The number of types of wire welding that circulate on the market and the development of welding technology, especially related to current welding, create a lack of information related to the quality of welding results for several types of materials. This can cause the strength of the welding connection to not be maximized. Therefore, this study aims to optimize the use of three types of wire welding and three current welding on the strength of the welding connection in two types of material testing using the response surface methodology. Box-Behnken, coupled with the RSM and the desirability function, was used to optimize the strength of the welding connection of the wire types (RD-46, LB-52, and RB-26), and current welding (100, 130, and 160 A) against two types of material testing (IWF-150 and ASTM-A517-G70). The strength of the welding connection observed in response included the tensile strength, Charpy impact-absorbed energy, hardness values in the welding metal and the hardness values in the main metal. Optimization of the strength of the welding connection in this study recommends the application of wire types RB-26, current welding of 100 A, and ASTM-A517-G70 material testing with the highest desirability value of 71.6%. Optimization of tensile strength, Charpy impact-absorbed energy, hardness values in welding metal, and hardness values in main metal by applying this parameter are 575.64 MPa, 110.69 J, 216.75 (HV10) and 126.6 (HV10), respectively. The results proved that an appropriate welding connection strength could be achieved using wire welding types and current welding in material testing.

Nowadays, the significant demand for concrete has become a problem in concrete using aggregate from waste. Using standard concrete is recommended to reduce the breakdown of buildings. Unfortunately, standard materials used to produce previous concrete are not entirely environmentally friendly. As a result, many researchers have committed their awareness to identifying eco-friendlier substitutions in manufacturing concrete substitution aggregate from waste. In this respect, this paper discussed the proposed efficient procedure to indicate the compressive strength from mixed proportioning cockle shell, glass powder, and epoxy resin as concrete under hot water curing conditions (60°C, 4 hr) using response surface methodology. The experimental design used in this research uses a response surface methodology. There are three aggregates to be investigated, namely cockle shell powder, glass powder and epoxy resin under hot water curing condition (60°C, 4 hr). Under hot water curing conditions, this research discovered that adding 4.0% cockle shell powder and 10.0 % glass powder increased the compressive strength to 104.68 MPa. On the other hand, 4.0% cockle shell powder, 10.0% glass powder and 2% epoxy resin under hot water curing conditions improved the compressive strength to 115.70 MPa. It was therefore inferred that the use of both cockle shell powder and glass powder to produce cleaner and compressive strength concrete is applicable, both mechanically and environmentally.

Nowadays, with increased demand for aggregates for concrete and an awareness of the need of protecting natural resources, experts are becoming increasingly interested in waste material as a building material substitute. However, the compressive strength is influenced by the composition of concrete. In this study, the compressive strength of concrete under substitution using waste from cockle shells and glass was investigated using Response Surface Methodology (RSM). Central Composite Design (CCD) based on RSM was used to assess the influence of epoxy resin, cockle shells powder, and glass powder on compressive strength responses. RSM developed first-order and second-order mathematical models with findings from experimental design. Analysis of variance was used to determine the correctness of CCD's mathematical models. Desirability analysis was then employed to optimize epoxy resin, cockle shells powder, and glass powder yielding maximum compressive strength. The RSM analysis revealed that the empirical results fit well into linear and quadratic models of concrete compressive strength. The mixing components will produce cement with compressive strength in each formulation of 54.71 MPa (4.88% epoxy resin and 4.0% cockle shells powder), 47.82 MPa (6.85% epoxy resin and 8.0% glass powder), 147.0 MPa, (4% cockle shells powder and 8% glass powder), and 56.08 MPa (4.4% epoxy resin, 4.0% cockle shells powder, and 8.0% glass powder). The results confirmed that a reasonable compressive strength of concrete could be achieved using epoxy resin, cockle shells powder, and glass powder.