If necessary can we make concrete with sea sand and even seawater?

I find an answer !!! amazing one!Yes we can!Both "sea water and sea sand " can be used for plain concrete " no steel reinforcement"we can wash the sea sand then use it but it will be more expensive than the others.Also we can get benefits from this CONCLUSIONS of a research was done by japanese scientist after tests for20 years:

From the test results and discussions shown above. The authors are confident to safely use seawater as mixing water. The countermeasures of using sea water as mixing water are as follows;1) Use BFS cement or other blended cement instead of OPC2) Use corrosion inhibitor.3) Reinforced with stainless steel or corrosion resistant reinforcement.Nowadays, the design method is changing to “Performance based design”, so if theperformance in the expected life can be proved over the required level, the concrete mixed with seawater can be used.Of course, there are some problems which need more research.

You can follow the this link

 http://www.cipremier.com/e107_files/downloads/Papers/100/36/.pdf

yes we can! there are tested products with seasand and seawater, long term strength, quality tests. It has the test results from TNO in the Netherlands, well established. I have a sample with me.

Yes, is the answer, on the Sea sand, as long the sand is taken from the beach, and not the dunes, the sand is fine, as the wind buffets the dunes, deposits salt taken from the seawater, whatever salt content on it, is basically nil, as e get wash, as you move, and load the sand, the on the part as to make concrete, whit Seawater, is also fine as long as your concrete is not reinforced, and if it need be, is getting some corrosion protection, epoxy, or like stainless steel bars, and not galvanize, the salt content depending of the place, is no clear cut on this but the normal average, is below4%

Not at all. The salt in the sea sand or the seawater will defeat the purpose of construction.