Page 5 - Masonry and Concrete

Introduction to Concrete and Masonry
4 CHAPTER ONE

absorb at least some heat, higher density and greater mass cause
slower absorption and longer retention. Metals heat up and cool down
very quickly. Concrete and masonry are heavy, so they can absorb and
store heat and substantially retard its migration through a wall. This
characteristic is measured by the elapsed time required to achieve
equilibrium between inside and outside wall surface temperatures.
The midday sun load on the south face of a building will not com-
pletely penetrate a 12-in. solid masonry wall for approximately 8
hours. It is this thermal lag, in fact, which contributes to concrete and
masonry fire safety by delaying heat transfer through the walls of burn-
ing buildings.
The effectiveness of wall mass on heat transfer is dependent on the
magnitude of the daily temperature range. Warm climates with cool
nights benefit most. Climates in which there is only a small daily tem-
perature range benefit the least. In any climate where there are large
fluctuations in the daily temperature cycle, the thermal inertia of
masonry walls can contribute substantially to increased comfort and
energy efficiency. The time lag created by delayed heat transfer
through the walls reduces peak cooling demands to a great extent, and
may reduce the size of air conditioning and heating equipment
required.

1.2 Job Site Safety

Portland cement is alkaline in nature, so wet concrete and other
cement-based mixes are caustic and will burn the skin after prolonged
contact. Contact with wet concrete, masonry mortar, cement, and
cement mixes can cause skin irritation, severe chemical burns, and
serious eye damage. Wear sturdy work gloves, long sleeves, and full-
length trousers to protect your hands, arms, and legs. Indirect contact
through clothing can be as serious as direct contact, so promptly rinse
out wet concrete or mortar from clothing. Wear rubber boots when
placing and handling concrete for slabs and flatwork, because you may
sometimes have to stand in the wet mix to spread and screed the con-
crete. Make sure the boots are high enough to prevent concrete from
getting inside them. To protect your eyes from cement dust and from
splattered mortar or concrete, wear safety glasses or goggles. Since
masonry involves heavy lifting, be careful to avoid back strain and

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