian NGO Mercy Association for Children began building a school for handicapped children in Gaza City on 24 May to test a recently developed method using clay blocks, salt and rubble. The source material coming mainly from the hundreds of buildings demolished during the Israeli offensive (27 December 2008 – 18 January 2009).
Fourteen construction workers on the 5,000 square metre building site in the Shujayah neighbourhood of the city haul buckets of clay for moulding into large blocks from which the structure, with its domed ceiling, will be made.
“If the school, upon completion, proves structurally sound we will move forward with other construction projects in Gaza,” said lead engineer Maher Batroukh of the Mercy Association for Children. “The school is the first building of its kind in Gaza.”
The three-storey school, occupying about 1,025 square metres, will contain no steel, cement or concrete, said Batroukh.
The US$190,000 project is being funded by the Kuwaiti charity Arab Fund for Social and Economic Development, and will take at least six months to complete, according to Mercy Association for Children project manager Muna Abu Shareh.
Watching
International organizations and UN agencies in Gaza are watching the project to assess the potential of the building technology in Gaza.
“If they succeed…, it will be relevant in terms of responding to the destruction from the war,” said Norwegian Refugee Council (NRC) architect Jonathan Dames. NRC leads the “shelter cluster”, a coalition of international organizations and UN agencies working on post-conflict shelter issues in Gaza.
“After one or two winter seasons we will be able to see how the material responds,” Dames said.
Gaza’s environment authority and the public works ministry would also be monitoring the project, amid concerns that the use of large quantities of clay could affect agriculture.
“It may be a good method in the future, but the use of clay on a large scale could harm agricultural land, already scarce in Gaza,” said Gaza environment authority engineer Al-Ghaza. “It must first be studied.”
Engineer Batroukh of Mercy Association said the school would be tested to ensure the structure was safe by placing cement blocks on the ceiling and by stress testing individual clay blocks at the Islamic University of Gaza.
Owing to space restrictions in densely populated Gaza, for a building technology to be relevant it must be able to cope with at least four-storey buildings, Dames said. He explained that several clay-only houses had been constructed, but all were single storey homes.
18 | ashmann
10 de July de 2009 to ● 9:50 am
First CarbonNeutral Development in Singapore and Asia Pacific
The “Green Concrete” that was used for Tampines Concourse comprises a number of sustainable materials, namely copper slag, recycled concrete aggregates (RCA) and ground granulated blast furnace slag (GGBS).
(SINGAPORE) — In support of the Government’s strategy for sustainable development in Singapore, City Developments Limited (CDL) as a green developer, is taking an affirmative step, setting yet another milestone for Singapore in environmental sustainability.
Today, at a ceremony officiated by Guest-of-Honour, Mr Mah Bow Tan, Minister for National Development, CDL’s newly-completed 11 Tampines Concourse was unveiled as the first CarbonNeutral® development in Singapore and Asia Pacific.
The establishment of Tampines Concourse as a CarbonNeutral® development represents a natural progression of CDL’s commitment towards building greener properties. It is a forward-looking approach towards long-term sustainability.
Mr Kwek Leng Joo, Managing Director of CDL, explained the Group’s bold move, “This voluntary initiative reaffirms our commitment to reduce our carbon footprint. For many years now, we have been consciously monitoring and taking deliberate efforts to reduce our carbon emissions as part of our Environmental, Health and Safety policy.
Carbon offsetting is relatively new in this part of the world and being the first to foray into uncharted territory, we hope to encourage more Singapore corporations to take a stronger stand in tackling climate change. In addition to Tampines Concourse, we have also embarked on neutralizing the carbon emissions of our corporate office operations. Going CarbonNeutral® is in line with CDL’s overall Corporate Social Responsibility (CSR) commitment.”
Designed and built with environmental sustainability in mind, Tampines Concourse, awarded the BCA Green Mark GoldPlus this year, is a sterling example of a green development from start to finish. Beyond sustainable design features such as an energy-efficient building envelope design and ecofriendly fittings for energy and water efficiency, concerted efforts were made to introduce innovative building materials to reduce the usage of natural resources in the construction process.
Tampines Concourse is the first building project in Singapore to be constructed with a wide range of recycled materials for its structural building components.
The “Green Concrete” that was used for Tampines Concourse comprises a number of sustainable materials, namely copper slag, recycled concrete aggregates (RCA) and ground granulated blast furnace slag (GGBS). Apart from sustainable construction materials, other prominent green features include a natural day-lighting system to leverage on natural lighting in areas such as the atrium and lift lobbies. It is also the first development in Asia Pacific to incorporate an innovative, indoor non-compressor fresh air cooling system for smart temperature and humidity control. This system uses water as a cooling agent instead of ozone-depleting chemical refrigerants to cool incoming outdoor air through a natural heat exchange process. Together, these features are expected to result in energy savings of over 620,000 kWh per year, for the 108,000 lettable square feet complex, resulting in the lowering of the building’s carbon footprint.
