We make use of ALMA continuum observations of $15$ luminous Lyman-break galaxies at $z$$\sim$$7$$-$$8$ to probe their dust-obscured star-formation. These observations are sensitive enough to probe to obscured SFRs of $20$ $M\odot$$/$$yr$ ($3\sigma$). Six of the targeted galaxies show significant ($\ge$$3$$\sigma$) dust continuum detections, more than doubling the number of known dust-detected galaxies at $z$$>$$6.5$. Their IR luminosities range from $2.7$$\times$$1011$ $L\odot$ to $1.1$$\times$$1012$ $L\odot$, equivalent to obscured SFRs of $20$ to $105$ $M\odot$$/$$yr$. We use our results to quantify the correlation of the infrared excess IRX on the UV-continuum slope $\beta UV$ and stellar mass. Our results are most consistent with an SMC attenuation curve for intrinsic $UV$-slopes $\beta UV,intr$ of $-2.63$ and most consistent with an attenuation curve in-between SMC and Calzetti for $\beta UV,intr$ slopes of $-2.23$, assuming a dust temperature $Td$ of $50$ K. Our fiducial IRX-stellar mass results at $z$$\sim$$7$$-$$8$ are consistent with marginal evolution from $z$$\sim$$0$. We then show how both results depend on $Td$. For our six dust-detected sources, we estimate their dust masses and find that they are consistent with dust production from SNe if the dust destruction is low ($90$%). Finally we determine the contribution of dust-obscured star formation to the star formation rate density for $UV$ luminous ($-$$21.5$ mag: $\gtrsim$$1.7$$LUV\ast$) $z$$\sim$$7$$-$$8$ galaxies, finding that the total SFR density at $z$$\sim$$7$ and $z$$\sim$$8$ from bright galaxies is $0.18-0.10+0.08$ dex and $0.20-0.09+0.05$ dex higher, respectively, i.e. $\sim$$13$ of the star formation in $\gtrsim$$1.7$$LUV\ast$ galaxies at $z$$\sim$$7$$-$$8$ is obscured by dust.