Cement is a finely ground powder that when mixed with water forms a paste capable of binding aggregates like sand and gravel into a hardened mass kn
Cement is a finely ground powder that when mixed with water forms a paste capable of binding aggregates like sand and gravel into a hardened mass known as concrete.
In South Africa like most of the world the primary type of cement used is Portland cement. This consists mainly of clinker (produced by heating limestone and clay in a kiln), gypsum and supplementary cementitious materials like fly ash, slag or silica fume.
When water is added to cement a series of chemical reactions occur, known as hydration. The key compounds in cement, primarily tricalcium silicate (C3S) and dicalcium silicate (C2S), react with water to form calcium silicate hydrate (C-S-H) and calcium hydroxide (CH).
1. Tricalcium silicate (C3S) reaction: This is responsible for early strength development:
2. Dicalcium silicate (C2S) reaction: This contributes to long-term strength:
The calcium silicate hydrate (C-S-H) forms a gel-like structure that provides most of the strength in a hardened cement paste. Calcium hydroxide, on the other hand, is a byproduct that contributes to alkalinity but does not enhance strength.
When Does Cement Become Concrete?
Cement becomes concrete when it is mixed with aggregates and water. The curing process allows the hydration reaction to continue gradually strengthening the material. Concrete usually achieves most of its strength within 28 days, but hydration can continue for years and keeps improving durability. Proper curing is critical as inadequate moisture can lead to shrinkage cracks and reduced strength.
In everyday language, people often use the words “cement” and “concrete” interchangeably, referring to a “cement wall” or “cement floor” when they actually mean “concrete wall” or “concrete floor.” Cement is only a component of concrete and using the terms incorrectly can create confusion.
The cement market in South Africa
South Africa has a well-established cement industry with major local manufacturers including:
• PPC Ltd (Pretoria Portland Cement) – The largest cement producer in South Africa.
• AfriSam – A major supplier of construction materials.
• Sephaku Cement – A newer entrant supported by Dangote Cement.
• Lafarge South Africa – Part of the global Holcim Group.
The local market is however facing challenges due to a flood of imported cement from countries like China, Vietnam and Pakistan. These imported products are often cheaper due to lower production costs and government subsidies in their home countries.
Imported cement has put pressure on local manufacturers, reducing their market share and profitability. This has led to:
• Job losses in local production facilities.
• Calls for increased tariffs on imported cement to protect local producers.
• Reduced investment in new cement plants and infrastructure.
The South African government has taken steps to impose anti-dumping duties on some imported cement but enforcement remains inconsistent.
Cement pricing predictions
Cement prices in South Africa are likely to be influenced by several factors:
• Inflation and energy costs: Cement production is energy-intensive and rising electricity prices from Eskom and high fuel costs continue to push prices higher.
• Increased infrastructure projects: Government-led infrastructure initiatives could drive demand, stabilising prices.
• Import restrictions: If stronger tariffs or import bans are introduced, local cement prices could rise due to reduced competition.
• Economic downturns: If the construction sector slows, excess supply may lead to price reductions.
Given these factors, a moderate price increase is expected in the short term due to production cost pressures. However, in the long term, market regulation and demand fluctuations will determine overall price stability.
