diff --git a/armi/materials/b4c.py b/armi/materials/b4c.py
index b9d8ad65a..b8444014c 100644
--- a/armi/materials/b4c.py
+++ b/armi/materials/b4c.py
@@ -159,18 +159,23 @@ def getMassEnrichmentFromNumEnrich(naturalB10NumberFraction: float) -> float:
 
     def density(self, Tk: float = None, Tc: float = None) -> float:
         """
-        mass density
+        Return density that preserves mass when thermally expanded in 2D.
+
+        Notes
+        -----
+        - applies theoretical density of B4C to parent method
         """
-        density = material.Material.density(self, Tk, Tc)
-        theoreticalDensityFrac = self.p.theoreticalDensityFrac
-        if theoreticalDensityFrac is None:
-            theoreticalDensityFrac = 1.0
-            runLog.warning(
-                "Assumption: 100% theoretical density",
-                label="Assumption: B4C is at 100% theoretical density",
-                single=True,
-            )
-        return density * theoreticalDensityFrac  # g/cc
+        return material.Material.density(self, Tk, Tc) * self.p.theoreticalDensityFrac
+
+    def density3(self, Tk: float = None, Tc: float = None) -> float:
+        """
+        Return density that preserves mass when thermally expanded in 3D.
+
+        Notes
+        -----
+        - applies theoretical density of B4C to parent method
+        """
+        return material.Material.density3(self, Tk, Tc) * self.p.theoreticalDensityFrac
 
     def linearExpansionPercent(self, Tk: float = None, Tc: float = None) -> float:
         """Boron carbide expansion. Very preliminary"""
diff --git a/armi/reactor/tests/test_components.py b/armi/reactor/tests/test_components.py
index 5ce88a202..3fda5277f 100644
--- a/armi/reactor/tests/test_components.py
+++ b/armi/reactor/tests/test_components.py
@@ -494,28 +494,39 @@ def test_changeNumberDensities(self):
 
 
 class TestComponentExpansion(unittest.TestCase):
-    # when comparing to 3D density, the comparison is not quite correct.
-    # We need a bigger delta, this will be investigated/fixed in another PR
+    tCold = 20
     tWarm = 50
     tHot = 500
     coldOuterDiameter = 1.0
 
-    def test_ComponentMassIndependentOfInputTemp(self):
-        coldT = 20
-        circle1 = Circle("circle", "HT9", coldT, self.tHot, self.coldOuterDiameter)
-        coldT += 200
+    def test_HT9Expansion(self):
+        self.runExpansionTests(mat="HT9", isotope="FE")
+
+    def test_UZrExpansion(self):
+        self.runExpansionTests(mat="UZr", isotope="U235")
+
+    def test_B4CExpansion(self):
+        self.runExpansionTests(mat="B4C", isotope="B10")
+
+    def runExpansionTests(self, mat: str, isotope: str):
+        self.componentMassIndependentOfInputTemp(mat)
+        self.expansionConservationHotHeightDefined(mat, isotope)
+        self.expansionConservationColdHeightDefined(mat)
+
+    def componentMassIndependentOfInputTemp(self, mat: str):
+        circle1 = Circle("circle", mat, self.tCold, self.tHot, self.coldOuterDiameter)
         # pick the input dimension to get the same hot component
         hotterDim = self.coldOuterDiameter * (
-            1 + circle1.material.linearExpansionFactor(coldT, 20)
+            1 + circle1.material.linearExpansionFactor(self.tCold + 200, self.tCold)
         )
-        circle2 = Circle("circle", "HT9", coldT, self.tHot, hotterDim)
+        circle2 = Circle("circle", mat, self.tCold + 200, self.tHot, hotterDim)
         self.assertAlmostEqual(circle1.getDimension("od"), circle2.getDimension("od"))
         self.assertAlmostEqual(circle1.getArea(), circle2.getArea())
         self.assertAlmostEqual(circle1.getMassDensity(), circle2.getMassDensity())
 
-    def test_ExpansionConservationHotHeightDefined(self):
+    def expansionConservationHotHeightDefined(self, mat: str, isotope: str):
         """
-        Demonstrate tutorial for how to expand and relation ships conserved at during expansion.
+        Demonstrate tutorial for how to expand and relationships conserved at during expansion.
 
         Notes
         -----
@@ -524,13 +535,13 @@ def test_ExpansionConservationHotHeightDefined(self):
         """
         hotHeight = 1.0
 
-        circle1 = Circle("circle", "HT9", 20, self.tWarm, self.coldOuterDiameter)
-        circle2 = Circle("circle", "HT9", 20, self.tHot, self.coldOuterDiameter)
+        circle1 = Circle("circle", mat, self.tCold, self.tWarm, self.coldOuterDiameter)
+        circle2 = Circle("circle", mat, self.tCold, self.tHot, self.coldOuterDiameter)
 
         # mass density is proportional to Fe number density and derived from
         # all the number densities and atomic masses
         self.assertAlmostEqual(
-            circle1.p.numberDensities["FE"] / circle2.p.numberDensities["FE"],
+            circle1.p.numberDensities[isotope] / circle2.p.numberDensities[isotope],
             circle1.getMassDensity() / circle2.getMassDensity(),
         )
 
@@ -615,7 +626,7 @@ def test_ExpansionConservationHotHeightDefined(self):
             mass1, circle1.getMassDensity() * circle1.getArea() * hotHeight
         )
 
-    def test_ExpansionConservationColdHeightDefined(self):
+    def expansionConservationColdHeightDefined(self, mat: str):
         """
         Demonstrate that material is conserved at during expansion
 
@@ -625,10 +636,12 @@ def test_ExpansionConservationColdHeightDefined(self):
           inputHeightsConsideredHot = False
         """
         coldHeight = 1.0
-        circle1 = Circle("circle", "HT9", 20, self.tWarm, self.coldOuterDiameter)
-        circle2 = Circle("circle", "HT9", 20, self.tHot, self.coldOuterDiameter)
+        circle1 = Circle("circle", mat, self.tCold, self.tWarm, self.coldOuterDiameter)
+        circle2 = Circle("circle", mat, self.tCold, self.tHot, self.coldOuterDiameter)
         # same as 1 but we will make like 2
-        circle1AdjustTo2 = Circle("circle", "HT9", 20, self.tWarm, 1.0)
+        circle1AdjustTo2 = Circle(
+            "circle", mat, self.tCold, self.tWarm, self.coldOuterDiameter
+        )
 
         # make it hot like 2
         circle1AdjustTo2.adjustDensityForHeightExpansion(self.tHot)
diff --git a/doc/release/0.2.rst b/doc/release/0.2.rst
index d0330d4a5..855c0bd8e 100644
--- a/doc/release/0.2.rst
+++ b/doc/release/0.2.rst
@@ -16,6 +16,7 @@ What's new in ARMI
 
 Bug fixes
 ---------
+#. Adjusted density3 in armi/materials/b4C.py to include the theoretical density. (`PR#942 <https://github.com/terrapower/armi/pull/942>`_)
 #. Fixed bug in ``fastFlux`` block parameter mapping in the ``UniformMeshConverter`` by applying it to the ``detailedAxialExpansion`` category.