20th May, 2014

Université Amar Telidji Laghouat

Question

Asked 12th Mar, 2014

Is there any method or technique by which we can estimate the composition of cement mortar and concrete in terms of cement and sand content with unknown mix design?

** A case as an example**

I have a concrete/mortar wall and do not know how much cement and sand was used to manufacture that wall. Can we estimate how much cement and sand was used to prepare that wall (either the percentage or cement:sand ratio or in other units)?

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you can estimate the strength of concrete in situ by using a sclerometer for example. knowing this resistance, we can estimate the composition of concrete using the Dreux Gorris abacus for example.

We can note that with the age of the concrete, other parameters may occur which are related to the environment. Therefore, the determined values are only an estimated composition of concrete.

2 Recommendations

Deleted profile

Also adding on the matter; the only acid digestion analysis is proven to give false results. An article by Mr. Norman Weiss, John Walsh and Jennifer Shark. is published in last two years in APT international Bulletin that takes on this problem.

Depending on the time period that the wall was build , the test might be as simple as just a chemical analysis. For historic materials you need a petrographic analysis to determine what types of materials you have in mortar and after that proceed with chemical analysis.

7 Recommendations

I think it can be done. Remember that the ratio of sand to cement and the amount of water added to the mix (and perhaps any other admixes) determine the strength of the mortar. The strength of the mortar of course may be measured in terms of its resistance to external force of deformation (or any other physical or chemical means). So, if you take a nail and try to hammer it into the mortar wall, your success at driving the nail into the wall is a function of the strength of the mortar. In other words, if the wall is very strong, your nail may not even scratch its surface but bend. On the other hand, if your wall is weak, say one portion of cement to 20 portions of sand, the nail will go straight through. This is perhaps a primitive approach which leads to relative assessment (or guess) that the mortar mix is 1:1, or 1:3 or 1:20 etc. If however you need precise numbers, you might consult some engineering companies and see if a digital method is available, I would be surprised if you fail to find something. The precision is what I cannot guarantee, but the tool you acquire for the investigation will come with its specifications.

2 Recommendations

I think chemical analysis of a small part of the mortar or concrete will give you the answer.

2 Recommendations

You could core a small diameter core hole in the wall and determine the

initial specific gravity, and volume, and the final specific gravity and volume

after removing the cement by using an acid ( Hydrochloric, or sulfuric ).

This will only work if the sand is a silica based sand , and not a shell, or

limestone based sand, which would also dissolve.

The methodologies would require oven drying at the initial, and final

conditions to see what has changed after removal of the materials dissolved,

and following washing and drying of the remaining sand and aggregates.

The cementaceous materials removed from a mortar will have included

both the portland cement, and the lime. From a concrete, the removed

materials will include portland cement, and any pozzolan that is calcium

based.

If you collect calcium residue from using sulfuric acid, it should

dry into a white paste and form calcium sulfate ( gypsum ), with a change in

volume since sulfuric acid was an addition to the volume of the core.

3 Recommendations

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There are at least 2 different ASTM test methods for concrete and mortar.

The ASTM C1084 is used mostly in testing industry to determine the cement content in concrete.

The ASTM C1324 is used to determine the compositional ratios in mortar.

Keep in mind that the historic mortars and concrete have different types of materials and don't behave the same as contemporary portland cements based materials. The methods described in ASTM tests methods mentioned above are written mostly for products that are being produced today.

3 Recommendations

Deleted profile

Also adding on the matter; the only acid digestion analysis is proven to give false results. An article by Mr. Norman Weiss, John Walsh and Jennifer Shark. is published in last two years in APT international Bulletin that takes on this problem.

Depending on the time period that the wall was build , the test might be as simple as just a chemical analysis. For historic materials you need a petrographic analysis to determine what types of materials you have in mortar and after that proceed with chemical analysis.

7 Recommendations

Quantity of cement mortar is required for rate analysis of brickwork and plaster or estimation of masonry work for a building or structure. Cement mortar is used in various proportions, i.e. 1:1, 1:2, 1:3, 1:4, 1:6, 1:8 etc.

Calculation of quantity of cement mortar in brickwork and plaster:

For the calculation of cement mortar, let us assume that we use 1m3 of cement mortar. Procedure for calculation is:

1. Calculate the dry volume of materials required for 1m3 cement mortar. Considering voids in sands, we assume that materials consists of 60% voids. That is, for 1m3 of wet cement mortar, 1.6m3 of materials are required.

2. Now we calculate the volume of materials used in cement mortar based on its proportions.

Let’s say, the proportion of cement and sand in mortar is 1:X, where X is the volume of sand required.

Then, the volume of sand required for 1:X proportion of 1m3 cement mortar will be

3. Volume of cement will be calculated as:

Since the volume of 1 bag of cement is 0.0347 m3, so the number of bag of cement will be calculated as:

Example:

For cement mortar of 1:6, the quantity calculated will be as below:

Sand quantity:

Quantity of cement (in bags):

Volume of cement =

There number of bags required = = 6.58 bags.

3 Recommendations

When I first put forward my contribution to this matter I said I would be surprised if you failed to get the right tool for the task. Happily, Magdalena Malaj has put the finger on the product. Well done Mag. However, there is a word of caution here. The responses provided point to diversified procedures. They leave a wide margin for variability in the results obtained. For example, I work on measurements of tension in vibrating bodies. Some methods operate on the mass, others on the rate of vibration, and yet others on chemical etc characteristics of the body, thus producing different measurements for the same thing. It might be helpful to try different methods and then examine agreements among results obtained.

1 Recommendation

if you know the activity concentrations of NORM in your raw materials (cement and sand) and in your mortar, it would be easy to determine the mortar composition. Please have a look at my paper:

These were just my two cents.

Best regards,

Kosta (Konstantin) Kovler

Every method has its limitation in solving your problem. If the binder in the concrete/mortar consisted of only portland cement, it will be relatively simple. By optical microscopy and image analysis, the aggregate content is easy to be determined. Then using SEM to observe the microstructure of the cement paste phase, the unhydrated cement content and capillary porosity can be determined by image processing. If the age of the material is known (2 years, 3years, 10 years?), the degree of hydration can be estimated, then cement content in the concrete/mortar can also be obtained.

2 Recommendations

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