My only experience was an industrial application involving a leak in a tunnel. The “grout“ wasn’t a mortar type grout, but rather a chemical grout. When injected it looked like, and seemed to have the viscosity of honey, after combining with water and curing it looked like yellowish foam.
I was impressed with the results, and figure something similar would work for a basement.
maybe something like
this , if jibsey wants to experiment a little before incurring a big expense. Looks like would be better for a crack along the wall rather than at the floor/wall junction though, and if the basement is hollow block rather than solid concrete it may not work well either. But the basement HAS been dry for 40 years so if this was me I’d try some minimal remediation before going in big.
@jibsey it’s rained a lot lately, but it’s also rained a lot several times in the last 40 years and no problems till now. What changed? Upstream local development/paving causing more run off? (If so see the town engineer) Long shot, do you have a clogged roof downspout/gutter that is causing water to overtop the gutter where it should’t?