Who is primarily accountable for ensuring the concrete mix meets specifications?

The contractor is primarily accountable for ensuring that the concrete mix meets specifications because they are responsible for executing the project as per the contract requirements. This includes selecting the appropriate materials, mixture proportions, and methods that comply with the specified standards. The contractor must also implement quality control processes to verify that the materials and the processes used for mixing and placing concrete align with the project's specifications.

While other roles, such as quality control inspectors, project engineers, and operations managers, play important supportive roles in overseeing and verifying the quality and adherence to specifications, the ultimate responsibility lies with the contractor. This is established in the contractual obligations and the contractor’s duty to deliver a finished product that meets the design criteria and local codes. In essence, the contractor’s accountability encompasses both the choice of materials and the operational practices involved in producing the concrete mix.