The most important materials that need special attention in hot weather are the mortar and grout. Mortar temperatures and properties, masonry unit temperatures and properties, wind velocity and relative humidity can all have adverse effects on the performance of mortar in masonry.

As the temperature of the mortar increases, many physical properties change. For example, workability is reduced and more water must be added to maintain a proper workability. As the temperature increases, both initial and final set occur earlier. Also, depending on the surface characteristics, temperature and moisture content of the masonry units, moisture kiss from the mortar due to suction takes place much more rapidly.

Rapid water loss due to evaporation and suction reduces the amount of water available for hydration of the cement. Since hydration of cement is necessary for normal strength development of mortar, a reduction of strength ma development may occur under rapid drying conditions. Evaporation removes moisture more rapidly from the surface of mortar joints resulting in weaker mortar on the surface.

Covering the walls immediately after construction will effectively slow the rate of water loss from the masonry while the application of a fog spray during the first 72 hours can reduce the effects of hot, dry and windy weather. Strength development in masonry subjected to early dry-out often can be reactivated by spraying the masonry with water. Grout also sets quicker in higher ambient temperatures. However, the effects are primarily influenced by the temperature of the wall into which the grout is placed. Though this influence disturbs placement procedures, it has no adverse effect on final strength.

HEAT SURVIVAL

Hot day, hot job, high humidity and BINGO…another heat victim. No one is immune and construction workers are prime candidates for heat related illnesses…

HEAT EXHAUSTION: Symptoms are heavy sweating, nausea, headache, weakness, vomiting, tiredness & a fast pulse.

FIRST AID: Move to a cooler area, cool by wetting towels & wiping down forehead. Remove any wet or sweat soaked clothing. Fan the victim. Do not give any fluids to a victim unless fully conscious. Follow up with a medical visit.

HEAT CRAMPS: Symptoms are severe muscle spasms in the back, stomach arms & legs. Usually caused by drinking large amounts of water without replacing salt during periods of heavy perspiration.

FIRST AID: Move to a cooler area. Make sure that no water is given unless fully conscious. When you do give water, make sure that the victim takes only small sips. Fan the victim until medical help arrives.

HEAT STROKE: Symptoms are high temperature and dry skin, rapid breathing and pulse. Victims may appear disorganized & confused with headache, nausea, vomiting, seizures and possible coma.

FIRST AID: Very serious, move fast to cooler area and call an ambulance. Remove outer clothing and apply cool water to entire body. Fan the victim until medical help arrives.