CONS 2012

Site Visit Report

SPANCAST CARIBBEAN LIMITED

ContentsExecutive Summary.....................................................................................................................................2

Introduction.................................................................................................................................................2

Safety is First Priority...................................................................................................................................3

What is Pre-stressed Concrete?..................................................................................................................3

Spancast and Pre-stressed concrete............................................................................................................4

Contec Flooring System...........................................................................................................................4

Hollowcore Flooring System....................................................................................................................4

Super Piles...............................................................................................................................................5

AASHTO Bridge........................................................................................................................................5

Many Other Applications…..........................................................................................................................6

Water Tanks............................................................................................................................................6

Stadium Seats..........................................................................................................................................6

Pan Mixer................................................................................................................................................6

Manufacturing of Concrete blocks..........................................................................................................7

Interlocking Concrete Blocks...................................................................................................................7

V blocks...................................................................................................................................................8

Waste Concrete.......................................................................................................................................8

Appendix...................................................................................................................................................10

REFEERENCES............................................................................................................................................17

Executive Summary Spancast Caribbean Limited was incorporated in August 1990. The Trinidad branch is located in

O’Meara Industrial Estate, Arima. Spancast Caribbean Limited is involved in many building types that it is

not always easy to categorize their work. This report was done in order to highlight the various aspects

of the company which were introduced to us visiting. Upon initial research and later first hand

observation, it was noted that the company dealt with new technology in terms of concrete based

products such as Pre-stressed concrete and Concrete recycling as well an understanding on time being a

crucial factor in the construction industry.

IntroductionThe site visit to Spancast Caribbean Limited was deemed necessary because of the nature of the

work being done there in accordance with the education of the Civil Engineering Students of UTT, San

Fernando. The company introduces or maintains what is deemed “New Technology” in the Concrete

field. They strive for an improvement on the construction methods and materials of a contractor and by

extent, the employer. Where locals know a certain approach in construction, this company has explored

new as well as foreign methods and have had positive results in testing these methods.

Safety is First PriorityBefore the tour began, a safety session was conducted. This highlighted various aspects the

company worked under such as the OSHA act. It was explained that the company lay under 9 acres of

land and the ground was very rigid. There were 3 main hazards that were stressed on. The first and

foremost was that there was a risk of the tensile steel bursting. Even though it had never happened

before and the area around the steel is made very secure, there was still a risk and as such, a high level

of precaution was put in this area of the company. The second was that because they worked with

heavy machinery, there was a risk of being run over by a forklift. This, however would only occur outside

the designated areas and members were warned not to stray from the group. The third was that, the

company made concrete blocks and in order to do so, a few tonnes of hydraulic pressure was used. This

could pose a hazard if anyone were to get in the way of the hydraulics or even fall into a pressing area.

After the safety brief was concluded, the site visit began.

What is Pre-stressed Concrete?The company’s main product was pre-stressed concrete. Pre-stressed concrete is an

architectural and structural material of great strength. Pre-stressed architectural and structural concrete

units are given predetermined, engineered stresses which counteract the stresses that occur when a

unit is subjected to loads. This is accomplished by combining two quality materials: high tensile steel and

high strength concrete.

Concrete is cast around steel tendons—cables or bars—while they are under tension. The

concrete bonds to the tendons as it cures, and when the tension is released it is transferred to the

concrete as compression by static friction. Tension subsequently imposed on the concrete is transferred

directly to the tendons. Pre-tensioning requires strong, stable anchoring points between which the

tendons are to be stretched. Thus, it is prefabricated and transported to the construction site. This is

why the pre-stressed concrete is also faster – it takes a day or two to cure depending on the volume and

a few hours to install rather than traditional ways.

Spancast and Pre-stressed concreteSpancast Caribbean Limited makes its mark on the industry with Pre-Stressed concrete with its

various forms and applications.