“Sustainable construction through the use of recycled materials is an excellent strategy for Singapore’s continuing journey of sustainable development. It serves the twin objectives of prolonging the lifespan of our Semakau Landfill and also provides an alternative to natural materials that have to be imported. CDL’s holistic approach to environmental friendliness, especially in its use of sustainable construction methods and materials, has not only made Tampines Concourse an important milestone for CDL, but also an example and benchmark for the rest of the building industry.” says Dr John Keung, Chief Executive Officer of the Building and Construction Authority.
“We are happy to note that CDL has incorporated energy saving features and technologies from the design stage for this new development. This initiative is expected to result in significant energy savings for the development, and will contribute to the national efforts to improve resource efficiency. We encourage other developers to also integrate energy efficient design in their buildings”, says Mr Andrew Tan, Chairman of the Energy Efficiency Programme Office and Chief Executive Officer of the National Environment Agency.
In turning this development CarbonNeutral®, CDL will reduce carbon emissions to “net zero” for Tampines Concourse by offsetting some 6,750 tonnes of carbon dioxide equivalent. (tCO2-e) for 2009. The amount of CO2-e to be offset through this exercise represents the total estimated CO2-e generated during the construction phase (5,243 tCO2-e) and for the first year of operations (1,507 tCO2-e). Moving forward, the building’s carbon emissions will be measured and offset on an annual basis, which is estimated to be approximately 1,500 tCO2-e per year.
The process of attaining CarbonNeutral® development status was facilitated by The CarbonNeutral Company, one of the world’s leading carbon offset and carbon management companies with a proven track record of working with 300 large organisations and 200 carbon offset projects across six continents. Underpinned by a well-recognised standard known as the Carbon Neutral Protocol, every tonne of carbon sold by The CarbonNeutral Company is guaranteed such that, any shortfall is made up for in the unlikely situation of a project failure.
Jonathan Shopley, Managing Director, The CarbonNeutral Company said, “We are privileged to be working with CDL as they extend their leadership position on sustainability by taking Tampines Concourse CarbonNeutral®. This means CDL plays its part in a solution to tackle climate change as they chart a course for profitable growth while reducing greenhouse gases (GHG) emissions to net zero.”
Shopley continues, “Businesses in Singapore now have a viable alternative to demonstrate their commitment to the environment by locating in Tampines Concourse.”
In the case of Tampines Concourse, the estimated CO2 emissions generated during the construction and annual operational phases have been measured and will be offset by the purchase of carbon credits which will fund carbon offsetting projects in Asia through The CarbonNeutral Company.
For 2009, the carbon credits CDL has purchased under this exercise will fund three projects in Asia, including one renewable energy project (Guizhou Hydro Power Project in China) and two resource conservation projects (Fujian Landfill Project and Jilin Methane Power Project in China). All three projects have been verified to the international Voluntary Carbon Standard (VCS) and are pre-Clean Development Mechanism (CDM) projects.
Without the injection of carbon finance, these projects would be unviable. Beyond generating climate benefits, these projects also bring about social benefits such as employment and training opportunities, as well as improving the quality of life for the local community. This is also in line with CDL’s commitment to CSR.
Given the continual development of new carbon offsetting projects in Asia, CDL will maintain a flexible approach evaluating its portfolio of carbon offsetting projects on an annual basis, throughout the building’s lifetime.
As the first CarbonNeutral® development in Singapore and Asia Pacific, Tampines Concourse represents the ideal office address for like-minded businesses looking to enhance their position as an environmentally conscious company and reduce their carbon footprint.
19 | ashmann
10 de July de 2009 to ● 6:26 pm
Development and Implementation of Lightweight Concrete Mixes for KDOT Bridge Applications
Part A: Development of Lightweight Concrete Mixtures
This research project used three types of lightweight aggregate to develop lightweight concrete mixtures for a bridge deck and for prestressed bridge girders.
Two of the lightweight aggregates were expanded shale obtained locally from the Buildex Company. One deposit was located in Marquette, Kansas, and the other in New Market, Missouri. The third lightweight aggregate source was expanded slate obtained from the Stalite Company in North Carolina.
Aggregate properties including absorption, gradation, and L.A. Abrasion were evaluated. Over 150 lightweight concrete mixtures were created and tested and several mix design variables such as water-to-cement ratio, cement content, and coarse-to-fine aggregate ratio were evaluated.
From these results, optimized bridge deck and optimized prestressed concrete mixtures were developed for each type of lightweight aggregate.
Special concerns for lightweight aggregate concrete are addressed. These optimized concrete mixtures were then tested for Kansas Department of Transportation (KDOT) acceptability standards for the concrete properties of compressive strength, tensile strength, modulus of elasticity, freeze-thaw resistance, permeability, alkali-silica reactivity, drying shrinkage, and autogenous shrinkage.
20 | Poppy Scott
20 de July de 2010 to ● 12:43 pm
Ceramic pots or Clay Pots are still the best garden pots.::~
