Topics related to variations in the addition of materials to concrete, the use of recycled materials, and the improvement of the mechanical properties and durability of concrete are very popular areas of research in civil engineering.

A possible original title, not used before, could be:

"Impact of the addition of innovative materials on the microstructure and mechanical behaviour of concrete: an experimental study"

This title can bring a novel approach by mentioning "innovative materials" and highlights a detailed analysis of the microstructure, which adds a distinctive and less explored element compared to more common studies focusing only on the general properties of concrete.

Here are some suggestions for a civil engineering undergraduate thesis title on variations in adding materials to concrete:

1. Investigating the Impact of Supplementary Materials on the Mechanical Properties of Concrete

2. Effect of Recycled Aggregates on the Performance and Durability of Concrete Mixtures

3. Optimizing Concrete Strength with the Addition of Fly Ash and Silica Fume

4. Exploring the Role of Waste Materials in Enhancing Concrete Sustainability

5. Evaluating the Use of Natural Fibers for Improved Concrete Reinforcement

6. Influence of Nano-Silica Additives on the Microstructural Behavior of Concrete

7. Comparative Study on the Effects of Industrial Byproducts in Concrete Mix Design

These titles focus on various innovative materials and their influence on concrete performance, providing a strong foundation for research.

I agree with Carlos Francisco Lucena Gonzalez.

The question by Christhoper Panggabean itself is incomplete. Which properties of concrete is required to be modified by adding certain materials like additives - fly ash, silica fume ,..... etc, or admixtures like plasticizers, water reducing chemicals, etc... or fibres like steel, polypropylene, natural fibres ,........ etc. , is not clearly mentioned.

First decide problem statement in area of concrete technology , check probable solutions and literature then think possibility of innovation or further research work based on the resources available in your lab and institute.

For undergraduate level, in concrete technology area, normally small experimental works are preferred/ accepted as project so that students can strengthen their theory background in Concrete technology or they can further work in the areas in Concrete technology which is little bit beyond the syllabus of theory and practical, at graduation level.

Hope that you will able to redefine area of work.