diff --git a/src/thermophysicalModels/specie/transport/const/constTransport.H b/src/thermophysicalModels/specie/transport/const/constTransport.H
index c1e3120000c6a541fec680e8da07e744fddd1276..ec6bb6573732b1890023bfed41b23a0a06e6ba19 100644
--- a/src/thermophysicalModels/specie/transport/const/constTransport.H
+++ b/src/thermophysicalModels/specie/transport/const/constTransport.H
@@ -161,10 +161,13 @@ public:
 
     // Member operators
 
-        inline constTransport& operator=
-        (
-            const constTransport&
-        );
+        inline constTransport& operator=(const constTransport&);
+
+        inline void operator+=(const constTransport&);
+
+        inline void operator-=(const constTransport&);
+
+        inline void operator*=(const scalar);
 
 
     // Friend operators
diff --git a/src/thermophysicalModels/specie/transport/const/constTransportI.H b/src/thermophysicalModels/specie/transport/const/constTransportI.H
index e58aa79efa95828f2525b1349de8360ae48fcb0b..1581de144ef9d8324272aeb5d1fddb7985d7cff2 100644
--- a/src/thermophysicalModels/specie/transport/const/constTransportI.H
+++ b/src/thermophysicalModels/specie/transport/const/constTransportI.H
@@ -143,6 +143,52 @@ inline Foam::constTransport<Thermo>& Foam::constTransport<Thermo>::operator=
 }
 
 
+template<class Thermo>
+inline void Foam::constTransport<Thermo>::operator+=
+(
+    const constTransport<Thermo>& st
+)
+{
+    scalar molr1 = this->nMoles();
+
+    Thermo::operator+=(st);
+
+    molr1 /= this->nMoles();
+    scalar molr2 = st.nMoles()/this->nMoles();
+
+    mu_ = molr1*mu_ + molr2*st.mu_;
+    rPr_ = molr1*rPr_ + molr2*st.rPr_;
+}
+
+
+template<class Thermo>
+inline void Foam::constTransport<Thermo>::operator-=
+(
+    const constTransport<Thermo>& st
+)
+{
+    scalar molr1 = this->nMoles();
+
+    Thermo::operator-=(st);
+
+    molr1 /= this->nMoles();
+    scalar molr2 = st.nMoles()/this->nMoles();
+
+    mu_ = molr1*mu_ - molr2*st.mu_;
+    rPr_ = molr1*rPr_ - molr2*st.rPr_;
+}
+
+
+template<class Thermo>
+inline void Foam::constTransport<Thermo>::operator*=
+(
+    const scalar s
+)
+{
+    Thermo::operator*=(s);
+}
+
+
 // * * * * * * * * * * * * * * * Friend Operators  * * * * * * * * * * * * * //
 
 template<class Thermo>
diff --git a/src/thermophysicalModels/specie/transport/sutherland/sutherlandTransport.H b/src/thermophysicalModels/specie/transport/sutherland/sutherlandTransport.H
index f8ac0722dd6178efda9d62653d2c218c1b68c1fd..55f5f27e5a27bc0222b83bd2d5f2386f874e1ec0 100644
--- a/src/thermophysicalModels/specie/transport/sutherland/sutherlandTransport.H
+++ b/src/thermophysicalModels/specie/transport/sutherland/sutherlandTransport.H
@@ -180,10 +180,13 @@ public:
 
     // Member operators
 
-        inline sutherlandTransport& operator=
-        (
-            const sutherlandTransport&
-        );
+        inline sutherlandTransport& operator=(const sutherlandTransport&);
+
+        inline void operator+=(const sutherlandTransport&);
+
+        inline void operator-=(const sutherlandTransport&);
+
+        inline void operator*=(const scalar);
 
 
     // Friend operators
diff --git a/src/thermophysicalModels/specie/transport/sutherland/sutherlandTransportI.H b/src/thermophysicalModels/specie/transport/sutherland/sutherlandTransportI.H
index ac79418ed34435d4ca2c16857ef03316a5c8d897..56fcaf6e8f080530b2f4d96be0914360daf92bfe 100644
--- a/src/thermophysicalModels/specie/transport/sutherland/sutherlandTransportI.H
+++ b/src/thermophysicalModels/specie/transport/sutherland/sutherlandTransportI.H
@@ -180,6 +180,52 @@ Foam::sutherlandTransport<Thermo>::operator=
 }
 
 
+template<class Thermo>
+inline void Foam::sutherlandTransport<Thermo>::operator+=
+(
+    const sutherlandTransport<Thermo>& st
+)
+{
+    scalar molr1 = this->nMoles();
+
+    Thermo::operator+=(st);
+
+    molr1 /= this->nMoles();
+    scalar molr2 = st.nMoles()/this->nMoles();
+
+    As_ = molr1*As_ + molr2*st.As_;
+    Ts_ = molr1*Ts_ + molr2*st.Ts_;
+}
+
+
+template<class Thermo>
+inline void Foam::sutherlandTransport<Thermo>::operator-=
+(
+    const sutherlandTransport<Thermo>& st
+)
+{
+    scalar molr1 = this->nMoles();
+
+    Thermo::operator-=(st);
+
+    molr1 /= this->nMoles();
+    scalar molr2 = st.nMoles()/this->nMoles();
+
+    As_ = molr1*As_ - molr2*st.As_;
+    Ts_ = molr1*Ts_ - molr2*st.Ts_;
+}
+
+
+template<class Thermo>
+inline void Foam::sutherlandTransport<Thermo>::operator*=
+(
+    const scalar s
+)
+{
+    Thermo::operator*=(s);
+}
+
+
 // * * * * * * * * * * * * * * * Friend Operators  * * * * * * * * * * * * * //
 
 template<class Thermo>