Contec Flooring System. This used a form of the Pre-stressed concrete as well as a form of interlocking concrete. The

design was based off wooden floors. It consisted of a Floor Joist which was a T shaped beam of pre

stressed concrete supported at both ends and laying across an open area with the front view looking like

an upside down T. the blocks were specially manufactured for this. They were thinner with “wings” on

both ends along the height of the block. The floor joists were placed close enough to allow the “wings”

to rest on them and the blocks lined the beam along the entire length. A large spaced wire mesh was

placed on top of this and tied to the supporting steel rods. Concrete then cover the entire area. This is

meant to replace the system where a decking/floor is cast and has to be supported by stilts until it dries

completely. Where this old system would take a week or more, this takes a day or 2 depending on the

length. It is drastically stronger as well as faster.

Hollowcore Flooring System.This is another form of pre-stressed concrete. It is typically used in commercial buildings

because of its design. The concrete is poured over pre stressed wire using a mold design that allows

tubular voids that extend the full length of the slab, usually a diameter equal to 2/3 – 3/4 of the slab.

The slab is then cut to facilitate the desired lengths. The design allows for a much lighter yet stronger

floor slab of equal thickness which would have even cost a great deal more. Factory production provides

the obvious advantages of reduced time, labor and training.

Super Piles Another useful product which Spancast produces is prefabricated Super piles .They are normally

manufactured at 12x12, 16x16 and 20x20 dimensions .These piles are formed using pile bed molds

located on Spancast’s premises. These molds are made out of high strength steel and are very long so as

to facilitate any length needed. An example of this being used is in Michael Rahael Boulevard, South

Park San Fernando. Spancast’s piles are reinforced with rebar and are often pre stressed.

AASHTO Bridge Precast pre-stressed bridge components are manufactured by Spancast Caribbean Ltd, each

bridge component is independently designed based on the requirements on the construction site. The

reason for pre stressing the concrete is to overcome concrete’s natural weakness in tension, this aids in

producing longer spans than is practical with ordinary reinforced concrete. The concrete is cast around

steel bars while under tension and when this tension is released it is transferred to the concrete as

compression by static friction the tension subsequently imposed on the concrete is transferred directly

to the tendons.

Many Other Applications…Spancast, however, doesn’t limit itself to these alone. They have many different applications of

concrete that are not necessarily pre stressed.

Water TanksThis is a new technology being researched and done by Spancast. It involves casting semicircular

molds of concrete individually and joining them on site to create a giant cylindrical shape. They are then

post tensioned by being pulled together by steel cables. They interlock each other and are supposedly

waterproof when casted together.

Stadium Seats Fresh concrete or a combination of regrind is used to produce precast stadium risers and mini

pavilions. Spancast has a wide range of designs for stadium risers and pavilions and are applicable in

many different structures .They are a manufacture at higher strength to withstand structural damages

to external forces therefore being important to the construction industry. Because it is a precast

component they are erected relatively quickly and are cost effective.

Pan Mixer3/8 and 3/4 aggregates are stockpiled to the back of the pan mixer separated by a wall. A

backhoe loader pushes the aggregates into a underground scale which weighs the individual aggregates

to a specified proportion, moisture meters which are present measures the water / aggregate ratio to

aid in computing the quantity of water needed .After weighing and moisture calculations the aggregates

are introduced to the pan mixer along with cement and water . The mixture which is produced is a

relatively dry and stiff therefore having a low water /cement ratio, to improve the workability and

change its fresh early age or hardened state. Conplast SP430 is added during the mixing stage. When

mixing is completed after several minutes the fresh concrete is emptied into a concrete hopper, it is

then transported by a rough terrain forklift to another holding hopper/ concrete bucket for the use with

the slip-former.

