Can we increase the concrete compressive strength with adding cement to the water /cement ratio without using concrete admixtures?

Better to reduce the water rather than increasing the cement, because;

1- Adding cement will cost more than reducing the water

2- By reducing the water you will get lower w/c ratio which leads to higher compressive strength.

3- We use water in the mix because of (hydration, absorption and workability):

Hydration (cement + water): you need only about25-28 % of the added water to complete the hydration process.

Absorption: of the fine and coarse aggregates (if you don't wash)

Workability: which gives the mix the mobility and the ability to be places

Water is essential for the hydration, but you can compensate for the other2 (absorption and workability) as for the absorption you can wash the aggregates and for the workability you can use admixtures.

4- Increasing the cement will be costly than using admixtures.

So in my opinion, reduce the water, don't increase the cement (cost wise) and use admixtures to compensate the workability

tip: don't forget the coarse aggregate plays a great role in increasing the compressive strength

To increasing the compressive strength of concrete, we must increase cement and decrease water quantity. For example, M15 grade of concrete when we use50 kg of cement,480 kg aggregates and32 liters water we get15N/sq.mm compressive strength after28 days by15 cm. cube test. But for M20 grade of concrete when we use50 kg of cement,360 kg aggregates and30 liters water we get20N/sq.mm compressive strength after28 days by15 cm. cube test. But remember here, volume of M20 concrete is less then volume of M15 concrete. So if we increase the compressive strength of concrete,then we have to increase the quantity of cement and water. Thank you.

It has limited effect to increase compressive strength , because you have many parameters in mix design like aggregate , sand and control slump, but admixtures for increase strength are more effective .

it is posible, but will not help a lot and will give you a greater chance for cracks.Its better to change the type of cement or ask for a specific strength and leave it up to the plant expert and structural engineer

oh thank you so much Bedadyuti,actually i have seen an increasing compressive strength withing4 months when the cemnet ratio has been a little more than mix design,i know that aggregates also have a very special effect on the strength as well as water has but in hot weather concreting the most important thing is micro silis and other super plastisizers in order to make the concrete more movable and better to implace without adding to the water and i have seen very perfect results this way,by the way thanks for the attention and reply

cement is just binding material, it dosen't take part in increasing compressive strength by adding more cement (of same compressive stress) in  concrete. but if we use cement of high strength then the compressive value will increase.

If we plot a curve taking strength on Y-axis and Cement content on X-axis keeping water cement ratio constant, other ingredients fixed, the strength gradually increases and after that it will decrease. All concrete codes of different countries fixed the upper limit of cement that can be put (Used) in a cubic meter of concrete. To get higher strength adding cement is never a criteria. Shrinkage, Thermal cracking, etc deteriorate  the concrete early as we increase cement content beyond certain limit. To over come these ill effects, we add admixtures (mineral : Micro Silica,  Flyash, RHA, GGBS, Metakayoline, etc. and Chemical type) to concrete in making workable and required strength concrete.

yes

I have reviewed all the details as narrated by experts and I really appreciate to all particularly Mr.  Mohamed Hassan   he described in details.

I just want to add my point of view with my little experience as follows:

If you make concrete without admixture it will be ok for small construction works (without standards requirements like small house etc.) but if you come to the qualitative and quantitative works than you cannot ignore the importance admixtures (depends upon the types of chemicals.)

Here In your case I would advise you to use Type F (High Range Water Reducing) or Type G (High Range Water Reducing and Retarding)

Using of such admixtures can decrease the requirement of Water demand from12 to40% depending upon doses on the same quantity of cement.

Eventually you will get high strength without increasing cement content.

Using of admixture makes the concrete more workable, pump able and place able and ultimately it will cheaper than only cement based concrete.

Otherwise, your concrete will get effected by cracks and other chemical alteration will take place depends upon type and finesses of cement etc.

Recommendation:

Use green concrete it will more cheaper than any other concrete.

cement in not the only thing provides the concrete the compressive strenght. aggregates are also responsible for strenght. so to increase the compressive strenght we have to think about all the contents of concrete. But if we talk about new generation concrete , there is no requirement of cement. yes, im talking about geopolymer concrete. EXAMPLE: HySSIL i.e high strenght, structural, insulative,  light weight concrete. It provides5 times more compressive strenght than other general cement concrete but its weight is almost half of the general cement concrete. Thank you.