▁c ement ing ▁comp ounds ▁in ▁the ▁concrete : ▁calci um ▁sil icate ▁hyd rate ▁( C - S - H ) ▁and ▁calci um ▁hydro x ide ▁( Ca ( OH ) 2 ). ▁This ▁reaction ▁can ▁be ▁noted ▁in ▁three ▁ways , ▁as ▁follows : ▁▁ ▁Standard ▁notation :    Ca 3 Si O 5 ▁+ ▁H 2 O ▁-> ▁( Ca O ) ▁* ▁( Si O 2 ) ▁* ▁( H 2 O ) ▁+ ▁Ca ( OH ) 2 ▁▁ ▁Bal anced :    2 Ca 3 Si O 5 ▁+ ▁ 7 H 2 O ▁-> ▁ 3 Ca O ▁* ▁ 2 Si O 2 ▁* ▁ 4 H 2 O ▁ ▁+ ▁▁ 3 Ca ( OH ) 2 ▁▁ ▁C ement ▁chem ist ▁notation ▁( the ▁hy phen ation ▁denotes ▁the ▁variable ▁sto ichi ometry ):    C 3 S    +    H      →      C - S - H    +    CH ▁ ▁The ▁underlying ▁hyd r ation ▁reaction ▁forms ▁two ▁products : ▁▁ ▁Cal ci um ▁sil icate ▁hyd rate ▁( C - S - H ), ▁which ▁gives ▁concrete ▁its ▁strength ▁and ▁dimensional ▁stability . ▁The ▁cry stal ▁structure ▁of ▁C - S - H ▁in ▁c ement ▁paste ▁has ▁not ▁been ▁fully ▁resolved ▁yet ▁and ▁there ▁is ▁still ▁on going ▁debate ▁over ▁its ▁nan ost ruct ure . ▁ ▁Cal ci um ▁hydro x ide ▁( Ca ( OH ) 2 ), ▁which ▁in ▁concrete