Manufacturing of Concrete blocksThe aggregates mainly sand or regrind to be used are stored at the back of the block making

facility which is separated by using the Mass concrete retaining walls which themselves produce. The

aggregates are then transported by using a skid steer loader, subsequently each material is weighed to

ensure proportions are adequate. The weighed material is then added to the concrete mixer which

blends all the dry material, and a small amount of water is then added. The system is not fully

automated therefore manual introduction of the cement is required at the mixing stage. It is noted that

a very stiff dry mixture is produced so that the blocks will hold its shape when it is removed from the

block mold. Once the mixing process has been completed, the fresh concrete is discharged onto a

conveyor belt underneath the mixer, and carried up and into the holding hopper of the block machine

itself. The mixing cycle is then began for the next load. In the block machine the concrete is forced

downwards into molds which consists of an outer mold box containing several liners which determines

the outer shape of the blocks an inner shape of the block cavities .The blocks are then shaped and made

due to a small degree of compaction but mainly because of heavy vibration. In this process three

concrete blocks are manufactured simultaneously. The blocks then leave the machine on pallets and are

most times inspected by the workers .The pallets are then lifted and place on racks for curing overnight.

Interlocking Concrete BlocksThis is a relatively new form of concrete blocks which has a pinnacle on one end, a grove on the

other (to fit the pinnacle) and a shallow grove on top and bottom in order to house a steel rod. This

technology is self-straitening with the ends and is reinforced by the steel rods on the top. Because there

is no need to use mortar to hold them in place and use nylon lines to straighten them, there is a drastic

increase in time as well as accuracy. It is mentioned that with these blocks, walls are erected much

faster (a wall that would have taken a day, now takes a few hours) and they are much stronger. An

example of this being used is under the TOYOTA building in South Park, San Fernando. Here, the bricks

were used, along with post tensioned decks in order to create an underground drain.

V blocks Spancast Caribbean Ltd is also in the business of producing what is known as Gravity Retaining

walls by utilizing Mass concrete in the form of large blocks. These blocks are interlocking and rely solely

on its own weight to withstand pressures from backfilling soil or just to stand up on its own acting as a

wall barrier. The density of Spancast’s concrete blocks are approximately 2300 kg /m3 and weigh an

approximate 800kg each. These blocks can be laid together by using mortar to join them or by simply

stacking them upon each other since their interlocking design caters for this, it is all dependent on the

design requirements .Regrind is normally combined with fresh concrete to manufacture these blocks

since there is no detrimental effect on the strength of the concrete mass; a higher strength may even be

produced. Reinforced steel bars are not used in the manufacturing of these blocks since little to no

tensional forces are applied to the blocks.

Waste Concrete Concrete, being a very rigid and hard material cannot be dumped as easily. The company saw a

buildup of 30 years of waste concrete. As such, Spancast has begun recycling it and using it as aggregate

in their products and the result is a much stronger block that if new material was used. This is due to the

unreacted cement grains in the crushed material being mixed with more cement and as such creating a

stronger product. A chemical reaction with massive physical properties. The waste is grounded to

different sizes for different uses and even sold to other concrete based companies as it has such positive

results and also that Spancast is the only company now that recycles waste concrete. This helps the

company save money as well as reduce the need for new material.

Appendix

FIG 1. Contec Flooring System close up

FIG 2. Contec Flooring System showing Beams, Blocks, Wire Mesh, Steel Rods and over layered concrete

FIG 3. Hollow core slabs being stacked up

FIG 4. Pile Bed Molds spanning a few hundred feet

FIG 5. Water Tanks (relatively new technology)

FIG 6. Backhoe shoveling material up to Pan Mixer

FIG 7. Mini Backhoe carrying aggregate to mixer FIG 8. V blocks stacked

FIG 9. Concrete mixer shown

FIG 10. Interlocking Blocks

FIG 11. Contec Flooring Blocks

FIG 12. Waste Concrete

FIG 13. Crusher

FIG 14. Waste Material Aggregate.

FIG 15. Manufacture of Pre Stressed Concrete

REFEERENCES

- University of Melborne, Site Visit Reports for Engineers,http://services.unimelb.edu.au/__data/assets/pdf_file/0010/471286/Site_Reports_for_Engineers_Update_051112.pdf

- Polígono Industrial de Juncaril Albolote (Granada) SPAIN, Process of production of concrete blocks, http://www.poyatos.com/concrete_blocks.asp

- Hornbostel, Caleb. Construction Materials, 2nd Edition. John Wiley and Sons, Inc., 1991