support structure will be fully described in connection with fig1 13 and 14 a horizontally oriented top pipe or air transport pipe 10 extends between first and second end brackets 12 and 14 two l shaped blades coupled back to back form a tee shaped front screed blade 16 an l shaped rear screed blade 18 is also coupled to the first and second end brackets 12 and 14 in the preferred embodiment the screed is fabricated in 5 foot and 71 2 foot lengths any combination of which can be joined together to form a screed having a length reasonably close to the desired length fig4 illustrates the manner in which a splice plate and a plurality of securing means such as nuts and bolts may be used to couple together abutting ends of each screed blade section fig3 illustrates the structure utilized to coupled adjacent sections of air transfer pipe 10 to form a single structural element air transfer pipe 10 forms an air tight conduit which supplied a source of air under pressure along the entire length of the screed the air transfer pipe junction illustrated in fig3 comprises a threaded coupling unit 20 having left hand threads on one end and right hand threads on the other end which is rotatably adjusted to provide the desired angle of incidence between adjacent screed section this adjustment provides the desired contour on the upper surface of the concrete being.