a method of reinforcing cement / concrete mixtures with alkali - intolerant reinforcements and / or aggregate , such as uncoated , common glass filament , plastic filament , fabric and roving made therefrom by reducing the ph of the mixture while in its plastic state , and / or after it has set and cured , to about 7 . with a neutral ph , the alkali - intolerant reinforcements need not be coated to protect them from degradation . in the absence of alkalinity , the reinforcement and / or aggregate material bonds with the cement mixture to form a relatively stronger mixture , which can be shaped as desired , made part of permanently poured structures , cement boards and many other small and large products . by selecting appropriate and , if desired , different materials for the reinforcements and / or aggregate , the strength , flexibility , etc . characteristics of the product can be readily changed to adapt the product to the intended use . the ph is reduced by migrating such materials as co 2 and / or co and o 3 into the cement after it has cured and , if desirable , also during curing . the co 2 and / or co and o 3 for the chemical reactions to reduce the ph are most suitably obtained from flue gases of independent combustion processes which would otherwise be discharged as atmospheric pollutants .