A large-scale additive manufacturing system for printing structures, the system comprising: an extrusion system comprising: a nozzle configured to receive a supply of structural material and to selectively dispense the structural material in flowable form; and a first gantry configured to move the nozzle along toolpaths defined according to a structure to be printed such that structural material may be dispensed along the toolpaths to print a series of structural layers, wherein the series of structural layers bond together to form all or a portion of the structure; characterized by a knitting system (220;300) comprising: a tow feeder (226;304) configured to feed a supply of tow material to a location proximate a current course of loops extending above an upper surface of a current structural layer or extending above a base surface in regions where no structural layer has been printed; and a hooking device configured to engage the tow material and bring it through the current course of loops to form a subsequent course of loops interwoven with the current course of loops; and a controller configured to operate the knitting system (220;300) to form additional subsequent courses of loops each interwoven with a current course of loops after each of the series of structural layers are printed, wherein the interwoven courses of loops create a reinforcement network of knitted loops embedded in the structure, and wherein the series of structural layers are tied together. a nozzle configured to receive a supply of structural material and to selectively dispense the structural material in flowable form; and a first gantry configured to move the nozzle along toolpaths defined according to a structure to be printed such that structural material may be dispensed along the toolpaths to print a series of structural layers, wherein the series of structural layers bond together to form all or a portion of the structure; characterized by a knitting system (220;300) comprising: a tow feeder (226;304) configured to feed a supply of tow material to a location proximate a current course of loops extending above an upper surface of a current structural layer or extending above a base surface in regions where no structural layer has been printed; and a hooking device configured to engage the tow material and bring it through the current course of loops to form a subsequent course of loops interwoven with the current course of loops; and a controller configured to operate the knitting system (220;300) to form additional subsequent courses of loops each interwoven with a current course of loops after each of the series of structural layers are printed, wherein the interwoven courses of loops create a reinforcement network of knitted loops embedded in the structure, and wherein the series of structural layers are tied together. a tow feeder (226;304) configured to feed a supply of tow material to a location proximate a current course of loops extending above an upper surface of a current structural layer or extending above a base surface in regions where no structural layer has been printed; and a hooking device configured to engage the tow material and bring it through the current course of loops to form a subsequent course of loops interwoven with the current course of loops; and a controller configured to operate the knitting system (220;300) to form additional subsequent courses of loops each interwoven with a current course of loops after each of the series of structural layers are printed, wherein the interwoven courses of loops create a reinforcement network of knitted loops embedded in the structure, and wherein the series of structural layers are tied together.