For more info on the answers you are looking for have a look at the article titled: Effect of Gypsum Stabilization on Mechanical Properties of Compressed Earth Blocks
The flexural and compressive strength of the mud block were improved by the presence of gypsum.
2. Too low or too high mixing water result mud block with low compressive strength.
3. There is a direct proportional relation between the amounts of gypsum as stabilizer and compressive strength, but this amount would be governed with the economical factor.
The quality of gypsum is one important factor that will affect strength of Mud Block. You said "waste Gypsum" is used to stabilize Mud block. Here , proportion of waste gypsum is not mentioned. Quantity of gypsum and in which form ( powder or dissolved in water or fragments ) gypsum is added, also matters. To achieve high compressive strength of mud block, determination of maximum density at optimum moisture content of Mud is essential. Method of mixing of mud and at what stage Gypsum is added into the mix, is also important factor that will affect workability of the mix .Ductility of block in this case means ability of material to deform without excessive cracks. To achieve good strength and ductility, one can use suitable fibres.
Dear Kamran Iqbal . See the following useful RG link: Article Influence of Waste Gypsum on the Microstructural Characteris...
Kindly see also the following very good RG link: Article Lime activated flyash-phosphogypsum blend as a low-cost alte...
Also check please the following good link: https://digibug.ugr.es/bitstream/handle/10481/70580/Bel-Anzu-_et_al-2021-Archaeological_and_Anthropological_Sciences.pdf?sequence=1&isAllowed=y