|
If it's specified and you must provide it per spec.'s per a contract definitely get a design mix from a reputable source, like a licensed professional engineer at concrete plant or firm that does this kind of work. ASTM reference standards may be helpful here, but is a little more engineering related than hands on. I would not place any material until you have a design mix that has either been used before or has been created by someone who knows what they are doing, sounds like this is a contract job, and aside from what we do at home, you do not want to place questionable material and be liable for it. It's one thing to use your own mix at home for misc. projects, but providing a defective mix on a job can be easily detected and linked to the contractor, thus making them a liable party. Once you have a design mix, you can convert the increments to be able to mix by hand, make sure you maintain the amounts per the mix, when you change the water to cementitious material ratio ( portland cement ) water/cement ratio you can easily change the compressive strength of the material, so if you make the mix, paying close attention to the amounts of the materials you use, and it's hot out and the mix stiffens, you decide to add water to loosen it up, you will weaken the compressive strength, so mix what you can use immediately do not add water then start over when you need more, don't mix more than you can use and let it sit too long either. Sounds like a masonry project, be it concrete masonry units (C.M.U./block, brick etc. also remember these can soak up the water in the mix quickly) so if your mix is too dry, hot out, it might also have an effect on the mix by absorbing the water too rapidly from the mortar mix, you may want the block/brick to have some moisture content and not be bone dry. You don't want the hydration process ( curing ) accelerated too much is the point I am making here, if it shrinks too much, too quickly you may not get a good bond to the substrate, be it block, brick, stone or whatever you are using. Also, you would be wise to go to a local materials testing company, and get mortar cube forms, get enough to test the mix before you do the job, 4 cubes should be taken per so much material mixed, or each batch made. They can break these 4 times at 7, 14, 21 and 28 days, you might be able to predict what the ultimate strength will be at 28 days from an earlier break. 28 days is what it takes to cure 99.9 percent. Then while doing the job, it would also be wise to take mortar cube forms and fill them with samples representing each batch you make, for each section of the work you do to conclusively prove that 5000 p.s.i. was the strength and is documented 100% for the job as being compliant to the documents. I know it sounds ridiculous, but trust me if you are ever called on questionable material, following a procedure like this will carry a lot of weight in a court of law, illustrating that the contractor was competent in performing the work and providing the specified materials per contract documents. Make a sketch of the work or a copy of the area from a contract drawing and record where each days work ends, matching the mortar cubes taken that day. You want to tag the cubes somehow and identify where it was used in the work. Don't mind me, was and still am a construction professional in the idustry for many years, you can apply the above suggestions as you wish, maybe it's just a small job and you don't need to be so stringent, however if you are liable for providing a specified material, or it is a structural component, trust me, this is sound procedure. Those mortar cubes and test reports are well worth doing trust me, and make sure to follow ASTM procedure for filling the test cube forms, might have to rod them ( pack ) a little. Concrete test cylinders are filled in 3rd's and rodded 25 times at each level, then neatly screeded off the top for example. If you are grouting a wall, use care and do it in lifts, just like concrete, lot of pressure, best to do so much at a time and or use some bracing, have seen blowouts, makes a mess and you get to to the work over again. Anyways, hope this is of some help.
|
