String concat in LR

Hi,

i have a functionality to update home address?

so i am getting actual adrees to {Address1} parameter and would like to append some string "loadtest" to the actual address and save the home address?

Here is the steps i tried:
char S1[10]="loadtest" ,S2
strcpy(S2,{Address1})
strcat(S2, S1)

"Name=ADDRESSES_V_ADDRESS1$0", "Value={S2}", ENDITEM,
but it is not working any suggestions?

Thanks