Bruce Strickland
National Marketing Manager
Sika Corporation
(800) 933–SIKA
Bruce has over 30 years experience in the admixture industry. In his career, he has held positions in product development, marketing, sales and sales management. Bruce has also spent time in...more»»
Polycarboxylate Admixtures
Posted by John on October 30, 2006
What is the amount of mixing time required for the new generation of HRWR to produce thier full effect on the slump of the mix? Where did you get that shirt.
Dear John,
I do not think there is a significant difference in the amount of time needed to mix conventional and new HRWR to achieve similar slump results. May be if the dosage of the HRWR is very low and it is added directly to the concrete and not along with the mixing water, it might take a little longer time for the HRWR to completely mix in the entire volume of the concrete and create the desired effect.
For the mixing time needed, follow the recommendations of the concrete mixer manufacturer and then use your our own judgment by observing concrete mixed for different times. Normally a ready mixed concrete mixer requires 75 revolutions for initial mixing and 30 revolutions (at mixing speed) when anything is added to a load that is already mixed.
As for the shirt, I got it from a golf course in Scottsdale, AZ. Thanks for asking.
Thanks
Concrete runoff
Posted by Joyce on October 27, 2006
Bruce,
This might seem like and unusual question…
I parked my car in a lot, under an overpass that is under construction. When I returned to the car it was covered in what I’m being told is runoff from the concrete. How do I get this off my car? I’ve taken it to the car wash, and tried scrubbing at home but it’s still stained.
Thanks for you help!
Joyce
Dear Joyce,
It seems some cement slurry from the concrete had leaked through the formwork and fallen on your car. In the construction industry, workers use stain removers which are generally based on dilute form of hydrochloric acid, to remove stains of concrete from tools and equipment. But I am not very sure if that can be used to remove stains from cars without damaging the paint of your car. If you wish, you can try by applying the stain remover on a small area, scrub with a cloth and see for yourself. You can also try a citric acid based cleaning product. These can be obtained from a construction products distributor. A small test area is still recommended. You can also try if the stains go using your laundry or dish cleaning detergent.
Otherwise, your best bet would be to ask a local auto shop if they can suggest you something for this problem or there are companies which specialize in stain removing products, you can either contact them or get their product from a local distributor.
Good luck.
tank footings
Posted by Jessica on October 23, 2006
Dear Sir, I need some product information for a proposed tank footing 14″ high by 24″ in diameter with a 18.5 kip load. This footing would be grounded on existing reinforced concrete slab, but is to help cleaning functionality. Any suggestions on products out there for this type of situation?
I suggest you contact the tank manufacturer for his recommendation. Also, a structural engineer may be needed. There are too many unknowns to suggest a solution. For example, is this a caustic solution? What is the temperature of the solution in the tanks and is corrosion resistance an issue. I don’t think I can be of much help in this situation.
concrete overlay
Posted by jeff on October 15, 2006
I would like to mix my own stampable concrete overlay. What would you recomend as far as mixtures?
It is difficult to give you exact quantities without more information. However, for an overlay I would start with a cement factor of 500 – 600 lbs per cu. Yd (depending on psi requirements). I would use a w/c of .40 - .45 and I would use a 3/8 inch top size coarse aggregate. This is only a starting point. After mixing (a trial batch is recommended) look at the results and make whatever adjustments are necessary.
I would like to give you more help but with the limited information I can only give you a starting point.
24 hour strength improvement
Posted by stephen on October 12, 2006
I have reading about the new polycarboxylate water reducers. I am making a concrete product that has to be polished within 24 hours. Normal water reducers create too many problems with finishability for my application but I understand that the EOPO water reducers can improve surface finishing.
I’m looking for improved 24 strength witout loss of workability. I have heard that additions of Calcium Nitrite along with the water reducer will significantly increase strength.
Which product would you reccomend for my application.
thanks
Stephan,
Water reducers either increase the workability of the concrete or allow you to reduce the amount of water needed to be added to concrete to achieve workability.
Accelerating admixtures are chemical accelerators which when added to concrete increase the rate of hydration of the cement, making the concrete set faster and give high early strength.
Calcium Nitrate is a type of an accelerating admixture, so it would help you to achieve high early strengths.
Water reducers allow you to reduce the amount of mixing water. This marginally increases the early age strength (within 24 hours) but significantly increases later age strengths. Whereas accelerators only help to increase the early age strength and do not increase the later age strengths.
In your case, I would suggest you to do the following. Try making small concrete samples by adding only an accelerator at a medium and highest allowable dosage as recommended by the supplier and see the finish of the concrete after 24 hours. If you feel the concrete is still too weak to be finished at 24 hours then in the next concrete sample add a water reducer to reduce the mixing water. Keep the accelerator at the same dosage. This should allow you faster set times.
Make sure the water reducer is not based on lignosulphonates, as lignosulphonates delay the set time of concrete. Polycarboxylates (PC’s) are the most powerful water reducers, but there are several versions of PC’s available. Ask the admixture supplier for a PC which enables high water reduction and faster set time.
